继承view的自定义控件示例

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首先说一下自定义控件可以分为继承view的用canvas画出来的控件，还有继承Android原生控件来重写出来的控件，还有就是混合控件。今天我来做的是第一种情况，即继承view用canvas画出来的控件，下面我们来实现下图的一个需求：

实现思路：先画一条弧线，在画2个圆形，组成一个圆环，其次给圆环添加点击事件。

先初始化画笔paint的设置，代码如下：

                rectF = new RectF(10, 200, screenWidth - 10, screenWidth - 10);paint_Arc = new Paint(Paint.ANTI_ALIAS_FLAG);// 设置抗锯齿paint_Arc.setAntiAlias(true);// 设置画笔宽度paint_Arc.setStrokeWidth(3);// 设置画笔颜色paint_Arc.setColor(Color.BLUE);// 设置空心paint_Arc.setStyle(Paint.Style.STROKE);// 设置模式paint_Arc.setXfermode(new PorterDuffXfermode(Mode.DARKEN));

其中这里有一个知识点就是那个设置模式。大家可以戳这里

这里就是图层模式相应的效果图。

再来在onDraw弧线和圆环：代码如下：

                canvas.drawArc(rectF, 180, 180, false, paint_Arc);paint_Arc.setStyle(Paint.Style.FILL);canvas.drawCircle(screenWidth / 2, 200, 100, paint_Arc);canvas.drawCircle(screenWidth / 6, 300, 100, paint_Arc);canvas.drawCircle(screenWidth * 5 / 6, 300, 100, paint_Arc);paint_Arc.setColor(Color.WHITE);canvas.drawCircle(screenWidth / 2, 200, 90, paint_Arc);canvas.drawCircle(screenWidth / 6, 300, 90, paint_Arc);canvas.drawCircle(screenWidth * 5 / 6, 300, 90, paint_Arc);

最后就是计算点击的坐标是否在圆环中，代码如下：

@SuppressLint("ClickableViewAccessibility")@Overridepublic boolean onTouchEvent(MotionEvent event) {switch (event.getAction()) {case MotionEvent.ACTION_DOWN:int x = (int) event.getX();int y = (int) event.getY();if (circleListener != null) {if (Math.abs(x - screenWidth / 6) <= 100&& Math.abs(y - 300) <= 100&& (screenWidth / 6 - x) * (screenWidth / 6 - x)+ (300 - y) * (300 - y) <= 100 * 100) {circleListener.onCircleListener(1);return true;}if (Math.abs(x - screenWidth / 2) <= 100&& Math.abs(y - 200) <= 100&& (screenWidth / 2 - x) * (screenWidth / 2 - x)+ (200 - y) * (200 - y) <= 100 * 100) {circleListener.onCircleListener(2);return true;}if (Math.abs(x - screenWidth * 5 / 6) <= 100&& Math.abs(y - 300) <= 100&& (screenWidth * 5 / 6 - x)* (screenWidth * 5 / 6 - x) + (300 - y)* (300 - y) <= 100 * 100) {circleListener.onCircleListener(3);return true;}}break;default:break;}return super.onTouchEvent(event);}public void setOnCircleListener(CircleListener circleListener){this.circleListener = circleListener;}public interface CircleListener{public abstract void onCircleListener(int circlePos);}

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