Android实现拖动小球跟随手指移动效果

public class DrawView extends View {
 public float currentX = 50;
 public float currentY = 50;

 public DrawView(Context context) {
  super(context);
 }
 public void onDraw(Canvas canvas){
  super.onDraw(canvas);
  Paint paint = new Paint();
  paint.setColor(Color.RED);
  canvas.drawCircle(currentX,currentY,10,paint);
 }
}

public class MainActivity extends Activity {

 public LinearLayout linearLayout;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  linearLayout = (LinearLayout) findViewById(R.id.root);

  final DrawView drawView = new DrawView(this);
  drawView.setOnTouchListener(new View.OnTouchListener() {
   @Override
   public boolean onTouch(View v, MotionEvent event) {
    drawView.currentX = event.getX();
    drawView.currentY = event.getY();
    //通过draw组件重绘
    drawView.invalidate();

    return true;
   }
  });
  linearLayout.addView(drawView);
 }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
 android:id="@+id/root"
 tools:context="com.syt.androidtest.androidtest1.MainActivity">


</LinearLayout>