How to Get Screen Display Metrics in Application Class

How to get screen display metrics in application class

Here, Context.getResource()

DisplayMetrics dm = getResources().getDisplayMetrics(); 
int densityDpi = dm.densityDpi;

How to get Screen metrics outside an Activity?

The simplest thing would be to pass a Context to the FruitPool constructor. It could then retrieve the display metrics by calling Context.getWindowManager(). (If you want to run that code outside the constructor, save context.getApplicationContext(), in case it was passed an Activity context.)

EDIT: If you adopt this approach and are passing an Activity to the FruitPool object, and the lifetime of the FruitPool object might exceed the lifetime of the activity, then you must not keep a reference to the activity. You should instead keep a reference to context.getApplicationContext(). Since getWindowManager() is only defined for an Activity, you can instead use this expression to obtain the WindowManager:

(WindowManager) context.getSystemService(Context.WINDOW_SERVICE)

How to get Display Metrics in Native Android App

You need to make a JNI call from Java side to native(c++) side and pass your width, height information as parameter to native method.

http://developer.android.com/training/articles/perf-jni.html

Also there is a good and simple example here :

http://www3.ntu.edu.sg/home/ehchua/programming/android/android_ndk.html

display.getRealMetrics() is deprecated

According to the official docs the recommended way is to use WindowManager#getCurrentWindowMetrics():

val metrics: WindowMetrics = context.getSystemService(WindowManager::class.java).currentWindowMetrics

If you use it to get screen size, please see my answer here.

I don't know how to get the screen density for use in a class

You need to access resources through a Context, as in context.resources.displayMetrics.density. An Activity is a Context, which is why you can just access resources directly (technically it's this.resources, where this is the Activity)

If you're calling that directly within an Activity, it shouldn't be a problem! If it's in another class, you'll have to get a Context from somewhere - ideally passing one in (e.g. if an Activity is calling a function, it can pass itself as a Context parameter).

There are a few things that are Contexts, but in this case specifically, you need to be careful:

After Build.VERSION_CODES#R, Resources must be obtained by Activity or Context created with Context.createWindowContext(int, Bundle). Application#getResources() may report wrong values in multi-window or on secondary displays.

Basically the Context needs to have an idea of how big the app window is, which an Activity will, but something like applicationContext might not.

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The main reason to be careful is that Activities are big, so you don't want to hold onto them when they're being passed as a Context, because you might keep them in memory after the Activity has been discarded - that would be a memory leak, and it might be what you're getting warned about!

Typically if you did need to hold onto the Context for future use, you'd do something like myContext = passedContext.applicationContext - so you're not holding on to whatever object was passed in, you're plucking out the shared application context which is always in memory anyway, so it doesn't matter if you keep it. That's a safe way to store one.

But like the docs mentioned above, that's no good here, so ideally your function would:

• use the Activity context to calculate whatever within the function, and use/store that value, discarding the context, or
• access something within the context (resources, displayMetrics etc) and store that if you need to access it later

that way you're storing what you need to, and not holding onto the Activity when you don't need it

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Contexts are weird when you're starting out, but they're basically something that provides access to information about the environment the code is running in, and system functions. And some are more specific - like an Activity is a visible component in your app, so it can provide info like the dimensions of its window, things like that.

So they're really important for Android apps, and you end up passing them around a lot (you'll see them as parameters in a lot of functions), but you also have to be careful of keeping Activitys in memory by storing references to them in components that outlive the Activity itself. Hope that makes some sense!

Get screen width and height in Android

Using this code, you can get the runtime display's width & height:

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

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In a view you need to do something like this:

((Activity) getContext()).getWindowManager()
                         .getDefaultDisplay()
                         .getMetrics(displayMetrics);

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In some scenarios, where devices have a navigation bar, you have to check at runtime:

public boolean showNavigationBar(Resources resources)
{
    int id = resources.getIdentifier("config_showNavigationBar", "bool", "android");
    return id > 0 && resources.getBoolean(id);
}

If the device has a navigation bar, then count its height:

private int getNavigationBarHeight() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
        DisplayMetrics metrics = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(metrics);
        int usableHeight = metrics.heightPixels;
        getWindowManager().getDefaultDisplay().getRealMetrics(metrics);
        int realHeight = metrics.heightPixels;
        if (realHeight > usableHeight)
            return realHeight - usableHeight;
        else
            return 0;
    }
    return 0;
}

So the final height of the device is:

int height = displayMetrics.heightPixels + getNavigationBarHeight();

Getting screen size not from Activity subclass

Yes there is a way, if you can pass the Context Object to your non activity class,

   int width= context.getResources().getDisplayMetrics().widthPixels;
   int height= context.getResources().getDisplayMetrics().heightPixels;

You don't need the Activity Object itself.

How to get screen dimensions as pixels in Android

If you want the display dimensions in pixels you can use getSize:

Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
int width = size.x;
int height = size.y;

If you're not in an Activity you can get the default Display via WINDOW_SERVICE:

WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
Display display = wm.getDefaultDisplay();

If you are in a fragment and want to acomplish this just use Activity.WindowManager (in Xamarin.Android) or getActivity().getWindowManager() (in java).

Before getSize was introduced (in API level 13), you could use the getWidth and getHeight methods that are now deprecated:

Display display = getWindowManager().getDefaultDisplay(); 
int width = display.getWidth();  // deprecated
int height = display.getHeight();  // deprecated

For the use case, you're describing, however, a margin/padding in the layout seems more appropriate.

Another way is: DisplayMetrics

A structure describing general information about a display, such as its size, density, and font scaling. To access the DisplayMetrics members, initialize an object like this:

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

We can use widthPixels to get information for:

"The absolute width of the display in pixels."

Example:

Log.d("ApplicationTagName", "Display width in px is " + metrics.widthPixels);

API level 30 update

final WindowMetrics metrics = windowManager.getCurrentWindowMetrics();
 // Gets all excluding insets
 final WindowInsets windowInsets = metrics.getWindowInsets();
 Insets insets = windowInsets.getInsetsIgnoringVisibility(WindowInsets.Type.navigationBars()
         | WindowInsets.Type.displayCutout());

 int insetsWidth = insets.right + insets.left;
 int insetsHeight = insets.top + insets.bottom;

 // Legacy size that Display#getSize reports
 final Rect bounds = metrics.getBounds();
 final Size legacySize = new Size(bounds.width() - insetsWidth,
         bounds.height() - insetsHeight);

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