Android开发手记(30) 触摸及手势操作
触摸操作在现在智能手机系统中起到举足轻重的作用,本文将对安卓中的触摸以及一些简单手势的操作进行简单的介绍。
1、触摸
首先是关于触摸的判断,有两种方法可以判断的触摸操作。
(1)setOnTouchListener
对于View类,我们可以为View添加setOnTouchListener来获取触摸事件。我们以TextView为例,由于TextView继承自View,所以我们可以为其添加一个触摸监听。然后将触摸事件交给OnTouchListener处理。比如,我们在触摸TextView时改变这个TextView的文字。
textView.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { int action = MotionEventCompat.getActionMasked(event); switch (action){ case MotionEvent.ACTION_DOWN : textView.setText("TextAction: DOWN"); return true; case MotionEvent.ACTION_UP : textView.setText("TextAction UP"); return true; default: return false; } } });
其中,我们通过getActionMasked(MotionEvent event)取得触摸事件的类型ID,然后对其分别判断。当然,还有一些其他的事件:
public static final int ACTION_DOWN = 0; //单点触摸动作 public static final int ACTION_UP = 1; //单点触摸离开动作 public static final int ACTION_MOVE = 2; //触摸点移动动作 public static final int ACTION_CANCEL = 3; //触摸动作取消 public static final int ACTION_OUTSIDE = 4; //触摸动作超出边界 public static final int ACTION_POINTER_DOWN = 5; //多点触摸动作 public static final int ACTION_POINTER_UP = 6; //多点离开动作
(2)onTouchEvent
对于Activity,我们可以通过重载onTouch方法来获取触摸事件。我们这里通过触摸MainActivity然后通过一个TextView来显示触摸的信息。
@Override public boolean onTouchEvent(MotionEvent event) { int action = MotionEventCompat.getActionMasked(event); switch (action){ case MotionEvent.ACTION_DOWN : textView.setText("MainAction: DOWN"); return true; case MotionEvent.ACTION_UP : textView.setText("MainAction UP"); return true; default: return super.onTouchEvent(event); } }
完整代码为:
import android.app.Activity; import android.os.Bundle; import android.support.v4.view.MotionEventCompat; import android.view.MotionEvent; import android.view.View; import android.widget.TextView; public class MainActivity extends Activity { private TextView textView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); textView = (TextView)findViewById(R.id.textView); textView.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { int action = MotionEventCompat.getActionMasked(event); switch (action) { case MotionEvent.ACTION_DOWN: textView.setText("TextAction: DOWN"); return true; case MotionEvent.ACTION_UP: textView.setText("TextAction UP"); return true; default: return false; } } }); } @Override public boolean onTouchEvent(MotionEvent event){ int action = MotionEventCompat.getActionMasked(event); switch (action){ case MotionEvent.ACTION_DOWN : textView.setText("MainAction: DOWN"); return true; case MotionEvent.ACTION_UP : textView.setText("MainAction UP"); return true; default: return super.onTouchEvent(event); } } }
2、手势识别
Android提供的onTouch方法只能处理一些简单的触摸操作比如触摸、离开、移动之类的,但是当我们处理一些复杂的手势时,这样判断就会很复杂,比如长按操作。好在Android SDK提供了另外的一些方法来处理手势的操作:GestureDetector。GestureDetector类对外提供了两个接口:OnGestureListener,OnDoubleTapListener,还有一个内部类SimpleOnGestureListener;SimpleOnGestureListener类是GestureDetector提供给我们的一个更方便的响应不同手势的类,它实现了上述两个接口,该类是static class,也就是说它实际上是一个外部类,我们可以在外部继承这个类,重写里面的手势处理方法。
使用GestureDetector,具体过程为,首先实现GestureDetector接口,然后实例化一个这个类对象,最后对Activity添加onTouchEvent处理方法即可。
(1)OnGestureListener
首先我们需要新建一个MyGesture类来实现GestureDetector的接口,这里我们需要注意的是我们必须实现所有提供的接口:
按下(onDown): 刚刚手指接触到触摸屏的那一刹那,就是触的那一下。
提拉(onFling): 手指在触摸屏上迅速移动,并松开的动作。
长按(onLongPress): 手指按在持续一段时间,并且没有松开。
滚动(onScroll): 手指在触摸屏上滑动。
按住(onShowPress): 手指按在触摸屏上,它的时间范围在按下起效,在长按之前。
抬起(onSingleTapUp):手指离开触摸屏的那一刹那。
class MyGesture implements GestureDetector.OnGestureListener{ @Override public boolean onDown(MotionEvent event) { textView.setText("onDown: " + event.toString()); return true; } @Override public boolean onFling(MotionEvent event1, MotionEvent event2, float velocityX, float velocityY) { textView.setText("onFling: " + event1.toString() + event2.toString()); return true; } @Override public void onLongPress(MotionEvent event) { textView.setText("onLongPress: " + event.toString()); } @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { textView.setText("onScroll: " + e1.toString() + e2.toString()); return true; } @Override public void onShowPress(MotionEvent event) { textView.setText("onShowPress: " + event.toString()); } @Override public boolean onSingleTapUp(MotionEvent event) { textView.setText("onSingleTapUp: " + event.toString()); return true; } }
然后在MainActivity的onCreate方法内实例化这个类;
gestureDetector = new GestureDetector(MainActivity.this, new MyGesture());
最后,根据我们实例化的对象为MainActivity添加时间处理方法:
@Override public boolean onTouchEvent(MotionEvent event){ gestureDetector.onTouchEvent(event); return super.onTouchEvent(event); }
完整的代码如下:
import android.app.Activity; import android.os.Bundle; import android.view.GestureDetector; import android.view.MotionEvent; import android.widget.TextView; public class MainActivity extends Activity { private TextView textView; private GestureDetector gestureDetector; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); textView = (TextView)findViewById(R.id.textView); gestureDetector = new GestureDetector(MainActivity.this, new MyGesture()); } @Override public boolean onTouchEvent(MotionEvent event){ gestureDetector.onTouchEvent(event); return super.onTouchEvent(event); } class MyGesture implements GestureDetector.OnGestureListener{ @Override public boolean onDown(MotionEvent event) { textView.setText("onDown: " + event.toString()); return true; } @Override public boolean onFling(MotionEvent event1, MotionEvent event2, float velocityX, float velocityY) { textView.setText("onFling: " + event1.toString() + event2.toString()); return true; } @Override public void onLongPress(MotionEvent event) { textView.setText("onLongPress: " + event.toString()); } @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { textView.setText("onScroll: " + e1.toString() + e2.toString()); return true; } @Override public void onShowPress(MotionEvent event) { textView.setText("onShowPress: " + event.toString()); } @Override public boolean onSingleTapUp(MotionEvent event) { textView.setText("onSingleTapUp: " + event.toString()); return true; } } }
(2)SimpleOnGestureListener
从上文可以看出,我们在使用OnGestureListener的时候,需要重载一些我们用不到的方法,好在Android也为我们考虑到了这种不便,所以为我们提供了一个SimpleOnGestureListener类来方便的实现我们需要的手势。
这里我们只需要继承一下SimpleOnGestureListener类即可:
class MyGesture extends GestureDetector.SimpleOnGestureListener{ @Override public boolean onDown(MotionEvent event) { textView.setText("onDown: " + event.toString()); return true; } //...其他实现方法 }
完整的代码入下:
import android.app.Activity; import android.os.Bundle; import android.view.GestureDetector; import android.view.MotionEvent; import android.widget.TextView; public class MainActivity extends Activity { private TextView textView; private GestureDetector gestureDetector; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); textView = (TextView)findViewById(R.id.textView); gestureDetector = new GestureDetector(MainActivity.this, new MyGesture()); } @Override public boolean onTouchEvent(MotionEvent event){ gestureDetector.onTouchEvent(event); return super.onTouchEvent(event); } class MyGesture extends GestureDetector.SimpleOnGestureListener{ @Override public boolean onDown(MotionEvent event) { textView.setText("onDown: " + event.toString()); return true; } @Override public boolean onFling(MotionEvent event1, MotionEvent event2, float velocityX, float velocityY) { textView.setText("onFling: " + event1.toString() + event2.toString()); return true; } @Override public void onLongPress(MotionEvent event) { textView.setText("onLongPress: " + event.toString()); } @Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) { textView.setText("onScroll: " + e1.toString() + e2.toString()); return true; } @Override public void onShowPress(MotionEvent event) { textView.setText("onShowPress: " + event.toString()); } @Override public boolean onSingleTapUp(MotionEvent event) { textView.setText("onSingleTapUp: " + event.toString()); return true; } } }