活動恢復時攝像頭預覽屏幕黑屏

Question

我一直在試圖讓我的應用上的攝像頭部分工作大約一週，並且在最終修復了一個錯誤之後，它創建了一個新的。

當我恢復活動時，預覽不起作用，錄製功能也不起作用。通過查看Logcat，我發現我的Camera對象等於null，並且我找不到重新創建它。

我在創建

mCamera = getCameraInstance();  
// Create preview view and set it as the content of our activity.  
mPreview = new CameraPreview(this, mCamera);  
preview = (FrameLayout) findViewById(R.id.previewer); 
preview.addView(mPreview); 

獲取

private Camera getCameraInstance() { 

     Camera c = null;  
     try {  
      //c = Camera.open(); // attempt to get a Camera instance  
      c = this.open(); // attempt to get a Camera instance  
     } catch (Exception e) {  
      // Camera is not available (in use or does not exist)  
     }  
     Log.i("TEST getCameraInstance", "" + c);  
     return c; // returns null if camera is unavailable   
} 

我的相機實例方法暫停

protected void onPause() { 

     super.onPause();  
     try {  
      // release the camera immediately on pause event  
      // releaseCamera();  
      mCamera.stopPreview();  
      mCamera.setPreviewCallback(null);  
      mCamera.release();  
      mCamera = null;  
     } catch (Exception e) {  
      e.printStackTrace();  
     }  
} 

我在簡歷

protected void onResume() { 

     super.onResume();  
     try {  
      mCamera = Camera.open();  
      mCamera = getCameraInstance();  
      Log.i("TEST onresume", "onResume Runing");  
      Log.i("TEST onresume", "camera " + mCamera);  
      mCamera.setPreviewCallback(null);  
      Log.i("TEST onresume", "camera " + mCamera);  
      //mCamera = getCameraInstance();  
      Log.i("TEST onresume", "camera " + mCamera);  
      // mCamera.setPreviewCallback(null);  
      mPreview = new CameraPreview(MainRecordScreen.this, mCamera);// set preview  
      Log.i("TEST onresume", "camera " + mCamera);                    
      preview.addView(mPreview);  
      Log.i("TEST onresume", "camera " + mCamera);  
      mCamera.startPreview();    
     } catch (Exception e) {  
      Log.d(TAG, "Error starting camera preview: " + e.getMessage());  
     }  
     Log.i("TEST onresume", "camera " + mCamera);  
} 

我logcat的

06-19 06:38:40.223: E/AndroidRuntime(16702): FATAL EXCEPTION: main 
06-19 06:38:40.223: E/AndroidRuntime(16702): java.lang.NullPointerException 
06-19 06:38:40.223: E/AndroidRuntime(16702): at com.plcd.test.MainRecordScreen.prepareVideoRecorder(MainRecordScreen.java:198) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at com.plcd.test.MainRecordScreen.access$7(MainRecordScreen.java:193) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at com.plcd.test.MainRecordScreen$3.onClick(MainRecordScreen.java:115) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at android.view.View.performClick(View.java:3511) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at android.view.View$PerformClick.run(View.java:14105) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at android.os.Handler.handleCallback(Handler.java:605) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at android.os.Handler.dispatchMessage(Handler.java:92) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at android.os.Looper.loop(Looper.java:137) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at android.app.ActivityThread.main(ActivityThread.java:4424) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at java.lang.reflect.Method.invokeNative(Native Method) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at java.lang.reflect.Method.invoke(Method.java:511) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
06-19 06:38:40.223: E/AndroidRuntime(16702): at dalvik.system.NativeStart.main(Native Method) 

mCamera返回從getCameraInstance()方法，如果它可以幫助空。

Answer 1

在你onResume()，你在呼喚：

mCamera = Camera.open(); 
mCamera = getCameraInstance(); 

這裏發生了什麼，是你通過Camera.open()得到一個攝像頭實例及本聲明以後，你又試圖通過調用getCameraInstance();讓相機實例這將返回null因爲你的活動已經得到了實例，因此mCamera實例正在得到null。

如果這不能解決您的問題，請告訴我，我會看到其他解決方案。