在其它站点看到的，Mark一下

1、近期打开的应用不在近期任务列表中显示

android:excludeFromRecents="true"

设置为true,则排除在近期任务列表之外，不在近期任务列表中显示

2、推断一个一个String str 是否为NULL或者是否为空字符串

TextUtils.isEmpty(str)

3、android:imeOptions="actionSearch|flagNoFullscreen"的使用方法

在做一个把EditText放到到ActionBar中作为搜索框的功能时，设置EditText的属性为android:imeOptions="actionSearch"，会遇到一个问题。当在横屏时。EditText的宽度会填充掉屏幕上除了软键盘之外的地方，与需求不符，改为android:imeOptions="actionSearch|flagNoFullscreen"后就OK了。

4、改变图片亮度的方法

1、使用image.setColorFilter(Color.GRAY,PorterDuff.Mode.MULTIPLY);能够使图片变暗。然后使用image.clearColorFilter();清除滤镜，恢复到原来的亮度。
2、使用
int brightness = -80;
ColorMatrix matrix = new ColorMatrix(); 
matrix.set(new float[] { 1, 0, 0, 0, brightness, 0, 1, 0, 0, 
brightness, 0, 0, 1, 0, brightness, 0, 0, 0, 1, 0 }); 
v.setColorFilter(new ColorMatrixColorFilter(matrix));
但这样的方法会使颜色不太正常。图片留有黑边。

5、用Handler来实现有时间间隔事件的推断

看到Android中GestureDetector.java是用以下代码实现手势的单击和双击推断的：

public boolean onTouchEvent(MotionEvent ev) {……case MotionEvent.ACTION_DOWN:if (mDoubleTapListener != null) {boolean hadTapMessage = mHandler.hasMessages(TAP);if (hadTapMessage) mHandler.removeMessages(TAP);if ((mCurrentDownEvent != null) && (mPreviousUpEvent != null) && hadTapMessage &&isConsideredDoubleTap(mCurrentDownEvent, mPreviousUpEvent, ev)) {// This is a second tapmIsDoubleTapping = true;// Give a callback with the first tap of the double-taphandled |= mDoubleTapListener.onDoubleTap(mCurrentDownEvent);// Give a callback with down event of the double-taphandled |= mDoubleTapListener.onDoubleTapEvent(ev);} else {// This is a first tapmHandler.sendEmptyMessageDelayed(TAP, DOUBLE_TAP_TIMEOUT);}}……
}private boolean isConsideredDoubleTap(MotionEvent firstDown, MotionEvent firstUp,MotionEvent secondDown) {if (!mAlwaysInBiggerTapRegion) {return false;}final long deltaTime = secondDown.getEventTime() - firstUp.getEventTime();if (deltaTime > DOUBLE_TAP_TIMEOUT || deltaTime < DOUBLE_TAP_MIN_TIME) {return false;}int deltaX = (int) firstDown.getX() - (int) secondDown.getX();int deltaY = (int) firstDown.getY() - (int) secondDown.getY();return (deltaX * deltaX + deltaY * deltaY < mDoubleTapSlopSquare);}private class GestureHandler extends Handler {GestureHandler() {super();}GestureHandler(Handler handler) {super(handler.getLooper());}@Overridepublic void handleMessage(Message msg) {switch (msg.what) {case SHOW_PRESS:mListener.onShowPress(mCurrentDownEvent);break;case LONG_PRESS:dispatchLongPress();break;case TAP:// If the user's finger is still down, do not count it as a tapif (mDoubleTapListener != null) {if (!mStillDown) {mDoubleTapListener.onSingleTapConfirmed(mCurrentDownEvent);} else {mDeferConfirmSingleTap = true;}}break;default:throw new RuntimeException("Unknown message " + msg); //never}}

详细能够參考源代码，这里是妙用了mHandler.sendEmptyMessageDelayed。假设在DOUBLE_TAP_TIMEOUT时间内mHandler把TAP消息发送出去了。就是单击时间，假设在这个时间内没有发送出去，就是双击事件。