Android提高第十九篇之"多方向"抽屉

在android上要实现类似Launch的抽屉效果，大家一定首先会想起SlidingDrawer。SlidingDrawer是android官方控件之一，本文的主角不是它，而是民间的控件工具集合~~~android-misc-widgets。android-misc-widgets里面包含几个widget：Panel、SmoothButton、Switcher、VirtualKeyboard,还有一些动画特效，本文主要介绍抽屉容器Panel的用法。android-misc-widgets的google工程地址：-widgets/http://code.google.com/p/android-misc，工程代码中Panel的演示效果如下：

       这个Panel控件可以轻易实现不同方向的抽屉效果，比SlidingDrawer有更强的扩展性！

       在多次使用Panel的过程中，发现Panel有个bug，会间断性出现“闪烁”，也就是在onTouchListener里面的触发ACTION_DOWN后，抽屉瞬间弹出然后瞬间回收(版本日期为Feb 3, 2009)。把原Panel的OnTouchListener，即以下代码：

OnTouchListener touchListener = new OnTouchListener() {
    int initX;
    int initY;
    boolean setInitialPosition;
    public boolean onTouch(View v, MotionEvent event) {
        if (mState == State.ANIMATING) {
            // we are animating
            return false;
        }
/           Log.d(TAG, "state: " + mState + " x: " + event.getX() + " y: " + event.getY());
        int action = event.getAction();
        if (action == MotionEvent.ACTION_DOWN) {
            if (mBringToFront) {
                bringToFront();
            }
            initX = 0;
            initY = 0;
            if (mContent.getVisibility() == GONE) {
                // since we may not know content dimensions we use factors here
                if (mOrientation == VERTICAL) {
                    initY = mPosition == TOP? -1 : 1;
                } else {
                    initX = mPosition == LEFT? -1 : 1;
                }
            }
            setInitialPosition = true;
        } else {
            if (setInitialPosition) {
                // now we know content dimensions, so we multiply factors...
                initX *= mContentWidth;
                initY *= mContentHeight;
                // ... and set initial panel's position
                mGestureListener.setScroll(initX, initY);
                setInitialPosition = false;
                // for offsetLocation we have to invert values
                initX = -initX;
                initY = -initY;
            }
            // offset every ACTION_MOVE & ACTION_UP event
            event.offsetLocation(initX, initY);
        }
        if (!mGestureDetector.onTouchEvent(event)) {
            if (action == MotionEvent.ACTION_UP) {
                // tup up after scrolling
                post(startAnimation);
            }
        }
        return false;
    }
};

替换为：

OnTouchListener touchListener = new OnTouchListener() {
    float touchX, touchY;

    public boolean onTouch(View v, MotionEvent event) {
        if (mState == State.ANIMATING) {
            // we are animating
            return false;
        }

        int action = event.getAction();
        if (action == MotionEvent.ACTION_DOWN) {
            if (mBringToFront) {
                bringToFront();
            }
            touchX = event.getX();
            touchY = event.getY();
        }

        if (!mGestureDetector.onTouchEvent(event)) {
            if (action == MotionEvent.ACTION_UP) {
                // tup up after scrolling
                int size = (int) (Math.abs(touchX - event.getX()) + Math
                        .abs(touchY - event.getY()));

                if (size == mContentWidth || size == mContentHeight) {
                    mState = State.ABOUT_TO_ANIMATE;
                    //Log.e("size", String.valueOf(size));
                    //Log.e(String.valueOf(mContentWidth),String.valueOf(mContentHeight));
                }

                post(startAnimation);
            }
        }
        return false;
    }
};