camera startPreview failed

Question

I am creating a camera app but I have problems on startPreview, it sends me:

java.lang.RuntimeException: startPreview failed

h

Answer 1

I had this error, and it's because I didn't call releaseCamera on the onPause the first time I start my app.
After a reboot, everything works fine ^^

Answer 2

public void surfaceCreated(SurfaceHolder holder) {
    // The Surface has been created, now tell the camera where to draw the preview.
    try {
        mCamera.setPreviewDisplay(holder);
        mCamera.getParameters().getSupportedPreviewSizes();
        mCamera.startPreview();
        Log.d(TAG, "Camera preview started.");
    } catch (IOException e) {
        Log.d(TAG, "Error setting camera preview: " + e.getMessage());
    }
}

Answer 3

Its late, but if someones looking for the answer

The variables w and h are not the optimal preview sizes . You can get optimal preview sizes using the function

public static Camera.Size getOptimalPreviewSize(List<Camera.Size> sizes, int w, int h) {
        final double ASPECT_TOLERANCE = 0.1;
        double targetRatio=(double)h / w;
        if (sizes == null) return null;

        Camera.Size optimalSize = null;
        double minDiff = Double.MAX_VALUE;

        int targetHeight = h;

        for (Camera.Size size : sizes) {
            double ratio = (double) size.width / size.height;
            if (Math.abs(ratio - targetRatio) > ASPECT_TOLERANCE) continue;
            if (Math.abs(size.height - targetHeight) < minDiff) {
                optimalSize = size;
                minDiff = Math.abs(size.height - targetHeight);
            }
        }

        if (optimalSize == null) {
            minDiff = Double.MAX_VALUE;
            for (Camera.Size size : sizes) {
                if (Math.abs(size.height - targetHeight) < minDiff) {
                    optimalSize = size;
                    minDiff = Math.abs(size.height - targetHeight);
                }
            }
        }
        return optimalSize;
    }

and you can call the function using

public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
..
size=getOptimalPreviewSize(parameters.getSupportedPreviewSizes(), w, h);
 parameters.setPreviewSize(size.getWidth(), size.getHeight());
..

}

Answer 4

Is (w, h) a valid preview size for your camera?

You can use mCamera.getParameters().getSupportedPreviewSizes() to get all of the valid preview sizes.

Answer 5

I have solved deleting some lines in surfaceChanged

 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());
        }
    }

So the error must be in i one of these lines:

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

Someone could explain me what was wrong in those lines?