Android基础知识之单点触摸

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:paddingBottom="@dimen/activity_vertical_margin"
 android:paddingLeft="@dimen/activity_horizontal_margin"
 android:paddingRight="@dimen/activity_horizontal_margin"
 android:paddingTop="@dimen/activity_vertical_margin"
 tools:context="com.example.touchevent.MainActivity" >

 <ImageView
 android:id="@+id/iv"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:src="@drawable/jiafeimao"
 android:scaleType="matrix" />

</RelativeLayout>

public class MainActivity extends Activity {

 private ImageView iv;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 iv = (ImageView) this.findViewById(R.id.iv);
 iv.setOnTouchListener(new OnTouchListener() {
  private float x;
  private float y;
  // 用来操作图片的模型
  private Matrix oldMatrix = new Matrix();
  private Matrix newMatrix = new Matrix();

  @Override
  public boolean onTouch(View v, MotionEvent event) {
  switch (event.getAction()) { // 判断操作类型
  case MotionEvent.ACTION_DOWN:
   //按下时记住x,y的坐标
   x = event.getX();
   y = event.getY();
   oldMatrix.set(iv.getImageMatrix());
   break;
  case MotionEvent.ACTION_MOVE://移动时
   //用另一个模型记住按下时的位置
   newMatrix.set(oldMatrix);
   //移动模型
   newMatrix.setTranslate(event.getX()-x, event.getY()-y);
   break;
  }
  //把图片放入移动后的模型中
  iv.setImageMatrix(newMatrix);
  return true;
  }
 });
 }
}