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：
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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？
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