android 验证码的实现

     突然发现自己开通博客已经两周年了。时间真是把杀猪刀，感觉时间过得太快了~

     自己断断续续地也写了一些博客，但是总感觉到自己写博客只是停留在表面上，缺乏深度。 在android开发这条路上，自己还只是一个小菜鸟，需要做的事情还有很多，一定要继续加油努力~

　　好了，言归正传，说一下我们经常使用的android APP在登陆时的需要验证码，下面我们说一下验证码的实现过程。

package com.jinfenglee.vertifycode;

import java.util.Random;

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

public class VertifyCode {

    private static VertifyCode bmpCode;
    private String code;
    private int paddingLeft, paddingTop;
    private Random random = new Random();
    

    public static VertifyCode getInstance() {
        if (bmpCode == null)
            bmpCode = new VertifyCode();
        return bmpCode;
    }


    /**
     * 生成验证码图片
     * @return
     */
    public Bitmap createBitmap() {
        paddingLeft = 0;

        Bitmap bitmap = Bitmap.createBitmap(Constants.DEFAULT_WIDTH, Constants.DEFAULT_HEIGHT,
                Config.ARGB_8888);
        Canvas c = new Canvas(bitmap);

        code = createCode();

        c.drawColor(Color.WHITE);
        Paint paint = new Paint();
        paint.setTextSize(Constants.DEFAULT_FONT_SIZE);

        for (int i = 0; i < code.length(); i++) {
            randomTextStyle(paint);
            randomPadding();
            c.drawText(code.charAt(i) + "", paddingLeft, paddingTop, paint);
        }

        for (int i = 0; i < Constants.DEFAULT_LINE_NUMBER; i++) {
            drawLine(c, paint);
        }

        c.save(Canvas.ALL_SAVE_FLAG);// 保存
        c.restore();
        
        return bitmap;
    }

    public String getCode() {
        return code;
    }

    /**
     * 生成 验证码
     * 
     * @return
     */
    private String createCode() {
        StringBuilder buffer = new StringBuilder();
        for (int i = 0; i < Constants.DEFAULT_CODE_LENGTH; i++) {
            buffer.append(Constants.CHARS[random.nextInt(Constants.CHARS.length)]);
        }
        
        return buffer.toString();
    }

    /**
     * 在画布上用画笔画线
     * @param canvas
     * @param paint
     */
    private void drawLine(Canvas canvas, Paint paint) {
        int color = randomColor();
        int startX = random.nextInt(Constants.DEFAULT_WIDTH);
        int startY = random.nextInt(Constants.DEFAULT_HEIGHT);
        int stopX = random.nextInt(Constants.DEFAULT_WIDTH);
        int stopY = random.nextInt(Constants.DEFAULT_HEIGHT);
        paint.setStrokeWidth(1);
        paint.setColor(color);
        canvas.drawLine(startX, startY, stopX, stopY, paint);
    }
    
    /**
     * 随机生成颜色值
     * @return
     */
    private int randomColor() {
        return randomColor(1);
    }

    private int randomColor(int rate) {
        int red = random.nextInt(256) / rate;
        int green = random.nextInt(256) / rate;
        int blue = random.nextInt(256) / rate;
        return Color.rgb(red, green, blue);
    }

    /**
     * 验证码字体样式
     * @param paint
     */
    private void randomTextStyle(Paint paint) {
        int color = randomColor();
        paint.setColor(color);
        paint.setFakeBoldText(random.nextBoolean()); 
    }

    private void randomPadding() {
        paddingLeft += Constants.BASE_PADDING_LEFT + random.nextInt(Constants.RANGE_PADDING_LEFT);
        paddingTop = Constants.BASE_PADDING_TOP + random.nextInt(Constants.RANGE_PADDING_TOP);
    }
}

MainActivity：

public class MainActivity extends Activity {

    private ImageView ivVertifyCode;
    private Button btnSwitch;

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

        ivVertifyCode = (ImageView) findViewById(R.id.iv_vertify_code);
        btnSwitch = (Button) findViewById(R.id.btn_switch_another);
        ivVertifyCode.setImageBitmap(VertifyCode.getInstance().createBitmap());

        btnSwitch.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                ivVertifyCode.setImageBitmap(VertifyCode.getInstance().createBitmap());
                Toast.makeText(getApplicationContext(),
                        VertifyCode.getInstance().getCode(), Toast.LENGTH_LONG).show();
            }
        });
    }

}