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
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.administrator.mygridview.MainActivity">
<ImageView
android:id="@+id/img"
android:layout_width="200dp"
android:layout_height="100dp" />
</LinearLayout>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