ListView特效2(列表拖拽)

即listView特效1,http://blog.csdn.net/pipisky2006/article/details/7393475，好久之后

列表的拖拽效果（参考Android源码下packages/apps/Music中的播放列表TouchInterceptor.java源码）

重写ListView中onInterceptTouchEvent(),onTouchEvent()方法来响应触控事件做相应的界面调整(选中，生成影像，拖动影像，数据更改后刷新界面)等等。

拖拽的动作实际上是WindowManager在最上层添加的ImageView随着手指移动被拖动。listView作为背景，数据随之变化。

下面是源码的分析

public class TouchInterceptor extends ListView {//继承自ListView    public TouchInterceptor(Context context, AttributeSet attrs) {        super(context, attrs);        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();//检测滑动状态的阀值        Resources res = getResources();        mItemHeightNormal = res.getDimensionPixelSize(R.dimen.normal_height);        mItemHeightHalf = mItemHeightNormal / 2;        mItemHeightExpanded = res.getDimensionPixelSize(R.dimen.expanded_height);    }}

下面是用到的变量：

  private ImageView mDragView;//被拖拽的ImageView  private WindowManager mWindowManager;  private WindowManager.LayoutParams mWindowParams;  private int mDragPos;   // which item is being dragged 被拖拽的View所在的当前的position  private int mFirstDragPos; // where was the dragged item originally 被拖拽的View的最初的position  private int mDragPoint;  // at what offset inside the item did the user grab it 在当前数据项中的位置  private int mCoordOffset; // the difference between screen coordinates and coordinates in this view 屏幕坐标和View坐标的差值，也就是getRawY和getY的差值  private int mUpperBound; //拖动的时候，开始向上滚动的边界  private int mLowerBound; //拖动的时候，开始向下滚动的边界  private int mHeight;  private Rect mTempRect = new Rect();  private Bitmap mDragBitmap;   private final int mTouchSlop; //判断滑动的一个距离值  private int mItemHeightNormal;  private int mItemHeightExpanded;  private int mItemHeightHalf;

捕捉down事件，在down事件中，判断是否需要拖动，如果是，我们做一些拖动的准备工作，准备影像。

    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {            switch (ev.getAction()) {                case MotionEvent.ACTION_DOWN://down事件                    int x = (int) ev.getX();                    int y = (int) ev.getY();                    int itemnum = pointToPosition(x, y);//选中的数据项位置，使用ListView自带的pointToPosition(x, y)方法                    if (itemnum == AdapterView.INVALID_POSITION) {                        break;                    }                    ViewGroup item = (ViewGroup) getChildAt(itemnum - getFirstVisiblePosition());//获取选中的View项                    mDragPoint = y - item.getTop();//点击位置在点击View内的相对位置                    mCoordOffset = ((int)ev.getRawY()) - y;                    View dragger = item.findViewById(R.id.icon);//选中项中的拖动识别View                    Rect r = mTempRect;                    dragger.getDrawingRect(r);                    // The dragger icon itself is quite small, so pretend the touch area is bigger                    if (x < r.right * 2) {                        item.setDrawingCacheEnabled(true);                        // Create a copy of the drawing cache so that it does not get recycled                        // by the framework when the list tries to clean up memory                        Bitmap bitmap = Bitmap.createBitmap(item.getDrawingCache());//获取拖动影像                        startDragging(bitmap, y);//准备拖动工作                        mDragPos = itemnum;                        mFirstDragPos = mDragPos;                        mHeight = getHeight();                        int touchSlop = mTouchSlop;                        mUpperBound = Math.min(y - touchSlop, mHeight / 3);//当在屏幕的上部(上面1/3区域)或者更上的区域，执行拖动的边界，下同理定义                        mLowerBound = Math.max(y + touchSlop, mHeight * 2 /3);                        return false;                    }                    stopDragging();                    break;            }        return super.onInterceptTouchEvent(ev);    }

//根据操作处理滑动和放置操作。

    @Override    public boolean onTouchEvent(MotionEvent ev) {        if (mDragView != null) {            int action = ev.getAction();             switch (action) {                case MotionEvent.ACTION_UP:                case MotionEvent.ACTION_CANCEL:                    Rect r = mTempRect;                    mDragView.getDrawingRect(r);                    stopDragging();//释放拖动影像                    if (mDropListener != null && mDragPos >= 0 && mDragPos < getCount()) {                        mDropListener.drop(mFirstDragPos, mDragPos);//放置工作的回调                    }                    unExpandViews(false);//放置后List内容的修正                    break;                                    case MotionEvent.ACTION_DOWN:                case MotionEvent.ACTION_MOVE:                    int x = (int) ev.getX();                    int y = (int) ev.getY();                    mWindowParams.y = y - mDragPoint + mCoordOffset;//更新坐标位置        mWindowManager.updateViewLayout(mDragView, mWindowParams);//更新拖拽view的界面                    int itemnum = getItemForPosition(y);//获取准确的position，考虑不可见view等情况，具体见其私有方法                    if (itemnum >= 0) {                        if (action == MotionEvent.ACTION_DOWN || itemnum != mDragPos) {                            if (mDragListener != null) {                                mDragListener.drag(mDragPos, itemnum);//拖动工作的回调                            }                            mDragPos = itemnum;                            doExpansion();//                        }                        int speed = 0;                        adjustScrollBounds(y);//调整滚动的阀值                        if (y > mLowerBound) {//拖动位置偏下，内容向上滚动                            // scroll the list up a bit                            speed = y > (mHeight + mLowerBound) / 2 ? 16 : 4;                        } else if (y < mUpperBound) {//拖动位置偏上，内容向下滚动                            // scroll the list down a bit                            speed = y < mUpperBound / 2 ? -16 : -4;                        }                        if (speed != 0) {                            int ref = pointToPosition(0, mHeight / 2);                            if (ref == AdapterView.INVALID_POSITION) {                                //we hit a divider or an invisible view, check somewhere else                                ref = pointToPosition(0, mHeight / 2 + getDividerHeight() + 64);                            }                            View v = getChildAt(ref - getFirstVisiblePosition());                            if (v!= null) {                                int pos = v.getTop();                                setSelectionFromTop(ref, pos - speed);//列表滚动                            }                        }                    }                    break;            }            return true;        }        return super.onTouchEvent(ev);    }

下面是具体的准备拖动影像和释放拖动影像的方法

    private void startDragging(Bitmap bm, int y) {        stopDragging();        mWindowParams = new WindowManager.LayoutParams();        mWindowParams.gravity = Gravity.TOP;        mWindowParams.x = 0;        mWindowParams.y = y - mDragPoint + mCoordOffset;//计算拖动的起始位置        mWindowParams.height = WindowManager.LayoutParams.WRAP_CONTENT;        mWindowParams.width = WindowManager.LayoutParams.WRAP_CONTENT;        mWindowParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE                | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE                | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON                | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN                | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS;        mWindowParams.format = PixelFormat.TRANSLUCENT;        mWindowParams.windowAnimations = 0;                Context context = getContext();        ImageView v = new ImageView(context);        int backGroundColor = context.getResources().getColor(R.color.dragndrop_background);        v.setBackgroundColor(backGroundColor);        v.setImageBitmap(bm);        mDragBitmap = bm;        mWindowManager = (WindowManager)context.getSystemService("window");        mWindowManager.addView(v, mWindowParams);//添加到窗口上        mDragView = v;    }    //释放    private void stopDragging() {        if (mDragView != null) {            WindowManager wm = (WindowManager)getContext().getSystemService("window");            wm.removeView(mDragView);            mDragView.setImageDrawable(null);//释放Imageview            mDragView = null;        }        if (mDragBitmap != null) {//释放bitmap            mDragBitmap.recycle();            mDragBitmap = null;        }    }

接下来响应操作是拖拽影像，影像动了后背后的列表内容也要配合变化，主要就是添加了个空内容格

 /** Adjust visibility and size to make it appear as though     * an item is being dragged around and other items are making     * room for it: 调整可见性和大小来表现的像一个内容项被拖动，其他在给他让位置。     * If dropping the item would result in it still being in the     * same place, then make the dragged listitem's size normal,     * but make the item invisible.     * Otherwise, if the dragged listitem is still on screen, make     * it as small as possible and expand the item below the insert     * point.     * If the dragged item is not on screen, only expand the item     * below the current insertpoint.     */    private void doExpansion() {        int childnum = mDragPos - getFirstVisiblePosition();        if (mDragPos > mFirstDragPos) {            childnum++;        }        View first = getChildAt(mFirstDragPos - getFirstVisiblePosition());        for (int i = 0;; i++) {            View vv = getChildAt(i);            if (vv == null) {                break;            }            int height = mItemHeightNormal;            int visibility = View.VISIBLE;            if (vv.equals(first)) {                // processing the item that is being dragged                if (mDragPos == mFirstDragPos) {                    // hovering over the original location                    visibility = View.INVISIBLE;                } else {                    // not hovering over it                    height = 1;                }            } else if (i == childnum) {                if (mDragPos < getCount() - 1) {                    height = mItemHeightExpanded;                }            }            ViewGroup.LayoutParams params = vv.getLayoutParams();            params.height = height;            vv.setLayoutParams(params);            vv.setVisibility(visibility);        }    }

放置后的操作

/**     * Restore size and visibility for all listitems     */    private void unExpandViews(boolean deletion) {        for (int i = 0;; i++) {            View v = getChildAt(i);            if (v == null) {                if (deletion) {                    // HACK force update of mItemCount                    int position = getFirstVisiblePosition();                    int y = getChildAt(0).getTop();                    setAdapter(getAdapter());                    setSelectionFromTop(position, y);                    // end hack                }                layoutChildren(); // force children to be recreated where needed                v = getChildAt(i);                if (v == null) {                    break;                }            }            ViewGroup.LayoutParams params = v.getLayoutParams();            params.height = mItemHeightNormal;            v.setLayoutParams(params);            v.setVisibility(View.VISIBLE);        }    }

剩下的几个私有方法

    /**     * pointToPosition() doesn't consider invisible views, but we     * need to, so implement a slightly different version.     */    private int myPointToPosition(int x, int y) {        if (y < 0) {            // when dragging off the top of the screen, calculate position            // by going back from a visible item            int pos = myPointToPosition(x, y + mItemHeightNormal);            if (pos > 0) {                return pos - 1;            }        }        Rect frame = mTempRect;        final int count = getChildCount();        for (int i = count - 1; i >= 0; i--) {            final View child = getChildAt(i);            child.getHitRect(frame);            if (frame.contains(x, y)) {                return getFirstVisiblePosition() + i;            }        }        return INVALID_POSITION;    }        private int getItemForPosition(int y) {        int adjustedy = y - mDragPoint - mItemHeightHalf;        int pos = myPointToPosition(0, adjustedy);        if (pos >= 0) {            if (pos <= mFirstDragPos) {                pos += 1;            }        } else if (adjustedy < 0) {            // this shouldn't happen anymore now that myPointToPosition deals            // with this situation            pos = 0;        }        return pos;    }        private void adjustScrollBounds(int y) {        if (y >= mHeight / 3) {            mUpperBound = mHeight / 3;        }        if (y <= mHeight * 2 / 3) {            mLowerBound = mHeight * 2 / 3;        }    }

参考： http://www.cnblogs.com/qianxudetianxia/archive/2011/06/12/2068761.html

http://www.cnblogs.com/qianxudetianxia/archive/2011/06/13/2079253.html

http://www.oschina.net/code/explore/android-2.2-froyo/com/android/music/TouchInterceptor.java

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