android - How to get screen width and height

Question

I tried to use following code to get screen width and height in android app development:

Display display = getWindowManager().getDefaultDisplay(); 
int screenWidth = display.getWidth();
int screenHeight = display.getHeight();

but I got NullPointerException for my display, why? how to get screen width and height then?

Answer 1

If you're calling this outside of an Activity, you'll need to pass the context in (or get it through some other call). Then use that to get your display metrics:

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

UPDATE: With API level 17+, you can use getRealSize:

Point displaySize = new Point();
activity.getWindowManager().getDefaultDisplay().getRealSize(displaySize);

If you want the available window size, you can use getDecorView to calculate the available area by subtracting the decor view size from the real display size:

Point displaySize = new Point();
activity.getWindowManager().getDefaultDisplay().getRealSize(displaySize);

Rect windowSize = new Rect();
ctivity.getWindow().getDecorView().getWindowVisibleDisplayFrame(windowSize);

int width = displaySize.x - Math.abs(windowSize.width());
int height = displaySize.y - Math.abs(windowSize.height());
return new Point(width, height);

getRealMetrics may also work (requires API level 17+), but I haven't tried it yet:

DisplayMetrics metrics = new DisplayMetrics();
activity.GetWindowManager().getDefaultDisplay().getRealMetrics(metrics);