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android 利用ZXING扫描二维码代码分析

2024-07-03 14:49:21   264人阅读

之前给公司做了一个摄影相关的应用，现在要添加二维码扫描的功能，网上找资料后，虽然已经成功集成到app里面，但是总感觉心里没底儿。所以趁这段时间不是很忙，总结一下。

首先是启动扫描的UI类：

1，Activity启动，当然是onCreate方法

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private CaptureActivityHandler handler;
private ViewfinderView viewfinderView;
private boolean hasSurface;
private Vector<BarcodeFormat> decodeFormats;
private String characterSet;
private InactivityTimer inactivityTimer;
private MediaPlayer mediaPlayer;
private boolean playBeep;
private static final float BEEP_VOLUME = 0.10f;
private boolean vibrate;
 
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_capture);
    // ViewUtil.addTopView(getApplicationContext(), this,
    // R.string.scan_card);
    CameraManager.init(getApplication());
    viewfinderView = (ViewfinderView) findViewById(R.id.viewfinder_view);
 
    Button mButtonBack = (Button) findViewById(R.id.button_back);
    mButtonBack.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            Scaner.this.finish();
        }
    });
    hasSurface = false;
    inactivityTimer = new InactivityTimer(this);
}
 
@Override
protected void onResume() {
    super.onResume();
    SurfaceView surfaceView = (SurfaceView) findViewById(R.id.preview_view);
    SurfaceHolder surfaceHolder = surfaceView.getHolder();
    if (hasSurface) {
        initCamera(surfaceHolder);
    } else {
        surfaceHolder.addCallback(this);
        surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }
    decodeFormats = null;
    characterSet = null;
 
    playBeep = true;
    AudioManager audioService = (AudioManager) getSystemService(AUDIO_SERVICE);
    if (audioService.getRingerMode() != AudioManager.RINGER_MODE_NORMAL) {
        playBeep = false;
    }
    initBeepSound();
    vibrate = true;
 
}
 
@Override
protected void onPause() {
    super.onPause();
    if (handler != null) {
        handler.quitSynchronously();
        handler = null;
    }
    CameraManager.get().closeDriver();
}
 
@Override
protected void onDestroy() {
    inactivityTimer.shutdown();
    super.onDestroy();
}
 
/**
 *
*
*
* @param @param result
* @param @param barcode
 
* @author  Administrator
* @return void
 */
public void handleDecode(Result result, Bitmap barcode) {
    inactivityTimer.onActivity();
    playBeepSoundAndVibrate();
    String resultString = result.getText();
    if (resultString.equals("")) {
        Toast.makeText(Scaner.this, "Scan failed!",3000).show();
    } else {
        //查询keycode 本地数据库 1，优先查询本地库，2，没有本地库，直接跳到知道链接
        //分析出keyCode
        Log.i("testMain","scan_result=====>"+resultString);
 
        String keyCode="";
        String[] split1;
        if(resultString.lastIndexOf("?")<0){
            Intent intent = new Intent(this, InnerBrowser.class);
            Bundle bundle = new Bundle();
            bundle.putString("result", resultString);
            //bundle.putParcelable("bitmap", barcode);
            intent.putExtras(bundle);
            startActivity(intent);Scaner.this.finish();return;
        }
        String[] attr = resultString.substring(resultString.lastIndexOf("?")-1, resultString.length()).split("&");
        for (String string : attr) {
             split1 = string.split("=");
            if(split1[0].equalsIgnoreCase("keycode")){
                //找到
                if(split1.length==2){
                    keyCode=split1[1];
                }
            }
        }
        Log.i("testMain","keyCode=====>"+keyCode);
        if(!StringUtils.isBlank(keyCode)){
            AttractionDAO dao=new AttractionDAO(Scaner.this);
            Attraction a=dao.findAttrByKeyCode(keyCode);
            Log.i("testMain","a=====>"+a);
            if(a!=null){
                Intent it=new Intent();
                it.setClass(Scaner.this, UIAttractionDetail.class);
                it.putExtra("a", a);
                startActivity(it);
            }else{
                Intent intent = new Intent(this, InnerBrowser.class);
                Bundle bundle = new Bundle();
                bundle.putString("result", resultString);
                //bundle.putParcelable("bitmap", barcode);
                intent.putExtras(bundle);
                startActivity(intent);
                //this.setResult(RESULT_OK, resultIntent);
                //使用内置浏览器打开网站内容
            }
        }else{
            Intent intent = new Intent(this, InnerBrowser.class);
            Bundle bundle = new Bundle();
            bundle.putString("result", resultString);
            //bundle.putParcelable("bitmap", barcode);
            intent.putExtras(bundle);
            startActivity(intent);
            //this.setResult(RESULT_OK, resultIntent);
            //使用内置浏览器打开网站内容
        }
    }
    Scaner.this.finish();
}
 
private void initCamera(SurfaceHolder surfaceHolder) {
    try {
        CameraManager.get().openDriver(surfaceHolder);
    } catch (IOException ioe) {
        return;
    } catch (RuntimeException e) {
        return;
    }
    if (handler == null) {
        handler = new CaptureActivityHandler(this, decodeFormats,
                characterSet);
    }
}
 
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {
 
}
 
@Override
public void surfaceCreated(SurfaceHolder holder) {
    if (!hasSurface) {
        hasSurface = true;
        initCamera(holder);
    }
 
}
 
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    hasSurface = false;
 
}
 
public ViewfinderView getViewfinderView() {
    return viewfinderView;
}
 
public Handler getHandler() {
    return handler;
}
 
public void drawViewfinder() {
    viewfinderView.drawViewfinder();
 
}
 
private void initBeepSound() {
    if (playBeep && mediaPlayer == null) {
        // The volume on STREAM_SYSTEM is not adjustable, and users found it
        // too loud,
        // so we now play on the music stream.
        setVolumeControlStream(AudioManager.STREAM_MUSIC);
        mediaPlayer = new MediaPlayer();
        mediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
        mediaPlayer.setOnCompletionListener(beepListener);
 
        AssetFileDescriptor file = getResources().openRawResourceFd(
                R.raw.beep);
        try {
            mediaPlayer.setDataSource(file.getFileDescriptor(),
                    file.getStartOffset(), file.getLength());
            file.close();
            mediaPlayer.setVolume(BEEP_VOLUME, BEEP_VOLUME);
            mediaPlayer.prepare();
        } catch (IOException e) {
            mediaPlayer = null;
        }
    }
}
 
private static final long VIBRATE_DURATION = 200L;
 
private void playBeepSoundAndVibrate() {
    if (playBeep && mediaPlayer != null) {
        mediaPlayer.start();
    }
    if (vibrate) {
        Vibrator vibrator = (Vibrator) getSystemService(VIBRATOR_SERVICE);
        vibrator.vibrate(VIBRATE_DURATION);
    }
}
 
/**
 * When the beep has finished playing, rewind to queue up another one.
 */
private final OnCompletionListener beepListener = new OnCompletionListener() {
    public void onCompletion(MediaPlayer mediaPlayer) {
        mediaPlayer.seekTo(0);
    }
};

从上面代码可以看出，做了三件事儿：加载布局文件；初始化了一个相机管理器；设置按钮监听，初始化了一个InactivityTimer实例；

然后，最重要的是他实现了一个CallBack函数：具体参见： 

SurfaceHolder.Callback 译文

此时，

1
surfaceCreated

这个方法会调用然后就初始化相机的一些参数：


前两个我们好理解，第三个是干嘛的？

我们先看布局文件：

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<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
 
        <SurfaceView
            android:id="@+id/preview_view"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:layout_gravity="center" />
 
        <com.euc.app.scan.view.ViewfinderView
            android:id="@+id/viewfinder_view"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
 
        <include
            android:id="@+id/include1"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            layout="@layout/activity_title" />
    </RelativeLayout>
 
</FrameLayout>

可以看到里面有一个自定义的View及surfaceView，

对于我这样的初学者来说，surfaceView 是什么东西？

csdn上看到这个文章

Android中SurfaceView的使用详解

虽然不是很明白，但是大致明白这是个什么东西了。

了解了生命周期之后，我们来看他执行的方法：

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private void initCamera(SurfaceHolder surfaceHolder) {
        try {
            CameraManager.get().openDriver(surfaceHolder);//配置摄像头
        } catch (IOException ioe) {
            return;
        } catch (RuntimeException e) {
            return;
        }
        if (handler == null) {
            handler = new CaptureActivityHandler(this, decodeFormats,
                    characterSet);//初始化方法里面开启摄像头预览界面。
        }
    }
 
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
 
    }
 
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        if (!hasSurface) {
            hasSurface = true;
            initCamera(holder);
        }
 
    }
 
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        hasSurface = false;
 
    }

这个surfaceView 创建出来之后，其实也把摄像头的配置信息以及硬件信息初始化好了。

OK，经过上面一个oncreate以及布局文件的加载，我们已经知道，摄像头预览成功，

这个自定义的View又是干嘛的？我们继续看源码：

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private final int maskColor;
private final int resultColor;
 
private final int resultPointColor;
private Collection<ResultPoint> possibleResultPoints;
private Collection<ResultPoint> lastPossibleResultPoints;
 
boolean isFirst;
 
public ViewfinderView(Context context, AttributeSet attrs) {
    super(context, attrs);
 
    density = context.getResources().getDisplayMetrics().density;
    //将像素转换成dp
    ScreenRate = (int)(20 * density);
 
    paint = new Paint();
    Resources resources = getResources();
    maskColor = resources.getColor(R.color.viewfinder_mask);
    resultColor = resources.getColor(R.color.result_view);
 
    resultPointColor = resources.getColor(R.color.possible_result_points);
    possibleResultPoints = new HashSet<ResultPoint>(5);
}
 
@Override
public void onDraw(Canvas canvas) {
    //中间的扫描框，你要修改扫描框的大小，去CameraManager里面修改
    Rect frame = CameraManager.get().getFramingRect();
    if (frame == null) {
        return;
    }
 
    //初始化中间线滑动的最上边和最下边
    if(!isFirst){
        isFirst = true;
        slideTop = frame.top;
        slideBottom = frame.bottom;
    }
 
    //获取屏幕的宽和高
    int width = canvas.getWidth();
    int height = canvas.getHeight();
 
    paint.setColor(resultBitmap != null ? resultColor : maskColor);
 
    //画出扫描框外面的阴影部分，共四个部分，扫描框的上面到屏幕上面，扫描框的下面到屏幕下面
    //扫描框的左边面到屏幕左边，扫描框的右边到屏幕右边
    canvas.drawRect(0, 0, width, frame.top, paint);
    canvas.drawRect(0, frame.top, frame.left, frame.bottom + 1, paint);
    canvas.drawRect(frame.right + 1, frame.top, width, frame.bottom + 1,
            paint);
    canvas.drawRect(0, frame.bottom + 1, width, height, paint);
 
 
 
    if (resultBitmap != null) {
        // Draw the opaque result bitmap over the scanning rectangle
        paint.setAlpha(OPAQUE);
        canvas.drawBitmap(resultBitmap, frame.left, frame.top, paint);
    } else {
 
        //画扫描框边上的角，总共8个部分
        paint.setColor(Color.GREEN);
        canvas.drawRect(frame.left, frame.top, frame.left + ScreenRate,
                frame.top + CORNER_WIDTH, paint);
        canvas.drawRect(frame.left, frame.top, frame.left + CORNER_WIDTH, frame.top
                + ScreenRate, paint);
        canvas.drawRect(frame.right - ScreenRate, frame.top, frame.right,
                frame.top + CORNER_WIDTH, paint);
        canvas.drawRect(frame.right - CORNER_WIDTH, frame.top, frame.right, frame.top
                + ScreenRate, paint);
        canvas.drawRect(frame.left, frame.bottom - CORNER_WIDTH, frame.left
                + ScreenRate, frame.bottom, paint);
        canvas.drawRect(frame.left, frame.bottom - ScreenRate,
                frame.left + CORNER_WIDTH, frame.bottom, paint);
        canvas.drawRect(frame.right - ScreenRate, frame.bottom - CORNER_WIDTH,
                frame.right, frame.bottom, paint);
        canvas.drawRect(frame.right - CORNER_WIDTH, frame.bottom - ScreenRate,
                frame.right, frame.bottom, paint);
 
 
        //绘制中间的线,每次刷新界面，中间的线往下移动SPEEN_DISTANCE
        slideTop += SPEEN_DISTANCE;
        if(slideTop >= frame.bottom){
            slideTop = frame.top;
        }
        canvas.drawRect(frame.left + MIDDLE_LINE_PADDING, slideTop - MIDDLE_LINE_WIDTH/2, frame.right - MIDDLE_LINE_PADDING,slideTop + MIDDLE_LINE_WIDTH/2, paint);
 
 
        //画扫描框下面的字
        paint.setColor(Color.WHITE);
        paint.setTextSize(TEXT_SIZE * density);
        paint.setAlpha(0x40);
        paint.setTypeface(Typeface.create("System", Typeface.BOLD));
        canvas.drawText(getResources().getString(R.string.scan_text), frame.left, (float) (frame.bottom + (float)TEXT_PADDING_TOP *density), paint);
 
 
 
        Collection<ResultPoint> currentPossible = possibleResultPoints;
        Collection<ResultPoint> currentLast = lastPossibleResultPoints;
        if (currentPossible.isEmpty()) {
            lastPossibleResultPoints = null;
        } else {
            possibleResultPoints = new HashSet<ResultPoint>(5);
            lastPossibleResultPoints = currentPossible;
            paint.setAlpha(OPAQUE);
            paint.setColor(resultPointColor);
            for (ResultPoint point : currentPossible) {
                canvas.drawCircle(frame.left + point.getX(), frame.top
                        + point.getY(), 6.0f, paint);
            }
        }
        if (currentLast != null) {
            paint.setAlpha(OPAQUE / 2);
            paint.setColor(resultPointColor);
            for (ResultPoint point : currentLast) {
                canvas.drawCircle(frame.left + point.getX(), frame.top
                        + point.getY(), 3.0f, paint);
            }
        }
 
 
        //只刷新扫描框的内容，其他地方不刷新
        postInvalidateDelayed(ANIMATION_DELAY, frame.left, frame.top,
                frame.right, frame.bottom);
 
    }
}
 
public void drawViewfinder() {
    resultBitmap = null;
    invalidate();
}
 
/**
 * Draw a bitmap with the result points highlighted instead of the live
 * scanning display.
 *
 * @param barcode
 *            An image of the decoded barcode.
 */
public void drawResultBitmap(Bitmap barcode) {
    resultBitmap = barcode;
    invalidate();
}
 
public void addPossibleResultPoint(ResultPoint point) {
    possibleResultPoints.add(point);
}

哦，这个就是定义了一个有动态效果的扫描界面

上面的虽然代码不多，当时我们现在回忆一下步骤：

1，启动activity，加载布局文件，初始化surfaceView,初始化自定义的View（动态界面），

2，在初始化surfaceView的时候，同时初始化了摄像头的参数，初始化的handler处理器，启动了摄像头预览。

问题：那什么时候开始监听扫描二维码的呢？

初始化handler 的时候就开始监听了，看一下其构造函数：

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public CaptureActivityHandler(Scaner activity, Vector<BarcodeFormat> decodeFormats,
      String characterSet) {
    this.activity = activity;
    decodeThread = new DecodeThread(activity, decodeFormats, characterSet,
        new ViewfinderResultPointCallback(activity.getViewfinderView()));
    decodeThread.start();
    state = State.SUCCESS;
    // Start ourselves capturing previews and decoding.
    CameraManager.get().startPreview();
    restartPreviewAndDecode();
  }

再来一个：上面构造函数new了一个对象，这个对象就是用来监听获取扫描的图像的。

直到获取了二维码图像，调用回调函数就结束。

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final class DecodeThread extends Thread {
 
  public static final String BARCODE_BITMAP = "barcode_bitmap";
  private final Scaner activity;
  private final Hashtable<DecodeHintType, Object> hints;
  private Handler handler;
  private final CountDownLatch handlerInitLatch;
 
  DecodeThread(Scaner activity,
               Vector<BarcodeFormat> decodeFormats,
               String characterSet,
               ResultPointCallback resultPointCallback) {
 
    this.activity = activity;
    handlerInitLatch = new CountDownLatch(1);
 
    hints = new Hashtable<DecodeHintType, Object>(3);
 
    if (decodeFormats == null || decodeFormats.isEmpty()) {
         decodeFormats = new Vector<BarcodeFormat>();
         decodeFormats.addAll(DecodeFormatManager.ONE_D_FORMATS);
         decodeFormats.addAll(DecodeFormatManager.QR_CODE_FORMATS);
         decodeFormats.addAll(DecodeFormatManager.DATA_MATRIX_FORMATS);
    }
 
    hints.put(DecodeHintType.POSSIBLE_FORMATS, decodeFormats);
 
    if (characterSet != null) {
      hints.put(DecodeHintType.CHARACTER_SET, characterSet);
    }
 
    hints.put(DecodeHintType.NEED_RESULT_POINT_CALLBACK, resultPointCallback);
  }
 
  Handler getHandler() {
    try {
      handlerInitLatch.await();
    } catch (InterruptedException ie) {
      // continue?
    }
    return handler;
  }
 
  @Override
  public void run() {
    Looper.prepare();
    handler = new DecodeHandler(activity, hints);
    handlerInitLatch.countDown();
    Looper.loop();
  }
 
}

回调函数：

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public void handleDecode(Result result, Bitmap barcode) {
    inactivityTimer.onActivity();
    playBeepSoundAndVibrate();
    String resultString = result.getText();
    if (resultString.equals("")) {
        Toast.makeText(Scaner.this, "Scan failed!",3000).show();
    } else { 
        //扫描结果的处理。
    }
    Scaner.this.finish();
}

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