Android camera preview - 'no file - can't switch camera'

Question

I'm trying to create a very simple app that simply shows what the camera is viewing on the screen. I created the app with an emulator(same specification as the phone I used) which shows the black and white squared background with the grey viewing box moving over it, so I'm pretty sure I've got all code and permissions correct.

When I try to run the App on my Wildfire Phone(Android Version: 2.2.1) It force closes before anything is shown and when I check the logs this error is shown.

• 12-08 12:41:42.649: W/CameraSwitch(3004): open main camera
• 12-08 12:41:42.659: W/CameraSwitch(3004): no file - can't switch camera
• 12-08 12:41:43.239: D/AndroidRuntime(3004): Shutting down VM

I looked through some sites and it seems it might be a problem with the OS or the hardware. Has anyone found a work around?

I'm going to post my code just in case I've made a foolish mistake.

import android.app.Activity;
import android.content.pm.ActivityInfo;
import android.os.Bundle;

public class InformationPassingTestActivity extends Activity {

Preview preview;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    preview = new Preview(this);
    setContentView(preview);
    }
}

my preview class that handles the camera

class Preview extends SurfaceView implements SurfaceHolder.Callback {

SurfaceHolder mHolder;
public Camera camera;

Preview(Context context) {
    super(context);

    mHolder = getHolder();
    mHolder.addCallback(this);
    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}

public void surfaceCreated(SurfaceHolder holder) {

    camera = Camera.open();
    try {
        camera.setPreviewDisplay(holder);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public void surfaceDestroyed(SurfaceHolder holder) {
    camera.stopPreview();
    camera = null;
}

public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    Camera.Parameters parameters = camera.getParameters();
    parameters.setPreviewSize(width, height);
    camera.setParameters(parameters);
    camera.startPreview();
}   
}

Manifest.xml

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />

<uses-sdk android:minSdkVersion="8" />
<application android:icon="@drawable/ic_launcher" android:label="@string/app_name" >
<activity android:label="@string/app_name"         android:name=".InformationPassingTestActivity" >
    <intent-filter>
    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
    </activity>
</application>

Any help would be amazing :)

Answer 1

Your problem is probably from this line (or if it isn't yet it will be): parameters.setPreviewSize(width, height);

Actual cameras can't support every preview size. You need to choose a preview size that is close to the size of your surface and supported by the camera hardware. Here's a sample method to do that:

private  Camera.Size getBestPreviewSize(int width, int height,
                                          Camera.Parameters parameters) {
     Camera.Size result=null;

    for ( Camera.Size size : parameters.getSupportedPreviewSizes()) {
      if (size.width<=width && size.height<=height) {
        if (result==null) {
          result=size;
        }
        else {
          int resultArea=result.width*result.height;
          int newArea=size.width*size.height;

          if (newArea>resultArea) {
            result=size;
          }
        }
      }
    }

    return(result);
  }

You may also have a problem calling Camera.open() in surfaceCreated without checking whether or not the camera has already been opened. Try moving that call to your onCreate and onResume methods and adding a call to Camera.release() in your onPause method so that you don't attempt to open the camera more than once.