Android NullPointerException Error at Runtime

Question

I'm developing a simple camera app which is based on the android developers tutorial but my I'm having some issues getting it running.

Here is my LogCat printout.

enter image description here

Now I have traced the NullPointerException to be at line 30 in CameraPreview as you have probably figured out to so the code for CameraPreview is below. I can code in Java and know that a NullPointer is when something is there which hasn't been created yet but as far as I can tell it has been.

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

@SuppressWarnings("deprecation")
public CameraPreview(Context context, Camera camera){
    super(context);
    mCamera = camera;

    //Install callback to get notifications from the app
    mHolder = getHolder();
    mHolder.addCallback(this);
    mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); //deprecated but required for Android Version 3.0 and under
}

public void surfaceCreated(SurfaceHolder holder) {
    //Surface been created now need to tell app where to draw PREVIEW
            try{
                mCamera.setPreviewDisplay(holder);
                mCamera.startPreview();
            }
            catch(IOException e){
                Log.d(TAG, "Camera preview error: " + e.getMessage());
            }

}

Line 30 is the code snippet here - mCamera.setPreviewDisplay(holder);

From what I can tell is that there is an instance of mCamera in the 'global' variable private Camera mCamera.

Anyone got any ideas? Sorry its a long question formatted as best I could.

Thanks, Dan

P.S. I know there are other methods required in this class this is merely the 'problem snippet'.

@Robert which class do you mean Camera? because that's imported from android.hardware.Camera.... — WebDevDanno
– WebDevDanno, Commented Aug 1, 2012 at 11:22
I believe you mCamera instance is null, check if it initializes properly. — Luke Taylor
– Luke Taylor, Commented Aug 1, 2012 at 11:23

Bo A · Accepted Answer · 2012-08-01 11:43:23Z

1

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

Looks like camera is getting passed on to CameraPreview as null.

Make sure you have these in your Manifest:

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

Also, what's your getCameraInstance() method?

edited Aug 1, 2012 at 11:43

answered Aug 1, 2012 at 11:25

Bo A

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24 Comments

Bo A Over a year ago

@DanielD Post the method where you pass camera to CameraPreview and I'll have a look.

WebDevDanno Over a year ago

the only place camera and CameraPreview are is in my constructor?

Bo A Over a year ago

@DanielD It's where you pass the variables to the CameraPreview, it has to be somewhere. (eg. CameraPreview cp = new CameraPreview(context, camera).

WebDevDanno Over a year ago

public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_camera_demo); //get an instance of Camera mCamera = getCameraInstance(); // Create our Preview view and set it as the content of our activity. mPreview = new CameraPreview(this, mCamera); FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview); preview.addView(mPreview);

This is in CameraDemo.java is this what you mean?

Bo A Over a year ago

@DanielD Yes, that's it. I'll have a look at it now.

|

oliholz · Accepted Answer · 2012-08-01 11:23:39Z

1

Where is CameraPreview created?

Looks like new CameraPreview(context, null).

You have to be sure that CameraPreview get not a null-Camera.

answered Aug 1, 2012 at 11:23

oliholz

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4 Comments

WebDevDanno Over a year ago

surely CameraPreview is created in my constructor?

oliholz Over a year ago

Post your line, what is the 2nd Argument for CameraPreview?

oliholz Over a year ago

getCameraInstance() brings null. post this method.

oliholz Over a year ago

does Camera.open() throws an exception?

Niko · Accepted Answer · 2012-08-01 11:26:25Z

0

Use Camera android.hardware.Camera.open() to initialize the camera when you start your activity.

answered Aug 1, 2012 at 11:26

Niko

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2 Comments

WebDevDanno Over a year ago

where would that go in my code, the onCreate method in the main application class? i.e. CameraDemo?

Niko Over a year ago

where you instantiate the CameraPreview, pass the camera using that function.

Hardikgiri Goswami · Accepted Answer · 2012-08-01 11:27:42Z

-1

mCamera = camera.

at this line your 'camera' object could be null.... so check it first... like

if(camera==null){

Log.e("Camera","my camera is null...");

}

Try this.... at this way you can find the exact where the nullPointer occurs...

answered Aug 1, 2012 at 11:27

Hardikgiri Goswami

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