Question

我正在尝试将一些iOS功能移植到Android。

我打算创建一个表格，向左滑动显示2按钮：编辑和删除。

我一直在玩它，我知道我非常接近。秘密真正在于OnChildDraw方法。

我想绘制一个适合文本删除的Rect，然后使用各自的背景颜色绘制除此之外的编辑文本。单击时剩余的空白区域应将行恢复到其初始位置。

我设法在用户滑动到两侧时绘制背景，但我不知道如何添加侦听器，一旦将其滑到一边，拖动功能就会开始行为不端。

我正在开发Xamarin，但纯java解决方案也被接受，因为我可以轻松地将它们移植到c＃。

    public class SavedPlacesItemTouchHelper : ItemTouchHelper.SimpleCallback
    {
        private SavedPlacesRecyclerviewAdapter adapter;
        private Paint paint = new Paint();
        private Context context;

        public SavedPlacesItemTouchHelper(Context context, SavedPlacesRecyclerviewAdapter adapter) : base(ItemTouchHelper.ActionStateIdle, ItemTouchHelper.Left)
        {
            this.context = context;
            this.adapter = adapter;
        }

        public override bool OnMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target)
        {
            return false;
        }

        public override void OnSwiped(RecyclerView.ViewHolder viewHolder, int direction)
        {
        }

        public override void OnChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, bool isCurrentlyActive)
        {
            float translationX = dX;
            View itemView = viewHolder.ItemView;
            float height = (float)itemView.Bottom - (float)itemView.Top;

            if (actionState == ItemTouchHelper.ActionStateSwipe && dX <= 0) // Swiping Left
            {
                 translationX = -Math.Min(-dX, height * 2);
                paint.Color = Color.Red;
                RectF background = new RectF((float)itemView.Right + translationX, (float)itemView.Top, (float)itemView.Right, (float)itemView.Bottom);
                c.DrawRect(background, paint);

                //viewHolder.ItemView.TranslationX = translationX;
            }
            else if (actionState == ItemTouchHelper.ActionStateSwipe && dX > 0) // Swiping Right
            {
                translationX = Math.Min(dX, height * 2);
                paint.Color = Color.Red;
                RectF background = new RectF((float)itemView.Right + translationX, (float)itemView.Top, (float)itemView.Right, (float)itemView.Bottom);
                c.DrawRect(background, paint);
            }

            base.OnChildDraw(c, recyclerView, viewHolder, translationX, dY, actionState, isCurrentlyActive);
        }
    }
}

这就是我现在所拥有的。

如果您知道如何添加听众或任何建议，请发表评论！

更新：

我刚刚意识到，在该行的白色剩余空间上双击已经将行恢复到其初始状态。虽然不是一次点击:(

Answer 1

我在同样的问题上挣扎，并试图在线找到解决方案。大多数解决方案使用两层方法（一层视图项，另一层图层按钮），但我想坚持使用ItemTouchHelper。最后，我提出了一个有效的解决方案。请查看以下内容。

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.Rect;
import android.graphics.RectF;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.helper.ItemTouchHelper;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;

public abstract class SwipeHelper extends ItemTouchHelper.SimpleCallback {

    public static final int BUTTON_WIDTH = YOUR_WIDTH_IN_PIXEL_PER_BUTTON
    private RecyclerView recyclerView;
    private List<UnderlayButton> buttons;
    private GestureDetector gestureDetector;
    private int swipedPos = -1;
    private float swipeThreshold = 0.5f;
    private Map<Integer, List<UnderlayButton>> buttonsBuffer;
    private Queue<Integer> recoverQueue;

    private GestureDetector.SimpleOnGestureListener gestureListener = new GestureDetector.SimpleOnGestureListener(){
        @Override
        public boolean onSingleTapConfirmed(MotionEvent e) {
            for (UnderlayButton button : buttons){
                if(button.onClick(e.getX(), e.getY()))
                    break;
            }

            return true;
        }
    };

    private View.OnTouchListener onTouchListener = new View.OnTouchListener() {
        @Override
        public boolean onTouch(View view, MotionEvent e) {
            if (swipedPos < 0) return false;
            Point point = new Point((int) e.getRawX(), (int) e.getRawY());

            RecyclerView.ViewHolder swipedViewHolder = recyclerView.findViewHolderForAdapterPosition(swipedPos);
            View swipedItem = swipedViewHolder.itemView;
            Rect rect = new Rect();
            swipedItem.getGlobalVisibleRect(rect);

            if (e.getAction() == MotionEvent.ACTION_DOWN || e.getAction() == MotionEvent.ACTION_UP ||e.getAction() == MotionEvent.ACTION_MOVE) {
                if (rect.top < point.y && rect.bottom > point.y)
                    gestureDetector.onTouchEvent(e);
                else {
                    recoverQueue.add(swipedPos);
                    swipedPos = -1;
                    recoverSwipedItem();
                }
            }
            return false;
        }
    };

    public SwipeHelper(Context context, RecyclerView recyclerView) {
        super(0, ItemTouchHelper.LEFT);
        this.recyclerView = recyclerView;
        this.buttons = new ArrayList<>();
        this.gestureDetector = new GestureDetector(context, gestureListener);
        this.recyclerView.setOnTouchListener(onTouchListener);
        buttonsBuffer = new HashMap<>();
        recoverQueue = new LinkedList<Integer>(){
            @Override
            public boolean add(Integer o) {
                if (contains(o))
                    return false;
                else
                    return super.add(o);
            }
        };

        attachSwipe();
    }


    @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        return false;
    }

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {
        int pos = viewHolder.getAdapterPosition();

        if (swipedPos != pos)
            recoverQueue.add(swipedPos);

        swipedPos = pos;

        if (buttonsBuffer.containsKey(swipedPos))
            buttons = buttonsBuffer.get(swipedPos);
        else
            buttons.clear();

        buttonsBuffer.clear();
        swipeThreshold = 0.5f * buttons.size() * BUTTON_WIDTH;
        recoverSwipedItem();
    }

    @Override
    public float getSwipeThreshold(RecyclerView.ViewHolder viewHolder) {
        return swipeThreshold;
    }

    @Override
    public float getSwipeEscapeVelocity(float defaultValue) {
        return 0.1f * defaultValue;
    }

    @Override
    public float getSwipeVelocityThreshold(float defaultValue) {
        return 5.0f * defaultValue;
    }

    @Override
    public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        int pos = viewHolder.getAdapterPosition();
        float translationX = dX;
        View itemView = viewHolder.itemView;

        if (pos < 0){
            swipedPos = pos;
            return;
        }

        if(actionState == ItemTouchHelper.ACTION_STATE_SWIPE){
            if(dX < 0) {
                List<UnderlayButton> buffer = new ArrayList<>();

                if (!buttonsBuffer.containsKey(pos)){
                    instantiateUnderlayButton(viewHolder, buffer);
                    buttonsBuffer.put(pos, buffer);
                }
                else {
                    buffer = buttonsBuffer.get(pos);
                }

                translationX = dX * buffer.size() * BUTTON_WIDTH / itemView.getWidth();
                drawButtons(c, itemView, buffer, pos, translationX);
            }
        }

        super.onChildDraw(c, recyclerView, viewHolder, translationX, dY, actionState, isCurrentlyActive);
    }

    private synchronized void recoverSwipedItem(){
        while (!recoverQueue.isEmpty()){
            int pos = recoverQueue.poll();
            if (pos > -1) {
                recyclerView.getAdapter().notifyItemChanged(pos);
            }
        }
    }

    private void drawButtons(Canvas c, View itemView, List<UnderlayButton> buffer, int pos, float dX){
        float right = itemView.getRight();
        float dButtonWidth = (-1) * dX / buffer.size();

        for (UnderlayButton button : buffer) {
            float left = right - dButtonWidth;
            button.onDraw(
                    c,
                    new RectF(
                            left,
                            itemView.getTop(),
                            right,
                            itemView.getBottom()
                    ),
                    pos
            );

            right = left;
        }
    }

    public void attachSwipe(){
        ItemTouchHelper itemTouchHelper = new ItemTouchHelper(this);
        itemTouchHelper.attachToRecyclerView(recyclerView);
    }

    public abstract void instantiateUnderlayButton(RecyclerView.ViewHolder viewHolder, List<UnderlayButton> underlayButtons);

    public static class UnderlayButton {
        private String text;
        private int imageResId;
        private int color;
        private int pos;
        private RectF clickRegion;
        private UnderlayButtonClickListener clickListener;

        public UnderlayButton(String text, int imageResId, int color, UnderlayButtonClickListener clickListener) {
            this.text = text;
            this.imageResId = imageResId;
            this.color = color;
            this.clickListener = clickListener;
        }

        public boolean onClick(float x, float y){
            if (clickRegion != null && clickRegion.contains(x, y)){
                clickListener.onClick(pos);
                return true;
            }

            return false;
        }

        public void onDraw(Canvas c, RectF rect, int pos){
            Paint p = new Paint();

            // Draw background
            p.setColor(color);
            c.drawRect(rect, p);

            // Draw Text
            p.setColor(Color.WHITE);
            p.setTextSize(LayoutHelper.getPx(MyApplication.getAppContext(), 12));

            Rect r = new Rect();
            float cHeight = rect.height();
            float cWidth = rect.width();
            p.setTextAlign(Paint.Align.LEFT);
            p.getTextBounds(text, 0, text.length(), r);
            float x = cWidth / 2f - r.width() / 2f - r.left;
            float y = cHeight / 2f + r.height() / 2f - r.bottom;
            c.drawText(text, rect.left + x, rect.top + y, p);

            clickRegion = rect;
            this.pos = pos;
        }
    }

    public interface UnderlayButtonClickListener {
        void onClick(int pos);
    }
}

用法：

SwipeHelper swipeHelper = new SwipeHelper(this, recyclerView) {
    @Override
    public void instantiateUnderlayButton(RecyclerView.ViewHolder viewHolder, List<UnderlayButton> underlayButtons) {
        underlayButtons.add(new SwipeHelper.UnderlayButton(
                "Delete",
                0,
                Color.parseColor("#FF3C30"),
                new SwipeHelper.UnderlayButtonClickListener() {
                    @Override
                    public void onClick(int pos) {
                        // TODO: onDelete
                    }
                }
        ));

        underlayButtons.add(new SwipeHelper.UnderlayButton(
                "Transfer",
                0,
                Color.parseColor("#FF9502"),
                new SwipeHelper.UnderlayButtonClickListener() {
                    @Override
                    public void onClick(int pos) {
                        // TODO: OnTransfer
                    }
                }
        ));
        underlayButtons.add(new SwipeHelper.UnderlayButton(
                "Unshare",
                0,
                Color.parseColor("#C7C7CB"),
                new SwipeHelper.UnderlayButtonClickListener() {
                    @Override
                    public void onClick(int pos) {
                        // TODO: OnUnshare
                    }
                }
        ));
    }
};

注意：此助手类专为左滑动而设计。您可以在 SwipeHelper 构造函数中更改滑动方向，并相应地在 onChildDraw 方法中根据dX进行更改。

如果您想在按钮中显示图片，只需在 UnderlayButton 中使用 imageResId ，然后重新实施 onDraw 方法

有一个已知错误，当您从一个项目沿对角线方向滑动项目时，第一个触摸的项目会闪烁一点。这可以通过降低 getSwipeVelocityThreshold 的值来解决，但这会让用户更难刷一下该项目。您还可以通过更改 getSwipeThreshold 和 getSwipeEscapeVelocity 中的其他两个值来调整滑动感。检查ItemTouchHelper源代码，注释非常有用。

我相信有很多优化的地方。如果你想坚持使用ItemTouchHelper，这个解决方案只是给出了一个想法。如果您使用它有问题，请告诉我。下面是截图。

致谢：此解决方案主要受到AdamWei在此post

中的回答的启发

Answer 2

这是基于公认的答案方法的Kotlin版本。通过一些小的更改，我设法根据文本的固有大小而不是使用固定宽度来呈现按钮的宽度。

演示项目：https://github.com/ntnhon/RecyclerViewRowOptionsDemo

SwipeHelper的实现：

import android.annotation.SuppressLint
import android.content.Context
import android.graphics.*
import android.view.MotionEvent
import android.view.View
import androidx.annotation.ColorRes
import androidx.core.content.ContextCompat
import androidx.recyclerview.widget.ItemTouchHelper
import androidx.recyclerview.widget.RecyclerView
import java.util.*
import kotlin.math.abs
import kotlin.math.max

abstract class SwipeHelper(
    private val recyclerView: RecyclerView
) : ItemTouchHelper.SimpleCallback(
    ItemTouchHelper.ACTION_STATE_IDLE,
    ItemTouchHelper.LEFT
) {
    private var swipedPosition = -1
    private val buttonsBuffer: MutableMap<Int, List<UnderlayButton>> = mutableMapOf()
    private val recoverQueue = object : LinkedList<Int>() {
        override fun add(element: Int): Boolean {
            if (contains(element)) return false
            return super.add(element)
        }
    }

    @SuppressLint("ClickableViewAccessibility")
    private val touchListener = View.OnTouchListener { _, event ->
        if (swipedPosition < 0) return@OnTouchListener false
        buttonsBuffer[swipedPosition]?.forEach { it.handle(event) }
        recoverQueue.add(swipedPosition)
        swipedPosition = -1
        recoverSwipedItem()
        true
    }

    init {
        recyclerView.setOnTouchListener(touchListener)
    }

    private fun recoverSwipedItem() {
        while (!recoverQueue.isEmpty()) {
            val position = recoverQueue.poll() ?: return
            recyclerView.adapter?.notifyItemChanged(position)
        }
    }

    private fun drawButtons(
        canvas: Canvas,
        buttons: List<UnderlayButton>,
        itemView: View,
        dX: Float
    ) {
        var right = itemView.right
        buttons.forEach { button ->
            val width = button.intrinsicWidth / buttons.intrinsicWidth() * abs(dX)
            val left = right - width
            button.draw(
                canvas,
                RectF(left, itemView.top.toFloat(), right.toFloat(), itemView.bottom.toFloat())
            )

            right = left.toInt()
        }
    }

    override fun onChildDraw(
        c: Canvas,
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        dX: Float,
        dY: Float,
        actionState: Int,
        isCurrentlyActive: Boolean
    ) {
        val position = viewHolder.adapterPosition
        var maxDX = dX
        val itemView = viewHolder.itemView

        if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
            if (dX < 0) {
                if (!buttonsBuffer.containsKey(position)) {
                    buttonsBuffer[position] = instantiateUnderlayButton(position)
                }

                val buttons = buttonsBuffer[position] ?: return
                if (buttons.isEmpty()) return
                maxDX = max(-buttons.intrinsicWidth(), dX)
                drawButtons(c, buttons, itemView, maxDX)
            }
        }

        super.onChildDraw(
            c,
            recyclerView,
            viewHolder,
            maxDX,
            dY,
            actionState,
            isCurrentlyActive
        )
    }

    override fun onMove(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        target: RecyclerView.ViewHolder
    ): Boolean {
        return false
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        val position = viewHolder.adapterPosition
        if (swipedPosition != position) recoverQueue.add(swipedPosition)
        swipedPosition = position
        recoverSwipedItem()
    }

    abstract fun instantiateUnderlayButton(position: Int): List<UnderlayButton>

    //region UnderlayButton
    interface UnderlayButtonClickListener {
        fun onClick()
    }

    class UnderlayButton(
        private val context: Context,
        private val title: String,
        textSize: Float,
        @ColorRes private val colorRes: Int,
        private val clickListener: UnderlayButtonClickListener
    ) {
        private var clickableRegion: RectF? = null
        private val textSizeInPixel: Float = textSize * context.resources.displayMetrics.density // dp to px
        private val horizontalPadding = 50.0f
        val intrinsicWidth: Float

        init {
            val paint = Paint()
            paint.textSize = textSizeInPixel
            paint.typeface = Typeface.DEFAULT_BOLD
            paint.textAlign = Paint.Align.LEFT
            val titleBounds = Rect()
            paint.getTextBounds(title, 0, title.length, titleBounds)
            intrinsicWidth = titleBounds.width() + 2 * horizontalPadding
        }

        fun draw(canvas: Canvas, rect: RectF) {
            val paint = Paint()

            // Draw background
            paint.color = ContextCompat.getColor(context, colorRes)
            canvas.drawRect(rect, paint)

            // Draw title
            paint.color = ContextCompat.getColor(context, android.R.color.white)
            paint.textSize = textSizeInPixel
            paint.typeface = Typeface.DEFAULT_BOLD
            paint.textAlign = Paint.Align.LEFT

            val titleBounds = Rect()
            paint.getTextBounds(title, 0, title.length, titleBounds)

            val y = rect.height() / 2 + titleBounds.height() / 2 - titleBounds.bottom
            canvas.drawText(title, rect.left + horizontalPadding, rect.top + y, paint)

            clickableRegion = rect
        }

        fun handle(event: MotionEvent) {
            clickableRegion?.let {
                if (it.contains(event.x, event.y)) {
                    clickListener.onClick()
                }
            }
        }
    }
    //endregion
}

private fun List<SwipeHelper.UnderlayButton>.intrinsicWidth(): Float {
    if (isEmpty()) return 0.0f
    return map { it.intrinsicWidth }.reduce { acc, fl -> acc + fl }
}

用法：

private fun setUpRecyclerView() {
        binding.recyclerView.adapter = Adapter(listOf(
            "Item 0: No action",
            "Item 1: Delete",
            "Item 2: Delete & Mark as unread",
            "Item 3: Delete, Mark as unread & Archive"
        ))
        binding.recyclerView.addItemDecoration(DividerItemDecoration(this, DividerItemDecoration.VERTICAL))
        binding.recyclerView.layoutManager = LinearLayoutManager(this)

        val itemTouchHelper = ItemTouchHelper(object : SwipeHelper(binding.recyclerView) {
            override fun instantiateUnderlayButton(position: Int): List<UnderlayButton> {
                var buttons = listOf<UnderlayButton>()
                val deleteButton = deleteButton(position)
                val markAsUnreadButton = markAsUnreadButton(position)
                val archiveButton = archiveButton(position)
                when (position) {
                    1 -> buttons = listOf(deleteButton)
                    2 -> buttons = listOf(deleteButton, markAsUnreadButton)
                    3 -> buttons = listOf(deleteButton, markAsUnreadButton, archiveButton)
                    else -> Unit
                }
                return buttons
            }
        })

        itemTouchHelper.attachToRecyclerView(binding.recyclerView)
    }

    private fun toast(text: String) {
        toast?.cancel()
        toast = Toast.makeText(this, text, Toast.LENGTH_SHORT)
        toast?.show()
    }

    private fun deleteButton(position: Int) : SwipeHelper.UnderlayButton {
        return SwipeHelper.UnderlayButton(
            this,
            "Delete",
            14.0f,
            android.R.color.holo_red_light,
            object : SwipeHelper.UnderlayButtonClickListener {
                override fun onClick() {
                    toast("Deleted item $position")
                }
            })
    }

    private fun markAsUnreadButton(position: Int) : SwipeHelper.UnderlayButton {
        return SwipeHelper.UnderlayButton(
            this,
            "Mark as unread",
            14.0f,
            android.R.color.holo_green_light,
            object : SwipeHelper.UnderlayButtonClickListener {
                override fun onClick() {
                    toast("Marked as unread item $position")
                }
            })
    }

    private fun archiveButton(position: Int) : SwipeHelper.UnderlayButton {
        return SwipeHelper.UnderlayButton(
            this,
            "Archive",
            14.0f,
            android.R.color.holo_blue_light,
            object : SwipeHelper.UnderlayButtonClickListener {
                override fun onClick() {
                    toast("Archived item $position")
                }
            })
    }

Answer 3

根据Wenxi Zeng的回答here，如果你想让多行上的按钮中的文字，用这个替换UnderlayButton的onDraw方法：

public void onDraw(Canvas canvas, RectF rect, int pos){
        Paint p = new Paint();

        // Draw background
        p.setColor(color);
        canvas.drawRect(rect, p);

        // Draw Text
        TextPaint textPaint = new TextPaint();
        textPaint.setTextSize(UtilitiesOperations.convertDpToPx(getContext(), 15));
        textPaint.setColor(Color.WHITE);
        StaticLayout sl = new StaticLayout(text, textPaint, (int)rect.width(),
                Layout.Alignment.ALIGN_CENTER, 1, 1, false);

        canvas.save();
        Rect r = new Rect();
        float y = (rect.height() / 2f) + (r.height() / 2f) - r.bottom - (sl.getHeight() /2);
        canvas.translate(rect.left, rect.top + y);
        sl.draw(canvas);
        canvas.restore();

        clickRegion = rect;
        this.pos = pos;
    }

Answer 4

如果在向另一个方向滑动时也希望按钮也位于左侧，只需尝试在现有答案中添加以下简单行即可：

在drawButtons方法中：

private void drawButtons（画布c，查看itemView，列表缓冲区，int pos，float dX）{ 向右浮动= itemView.getRight（）; 向左浮动= itemView.getLeft（）; float dButtonWidth =（-1）* dX / buffer.size（）;

    for (UnderlayButton button : buffer) {
        if (dX < 0) {
            left = right - dButtonWidth;
            button.onDraw(
                    c,
                    new RectF(
                            left,
                            itemView.getTop(),
                            right,
                            itemView.getBottom()
                    ),
                    pos, dX //(to draw button on right)
            );

            right = left;
        } else if (dX > 0) {
            right = left - dButtonWidth;
            button.onDraw(c,
                    new RectF(
                            right,
                            itemView.getTop(),
                            left,
                            itemView.getBottom()
                    ), pos, dX //(to draw button on left)
            );


        }
    }
}

在onDraw方法中，检查dX的值并设置按钮的文本和颜色：

public void onDraw（画布c，RectF rect，int pos，float dX）{ Paint p = new Paint（）;

        // Draw background

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {


            if (dX > 0)
                p.setColor(Color.parseColor("#23d2c5"));
            else if (dX < 0)
                p.setColor(Color.parseColor("#23d2c5"));

            c.drawRect(rect, p);


            // Draw Text
            p.setColor(Color.WHITE);
            p.setTextSize(36);
            //  p.setTextSize(LayoutHelper.getPx(MyApplication.getAppContext(), 12));

            Rect r = new Rect();
            float cHeight = rect.height();
            float cWidth = rect.width();
            p.setTextAlign(Paint.Align.LEFT);
            p.getTextBounds(text, 0, text.length(), r);

            float x = cWidth / 2f - r.width() / 2f - r.left;
            float y = cHeight / 2f + r.height() / 2f - r.bottom;
            if (dX > 0) {
                p.setColor(Color.parseColor("#23d2c5"));
                c.drawText("Reject", rect.left + x, rect.top + y, p);
            } else if (dX < 0) {

                c.drawText(text, rect.left + x, rect.top + y, p);
            }
            clickRegion = rect;
            this.pos = pos;
        }

    }

Answer 5

对于所有想为此使用图书馆的人，请查看以下内容：

https://github.com/chthai64/SwipeRevealLayout

并且，对于此库的精简版本，请检出：

https://android.jlelse.eu/android-recyclerview-swipeable-items-46a3c763498d

P.S。您可以使用这些内容创建任何自定义布局（即使使用Image Buttons也可以作为隐藏布局。

Answer 6

我做了以下工作以能够绘制可绘制对象而不是文本：

在SwipeHelper中，我更改了

UnderlayButton(String text, int imageResId, int color, UnderlayButtonClickListener clickListener)

到

UnderlayButton(String text, Bitmap bitmap, int color, UnderlayButtonClickListener clickListener)

我当然删除了imageResId，而是创建了一个Bitmap bitmap，并使用this.bitmap = bitmap;作为其余变量将构造函数变量传递给它。

然后在SwipeHelper.onDaw()中调用drawBitmap()将位图应用于画布。例如：
```
c.drawBitmap(bitmap, rect.left, rect.top, p);
```
分别在c和p以及您的Canvas和Paint变量中。
在我称为UnderlayButton的活动中，我使用this method将可绘制对象（在我的情况下是VectorDrawable）转换为位图：
```
int idDrawable = R.drawable.ic_delete_white;
Bitmap bitmap = getBitmapFromVectorDrawable(getContext(), idDrawable);
```

剩下要做的就是图标的居中。

Answer 7

如果您使用def foo[T](as: T*)(implicit n: Numeric[T]) = as.foldLeft(0d)(_ + n.toDouble(_))，请尝试使用RecyclerView。做这样的事。

OnScrollListener

Answer 8

我也想在我的应用程序中使用这个触摸手势，在使用Itemtouchhelper工作太多之后我决定编写自己的触摸处理程序：

    private class TouchHelper : Java.Lang.Object, View.IOnTouchListener
    {
        ViewHolder vh;
        public TouchHelper(ViewHolder vh)
        { this.vh = vh;  }

        float DownX, DownY; bool isSliding;
        TimeSpan tsDown;
        public bool OnTouch(View v, MotionEvent e)
        {
            switch (e.Action)
            {
                case MotionEventActions.Down:
                    DownX = e.GetX(); DownY = e.GetY();
                    tsDown = TimeSpan.Now;
                    break;
                case MotionEventActions.Move:
                    float deltaX = e.GetX() - DownX, deltaY = e.GetX() - DownY;
                    if (Math.Abs(deltaX) >= Values.ScreenWidth / 20 || Math.Abs(deltaY) >= Values.ScreenWidth / 20)
                        isSliding = Math.Abs(deltaX) > Math.Abs(deltaY);

                    //TextsPlace is the layout that moves with touch
                    if(isSliding)
                        vh.TextsPlace.TranslationX = deltaX / 2;

                    break;
                case MotionEventActions.Cancel:
                case MotionEventActions.Up:
                    //handle if touch was for clicking
                    if (Math.Abs(deltaX) <= 50 && (TimeSpan.Now - tsDown).TotalMilliseconds <= 400)
                        vh.OnTextsPlaceClick(vh.TextsPlace, null);
                    break;
            }
            return true;
        }
    }

注意：当创建视图时，将其设置为视图内容的ontouchlistener。您可以添加动画以将项目返回到第一位。

您还可以编写自定义布局管理器，以便在项目滑动时阻止垂直滚动。

Answer 9

我有一个简单得多的解决方案：

在行XML中添加一个按钮，宽度为0，浮动在右侧：

> <Button
>     android:id="@+id/hidden"
>     android:layout_width="0dp"
>     android:layout_height="match_parent"
>     android:layout_alignParentRight = "true">

在onChildDraw（）中，只需将其宽度增加dX值即可。

 int position = viewHolder.getAdapterPosition();
 View v = recyclerView.getLayoutManager().findViewByPosition(position);
 Button hidden = v.findViewById(R.id.hidden);
 hidden.setLayoutParams(new LinearLayout.LayoutParams((int)-dX, -1));

确保不要调用默认的super.onChildDraw（）

Answer 10

由于我在任何地方都没有看到如何实现它，并且确实设法使它起作用，因此我将发布针对该问题的解决方案，该解决方案在c＃Xamarin Android中是有效的。

如果您需要本机android，则必须将其转换为android本机，这并不难。如果需要，我可以稍后再做。

这是我的ItemHelper基类：

 internal abstract class ItemTouchHelperBase : ItemTouchHelper.Callback
    {
        protected RecyclerViewAdapterBase adapter;
        public int currentPosition = -1;
        public Rect ItemRect = new Rect();

        private Paint backgroundPaint = new Paint();
        private Rect backgroundBounds = new Rect();
        private TextPaint textPaint = new TextPaint();
        private string deleteText;
        private readonly float textWidth;
        private readonly float textHeight;

        public ItemTouchHelperBase()
        {
            backgroundPaint.Color = new Color(ContextCompat.GetColor(Application.Context, Resource.Color.delete_red));
            textPaint.Color = Color.White;
            textPaint.AntiAlias = true;
            textPaint.TextSize = FontHelper.GetFontSize(Application.Context, Resource.Dimension.font_size_button);
            deleteText = "  " + StringResource.delete + "  ";

            Rect textBounds = new Rect();
            textPaint.GetTextBounds(deleteText, 0, deleteText.Length, textBounds);

            textHeight = textBounds.Height();
            textWidth = textPaint.MeasureText(deleteText);
        }

        public override bool OnMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target)
        {
            return false;
        }

        public override void ClearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder)
        {
            if (adapter != null)
            {
                ItemRect = new Rect();
            }
            base.ClearView(recyclerView, viewHolder);
        }

        public override void OnSwiped(RecyclerView.ViewHolder viewHolder, int direction)
        {
        }

        public override void OnChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, bool isCurrentlyActive)
        {
            // Note: Don't create variables inside OnDraw due to performance issues
            try
            {
                if (actionState == ItemTouchHelper.ActionStateSwipe)
                {
                    if (dX <= 0) // Left swipe
                    {
                        // Swipe up to text width accordingly to ratio
                        dX /= viewHolder.ItemView.Right / textWidth;

                        //Draw background
                        backgroundBounds = new Rect(
                            viewHolder.ItemView.Right + (int) dX,
                            viewHolder.ItemView.Top,
                            viewHolder.ItemView.Right,
                            viewHolder.ItemView.Bottom);
                        c.DrawRect(backgroundBounds, backgroundPaint);

                        if (adapter != null)
                        {
                            ItemRect = backgroundBounds;
                        }

                        //Draw text
                        c.DrawText(
                            deleteText,
                            (float) viewHolder.ItemView.Right - textWidth, viewHolder.ItemView.Top + (viewHolder.ItemView.Height / 2) + (textHeight / 2),
                            textPaint);
                    }

                    base.OnChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
                }
            }
            catch (Exception)
            {
            }
        }

        internal void AttachToRecyclerview(RecyclerView recycleview)
        {
            new ItemTouchHelper(this).AttachToRecyclerView(recycleview);
        }

        public void ClickOutsideDeleteButton()
        {
            try
            {
                if (currentPosition != -1)
                {
                    PutRowBackToDefault();
                }
            }
            catch (Exception)
            {
            }
        }

        protected void PutRowBackToDefault()
        {
            adapter.NotifyItemChanged(currentPosition);
            currentPosition = -1;
        }
    }

然后在您的项目助手类中：

 internal class MyItemsTouchHelperCallback : ItemTouchHelperBase
    {
        public MyItemsTouchHelperCallback (MyAdapter adapter)
        {
            this.adapter = adapter;
        }

        public override int GetMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder)
        {
            try
            {
                if (currentPosition != -1 && currentPosition != viewHolder.AdapterPosition)
                {
                    PutRowBackToDefault();
                }
                currentPosition = viewHolder.AdapterPosition;
            }
            catch (Exception)
            {
            }

            int swipeFlags = viewHolder is MyViewHolder ? ItemTouchHelper.Start : ItemTouchHelper.ActionStateIdle;
            return MakeMovementFlags(ItemTouchHelper.ActionStateIdle, swipeFlags);
        }
    }

然后在您的活动中进行以下操作：

将此OnCreate放置

        recycleViewLayoutManager = new LinearLayoutManager(this);
        recycler_view_main.SetLayoutManager(recycleViewLayoutManager);
        recyclerAdapter = new MyAdapter(this, this);
        recycler_view_main.SetAdapter(recyclerAdapter);
        myItemsTouchHelperCallback = new MyItemsTouchHelperCallback (recyclerAdapter);
        myItemsTouchHelperCallback .AttachToRecyclerview(recycler_view_main);

然后在活动中，您将覆盖此方法：

 public override bool DispatchTouchEvent(MotionEvent e)
            {
                int[] recyclerviewLocationOnScreen = new int[2];
                recycler_view_main.GetLocationOnScreen(recyclerviewLocationOnScreen);

                TouchEventsHelper.TouchUpEvent(
                    e.Action,
                    e.GetX() - recyclerviewLocationOnScreen[0],
                    e.GetY() - recyclerviewLocationOnScreen[1],
                    myItemsTouchHelperCallback .ItemRect,
                    delegate
                    {
                        // Delete your row
                    },
                    delegate
                    { myItemsTouchHelperCallback .ClickOutsideDeleteButton(); });


                return base.DispatchTouchEvent(e);
            }

这是我创建的供分派事件使用的辅助方法：

internal static void TouchUpEvent(MotionEventActions eventActions, float x, float y, Rect rectangle, Action ActionDeleteClick, Action NormalClick)
        {
            try
            {
                if (rectangle.Contains((int) x, (int) y))
                {
                    //inside delete button
                    if (eventActions == MotionEventActions.Down)
                    {
                        isClick = true;
                    }
                    else if (eventActions == MotionEventActions.Up || eventActions == MotionEventActions.Cancel)
                    {
                        if (isClick)
                        {
                            ActionDeleteClick.Invoke();
                        }
                    }
                }
                else if (eventActions == MotionEventActions.Up ||
                         eventActions == MotionEventActions.Cancel ||
                         eventActions == MotionEventActions.Down)
                {
                    //click anywhere outside delete button
                    isClick = false;
                    if (eventActions == MotionEventActions.Down)
                    {
                        NormalClick.Invoke();
                    }
                }
            }
            catch (Exception)
            {
            }
        }

这有点复杂，但是效果很好。我已经以多种方式对此进行了测试。让我知道您在执行此操作时是否遇到任何困难

Answer 11

我参加聚会很晚，但是如果有人在寻找UIKit UITableView删除按钮的行为，那么您可以在Xamarin.Android中的RecyclerView上使用类似的东西：

public class SwipeDeleteHelper : ItemTouchHelper.Callback
{
    private int _startingWidth = 0;
    private bool? _rightAlignedText = null;
    private bool _alreadyClicked = false;

    private static float _previousDx = float.NegativeInfinity;
    private static float _viewWidth = float.NegativeInfinity;
    private static float _permanentlyDeleteThreshold = float.NegativeInfinity;

    private static RecyclerView.ViewHolder _currentViewHolder;
    private RecyclerView.ViewHolder CurrentViewHolder
    {
        get => _currentViewHolder;

        set
        {
            _startingWidth = 0;
            _rightAlignedText = null;
            _alreadyClicked = false;

            _previousDx = float.NegativeInfinity;

            _currentViewHolder = value;
        }
    }
    /*
    You can create a method in a utility class for the buttonwidth conversion like this:
    public static float GetPxFromDp(float dp)
    {
        return dp * Application.Context.ApplicationContext.Resources.DisplayMetrics.Density;
    }
    Also you can use text width measurement to determine the optimal width of the button for your delete text.
    */
    public static int buttonWidth = 60 * Application.Context.ApplicationContext.Resources.DisplayMetrics.Density;

    public override int GetMovementFlags(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder)
    {
        if (viewHolder is EntryCell)
        {
            return MakeMovementFlags(ItemTouchHelper.ActionStateIdle, ItemTouchHelper.Left | ItemTouchHelper.Start | ItemTouchHelper.Right | ItemTouchHelper.End);
        }

        return MakeMovementFlags(ItemTouchHelper.ActionStateIdle, ItemTouchHelper.ActionStateIdle);
    }

    public override void OnSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState)
    {
        if (float.IsNegativeInfinity(_permanentlyDeleteThreshold))
        {
            _viewWidth = viewHolder.ItemView.Width;
            _permanentlyDeleteThreshold = (viewHolder.ItemView.Width * 3f / 4f);
        }

        if (viewHolder != CurrentViewHolder)
        {
            if (viewHolder != null) // This is a new selection and the button of the previous viewHolder should get hidden.
            {
                (CurrentViewHolder as EntryCell)?.ResetView(CurrentViewHolder);

                CurrentViewHolder = viewHolder;
            }
            else if (CurrentViewHolder != null) // This is the end of the previous selection
            {
                var hidden = CurrentViewHolder.ItemView.FindViewById<Button>(Resource.Id.fileListDeleteButton);

                _previousDx = float.NegativeInfinity;

                if (hidden.LayoutParameters.Width > _permanentlyDeleteThreshold && !_alreadyClicked) // released in permanent delete area
                {
                    _alreadyClicked = true;

                    hidden.LayoutParameters.Width = CurrentViewHolder.ItemView.Width;

                    hidden.CallOnClick();

                    CurrentViewHolder = null;
                }
                else
                {
                    _startingWidth = hidden.LayoutParameters.Width >= buttonWidth ? buttonWidth : 0;

                    hidden.LayoutParameters.Width = _startingWidth;
                }

                AlignDeleteButtonText(hidden);

                hidden.RequestLayout();
            }
        }

        base.OnSelectedChanged(viewHolder, actionState);
    }

    public override void OnChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, bool isCurrentlyActive)
    {
        if (actionState == ItemTouchHelper.ActionStateSwipe && !_alreadyClicked)
        {
            var hidden = viewHolder.ItemView.FindViewById<Button>(Resource.Id.fileListDeleteButton);

            if (isCurrentlyActive) // swiping
            {
                if (float.IsNegativeInfinity(_previousDx)) // This is a new swipe
                {
                    _previousDx = dX;
                }

                if (Math.Abs(dX - _previousDx) > 0.1f && Math.Abs(dX - (-_viewWidth)) > 0.1f)
                {
                    hidden.LayoutParameters.Width = Math.Max(0, (int)Math.Round(hidden.LayoutParameters.Width - (dX >= _previousDx ? 1 : -1) * (Math.Abs(dX - _previousDx))));

                    _previousDx = dX;

                    AlignDeleteButtonText(hidden);

                    hidden.RequestLayout();
                }
            }
        }
    }

    private void AlignDeleteButtonText(Button hidden)
    {
        if (_rightAlignedText != false && hidden.LayoutParameters.Width >= _permanentlyDeleteThreshold) // pulled into permanent delete area
        {
            hidden.Gravity = GravityFlags.AxisSpecified | GravityFlags.AxisPullBefore | GravityFlags.CenterVertical;
            _rightAlignedText = false;
        }
        else if (_rightAlignedText != null && hidden.LayoutParameters.Width <= buttonWidth)
        {
            hidden.Gravity = GravityFlags.Center;
            _rightAlignedText = null;
        }
        else if (_rightAlignedText != true && hidden.LayoutParameters.Width > buttonWidth && hidden.LayoutParameters.Width < _permanentlyDeleteThreshold) // pulled back from permanent delete area
        {
            hidden.Gravity = GravityFlags.AxisSpecified | GravityFlags.AxisPullAfter | GravityFlags.CenterVertical;
            _rightAlignedText = true;
        }
    }

    public override bool OnMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) { return false; }

    public override void OnSwiped(RecyclerView.ViewHolder viewHolder, int direction) { }
}

EntryCell是MvxRecyclerViewHolder的后代，它应包含以下内容：

public class EntryCell : MvxRecyclerViewHolder
{
    public EntryCell(View itemView, IMvxAndroidBindingContext context) : base(itemView, context)
    {
        Button _delButton = itemView.FindViewById<Button>(Resource.Id.fileListDeleteButton);

        _delButton.Text = "Delete";
    }

    public void ResetView(RecyclerView.ViewHolder currentViewHolder)
    {
        var hidden = currentViewHolder.ItemView.FindViewById<Button>(Resource.Id.fileListDeleteButton);

        hidden.LayoutParameters.Width = 0;

        hidden.RequestLayout();
    }
}

您的视图中应该有一个按钮（在EntryCell中作为Resource.Id.fileListDeleteButton引用，因此该按钮的ID为fileListDeleteButton）。我使用XML作为视图，它看起来像这样：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    android:orientation="vertical">

<!-- The rest of your code... -->

<Button
    android:id="@+id/fileListDeleteButton"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_alignParentRight="true"
    android:paddingHorizontal="@dimen/abc_button_padding_horizontal_material"
    android:background="#f00"
    android:textColor="@android:color/white"
    android:textAllCaps="false"
    android:singleLine="true"
    android:ellipsize="none"
    android:text="dummy" />
</RelativeLayout>

在您的代码中，即RecyclerView所在的位置，像这样使用它：

ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new SwipeDeleteHelper());
itemTouchHelper.AttachToRecyclerView(yourRecyclerView);

我希望这对某人有帮助。

在轻扫上的RecyclerView ItemTouchHelper按钮

11 个答案: