android实现swipe的手势及页面拖动动画

Android SDK提供了一个listener类来侦测各种不同的手势:
SimpleOnGestureListener. 你只需要实现自己所关心的手势就可以了.
Swipe在android里面是叫Fling

首先创建自己的一个手势detector类:
Java代码

1. class MyGestureDetector extends SimpleOnGestureListener {
2. @Override
3. public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
4. }

class MyGestureDetector extends SimpleOnGestureListener { @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { }

一个划动的手势有几个特征, 比如是在x或者y轴上近乎直线的划动, 中途路径的偏差不能太大, 而且划动需要一定的速度, 所以我们定义几个定量:
Java代码

1. private static final int SWIPE_MIN_DISTANCE = 120;
2. private static final int SWIPE_MAX_OFF_PATH = 250;
3. private static final int SWIPE_THRESHOLD_VELOCITY = 200;

private static final int SWIPE_MIN_DISTANCE = 120; private static final int SWIPE_MAX_OFF_PATH = 250; private static final int SWIPE_THRESHOLD_VELOCITY = 200;

然后在onFling方法中, 判断是不是一个合理的swipe动作:
Java代码

1. if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
2. viewFlipper.setInAnimation(slideLeftIn);
3. viewFlipper.setOutAnimation(slideLeftOut);
4. viewFlipper.showNext();
5. } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
6. viewFlipper.setInAnimation(slideRightIn);
7. viewFlipper.setOutAnimation(slideRightOut);
8. viewFlipper.showPrevious();
9. }

if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { viewFlipper.setInAnimation(slideLeftIn); viewFlipper.setOutAnimation(slideLeftOut); viewFlipper.showNext(); } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { viewFlipper.setInAnimation(slideRightIn); viewFlipper.setOutAnimation(slideRightOut); viewFlipper.showPrevious(); }

这里的viewFlipper是含有多个view的一个container, 可以很方便的调用prev/next view, 加上animation动画, 可以达到一些不错的效果:
Java代码

1. viewFlipper = (ViewFlipper)findViewById(R.id.flipper);
2. slideLeftIn = AnimationUtils.loadAnimation(this, R.anim.slide_left_in);
3. slideLeftOut = AnimationUtils.loadAnimation(this, R.anim.slide_left_out);
4. slideRightIn = AnimationUtils.loadAnimation(this, R.anim.slide_right_in);
5. slideRightOut = AnimationUtils.loadAnimation(this, R.anim.slide_right_out);

viewFlipper = (ViewFlipper)findViewById(R.id.flipper); slideLeftIn = AnimationUtils.loadAnimation(this, R.anim.slide_left_in); slideLeftOut = AnimationUtils.loadAnimation(this, R.anim.slide_left_out); slideRightIn = AnimationUtils.loadAnimation(this, R.anim.slide_right_in); slideRightOut = AnimationUtils.loadAnimation(this, R.anim.slide_right_out);

自定义的animation可以查看具体的XML, 比如从左边进来的一个动画:
Xml代码

1. <set xmlns:android="http://schemas.android.com/apk/res/android">
2. <translate android:fromXDelta="100%p" android:toXDelta="0" android:duration="800"/>
3. </set>

<set xmlns:android="http://schemas.android.com/apk/res/android"> <translate android:fromXDelta="100%p" android:toXDelta="0" android:duration="800"/> </set>

当然最后不要忘记在你的Activity中override onTouch方法来获取手势action:
Java代码

1. @Override
2. public boolean onTouchEvent(MotionEvent event) {
3. if (gestureDetector.onTouchEvent(event))
4. return true;
5. else
6. return false;
7. }

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