自定义View26个字母索引

package com.example.zdyview;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
/*
* 王硕
* 2019.05.28
* 自定义view侧边栏
* */
public class MyView extends View {
    private int indext;
    private Paint paint;
    private char[] mCha=new char[26];
    private int mArea;
    private int left;
    private int right;

    public MyView(Context context) {
        this(context,null);

    }

    public MyView(Context context, AttributeSet attrs) {
        this(context, attrs,-1);

    }

    public MyView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        paint = new Paint();
        paint.setColor(Color.RED);//设置颜色
        paint.setStrokeWidth(5);//设置画笔宽度
        paint.setAntiAlias(true);//抗锯齿
        paint.setTextSize(30);//设置写出的文字大小
        paint.setTextAlign(Paint.Align.CENTER);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        int top=40;
        int down=getHeight()-40;
        right = getRight()-20;
        left = getWidth()-80;
        //上边的横线
        canvas.drawLine(left,top, right,top,paint);
        //左边的横线
        canvas.drawLine(left,top, left,down,paint);
        //下边的横线
        canvas.drawLine(left,down, right,down,paint);
        //右边的横线
        canvas.drawLine(right,top, right,down,paint);
        //获取画图的高度每个字母的高度

        int tot=down-top;

        mArea = tot/26;
        int stary=top+mArea/2;
        //写上文字
        for (int i = 0; i <mCha.length; i++) {

            mCha[i]= (char) +(i+'A');
            canvas.drawText( mCha[i]+"" , left +30,stary+mArea*i,paint);
        }

        paint.setTextSize(40);

        canvas.drawText(mCha[indext]+"",getWidth()/2,getHeight()/2,paint);

        }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();
        float y = event.getY();
        //获取你的点击的区域范围必须要在 矩形内
        if (x>=left && y>=20) {
            //获取下标，y-20是高度减去40然后在吧每一份的大小/一下获得点击的位置是哪里然后给下标赋值
            indext= (int) ((y-40)/mArea);
            Log.d("MyView", "indext:" + indext);
            //判断是否是超出了下标 如果超出了下标则非他设置成26
            if (indext>=mCha.length) {
                indext=mCha.length-1;
            }
            //刷新view

            invalidate();
            return  true;
        }
        return super.onTouchEvent(event);
    }
}