活动恢复时摄像头预览屏幕黑屏

Question

我一直在试图让我的应用上的摄像头部分工作大约一周，并且在最终修复了一个错误之后，它创建了一个新的。

当我恢复活动时，预览不起作用，录制功能也不起作用。通过查看Logcat，我发现我的Camera对象等于null，并且我找不到重新创建它。

我在创建

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); 

获取

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   
} 

我的相机实例方法暂停

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();  
     }  
} 

我在简历

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返回从getCameraInstance()方法，如果它可以帮助空。

Answer 1

在你onResume()，你在呼唤：

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

这里发生了什么，是你通过Camera.open()得到一个摄像头实例及本声明以后，你又试图通过调用getCameraInstance();让相机实例这将返回null因为你的活动已经得到了实例，因此mCamera实例正在得到null。

如果这不能解决您的问题，请告诉我，我会看到其他解决方案。