Zbar with Android：在浏览器中显示url后，扫描仪相机视口保持非活动状态并显示黑色

Question

我需要在我的项目中使用QR扫描仪。我使用ZBar来完成这项任务。主要是我对ZBar git示例给出的示例代码做了一个非常小的修改来完成这项工作。我需要在浏览器（如果url）或对话框（如果正常信息）中显示扫描结果。

除了如果我在浏览器中扫描qr代码之后尝试显示url，每件事情都会与我给出的代码一起工作。当我从浏览器返回到我的应用程序时，相机视口变黑并保持不活动状态。我试图找回活动的相机扫描另一个二维码，但我失败了。我试图在我的onResume（）函数中重新打开相机，但这会导致错误并强行退出应用程序。请帮我解决这个问题。

package com.myapp; 
    import net.sourceforge.zbar.Config; 
    import net.sourceforge.zbar.Image; 
    import net.sourceforge.zbar.ImageScanner; 
    import net.sourceforge.zbar.Symbol; 
    import net.sourceforge.zbar.SymbolSet; 
    import android.app.Activity; 
    import android.app.AlertDialog; 
    import android.content.DialogInterface; 
    import android.content.Intent; 
    import android.content.pm.ActivityInfo; 
    import android.hardware.Camera; 
    import android.hardware.Camera.AutoFocusCallback; 
    import android.hardware.Camera.PreviewCallback; 
    import android.hardware.Camera.Size; 
    import android.net.Uri; 
    import android.os.Bundle; 
    import android.os.Handler; 
    import android.webkit.URLUtil; 
    import android.widget.FrameLayout; 

    import com.myapp.CameraPreview; 
    /* Import ZBar Class files */ 

    public class QRScannerActivity extends Activity 
    { 
     private Camera mCamera; 
     private CameraPreview mPreview; 
     private Handler autoFocusHandler; 

     ImageScanner scanner; 

     private boolean barcodeScanned = false; 
     private boolean previewing = true; 

     static { 
      System.loadLibrary("iconv"); 
     } 

     @Override 
     protected void onCreate(Bundle savedInstanceState) { 

      super.onCreate(savedInstanceState); 

      setContentView(R.layout.qr_scanner_main); 

      setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); 

      autoFocusHandler = new Handler(); 
      mCamera = getCameraInstance(); 

      /* Instance barcode scanner */ 
      scanner = new ImageScanner(); 
      scanner.setConfig(0, Config.X_DENSITY, 3); 
      scanner.setConfig(0, Config.Y_DENSITY, 3); 

      mPreview = new CameraPreview(this, mCamera, previewCb, autoFocusCB); 
      FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview); 
      preview.addView(mPreview); 
     } 

     @Override 
     protected void onPause() { 
      super.onPause(); 
      releaseCamera(); 
      //finish(); 
     } 

     /** A safe way to get an instance of the Camera object. */ 
     public static Camera getCameraInstance(){ 
      Camera c = null; 
      try { 
       c = Camera.open(); 
      } catch (Exception e){ 
      } 
      return c; 
     } 

     private void releaseCamera() { 
      //Toast.makeText(QRScannerActivity.this, "Paused State", Toast.LENGTH_SHORT).show(); 
      if (mCamera != null) { 
       previewing = false; 
       mCamera.setPreviewCallback(null); 
       mPreview.getHolder().removeCallback(mPreview); 
       mCamera.release(); 
       mCamera = null; 
      } 

     } 

     private Runnable doAutoFocus = new Runnable() { 
       public void run() { 
        if (previewing) 
         mCamera.autoFocus(autoFocusCB); 
       } 
      }; 

     PreviewCallback previewCb = new PreviewCallback() { 
       public void onPreviewFrame(byte[] data, Camera camera) { 
        Camera.Parameters parameters = camera.getParameters(); 
        Size size = parameters.getPreviewSize(); 

        Image barcode = new Image(size.width, size.height, "Y800"); 
        barcode.setData(data); 

        int result = scanner.scanImage(barcode); 
        String QRScannerResult; 

        if (result != 0) { 
         previewing = false; 
         mCamera.setPreviewCallback(null); 
         mCamera.stopPreview(); 

         SymbolSet syms = scanner.getResults(); 
         for (Symbol sym : syms) { 
          QRScannerResult = sym.getData(); 
          showResultAction(QRScannerResult); 
          barcodeScanned = true; 

         } 
        } 
       } 
      }; 

     // Mimic continuous auto-focusing 
     AutoFocusCallback autoFocusCB = new AutoFocusCallback() { 
       public void onAutoFocus(boolean success, Camera camera) { 
        autoFocusHandler.postDelayed(doAutoFocus, 1000); 
       } 
      }; 

     private void showResultAction(String QRScannerResult){ 
       if (URLUtil.isValidUrl(QRScannerResult)) { 

        if (barcodeScanned) { 
         barcodeScanned = false; 
         mCamera.setPreviewCallback(previewCb); 
         mCamera.startPreview(); 
         previewing = true; 
         mCamera.autoFocus(autoFocusCB); 
        } 

        Intent i = new Intent(Intent.ACTION_VIEW); 
        i.setData(Uri.parse(QRScannerResult)); 
        startActivity(i); 

        }else { 
         new AlertDialog.Builder(this) 
         .setTitle("QR Data") 
         .setMessage(QRScannerResult) 
         .setPositiveButton("OK", new DialogInterface.OnClickListener() { 
          public void onClick(DialogInterface dialog, int which) { 
           if (barcodeScanned) { 
            barcodeScanned = false; 
            mCamera.setPreviewCallback(previewCb); 
            mCamera.startPreview(); 
            previewing = true; 
            mCamera.autoFocus(autoFocusCB); 
           } 
          } 
         }) 
         .show(); 
        } 

     } 
    } 

在此先感谢。 Sakib

Answer 1

最后，我成功地发现了我的代码问题并得到了解决方案。当我尝试用onResume()方法重新打开相机时，我错过了一部分。当我在onResume()中创建/打开新相机时，FrameLayout仍然保留了我以前的相机。所以我所做的就是将我以前的相机从FrameLayout上移除，方法是onPause()，然后在onResume（）方法上重新创建所有内容。这解决了我的问题，现在它很好地工作，没有任何错误。这里是我的onPause()和onResume()方法与修复。希望这可能有助于未来的人。

public void onPause() { 
     super.onPause(); 
     releaseCamera(); 
     FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview); 
     preview.removeView(mPreview); 
    } 

    public void onResume(){ 
     super.onResume(); 

     try { 
      if(mCamera==null){ 

      //setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); 
      autoFocusHandler = new Handler(); 
      mCamera = getCameraInstance(); 
      this.getWindowManager().getDefaultDisplay().getRotation(); 

      scanner = new ImageScanner(); 
      scanner.setConfig(0, Config.X_DENSITY, 3); 
      scanner.setConfig(0, Config.Y_DENSITY, 3); 

      mPreview = new CameraPreview(this, mCamera, previewCb, autoFocusCB); 
      FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview); 
      preview.addView(mPreview); 
      } 
     } catch (Exception e) { 
      // TODO Auto-generated catch block 

     } 
    } 

    /** A safe way to get an instance of the Camera object. */ 
    public static Camera getCameraInstance(){ 
     Camera c = null; 
     try { 
      c = Camera.open(); 
     } catch (Exception e){ 
     } 
     return c; 
    } 

    private void releaseCamera() { 
     //Toast.makeText(QRScannerActivity.this, "Paused State", Toast.LENGTH_SHORT).show(); 
     if (mCamera != null) { 
      previewing = false; 
      mCamera.setPreviewCallback(null); 
      mPreview.getHolder().removeCallback(mPreview); 
      mCamera.release(); 
      mCamera = null; 
      mPreview= null; 
     } 

    } 

感谢， Sakib