Question

据我所知，使用刷卡项目下方的背景（如许多谷歌应用程序）实现RecyclerView的刷卡到解除的一种可能性是实现ItemTouchHelper的简单回调并在方法中绘制背景onChildDraw。

这是我的实施：

ItemTouchHelper.SimpleCallback simpleItemTouchCallback = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT) {
    // create objects once and avoid allocating them in the onChildDraw method
    Drawable background;
    Drawable icon;
    int iconMargin;
    boolean initialized;

    private void init() {
        background = new ColorDrawable(Color.RED);
        icon = ContextCompat.getDrawable(mAppContext, R.drawable.ic_delete_white_24dp);
        iconMargin = (int) mAppContext.getResources().getDimension(R.dimen.fab_margin);
        initialized = true;
    }

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

    @Override
    public void onSwiped(RecyclerView.ViewHolder viewHolder, int swipeDir) {
        // remove swiped item from the list and notify the adapter
        int position = viewHolder.getAdapterPosition();
        mItemList.remove(position);
        mRecyclerViewAdapter.notifyDataSetChanged();
    }

    @Override
    public void onChildDraw(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
            if (dX > 0) {
                View itemView = viewHolder.itemView;
                // if viewHolder has been swiped away, don't do anything
                if (viewHolder.getAdapterPosition() == -1) {
                    return;
                }
                if (!initialized) {
                    init();
                }
                // draw background
                int dXSwipe = (int) (dX * 1.05); // increase slightly dX to avoid view flickering, compensating loss of precision due to int conversion 
                background.setBounds(itemView.getLeft(), itemView.getTop(),
                itemView.getLeft() + dXSwipe, itemView.getBottom());
                background.draw(c);
                // draw icon
                int top = (itemView.getTop() + itemView.getBottom() - icon.getIntrinsicHeight()) / 2;
                int left = itemView.getLeft() + iconMargin;
                icon.setBounds(left, top, left + icon.getIntrinsicWidth(), top + icon.getIntrinsicHeight());
                icon.draw(c);
            }
        }
        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
        }
    };
    ItemTouchHelper itemTouchHelper = new ItemTouchHelper(simpleItemTouchCallback);
    itemTouchHelper.attachToRecyclerView(mRecyclerView);

现在，问题是如何在下面的背景中为视图设置动画。可以从Google日历中获取此动画的示例：当刷新事件或提醒时，左侧的图标会根据水平位移量进行放大。

有人知道如何实现这一目标吗？是否有必要采用不同的方法，可能在ViewHolder中有两个视图，如此处RecyclerView Swipe with a view below it所提出的那样？

Answer 1

我发现了怎么做。

对于那些感兴趣的人，解决方案是使用两个视图（前景和背景）并在滑动过程中为背景设置动画。

布局：

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/item_delete_background">

    <ImageView
        android:id="@+id/item_delete_icon"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="@dimen/fab_margin"
        android:layout_marginStart="@dimen/fab_margin"
        app:srcCompat="@drawable/ic_delete_white_24dp" />

    <android.support.constraint.ConstraintLayout
        android:id="@+id/item_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/gray_bg">

        <!--recyclerview item layout-->

    </android.support.constraint.ConstraintLayout>

</FrameLayout>

观点持有人：

class MyViewHolder extends RecyclerView.ViewHolder {
    private ConstraintLayout mItemLayout;
    private ImageView mItemDeleteIcon;

    MyViewHolder(View v) {
        super(v);
        mItemLayout = (ConstraintLayout) v.findViewById(R.id.item_layout);
        mEventDeleteIcon = (ImageView) v.findViewById(R.id.item_delete_icon);
    }

    View getViewToSwipe() {
        return mItemLayout;
    }

    View getViewToAnimate() {
        return mItemDeleteIcon;
    }
}

和ItemTouchHelper回调：

ItemTouchHelper.SimpleCallback mItemTouchCallback = new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT) {

    // override methods

    public void onChildDrawOver(Canvas c, RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder,
                                float dX, float dY,
                                int actionState, boolean isCurrentlyActive) {
        // get the view which is currently swiped
        ConstraintLayout itemLayout = (ConstraintLayout) ((MyViewHolder) viewHolder).getViewToSwipe();
        // calculate relative horizontal displacement
        // with proportion dXRelative : 1 = dX : (layoutWidth / 3)
        float dXRelative = dX / itemLayout.getWidth() * 3;
        // check size boundaries
        if (dXRelative > 1) {
            dXRelative = 1;
        }
        if (dXRelative < 0) {
            dXRelative = 0;
        }
        // animate the icon with scaling on both dimensions
        ((MyViewHolder) viewHolder).getViewToAnimate().animate().scaleX(dXRelative).scaleY(dXRelative).setDuration(0).start();
        // call draw over
        getDefaultUIUtil().onDrawOver(c, recyclerView, ((MyViewHolder) viewHolder).getViewToSwipe(), dX, dY, actionState, isCurrentlyActive);
    }
};

在此帖子之后完成了基本行为（视图持有者中的前景/背景）的实现：Use ItemTouchHelper for Swipe-To-Dismiss with another View displayed behind the swiped out。

希望这可能对某人有用。

Android - 滑动以在背景上使用动画关闭RecyclerView

1 个答案: