在CardView中选择随机项

Question

在此picture中，您可以看到CardView，其中每个项目一次显示一个。我已经实现了滚动数据集的触摸功能。我现在想要实现随机选择项目的功能。以下是设置CardView的位置：

package com.chiemy.cardview.view;

import android.content.Context;
import android.database.DataSetObserver;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.SparseArray;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.animation.AccelerateInterpolator;
import android.widget.FrameLayout;
import android.widget.ListAdapter;

import com.nineoldandroids.animation.Animator;
import com.nineoldandroids.animation.AnimatorListenerAdapter;
import com.nineoldandroids.view.ViewHelper;
import com.nineoldandroids.view.ViewPropertyAnimator;

/**
 * @author chiemy
 * 
 */
public class CardView extends FrameLayout {
    private static final int ITEM_SPACE = 40;
    private static final int DEF_MAX_VISIBLE = 4;

    private int mMaxVisible = DEF_MAX_VISIBLE;
    private int itemSpace = ITEM_SPACE;

    private float mTouchSlop;
    private ListAdapter mListAdapter;
    private int mNextAdapterPosition;
    private SparseArray<View> viewHolder = new SparseArray<View>();
    private OnCardClickListener mListener;
    private int topPosition;
    private Rect topRect;

    public interface OnCardClickListener {
        void onCardClick(View view, int position);
    }

    public CardView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    public CardView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public CardView(Context context) {
        super(context);
        init();
    }

    private void init() {
        topRect = new Rect();
        ViewConfiguration con = ViewConfiguration.get(getContext());
        mTouchSlop = con.getScaledTouchSlop();
    }

    public void setMaxVisibleCount(int count) {
        mMaxVisible = count;
    }

    public int getMaxVisibleCount() {
        return mMaxVisible;
    }

    public void setItemSpace(int itemSpace) {
        this.itemSpace = itemSpace;
    }

    public int getItemSpace() {
        return itemSpace;
    }

    public ListAdapter getAdapter() {
        return mListAdapter;
    }

    public void setAdapter(ListAdapter adapter) {
        if (mListAdapter != null) {
            mListAdapter.unregisterDataSetObserver(mDataSetObserver);
        }
        mNextAdapterPosition = 0;
        mListAdapter = adapter;
        adapter.registerDataSetObserver(mDataSetObserver);
        removeAllViews();
        ensureFull();
    }

    public void setOnCardClickListener(OnCardClickListener listener) {
        mListener = listener;
    }

    private void ensureFull() {
        while (mNextAdapterPosition < mListAdapter.getCount()
                && getChildCount() < mMaxVisible) {
            int index = mNextAdapterPosition % mMaxVisible;
            View convertView = viewHolder.get(index);
            final View view = mListAdapter.getView(mNextAdapterPosition,
                    convertView, this);
            view.setOnClickListener(null);
            viewHolder.put(index, view);

            index = Math.min(mNextAdapterPosition, mMaxVisible - 1);
            ViewHelper.setScaleX(view,((mMaxVisible - index - 1) / (float) mMaxVisible) * 0.2f + 0.8f);
            int topMargin = (mMaxVisible - index - 1) * itemSpace;
            ViewHelper.setTranslationY(view, topMargin);
            ViewHelper.setAlpha(view, mNextAdapterPosition == 0 ? 1 : 0.5f);

            LayoutParams params = (LayoutParams) view.getLayoutParams();
            if (params == null) {
                params = new LayoutParams(LayoutParams.MATCH_PARENT,
                        LayoutParams.WRAP_CONTENT);
            }
            addViewInLayout(view, 0, params);

            mNextAdapterPosition += 1;
        }
        // requestLayout();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);

        int childCount = getChildCount();
        int maxHeight = 0;
        int maxWidth = 0;
        for (int i = 0; i < childCount; i++) {
            View child = getChildAt(i);
            this.measureChild(child, widthMeasureSpec, heightMeasureSpec);
            int height = child.getMeasuredHeight();
            int width = child.getMeasuredWidth();
            if (height > maxHeight) {
                maxHeight = height;
            }
            if (width > maxWidth) {
                maxWidth = width;
            }
        }
        int desireWidth = widthSize;
        int desireHeight = heightSize;
        if (widthMode == MeasureSpec.AT_MOST) {
            desireWidth = maxWidth + getPaddingLeft() + getPaddingRight();
        }
        if (heightMode == MeasureSpec.AT_MOST) {
            desireHeight = maxHeight + (mMaxVisible - 1) * itemSpace + getPaddingTop() + getPaddingBottom();
        }
        setMeasuredDimension(desireWidth, desireHeight);
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right,
            int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        View topView = getChildAt(getChildCount() - 1);
        if (topView != null) {
            topView.setOnClickListener(listener);
        }
    }

    float downX, downY;

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
        case MotionEvent.ACTION_MOVE:
            if (goDown()) {
                downY = -1;
            }
            break;
        }
        return super.onTouchEvent(event);
    }

    /**
     * 下移所有视图
     */
    private boolean goDown() {
        final View topView = getChildAt(getChildCount() - 1);
        if(!topView.isEnabled()){
            return false;
        }
        // topView.getHitRect(topRect); 在4.3以前有bug，用以下方法代替
        topRect = getHitRect(topRect, topView);
        // 如果按下的位置不在顶部视图上，则不移动
        if (!topRect.contains((int) downX, (int) downY)) {
            return false;
        }
        topView.setEnabled(false);
        ViewPropertyAnimator anim = ViewPropertyAnimator
                .animate(topView)
                .translationY(
                        ViewHelper.getTranslationY(topView)
                                + topView.getHeight()).alpha(0).scaleX(1)
                .setListener(null).setDuration(200);
        anim.setListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                topView.setEnabled(true);
                removeView(topView);
                ensureFull();
                final int count = getChildCount();
                for (int i = 0; i < count; i++) {
                    final View view = getChildAt(i);
                    float scaleX = ViewHelper.getScaleX(view)
                            + ((float) 1 / mMaxVisible) * 0.2f;
                    float tranlateY = ViewHelper.getTranslationY(view)
                            + itemSpace;
                    if (i == count - 1) {
                        bringToTop(view);
                    } else {
                        if ((count == mMaxVisible && i != 0)
                                || count < mMaxVisible) {
                            ViewPropertyAnimator
                                    .animate(view)
                                    .translationY(tranlateY)
                                    .setInterpolator(
                                            new AccelerateInterpolator())
                                    .setListener(null).scaleX(scaleX)
                                    .setDuration(200);
                        }
                    }
                }
            }
        });
        return true;
    }

    private void bringToTop(final View view) {
        topPosition++;
        float scaleX = ViewHelper.getScaleX(view) + ((float) 1 / mMaxVisible)
                * 0.2f;
        float tranlateY = ViewHelper.getTranslationY(view) + itemSpace;
        ViewPropertyAnimator.animate(view).translationY(tranlateY)
                .scaleX(scaleX).setDuration(200).alpha(1)
                .setInterpolator(new AccelerateInterpolator());
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        float currentY = ev.getY();
        switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            downX = ev.getX();
            downY = ev.getY();
            break;
        case MotionEvent.ACTION_MOVE:
            float distance = currentY - downY;
            if (distance > mTouchSlop) {
                return true;
            }
            break;
        }
        return false;
    }

    public static Rect getHitRect(Rect rect, View child) {
        rect.left = child.getLeft();
        rect.right = child.getRight();
        rect.top = (int) (child.getTop() + ViewHelper.getTranslationY(child));
        rect.bottom = (int) (child.getBottom() + ViewHelper
                .getTranslationY(child));
        return rect;
    }

    private final DataSetObserver mDataSetObserver = new DataSetObserver() {
        @Override
        public void onChanged() {
            super.onChanged();
        }

        @Override
        public void onInvalidated() {
            super.onInvalidated();
        }
    };

    private OnClickListener listener = new OnClickListener() {
        @Override
        public void onClick(View v) {
            if (mListener != null) {
                mListener.onCardClick(v, topPosition);
            }
        }
    };
}

这是我的CardView适配器类：

package com.chiemy.cardview.view;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;

import com.chiemy.cardview.R;

public abstract class CardAdapter<T> extends BaseCardAdapter {
    private final Context mContext;

    private ArrayList<T> mData;

    public CardAdapter(Context context) {
        mContext = context;
        mData = new ArrayList<T>();
    }

    public CardAdapter(Context context, Collection<? extends T> items) {
        mContext = context;
        mData = new ArrayList<T>(items);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        FrameLayout wrapper = (FrameLayout) convertView;
        View cardView;
        View convertedCardView;
        if (wrapper == null) {
            wrapper = new FrameLayout(mContext);
            wrapper.setBackgroundResource(R.drawable.card_background_shadow);
            cardView = getCardView(position, null, wrapper);
            wrapper.addView(cardView);
        } else {
            cardView = wrapper.getChildAt(0);
            convertedCardView = getCardView(position, cardView, wrapper);

            wrapper.removeView(cardView);
            wrapper.addView(convertedCardView);
            if (convertedCardView != cardView) {
            }
        }
        return wrapper;
    }

    protected abstract View getCardView(int position, View convertView, ViewGroup parent);

    public void addAll(List<T> items){
        mData.addAll(items);
    }

    @Override
    public T getItem(int position) {
        return mData.get(position);
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public long getItemId(int position) {
        return getItem(position).hashCode();
    }

    public Context getContext() {
        return mContext;
    }

    public void clear(){
        if(mData != null){
            mData.clear();
        }
    }
}

有关如何实现这一目标的任何建议吗？

Answer 1

要随机化ArrayList<>，在您的情况下，这将是改组解决方案，您可以使用此代码：

long seed = System.nanoTime();
Collections.shuffle(list_of_items, new Random(seed));

您需要将ArrayList<>设置回CardView，您的项目将随机播放。要检索随机项，请访问this页面，了解如何从ArrayList<>获取随机项。如果需要，请看你如何去寻求更多帮助。