自定义view 随机数

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.bwie.test.lianxiview.MainActivity">

    <com.bwie.test.lianxiview.MyYanZheng
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
       />

    <com.bwie.test.lianxiview.MyYanZheng
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="58dp"
        android:layout_below="@+id/myYanZheng"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
</RelativeLayout>

attars

package com.bwie.test.lianxiview;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by 景瑾 on 2017/9/28.
 */

public class MyYanZheng extends View {
    private Paint codePaint;
    private Paint rectPaint;
    private String data = "1234";
    private Rect rectString;

    public MyYanZheng(Context context) {
        super(context);
    }

    public MyYanZheng(Context context, AttributeSet attrs) {
        super(context, attrs);
        //初始化
        init();
        //设置监听，点击一次就重新生成一次验证码
        this.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                data = getRandom2();
                //重新绘制，让点击前的重置为无效
                invalidate();
            }
        });
    }

    public MyYanZheng(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes, Rect rectString, Paint codePaint, Paint rectPaint, String data) {
        super(context, attrs, defStyleAttr, defStyleRes);
        this.rectString = rectString;
        this.codePaint = codePaint;
        this.rectPaint = rectPaint;
        this.data = data;
    }

    //初始化画笔
    private void init() {
        //设置生成代码的画笔的属性
        codePaint = new Paint();
        codePaint.setColor(Color.RED);
        codePaint.setStrokeWidth(10);
        codePaint.setTextSize(80);
        //设置矩形画笔属性
        rectPaint = new Paint();
        //rectPaint.setStyle(Paint.Style.STROKE);//空心风格
        rectPaint.setColor(Color.GREEN);
        rectPaint.setStrokeWidth(15);
        //通过一个矩形将绘制文字包裹在里面，那么你的控件大小就转换成矩形的大小
        rectString = new Rect();
        /**
         * 1,字符串内容  2，字符串起点  3，字符串长度  4，空矩形
         */
        codePaint.getTextBounds(data, 0, data.length(), rectString);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //记住显示的顺序不要写反了，否则图层覆盖，影响显示
        //画矩形
        canvas.drawRect(0, 0, getWidth(), getHeight(), rectPaint);
        //画验证码
        canvas.drawText(data, 0, getHeight(), codePaint);

    }

    //生成四位随机数的方法一
//    public String getRandom() {
//        Random random = new Random();
//        Set<Integer> set = new HashSet<>();
//        循环注意终止条件是set.size()<4
//        for (int i = 0; set.size() < 4; i++) {
//            int value = random.nextInt(10);
//            set.add(value);
//        }
//        //将生成的验证码装载stringbuffer里面
//        StringBuffer stringBuffer = new StringBuffer();
//        for (Integer i : set) {
//            stringBuffer.append(i);
//        }
//        return stringBuffer.toString();
//    }

    //生成四位随机数的方法二（弊端：只能生成>1000的数字，如0069此法无法生成）
    public String getRandom2() {
        //(int) (Math.random() * (大数 - 小数 + 1) + 小数)
        String codeStr = (int) (Math.random() * (9999 - 1000 + 1) + 1000) + "";
        return codeStr;
    }

    /**
     * 当设置wrap_content属性的时候，系统测量的不准确你需重新计算
     * MeasureSpec这个类可以帮助我们进行计算和获取当前在布局里面设置的模式
     * At_most-------wrap_content
     * Exactly-------match_parent,或者固定尺寸，如100dp;
     * At_most通常计算不准确，需要自己计算
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        //  super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        //获取当前宽度设置模式
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        //获取宽度参考值，下面高度同理分别获取
        int widthCK = MeasureSpec.getSize(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightCK = MeasureSpec.getSize(heightMeasureSpec);

        int width, height;
        if (widthMode == MeasureSpec.EXACTLY) {
            //如果精确测量模式，直接赋值
            width = widthCK;
        } else {
            //如果不是精确测量模式，取字符串的宽度来赋值
            width = rectString.width();
        }
        if (heightMode == MeasureSpec.EXACTLY) {
            height = heightCK;
        } else {
            height = rectString.height();
        }
        //重新设置计算的值
        setMeasuredDimension(width, height);
    }
}