Android登录图形验证码的生成

activity_main.xml 
布局代码：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:layout_height="match_parent"  
    tools:context="${relativePackage}.${activityClass}" >  

    <LinearLayout   
        android:layout_width="match_parent"  
        android:layout_height="match_parent"  
        android:layout_marginLeft="10dp"  
        android:orientation="vertical">  
        <ImageView   
            android:id="@+id/image"  
            android:layout_width="wrap_content"  
            android:layout_height="wrap_content"  
            android:layout_marginTop="10dp"  
            android:src="@drawable/ic_launcher"/>  
        <EditText   
            android:id="@+id/et"  
            android:layout_width="match_parent"  
            android:layout_height="wrap_content"  
            android:layout_marginTop="10dp"  
            android:hint="输入验证码"/>  
        <Button   
            android:id="@+id/btn"  
            android:layout_width="wrap_content"  
            android:layout_height="wrap_content"  
            android:layout_marginTop="10dp"  
            android:text="获得验证码"/>  
        <Button   
            android:id="@+id/btn_submit"  
            android:layout_width="wrap_content"  
            android:layout_height="wrap_content"  
            android:layout_marginTop="10dp"  
            android:text="提交"/>  
    </LinearLayout>  

</RelativeLayout>  

 mainactivity代码：

package com.example.codedemo;  

import android.app.Activity;  
import android.graphics.Bitmap;  
import android.os.Bundle;  
import android.text.TextUtils;  
import android.util.Log;  
import android.view.View;  
import android.view.View.OnClickListener;  
import android.widget.Button;  
import android.widget.EditText;  
import android.widget.ImageView;  
import android.widget.Toast;  

public class MainActivity extends Activity implements OnClickListener {  

    private ImageView image;  
    private EditText et;  
    private Button btn,submit;  
    private String codeStr;  
    private CodeUtils codeUtils;  

    @Override  
    protected void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  

        initView();  

    }  

    private void initView() {  
        image = (ImageView) findViewById(R.id.image);  
        et = (EditText) findViewById(R.id.et);  
        btn = (Button) findViewById(R.id.btn);  
        submit = (Button) findViewById(R.id.btn_submit);  
        btn.setOnClickListener(this);  
        submit.setOnClickListener(this);  

    }  

    @Override  
    public void onClick(View v) {  
        switch (v.getId()) {  
        case R.id.btn:  
            codeUtils = CodeUtils.getInstance();  
            Bitmap bitmap = codeUtils.createBitmap();  
            image.setImageBitmap(bitmap);  

            break;  
        case R.id.btn_submit:  
            codeStr = et.getText().toString().trim();  
            Log.e("codeStr", codeStr);  
            if (null == codeStr || TextUtils.isEmpty(codeStr)) {  
                Toast.makeText(this, "请输入验证码", 0).show();  
                return;  
            }  
            String code = codeUtils.getCode();  
            Log.e("code", code);  
            if (code.equalsIgnoreCase(codeStr)) {  
                Toast.makeText(this, "验证码正确", 0).show();  
            } else {  
                Toast.makeText(this, "验证码错误", 0).show();  
            }  
            break;  
        default:  
            break;  
        }  

    }  
}  

 最后附上CodeUtils代码：

package com.example.codedemo;  

import android.graphics.Bitmap;    
import android.graphics.Bitmap.Config;    
import android.graphics.Canvas;    
import android.graphics.Color;    
import android.graphics.Paint;    

import java.util.Random;    

/**  
 * Created by yao  
 * 用于图片验证码的工具类  
 */    
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 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_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 = 20; //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    
    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, 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);    
    }    
}

 其中，在Default Settings中可以设置验证码图形的大小，验证码的长度，内边距，随机距离等可以根据需要进行调整。