自定义View圆的点击事件实现

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.webkit.WebView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        DisplayMetrics metrics = new DisplayMetrics();
        this.getWindowManager().getDefaultDisplay().getMetrics(metrics);

        // 屏幕的分辨率
        int width = metrics.widthPixels;
        int height = metrics.heightPixels;

        setContentView(new MyCircle(this, width, height));
    }

    class MyCircle extends View {

        private Context context;

        /**
         * 屏幕的宽
         */
        private int width;

        /**
         * 屏幕的高
         */
        private int height;

        /**
         *  颜色区分区域
         */
        private int[] colors = new int[] { Color.BLACK, Color.BLUE, Color.CYAN,
                Color.GREEN, Color.GRAY, Color.MAGENTA, Color.RED, Color.LTGRAY};
        private String[] colorStrs = new String[] {
                "黑色", "蓝色", "青绿色", "绿色", "灰色", "洋红色", "红色", "浅灰色"};

        /**
         * 大园半径
         */
        private float bigR;

        /**
         * 小圆半径
         */
        private float litterR;

        /**
         * 屏幕中间点的X坐标
         */
        private float centerX;

        /**
         * 屏幕中间点的Y坐标
         */
        private float centerY;

        public MyCircle(Context context, int width, int height) {
            super(context);
            this.context = context;
            this.width = width;
            this.height = height;
            setFocusable(true);

            System.out.println("width="+width+"<---->height="+height);
            // 设置两个圆的半径
            bigR = (width - 20)/2;
            litterR = bigR/2;

            centerX = width/2;
            centerY = height/2;
        }

        @Override
        protected void onDraw(Canvas canvas) {
            // 画背景颜色
            Paint bg = new Paint();
            bg.setColor(Color.WHITE);
            Rect bgR = new Rect(0, 0, width, height);
            canvas.drawRect(bgR, bg);

            float start = 0F;
            Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
            for(int i = 0; i < 4; i ++) {
                //注意一定要先画大圆，再画小圆，不然看不到效果，小圆在下面会被大圆覆盖
                // 画大圆
                RectF bigOval = new RectF(centerX - bigR, centerY - bigR,
                        centerX + bigR, centerY + bigR);
                paint.setColor(colors[i]);
                canvas.drawArc(bigOval, start, 90, true, paint);

                // 画小圆
                RectF litterOval = new RectF(centerX - litterR, centerY - litterR,
                        centerX + litterR, centerY + litterR);
                paint.setColor(colors[i+2]);
                canvas.drawArc(litterOval, start, 90, true, paint);

                start += 90F;
            }

            super.onDraw(canvas);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
            // 获取点击屏幕时的点的坐标
            float x = event.getX();
            float y = event.getY();
            whichCircle(x, y);
            return super.onTouchEvent(event);
        }

        /**
         * 确定点击的点在哪个圆内
         * @param x
         * @param y
         */
        private void whichCircle(float x, float y) {
            // 将屏幕中的点转换成以屏幕中心为原点的坐标点
            float mx = x - centerX;
            float my = y - centerY;
            float result = mx * mx + my * my;

            StringBuilder tip = new StringBuilder();
            tip.append("您点击了");
            // 高中的解析几何
            if(result <= litterR*litterR) {// 点击的点在小圆内
                tip.append("小圆的");
                tip.append(colorStrs[whichZone(mx, my)+2]);
                tip.append("区域");
            } else if(result <= bigR * bigR) {// 点击的点在大圆内
                tip.append("大圆的");
                tip.append(colorStrs[whichZone(mx, my)]);
                tip.append("区域");
            } else {// 点不在作作区域
                tip.append("作用区域以外的区域");
            }

            Toast.makeText(context, tip, Toast.LENGTH_SHORT).show();
        }

        /**
         * 判断点击了圆的哪个区域
         * @param x
         * @param y
         * @return
         */
        private int whichZone(float x, float y) {
            // 简单的象限点处理
            // 第一象限在右下角，第二象限在左下角，代数里面的是逆时针，这里是顺时针
            if(x > 0 && y > 0) {
                return 0;
            } else if(x > 0 && y < 0) {
                return 3;
            } else if(x < 0 && y < 0) {
                return 2;
            } else if(x < 0 && y > 0) {
                return 1;
            }

            return -1;
        }

    }

}