Android提高21篇之十九：“多方向”抽屜

       在android上要實現類似Launch的抽屜效果，大家一定首先會想起SlidingDrawer。SlidingDrawer是android官方控件之一，本文的主角不是它，而是民間的控件工具集合~~~android-misc-widgets。android-misc-widgets裡面包含幾個widget：Panel、SmoothButton、Switcher、VirtualKeyboard,還有一些動畫特效，本文主要介紹抽屜容器Panel的用法。android-misc-widgets的google工程地址：-widgets/http://code.google.com/p/android-misc，工程代碼中Panel的演示效果如下：

　　這個Panel控件可以輕易實現不同方向的抽屜效果，比SlidingDrawer有更強的擴展性！

　　在多次使用Panel的過程中，發現Panel有個bug，會間斷性出現“閃爍”，也就是在onTouchListener裡面的觸發ACTION_DOWN後，抽屜瞬間彈出然後瞬間回收(版本日期為Feb 3, 2009)。把原Panel的OnTouchListener，即以下代碼：

1. OnTouchListener touchListener = new OnTouchListener() {  
2.                int initX;  
3.                int initY;  
4.                boolean setInitialPosition;  
5.                public boolean onTouch(View v, MotionEvent event) {  
6.                        if (mState == State.ANIMATING) {  
7.                                // we are animating  
8.                                return false;  
9.                        }  
10. /                        Log.d(TAG, "state: " + mState + " x: " + event.getX() + " y: " + event.getY());  
11.                        int action = event.getAction();  
12.                        if (action == MotionEvent.ACTION_DOWN) {  
13.                                if (mBringToFront) {  
14.                                        bringToFront();  
15.                                }  
16.                                initX = 0;  
17.                                initY = 0;  
18.                                if (mContent.getVisibility() == GONE) {  
19.                                        // since we may not know content dimensions we use factors here  
20.                                        if (mOrientation == VERTICAL) {  
21.                                                initY = mPosition == TOP? -1 : 1;  
22.                                        } else {  
23.                                                initX = mPosition == LEFT? -1 : 1;  
24.                                        }  
25.                                }  
26.                                setInitialPosition = true;  
27.                        } else {  
28.                                if (setInitialPosition) {  
29.                                        // now we know content dimensions, so we multiply factors...  
30.                                        initX *= mContentWidth;  
31.                                        initY *= mContentHeight;  
32.                                        // ... and set initial panel's position  
33.                                        mGestureListener.setScroll(initX, initY);  
34.                                        setInitialPosition = false;  
35.                                        // for offsetLocation we have to invert values  
36.                                        initX = -initX;  
37.                                        initY = -initY;  
38.                                }  
39.                                // offset every ACTION_MOVE & ACTION_UP event   
40.                                event.offsetLocation(initX, initY);  
41.                        }  
42.                        if (!mGestureDetector.onTouchEvent(event)) {  
43.                                if (action == MotionEvent.ACTION_UP) {  
44.                                        // tup up after scrolling  
45.                                        post(startAnimation);  
46.                                }  
47.                        }  
48.                        return false;  
49.                }  
50.        };  

　　替換為：

1. OnTouchListener touchListener = new OnTouchListener() {  
2.                float touchX, touchY;  
3.   
4.                public boolean onTouch(View v, MotionEvent event) {  
5.                        if (mState == State.ANIMATING) {  
6.                                // we are animating  
7.                                return false;  
8.                        }  
9.   
10.                        int action = event.getAction();  
11.                        if (action == MotionEvent.ACTION_DOWN) {  
12.                                if (mBringToFront) {  
13.                                        bringToFront();  
14.                                }  
15.                                touchX = event.getX();  
16.                                touchY = event.getY();  
17.                        }  
18.   
19.                        if (!mGestureDetector.onTouchEvent(event)) {  
20.                                if (action == MotionEvent.ACTION_UP) {  
21.                                        // tup up after scrolling  
22.                                        int size = (int) (Math.abs(touchX - event.getX()) + Math  
23.                                                        .abs(touchY - event.getY()));  
24.   
25.                                        if (size == mContentWidth || size == mContentHeight) {  
26.                                                mState = State.ABOUT_TO_ANIMATE;  
27.                                                //Log.e("size", String.valueOf(size));  
28.                                                //Log.e(String.valueOf(mContentWidth),String.valueOf(mContentHeight));  
29.                                        }  
30.   
31.                                        post(startAnimation);  
32.                                }  
33.                        }  
34.                        return false;  
35.                }  
36.        };  

　　即可修復這個bug，並且也同樣實現了OnClickListener的功能，可以把原Panel的OnClickListener給刪掉了！