我們知道在一般情況下,處理android的TouchEvent,我們只需要利用OnTouchListener,OnKeyListener接口,通過setOnTouchListener(),setOnKeyListener()來註冊監聽器,然後在OnTouch(), OnKey()方法中實現我們想要的操作,當系統dispatch特定的事件到該View時,該View就會自動調用callback方法。
例如:
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;
}
}
我們可以通過MotionEvent的getAction()方法來獲取Touch事件的類型,包括 ACTION_DOWN(按下觸摸屏), ACTION_MOVE(按下觸摸屏後移動受力點), ACTION_UP(鬆開觸摸屏)和ACTION_CANCEL(不會由用戶直接觸發)。藉助對於用戶不同操作的判斷,結合getRawX()、getRawY()、getX()和getY()等方法來獲取座標後,我們可以實現諸如拖動某一個按鈕,拖動滾動條等功能。
這種方法雖然比較簡單,但是對於各種各樣的用戶動作,顯得比較單一,幸好android爲我們提供了GestureDetector類以及GestureDetector.OnGestureListener接口,定義一個GestureDetector的實例,然後將OnTouch()方法捕捉到的MotionEvent交給他,他就會幫我們判斷用戶的Gesture,並自動調用GestureDetector.OnGestureListener裏面的方法,我們只需要在各個方法裏實現我們的功能就可以了。
示例如下:onDown(MotionEvent arg0),onShowPress(),onSingleTapUp() , ...都是OnGestureListener裏的方法
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,我們調用GestureDetector的onTouchEvent()方法,將捕捉到的MotionEvent交給GestureDetector
* 來分析是否有合適的callback函數來處理用戶的手勢
*/
public boolean onTouch(View v, MotionEvent event) {
return mGestureDetector.onTouchEvent(event);
}
// 用戶輕觸觸摸屏,由1個MotionEvent ACTION_DOWN觸發
public boolean onDown(MotionEvent arg0) {
Log.i("MyGesture", "onDown");
Toast.makeText(this, "onDown", Toast.LENGTH_SHORT).show();
return true;
}
/*
* 用戶輕觸觸摸屏,尚未鬆開或拖動,由一個1個MotionEvent ACTION_DOWN觸發
* 注意和onDown()的區別,強調的是沒有鬆開或者拖動的狀態
*/
public void onShowPress(MotionEvent e) {
Log.i("MyGesture", "onShowPress");
Toast.makeText(this, "onShowPress", Toast.LENGTH_SHORT).show();
}
// 用戶(輕觸觸摸屏後)鬆開,由一個1個MotionEvent ACTION_UP觸發
public boolean onSingleTapUp(MotionEvent e) {
Log.i("MyGesture", "onSingleTapUp");
Toast.makeText(this, "onSingleTapUp", Toast.LENGTH_SHORT).show();
return true;
}
// 用戶按下觸摸屏、快速移動後鬆開,由1個MotionEvent ACTION_DOWN, 多個ACTION_MOVE, 1個ACTION_UP觸發
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;
}
// 用戶按下觸摸屏,並拖動,由1個MotionEvent ACTION_DOWN, 多個ACTION_MOVE觸發
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;
}
// 用戶長按觸摸屏,由多個MotionEvent ACTION_DOWN觸發
public void onLongPress(MotionEvent e) {
Log.i("MyGesture", "onLongPress");
Toast.makeText(this, "onLongPress", Toast.LENGTH_LONG).show();
}
}
除了OnGestureListener接口,還有一個SimpleOnGestureListener接口
public class MyGesture extends Activity implements OnTouchListener {
private GestureDetector mGestureDetector;
public MyGesture() {
mGestureDetector = new GestureDetector(new MySimpleGesture());
}
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);
}
public boolean onTouch(View v, MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_UP) {
Log.i("MyGesture", "MotionEvent.ACTION_UP");
}
return mGestureDetector.onTouchEvent(event);
}
// SimpleOnGestureListener implements GestureDetector.OnDoubleTapListener, GestureDetector.OnGestureListener
private class MySimpleGesture extends SimpleOnGestureListener {
// 雙擊的第二下Touch down時觸發
public boolean onDoubleTap(MotionEvent e) {
Log.i("MyGesture", "onDoubleTap");
return super.onDoubleTap(e);
}
// 雙擊的第二下Touch down和up都會觸發,可用e.getAction()區分
public boolean onDoubleTapEvent(MotionEvent e) {
Log.i("MyGesture", "onDoubleTapEvent");
return super.onDoubleTapEvent(e);
}
// Touch down時觸發
public boolean onDown(MotionEvent e) {
Log.i("MyGesture", "onDown");
return super.onDown(e);
}
// Touch了滑動一點距離後,up時觸發
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
Log.i("MyGesture", "onFling");
return super.onFling(e1, e2, velocityX, velocityY);
}
// Touch了不移動一直Touch down時觸發
public void onLongPress(MotionEvent e) {
Log.i("MyGesture", "onLongPress");
super.onLongPress(e);
}
// Touch了滑動時觸發
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
Log.i("MyGesture", "onScroll");
return super.onScroll(e1, e2, distanceX, distanceY);
}
/*
* Touch了還沒有滑動時觸發
* (1)onDown只要Touch Down一定立刻觸發
* (2)Touch Down後過一會沒有滑動先觸發onShowPress再觸發onLongPress
* So: Touch Down後一直不滑動,onDown -> onShowPress -> onLongPress這個順序觸發。
*/
public void onShowPress(MotionEvent e) {
Log.i("MyGesture", "onShowPress");
super.onShowPress(e);
}
/*
* 兩個函數都是在Touch Down後又沒有滑動(onScroll),又沒有長按(onLongPress),然後Touch Up時觸發
* 點擊一下非常快的(不滑動)Touch Up: onDown->onSingleTapUp->onSingleTapConfirmed
* 點擊一下稍微慢點的(不滑動)Touch Up: onDown->onShowPress->onSingleTapUp->onSingleTapConfirmed
*/
public boolean onSingleTapConfirmed(MotionEvent e) {
Log.i("MyGesture", "onSingleTapConfirmed");
return super.onSingleTapConfirmed(e);
}
public boolean onSingleTapUp(MotionEvent e) {
Log.i("MyGesture", "onSingleTapUp");
return super.onSingleTapUp(e);
}
}
}