How to get screen width in fragment?

Question

so im using the following code to get my screen width in a fragment, but my app keeps crashing due to some null point exception, and i can't figure it out.

Here's the code im using.

            DisplayMetrics displayMetrics = new DisplayMetrics();
            getActivity().getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
            int height = displayMetrics.heightPixels;
            int width = displayMetrics.widthPixels;

It says im crashing on this line : getActivity().getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);

No idea what is going on hope someone can help!

Here is my stack trace:

 FATAL EXCEPTION: main
                                                                               Process: com.daprlabs.aaron.swipedeck2, PID: 25417
                                                                               java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.WindowManager android.support.v4.app.FragmentActivity.getWindowManager()' on a null object reference
                                                                                   at com.daprlabs.aaron.zivitApp.Main.FragmentDiscover$SwipeDeckAdapter.getView(FragmentDiscover.java:398)
                                                                                   at com.daprlabs.aaron.swipedeck.SwipeDeck.addNextView(SwipeDeck.java:215)
                                                                                   at com.daprlabs.aaron.swipedeck.SwipeDeck.onLayout(SwipeDeck.java:208)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
                                                                                   at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1079)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
                                                                                   at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
                                                                                   at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1799)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
                                                                                   at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
                                                                                   at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1193)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
                                                                                   at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
                                                                                   at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
                                                                                   at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
                                                                                   at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1743)
                                                                                   at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1586)
                                                                                   at android.widget.LinearLayout.onLayout(LinearLayout.java:1495)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:336)
                                                                                   at android.widget.FrameLayout.onLayout(FrameLayout.java:273)
                                                                                   at com.android.internal.policy.PhoneWindow$DecorView.onLayout(PhoneWindow.java:2720)
                                                                                   at android.view.View.layout(View.java:16668)
                                                                                   at android.view.ViewGroup.layout(ViewGroup.java:5439)
                                                                                   at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2202)
                                                                                   at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1955)
                                                                                   at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1125)
                                                                                   at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6100)
                                                                                   at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
                                                                                   at android.view.Choreographer.doCallbacks(Choreographer.java:670)
                                                                                   at android.view.Choreographer.doFrame(Choreographer.java:606)
                                                                                   at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
                                                                                   at android.os.Handler.handleCallback(Handler.java:739)
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                at android.os.
05-03 15:47:52.762 1218-4087/? W/ActivityManager:   Force finishing activity com.daprlabs.aaron.swipedeck2/com.daprlabs.aaron.zivitApp.Main.Main

Possible duplicate of [What is a NullPointerException, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — takendarkk, May 03 '17 at 22:53
`Attempt to invoke virtual method 'android.view.WindowManager android.support.v4.app.FragmentActivity.getWindowManager()' on a null object reference` getActivity() returned null. — takendarkk, May 03 '17 at 22:55

score 1 · Answer 1 · answered May 04 '17 at 03:04

try to use this

//get screen size
public static int sizeScreen(){
    return (int)((Resources.getSystem().getDisplayMetrics().widthPixels)/ Resources.getSystem().getDisplayMetrics().density);
}

//get screen height
public static int getHeight(Context context){
    return context.getResources().getDisplayMetrics().heightPixels;
}

//get witdh screen
public static int getWidth(Context context){
    return context.getResources().getDisplayMetrics().widthPixels;
}

Make sure you use onCreate instead of your constructor..

Do you mean onCreateView() or onCreate() in Fragment activity? And what do you mean by "use onCreate() — TheQ, May 04 '17 at 04:14

How to get screen width in fragment?

1 Answers1