Android实现跟随手指移动的小球

自定义view；

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);
  }
}

2、显示；

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);
  }
}

布局:

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 >