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>