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;  } }); }}