android 实现随机生成图片验证码

在app开发中，根据需求不同，有时我们需要随机生成图片验证码，点击可以随机切换，其实很简单，接下来我们就来看看把。

首先我们使用如下工具类，其实内部原理很简单，运用随机数随机将0-9数字和a-z字母随机排列的方式进行组合，效果图如下：

接下来我们就直接上代码把：

package com.example.administrator.panada;
import android.graphics.bitmap;
import android.graphics.canvas;
import android.graphics.color;
import android.graphics.paint;
import java.util.random;

public class codeutils {

//    private static final char[] chars = {
//            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
//            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
//            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
//            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
//            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'
//    };

    private static final char[] chars = {

            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',

    };

    private static codeutils mcodeutils;
    private int mpaddingleft, mpaddingtop;
    private stringbuilder mbuilder = new stringbuilder();
    private random mrandom = new random();

    //default settings
//    private static final int default_code_length = 6;//验证码的长度  这里是6位
    private static final int default_code_length = 4;//验证码的长度  这里是4位
    private static final int default_font_size = 60;//字体大小
    private static final int default_line_number = 3;//多少条干扰线
    private static final int base_padding_left = 40; //左边距
    private static final int range_padding_left = 30;//左边距范围值
    private static final int base_padding_top = 70;//上边距
    private static final int range_padding_top = 15;//上边距范围值
    private static final int default_width = 300;//默认宽度.图片的总宽
    private static final int default_height = 100;//默认高度.图片的总高
    private static final int default_color = 0xdf;//默认背景颜色值

    private string code;

    public static codeutils getinstance() {
        if (mcodeutils == null) {
            mcodeutils = new codeutils();
        }
        return mcodeutils;
    }

    //生成验证码图片  返回类型为bitmap 直接用imageview.setbitmap()即可
    public bitmap createbitmap() {
        mpaddingleft = 0; //每次生成验证码图片时初始化
        mpaddingtop = 0;

        bitmap bitmap = bitmap.createbitmap(default_width, default_height, bitmap.config.argb_8888);
        canvas canvas = new canvas(bitmap);

        code = createcode();

        canvas.drawcolor(color.rgb(default_color, default_color, default_color));
        paint paint = new paint();
        paint.settextsize(default_font_size);

        for (int i = 0; i < code.length(); i++) {
            randomtextstyle(paint);
            randompadding();
            canvas.drawtext(code.charat(i) + "", mpaddingleft, mpaddingtop, paint);
        }

        //干扰线
        for (int i = 0; i < default_line_number; i++) {
            drawline(canvas, paint);
        }

        canvas.save(canvas.all_save_flag);//保存
        canvas.restore();
        return bitmap;
    }

    /**
     * 得到图片中的验证码字符串
     *
     * @return
     */
    public string getcode() {
        return code;
    }

    //生成验证码
    public string createcode() {
        mbuilder.delete(0, mbuilder.length()); //使用之前首先清空内容

        for (int i = 0; i < default_code_length; i++) {
            mbuilder.append(chars[mrandom.nextint(chars.length)]);
        }

        return mbuilder.tostring();
    }

    //生成干扰线
    private void drawline(canvas canvas, paint paint) {
        int color = randomcolor();
        int startx = mrandom.nextint(default_width);
        int starty = mrandom.nextint(default_height);
        int stopx = mrandom.nextint(default_width);
        int stopy = mrandom.nextint(default_height);
        paint.setstrokewidth(1);
        paint.setcolor(color);
        canvas.drawline(startx, starty, stopx, stopy, paint);
    }

    //随机颜色
    private int randomcolor() {
        mbuilder.delete(0, mbuilder.length()); //使用之前首先清空内容

        string haxstring;
        for (int i = 0; i < 3; i++) {
            haxstring = integer.tohexstring(mrandom.nextint(0xff));
            if (haxstring.length() == 1) {
                haxstring = "0" + haxstring;
            }

            mbuilder.append(haxstring);
        }

        return color.parsecolor("#" + mbuilder.tostring());
    }

    //随机文本样式
    private void randomtextstyle(paint paint) {
        int color = randomcolor();
        paint.setcolor(color);
        paint.setfakeboldtext(mrandom.nextboolean());  //true为粗体，false为非粗体
        float skewx = mrandom.nextint(11) / 10;
        skewx = mrandom.nextboolean() ? skewx : -skewx;
        paint.settextskewx(skewx); //float类型参数，负数表示右斜，整数左斜
//        paint.setunderlinetext(true); //true为下划线，false为非下划线
//        paint.setstrikethrutext(true); //true为删除线，false为非删除线
    }

    //随机间距
    private void randompadding() {
        mpaddingleft += base_padding_left + mrandom.nextint(range_padding_left);
        mpaddingtop = base_padding_top + mrandom.nextint(range_padding_top);
    }
}

来看看布局代码，也就是一个imageview

来看mainactivity中的代码吧：

public class mainactivity extends appcompatactivity implements view.onclicklistener {

    private imageview img;

    @override
    protected void oncreate(bundle savedinstancestate) {
        super.oncreate(savedinstancestate);
        setcontentview(r.layout.activity_main);
        initview();
    }


    private void initview() {
        img = (imageview) findviewbyid(r.id.img);

??????

img.setimagebitmap(codeutils.getinstance().createbitmap()); //我们在控件初始化时设置随机生成图片验证码，防止运行第一次出现图片白色情况

img.setonclicklistener(new view.onclicklistener() { @override public void onclick(view v) { string code = codeutils.getinstance().getcode(); //获取图片验证码上的内容 img.setimagebitmap(codeutils.getinstance().createbitmap()); //随机生成图片验证码 } });代码很简单，有木有学会呢？