The custom View circle moves with the finger, and the view circle

The custom View circle moves with the finger, and the view circle

Custom View is used to implement functions that cannot be implemented by built-in controls.

To customize a View (small circle), you must first inherit a View

Public class CircleView extends View {private float cx = 100; private float cy = 100; public CircleView (Context context) {super (context);} public CircleView (Context context, @ Nullable AttributeSet attrs) {super (context, attrs);} public CircleView (Context context, @ Nullable AttributeSet attrs, int records) {super (context, attrs, defStyleAttr );} @ Override protected void onDraw (Canvas canvas) {super. onDraw (canvas); Paint paint = new Paint (); paint. setColor (Color. RED); paint. setAntiAlias (true); paint. setStyle (Paint. style. FILL); canvas. drawCircle (cx, cy, 100, paint);} // This is to solve the event conflict @ Override public boolean onTouchEvent (MotionEvent event) {switch (event. getAction () {case MotionEvent. ACTION_DOWN: // press cx = event. getX (); cy = event. getY (); break; case MotionEvent. ACTION_MOVE: // move cx = event. getX (); cy = event. getY (); break; case MotionEvent. ACTION_UP: // lift cx = event. getX (); cy = event. getY (); break;} // You Need to redraw a new shape // invalidate (); // However, you can only draw a graph in the main thread postInvalidate (); // you can use both the main thread and sub-thread .... when the two methods are called, The onDraw method will be automatically called // The touch event will handle the return true ;}

And then use it in the layout.