Null Pointer Exception in combining two Bitmap Images

Question

I am using a method to combine two Bitmap Images and write in the SDCard. The App. works fine in the emulator, but when I tried to execute in on the Real Device it throughs Null Pointer Exception at this line cs = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888); that is to create a new Bitmap on which I will draw both the images that are to be combined using Canvas.

Now, here in combineImages(Bitmap background, Bitmap foreground) the first argument is the Bitmap from Camera Picture and the second is the forefround Gallery item. The Bitmap taken from Camera is a static Bitmap, I guess that is the only thing that is running me into trouble. So, could someone give me a nice solution to save a picture taken from Camera as a temporary storage so that I doesn't make any issue which using it further.

public void combineImages(Bitmap background, Bitmap foreground) { 

        Bitmap cs = null;
        int width = 0, height = 0;
        width = background.getWidth();
        height = background.getHeight();
        cs = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
        Canvas comboImage = new Canvas(cs);
        comboImage.drawBitmap(background, 0, 0, null);
        comboImage.drawBitmap(foreground, 100, 300, null);

        String tmpImg = String.valueOf(System.currentTimeMillis()) + ".png";
        OutputStream os = null;
        try {
            os = new FileOutputStream(Environment.getExternalStorageDirectory() + File.separator + tmpImg);
            cs.compress(CompressFormat.PNG, 100, os);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

Here is my Logcat Output when I tried on Real Device.(LG Optimus Black P-970)

10-04 12:36:08.329: ERROR/AndroidRuntime(16356): FATAL EXCEPTION: main
10-04 12:36:08.329: ERROR/AndroidRuntime(16356): java.lang.NullPointerException
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at android.graphics.Bitmap.createBitmap(Bitmap.java:469)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at com.cam.GalleryImageSelected.combineImages(GalleryImageSelected.java:66)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at com.cam.GalleryImageSelected$1.onClick(GalleryImageSelected.java:90)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at com.android.internal.app.AlertController$AlertParams$3.onItemClick(AlertController.java:874)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at android.widget.AdapterView.performItemClick(AdapterView.java:294)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at android.widget.ListView.performItemClick(ListView.java:3387)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at android.widget.AbsListView$PerformClick.run(AbsListView.java:2408)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at android.os.Handler.handleCallback(Handler.java:587)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at android.os.Handler.dispatchMessage(Handler.java:92)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at android.os.Looper.loop(Looper.java:123)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at android.app.ActivityThread.main(ActivityThread.java:4627)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at java.lang.reflect.Method.invokeNative(Native Method)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at java.lang.reflect.Method.invoke(Method.java:521)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:876)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:634)
10-04 12:36:08.329: ERROR/AndroidRuntime(16356):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

I guess the problem might be the size of the Bitmap that you are generating by taking a picture from the Camera. So, better try using Bitmap.createScaledBitmap() method.

width = getWindowManager().getDefaultDisplay().getWidth();
height = getWindowManager().getDefaultDisplay().getHeight();

background = Bitmap.createScaledBitmap(background, width, height, true);

This will scale your image according to the height-width of the device height-width. Hope this helps.

Answer 2

You basically can't get a Null Pointer Exception at the line you indicated, assuming that Bitmap is correctly implemented:

cs = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

createBitmap is static. Bitmap.Config.ARGB_8888 is static. width, height are ints.

What could possibly be null? Could you post the stack trace of the exception? Are you sure about the line?