android 利用ZXING掃描二維碼代碼分析

以前給公司作了一個攝影相關的應用，如今要添加二維碼掃描的功能，網上找資料後，雖然已經成功集成到app裏面，可是總感受內心沒底兒。因此趁這段時間不是很忙，總結一下。

首先是啓動掃描的UI類：

1，Activity啓動，固然是onCreate方法

    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 {
            //查詢keycode 本地數據庫 1，優先查詢本地庫，2，沒有本地庫，直接跳到知道連接
            //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);
                    //使用內置瀏覽器打開網站內容
                }
            }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);
                //使用內置瀏覽器打開網站內容
            }
        }
        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);
        }
    };

從上面代碼能夠看出，作了三件事兒：加載佈局文件；初始化了一個相機管理器；設置按鈕監聽，初始化了一個InactivityTimer實例；

而後，最重要的是他實現了一個CallBack函數：具體參見： 

SurfaceHolder.Callback 譯文

此時，

surfaceCreated

這個方法會調用而後就初始化相機的一些參數：

前兩個咱們好理解，第三個是幹嗎的？

咱們先看佈局文件：

<?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>

能夠看到裏面有一個自定義的View及surfaceView，

對於我這樣的初學者來講，surfaceView 是什麼東西？

csdn上看到這個文章

Android中SurfaceView的使用詳解

雖然不是很明白，可是大體明白這是個什麼東西了。

瞭解了生命週期以後，咱們來看他執行的方法：

private void initCamera(SurfaceHolder surfaceHolder) {
        try {
            CameraManager.get().openDriver(surfaceHolder);//配置攝像頭
        } catch (IOException ioe) {
            return;
        } catch (RuntimeException e) {
            return;
        }
        if (handler == null) {
            handler = new CaptureActivityHandler(this, decodeFormats,
                    characterSet);//初始化方法裏面開啓攝像頭預覽界面。
        }
    }

    @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;

    }

這個surfaceView 建立出來以後，其實也把攝像頭的配置信息以及硬件信息初始化好了。

OK，通過上面一個oncreate以及佈局文件的加載，咱們已經知道，攝像頭預覽成功，

這個自定義的View又是幹嗎的？咱們繼續看源碼：

    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;
        //將像素轉換成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) {
        //中間的掃描框，你要修改掃描框的大小，去CameraManager裏面修改
        Rect frame = CameraManager.get().getFramingRect();
        if (frame == null) {
            return;
        }

        //初始化中間線滑動的最上邊和最下邊
        if(!isFirst){
            isFirst = true;
            slideTop = frame.top;
            slideBottom = frame.bottom;
        }

        //獲取屏幕的寬和高
        int width = canvas.getWidth();
        int height = canvas.getHeight();

        paint.setColor(resultBitmap != null ? resultColor : maskColor);

        //畫出掃描框外面的陰影部分，共四個部分，掃描框的上面到屏幕上面，掃描框的下面到屏幕下面
        //掃描框的左邊面到屏幕左邊，掃描框的右邊到屏幕右邊
        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 {

            //畫掃描框邊上的角，總共8個部分
            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);


            //繪製中間的線,每次刷新界面，中間的線往下移動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);


            //畫掃描框下面的字
            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);
                }
            }


            //只刷新掃描框的內容，其餘地方不刷新
            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，這個就是定義了一個有動態效果的掃描界面

---

上面的雖然代碼很少，當時咱們如今回憶一下步驟：

1，啓動activity，加載佈局文件，初始化surfaceView,初始化自定義的View（動態界面），

2，在初始化surfaceView的時候，同時初始化了攝像頭的參數，初始化的handler處理器，啓動了攝像頭預覽。

---

問題：那何時開始監聽掃描二維碼的呢？

初始化handler 的時候就開始監聽了，看一下其構造函數：

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();
  }

再來一個：上面構造函數new了一個對象，這個對象就是用來監聽獲取掃描的圖像的。

直到獲取了二維碼圖像，調用回調函數就結束。

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();
  }

}

回調函數：

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 {  
        //掃描結果的處理。
    }
    Scaner.this.finish();
}

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