1：自定義一個類繼承View;

private float x=100;
private float y=100;
private Paint paint;

2：重寫三到四個構造方法

3：在構造方法中初始化筆

public CircleView(Context context, AttributeSet attrs) {
    super(context, attrs);
    //初始化畫筆
paint = new Paint();
    //設定顏色
paint.setColor(Color.YELLOW);
    //抗鋸齒
paint.setAntiAlias(true);
}

protected void 
 
onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.drawCircle(x,y,100,paint);
}

public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:

                break;
            case MotionEvent.ACTION_MOVE:               

                //在拖動圖形時獲得x值，y值；