android - 相机启动预览失败

Question

我正在创建一个相机应用程序，但我在 startPreview 上遇到问题，它向我发送:

java.lang.RuntimeException: startPreview failed

这是我的相机 Activity :

public class CameraActivity extends Activity {

private Camera mCamera;
private CameraPreview  mPreview;
private Target_Frame targetFrame;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.camera_layout);




    mCamera=getCameraInstance();
    mPreview=new CameraPreview(this, mCamera);




    FrameLayout preview=(FrameLayout)findViewById(R.id.camera_preview);
    preview.addView(mPreview);

}




/** Check if this device has a camera only if not specified in the manifest */
public boolean checkCameraHardware(Context context) {
    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
        // this device has a camera
        return true;
    } else {
        // no camera on this device
        return false;
    }
}

/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
    Camera c = null;
    try {
        c = Camera.open(); // attempt to get a Camera instance
    }
    catch (Exception e){
        // Camera is not available (in use or does not exist)
    }
    return c; // returns null if camera is unavailable
}

/**Check if the device has flash*/
public boolean checkFlash(Context context){
    if(context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH)){
        //the device has flash
        return true;
    }else{
        //no flash
        return false;
    }

}




@Override
protected void onDestroy() {
    // TODO Auto-generated method stub
    super.onDestroy();
    releaseCamera();
}




@Override
protected void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
    releaseCamera();
}




@Override
protected void onResume() {
    // TODO Auto-generated method stub
    super.onResume();

    //Test if i have to put all this code like in onCreate
    if(mCamera!=null){
        return;
    }
    mCamera=getCameraInstance();

    if(mPreview!=null){
        return;
    }
    mPreview=new CameraPreview(this, mCamera);
    FrameLayout preview=(FrameLayout)findViewById(R.id.camera_preview);
    preview.addView(mPreview);


}


private void releaseCamera(){
    if (mCamera != null){
        mCamera.release();        // release the camera for other applications
        mCamera = null;
    }
}}

这是我的 SurfaceView 代码:

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
    private static final String TAG = "CameraPreview";
    private SurfaceHolder mHolder;
    private Camera mCamera;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, now tell the camera where to draw the preview.
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();

        } catch (IOException e) {
            Log.d(TAG, "Error setting camera preview: " + e.getMessage());
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // empty. Take care of releasing the Camera preview in your activity.
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.

        if (mHolder.getSurface() == null){
          // preview surface does not exist
          return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
          // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here
        Parameters parameters= mCamera.getParameters();
        parameters.setPreviewSize(w, h);
        mCamera.setParameters(parameters);

        // start preview with new settings
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e){
            Log.d(TAG, "Error starting camera preview: " + e.getMessage());
        }
    }
}

这是我的错误日志:

12-01 13:17:01.135: E/AndroidRuntime(1161): FATAL EXCEPTION: main

12-01 13:17:01.135: E/AndroidRuntime(1161): java.lang.RuntimeException: startPreview

12-01 13:17:01.135: E/AndroidRuntime(1161):     at com.example.prueba.CameraPreview.surfaceCreated(CameraPreview.java:36) 

Answer 1

我已经解决了删除 surfaceChanged 中的一些行

 public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.
        Log.d("Function", "surfaceChanged iniciado");
        if (mHolder.getSurface() == null){
          // preview surface does not exist
          return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
          // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here


        // start preview with new settings
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e){
            Log.d(TAG, "Error starting camera preview: " + e.getMessage());
        }
    }

所以错误一定在我这些行之一:

Parameters parameters= mCamera.getParameters();
    parameters.setPreviewSize(w, h);
    mCamera.setParameters(parameters);

有人可以向我解释这些行中有什么问题吗？