GestureDetector.OnGestureListener 详解
感谢android中国开发者的众多先驱,本文主要内容来自于总结,一小部分是自己的体会。主要参考文章为:
http://www.williamhua.com/2009/04/23/android-touchscreen-gesture-recogniton/
http://goro.iteye.com/blog/402163
Android Touch Screen 与传统Click Touch Screen不同,会有一些手势(Gesture),例如Fling,Scroll等等。这些Gesture会使用户体验大大提升。Android中的Gesture识别(detector)是通过GestureDetector.OnGestureListener接口实现的。
首先,Android事件处理机制是基于Listener实现的,比如触摸屏相关的事件,就是通过onTouchListener实现;
其次,所有View的子类都可以通过setOnTouchListener()、setOnKeyListener()等方法来添加对某一类事件的Listener;
第三,Listener一般会以Interface的方式来提供,其中包含一个或多个abstract方法,我们需要实现这些方法来完成onTouch()、onKey()等操作。这样,程序便可以在特定的事件被dispatch到该view的时候,通过callback函数给予适当的响应。
1. Touch Screen Click举例
Java代码- publicclassMyGestureextendsActivityimplementsOnTouchListener{
- publicvoidonCreate(BundlesavedInstanceState){
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- TextViewtv=(TextView)findViewById(R.id.tv);
- tv.setOnTouchListener(this);
- }
- publicbooleanonTouch(Viewv,MotionEventevent){
- Toast.makeText(this,"TouchTouch",Toast.LENGTH_SHORT).show();
- returnfalse;
- }
- }
public class MyGesture extends Activity implements OnTouchListener { public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); TextView tv = (TextView) findViewById(R.id.tv); tv.setOnTouchListener(this); }public boolean onTouch(View v, MotionEvent event) {Toast.makeText(this, "Touch Touch", Toast.LENGTH_SHORT).show();return false;}}
我们可以通过MotionEvent的getAction()方法来获取Touch事件的类型,包括 ACTION_DOWN(按下触摸屏), ACTION_MOVE(按下触摸屏后移动受力点), ACTION_UP(松开触摸屏)和ACTION_CANCEL(不会由用户直接触发)。借助对于用户不同操作的判断,结合getRawX()、getRawY()、getX()和getY()等方法来获取坐标后,我们可以实现诸如拖动某一个按钮,拖动滚动条等功能。
2. 回到今天的重点,当我们捕捉到Touch操作的时候,如何识别出用户的Gesture?这里我们需要GestureDetector.OnGestureListener接口的帮助,代码如下:
Java代码- publicclassMyGestureextendsActivityimplementsOnTouchListener,OnGestureListener{
- privateGestureDetectormGestureDetector;
- publicMyGesture(){
- mGestureDetector=newGestureDetector(this);
- }
- publicvoidonCreate(BundlesavedInstanceState){
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- TextViewtv=(TextView)findViewById(R.id.tv);
- tv.setOnTouchListener(this);
- tv.setFocusable(true);
- tv.setClickable(true);
- tv.setLongClickable(true);
- mGestureDetector.setIsLongpressEnabled(true);
- }
- /*
- *在onTouch()方法中,我们调用GestureDetector的onTouchEvent()方法,将捕捉到的MotionEvent交给GestureDetector
- *来分析是否有合适的callback函数来处理用户的手势
- */
- publicbooleanonTouch(Viewv,MotionEventevent){
- returnmGestureDetector.onTouchEvent(event);
- }
- //用户轻触触摸屏,由1个MotionEventACTION_DOWN触发
- publicbooleanonDown(MotionEventarg0){
- Log.i("MyGesture","onDown");
- Toast.makeText(this,"onDown",Toast.LENGTH_SHORT).show();
- returntrue;
- }
- /*
- *用户轻触触摸屏,尚未松开或拖动,由一个1个MotionEventACTION_DOWN触发
- *注意和onDown()的区别,强调的是没有松开或者拖动的状态
- */
- publicvoidonShowPress(MotionEvente){
- Log.i("MyGesture","onShowPress");
- Toast.makeText(this,"onShowPress",Toast.LENGTH_SHORT).show();
- }
- //用户(轻触触摸屏后)松开,由一个1个MotionEventACTION_UP触发
- publicbooleanonSingleTapUp(MotionEvente){
- Log.i("MyGesture","onSingleTapUp");
- Toast.makeText(this,"onSingleTapUp",Toast.LENGTH_SHORT).show();
- returntrue;
- }
- //用户按下触摸屏、快速移动后松开,由1个MotionEventACTION_DOWN,多个ACTION_MOVE,1个ACTION_UP触发
- publicbooleanonFling(MotionEvente1,MotionEvente2,floatvelocityX,floatvelocityY){
- Log.i("MyGesture","onFling");
- Toast.makeText(this,"onFling",Toast.LENGTH_LONG).show();
- returntrue;
- }
- //用户按下触摸屏,并拖动,由1个MotionEventACTION_DOWN,多个ACTION_MOVE触发
- publicbooleanonScroll(MotionEvente1,MotionEvente2,floatdistanceX,floatdistanceY){
- Log.i("MyGesture","onScroll");
- Toast.makeText(this,"onScroll",Toast.LENGTH_LONG).show();
- returntrue;
- }
- //用户长按触摸屏,由多个MotionEventACTION_DOWN触发
- publicvoidonLongPress(MotionEvente){
- Log.i("MyGesture","onLongPress");
- Toast.makeText(this,"onLongPress",Toast.LENGTH_LONG).show();
- }
- }
public class MyGesture extends Activity implements OnTouchListener, OnGestureListener { private GestureDetector mGestureDetector; public MyGesture() { mGestureDetector = new GestureDetector(this); } public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); TextView tv = (TextView) findViewById(R.id.tv); tv.setOnTouchListener(this); tv.setFocusable(true); tv.setClickable(true); tv.setLongClickable(true); mGestureDetector.setIsLongpressEnabled(true); } /* * 在onTouch()方法中,我们调用GestureDetector的onTouchEvent()方法,将捕捉到的MotionEvent交给GestureDetector * 来分析是否有合适的callback函数来处理用户的手势 */ public boolean onTouch(View v, MotionEvent event) {return mGestureDetector.onTouchEvent(event);}// 用户轻触触摸屏,由1个MotionEvent ACTION_DOWN触发public boolean onDown(MotionEvent arg0) {Log.i("MyGesture", "onDown");Toast.makeText(this, "onDown", Toast.LENGTH_SHORT).show();return true;}/* * 用户轻触触摸屏,尚未松开或拖动,由一个1个MotionEvent ACTION_DOWN触发 * 注意和onDown()的区别,强调的是没有松开或者拖动的状态 */public void onShowPress(MotionEvent e) {Log.i("MyGesture", "onShowPress");Toast.makeText(this, "onShowPress", Toast.LENGTH_SHORT).show();}// 用户(轻触触摸屏后)松开,由一个1个MotionEvent ACTION_UP触发public boolean onSingleTapUp(MotionEvent e) {Log.i("MyGesture", "onSingleTapUp");Toast.makeText(this, "onSingleTapUp", Toast.LENGTH_SHORT).show();return true;}// 用户按下触摸屏、快速移动后松开,由1个MotionEvent ACTION_DOWN, 多个ACTION_MOVE, 1个ACTION_UP触发public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {Log.i("MyGesture", "onFling");Toast.makeText(this, "onFling", Toast.LENGTH_LONG).show();return true;}// 用户按下触摸屏,并拖动,由1个MotionEvent ACTION_DOWN, 多个ACTION_MOVE触发public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {Log.i("MyGesture", "onScroll");Toast.makeText(this, "onScroll", Toast.LENGTH_LONG).show();return true;}// 用户长按触摸屏,由多个MotionEvent ACTION_DOWN触发public void onLongPress(MotionEvent e) {Log.i("MyGesture", "onLongPress");Toast.makeText(this, "onLongPress", Toast.LENGTH_LONG).show();}}
3. Fling事件的处理代码:除了第一个触发Fling的ACTION_DOWN和最后一个ACTION_MOVE中包含的坐标等信息外,我们还可以根据用户在X轴或者Y轴上的移动速度作为条件。比如下面的代码中我们就在用户移动超过100个像素,且X轴上每秒的移动速度大于200像素时才进行处理。
Java代码- publicbooleanonFling(MotionEvente1,MotionEvente2,floatvelocityX,floatvelocityY){
- //参数解释:
- //e1:第1个ACTION_DOWNMotionEvent
- //e2:最后一个ACTION_MOVEMotionEvent
- //velocityX:X轴上的移动速度,像素/秒
- //velocityY:Y轴上的移动速度,像素/秒
- //触发条件:
- //X轴的坐标位移大于FLING_MIN_DISTANCE,且移动速度大于FLING_MIN_VELOCITY个像素/秒
- finalintFLING_MIN_DISTANCE=100,FLING_MIN_VELOCITY=200;
- if(e1.getX()-e2.getX()>FLING_MIN_DISTANCE&&Math.abs(velocityX)>FLING_MIN_VELOCITY){
- //Flingleft
- Log.i("MyGesture","Flingleft");
- Toast.makeText(this,"FlingLeft",Toast.LENGTH_SHORT).show();
- }elseif(e2.getX()-e1.getX()>FLING_MIN_DISTANCE&&Math.abs(velocityX)>FLING_MIN_VELOCITY){
- //Flingright
- Log.i("MyGesture","Flingright");
- Toast.makeText(this,"FlingRight",Toast.LENGTH_SHORT).show();
- }
- returnfalse;
- }
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {// 参数解释:// e1:第1个ACTION_DOWN MotionEvent// e2:最后一个ACTION_MOVE MotionEvent// velocityX:X轴上的移动速度,像素/秒// velocityY:Y轴上的移动速度,像素/秒// 触发条件 :// X轴的坐标位移大于FLING_MIN_DISTANCE,且移动速度大于FLING_MIN_VELOCITY个像素/秒final int FLING_MIN_DISTANCE = 100, FLING_MIN_VELOCITY = 200;if (e1.getX() - e2.getX() > FLING_MIN_DISTANCE && Math.abs(velocityX) > FLING_MIN_VELOCITY) {// Fling leftLog.i("MyGesture", "Fling left");Toast.makeText(this, "Fling Left", Toast.LENGTH_SHORT).show();} else if (e2.getX() - e1.getX() > FLING_MIN_DISTANCE && Math.abs(velocityX) > FLING_MIN_VELOCITY) {// Fling rightLog.i("MyGesture", "Fling right");Toast.makeText(this, "Fling Right", Toast.LENGTH_SHORT).show();}return false;}
这个例子中,tv.setLongClickable(
true
)是必须的,因为
只有这样,view才能够处理不同于Tap(轻触)的hold(即ACTION_MOVE,或者多个ACTION_DOWN),我们同样可以通过layout定义中的android:longClickable来做到这一点。
4. SimpleOnGestureListener
Java代码- publicclassMyGestureextendsActivityimplementsOnTouchListener{
- privateGestureDetectormGestureDetector;
- publicMyGesture(){
- mGestureDetector=newGestureDetector(newMySimpleGesture());
- }
- publicvoidonCreate(BundlesavedInstanceState){
- super.onCreate(savedInstanceState);
- setContentView(R.layout.main);
- TextViewtv=(TextView)findViewById(R.id.tv);
- tv.setOnTouchListener(this);
- tv.setFocusable(true);
- tv.setClickable(true);
- tv.setLongClickable(true);
- }
- publicbooleanonTouch(Viewv,MotionEventevent){
- if(event.getAction()==MotionEvent.ACTION_UP){
- Log.i("MyGesture","MotionEvent.ACTION_UP");
- }
- returnmGestureDetector.onTouchEvent(event);
- }
- //SimpleOnGestureListenerimplementsGestureDetector.OnDoubleTapListener,GestureDetector.OnGestureListener
- privateclassMySimpleGestureextendsSimpleOnGestureListener{
- //双击的第二下Touchdown时触发
- publicbooleanonDoubleTap(MotionEvente){
- Log.i("MyGesture","onDoubleTap");
- returnsuper.onDoubleTap(e);
- }
- //双击的第二下Touchdown和up都会触发,可用e.getAction()区分
- publicbooleanonDoubleTapEvent(MotionEvente){
- Log.i("MyGesture","onDoubleTapEvent");
- returnsuper.onDoubleTapEvent(e);
- }
- //Touchdown时触发
- publicbooleanonDown(MotionEvente){
- Log.i("MyGesture","onDown");
- returnsuper.onDown(e);
- }
- //Touch了滑动一点距离后,up时触发
- publicbooleanonFling(MotionEvente1,MotionEvente2,floatvelocityX,floatvelocityY){
- Log.i("MyGesture","onFling");
- returnsuper.onFling(e1,e2,velocityX,velocityY);
- }
- //Touch了不移动一直Touchdown时触发
- publicvoidonLongPress(MotionEvente){
- Log.i("MyGesture","onLongPress");
- super.onLongPress(e);
- }
- //Touch了滑动时触发
- publicbooleanonScroll(MotionEvente1,MotionEvente2,floatdistanceX,floatdistanceY){
- Log.i("MyGesture","onScroll");
- returnsuper.onScroll(e1,e2,distanceX,distanceY);
- }
- /*
- *Touch了还没有滑动时触发
- *(1)onDown只要TouchDown一定立刻触发
- *(2)TouchDown后过一会没有滑动先触发onShowPress再触发onLongPress
- *So:TouchDown后一直不滑动,onDown->onShowPress->onLongPress这个顺序触发。
- */
- publicvoidonShowPress(MotionEvente){
- Log.i("MyGesture","onShowPress");
- super.onShowPress(e);
- }
- /*
- *两个函数都是在TouchDown后又没有滑动(onScroll),又没有长按(onLongPress),然后TouchUp时触发
- *点击一下非常快的(不滑动)TouchUp:onDown->onSingleTapUp->onSingleTapConfirmed
- *点击一下稍微慢点的(不滑动)TouchUp:onDown->onShowPress->onSingleTapUp->onSingleTapConfirmed
- */
- publicbooleanonSingleTapConfirmed(MotionEvente){
- Log.i("MyGesture","onSingleTapConfirmed");
- returnsuper.onSingleTapConfirmed(e);
- }
- publicbooleanonSingleTapUp(MotionEvente){
- Log.i("MyGesture","onSingleTapUp");
- returnsuper.onSingleTapUp(e);
- }
- }
- }
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