Bitmap.getWidth()' on a null object reference

Question

I just got into this problem on the line CreateScaledBitmap, I am trying to set this image as device's wallpaper and I need to scale this image to the device, thats why I am doing this method but unfortunately I cant fix this Bitmap width() error

            setWall.setOnClickListener(new View.OnClickListener() {
        @RequiresApi(api = Build.VERSION_CODES.KITKAT)
        @Override
        public void onClick(View view) {

            Picasso.with(getApplicationContext()).load(imageBrought).into(new Target() {
                @Override
                public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {

                    DisplayMetrics metrics = new DisplayMetrics();
                    getWindowManager().getDefaultDisplay().getMetrics(metrics);

                    int height = metrics.heightPixels;
                    int width = metrics.widthPixels;


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

                    WallpaperManager wallpaperManager = WallpaperManager.getInstance(AppMomentSelected.this);
                    wallpaperManager.setWallpaperOffsetSteps(1, 1);
                    wallpaperManager.suggestDesiredDimensions(width, height);


                    try {

                        wallpaperManager.setBitmap(bitmap);

                    } catch (IOException e) {

                        e.printStackTrace();
                    }

                }

                @Override
                public void onBitmapFailed(Drawable errorDrawable) {

                }

                @Override
                public void onPrepareLoad(Drawable placeHolderDrawable) {

                }
            });

bmap2 mustn't be null make a null checking before performing an action. — Yupi
– Yupi, Commented Jan 31, 2018 at 22:43
@Rino Hello, I did an if statemant and bmap2 is null.. I dont know why.. in any case, this is the error: E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.nicco.wallpapersapp, PID: 11771 java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference at android.graphics.Bitmap.createScaledBitmap(Bitmap.java:658) at com.example.nicco.wallpapersapp.AppMomentSelected$1.onClick(AppMomentSelected.java:85) — Nicco
– Nicco, Commented Feb 1, 2018 at 13:17
@Yupi Hi Yupi, I did an if statemant and yeah.. bmap2 is null.. I dont know why, how could I fix it? look, I updated the code in the question — Nicco
– Nicco, Commented Feb 1, 2018 at 13:21
What is imageBrought probably in it is problem? And can you this part change to getBytes("UTF-8"); — Yupi
– Yupi, Commented Feb 1, 2018 at 13:31

Yupi · Accepted Answer · 2018-02-01 15:05:54Z

1

You have Url of an image from your Firebase but approach you use to get Bitmap from Url is not efficient and probably not possible. Simple thing you need to do is to use some custom library for downloading images for example Picasso http://square.github.io/picasso/

Add to your app gradle: compile 'com.squareup.picasso:picasso:2.5.2'

And now you can use Picasso to download image from Url and convert to Bitmap:

                DisplayMetrics metrics = new DisplayMetrics();
                getWindowManager().getDefaultDisplay().getMetrics(metrics);

                int height = metrics.heightPixels;
                int width = metrics.widthPixels;
                WallpaperManager wallpaperManager = WallpaperManager.getInstance(AppMomentSelected.this);
                wallpaperManager.setWallpaperOffsetSteps(1, 1);
                wallpaperManager.suggestDesiredDimensions(width, height);

                Picasso.with(this)
                .load(imageBrought)
                .resize(width, height)
                .into(new Target() {
                 @Override
                  public void onBitmapLoaded (final Bitmap bitmap, Picasso.LoadedFrom from) {
                 /* Save the bitmap or do something with it here */
                 wallpaperManager.setBitmap(bitmap);
         }
    });

edited Feb 1, 2018 at 15:05

answered Feb 1, 2018 at 14:38

Yupi

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7 Comments

Nicco Over a year ago

look the question on top, I updated it with your solution, it works but I have a question, is it sure now, watching the code on top updated thanks by you, that the image gets scaled into the device?

Yupi Over a year ago

I think Picasso offers resizing option I will update the answer.

Nicco Over a year ago

I tried on the Nexus 5X emulator and it works fine but on my mom's Huawei it doesnt :/ its not scaled the image, it is zoomed

Yupi Over a year ago

You can hardcode width and height also putting the exact number

Nicco Over a year ago

how can I know that? I mean people may have different screen size, is there a way to fit it automatically? I am searching too on the web

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