How to determine the screen width in terms of dp or dip at runtime in Android?

问题

I need to code the layout of the android widgets using dip/dp (in java files). At runtime if I code,

int pixel=this.getWindowManager().getDefaultDisplay().getWidth();

this return the screen width in pixels (px). To convert this to dp, I coded:

int dp =pixel/(int)getResources().getDisplayMetrics().density ;

This does not seem to be returning correct answer. I made the emulator of WVGA800 whose screen resolution is 480 by 800. When the run the emulator and let the code print the values of pixel and dp, it came to 320 in both. This emulator is 240 dpi whose scale factor would be 0.75.

回答1:

Try this

Display display = getWindowManager().getDefaultDisplay();
DisplayMetrics outMetrics = new DisplayMetrics ();
display.getMetrics(outMetrics);

float density  = getResources().getDisplayMetrics().density;
float dpHeight = outMetrics.heightPixels / density;
float dpWidth  = outMetrics.widthPixels / density;

Thanks @Tomáš Hubálek

DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();    
float dpHeight = displayMetrics.heightPixels / displayMetrics.density;
float dpWidth = displayMetrics.widthPixels / displayMetrics.density;

回答2:

I stumbled upon this question from Google, and later on I found an easy solution valid for API >= 13.

For future references:

Configuration configuration = yourActivity.getResources().getConfiguration();
int screenWidthDp = configuration.screenWidthDp; //The current width of the available screen space, in dp units, corresponding to screen width resource qualifier.
int smallestScreenWidthDp = configuration.smallestScreenWidthDp; //The smallest screen size an application will see in normal operation, corresponding to smallest screen width resource qualifier.

See Configuration class reference

Edit: As noted by Nick Baicoianu, this returns the usable width/height of the screen (which should be the interesting ones in most uses). If you need the actual display dimensions stick to the top answer.

回答3:

You are missing default density value of 160.

    2 px = 3 dip if dpi == 80(ldpi), 320x240 screen
    1 px = 1 dip if dpi == 160(mdpi), 480x320 screen
    3 px = 2 dip if dpi == 240(hdpi), 840x480 screen

In other words, if you design you layout with width equal to 160dip in portrait mode, it will be half of the screen on all ldpi/mdpi/hdpi devices(except tablets, I think)

回答4:

How about using this instead ?

final DisplayMetrics displayMetrics=getResources().getDisplayMetrics();
final float screenWidthInDp=displayMetrics.widthPixels/displayMetrics.density;
final float screenHeightInDp=displayMetrics.heightPixels/displayMetrics.density;

回答5:

DisplayMetrics displayMetrics = new DisplayMetrics();

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

int width_px = Resources.getSystem().getDisplayMetrics().widthPixels;

int height_px =Resources.getSystem().getDisplayMetrics().heightPixels;

int pixeldpi = Resources.getSystem().getDisplayMetrics().densityDpi;


int width_dp = (width_px/pixeldpi)*160;
int height_dp = (height_px/pixeldpi)*160;

回答6:

Answer in kotlin:

  context?.let {
        val displayMetrics = it.resources.displayMetrics
        val dpHeight = displayMetrics.heightPixels / displayMetrics.density
        val dpWidth = displayMetrics.widthPixels / displayMetrics.density
    }

回答7:

Get Screen Width and Height in terms of DP with some good decoration:

Step 1: Create interface

public interface ScreenInterface {

   float getWidth();

   float getHeight();

}

Step 2: Create implementer class

public class Screen implements ScreenInterface {
    private Activity activity;

    public Screen(Activity activity) {
        this.activity = activity;
    }

    private DisplayMetrics getScreenDimension(Activity activity) {
        DisplayMetrics displayMetrics = new DisplayMetrics();
        activity.getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
        return displayMetrics;
    }

    private float getScreenDensity(Activity activity) {
        return activity.getResources().getDisplayMetrics().density;
    }

    @Override
    public float getWidth() {
        DisplayMetrics displayMetrics = getScreenDimension(activity);
        return displayMetrics.widthPixels / getScreenDensity(activity);
    }

    @Override
    public float getHeight() {
        DisplayMetrics displayMetrics = getScreenDimension(activity);
        return displayMetrics.heightPixels / getScreenDensity(activity);
    }
}

Step 3: Get width and height in activity:

Screen screen = new Screen(this); // Setting Screen
screen.getWidth();
screen.getHeight();

回答8:

If you just want to know about your screen width, you can just search for "smallest screen width" in your developer options. You can even edit it.

回答9:

Your problem is with casting the float to an int, losing precision. You should also multiply with the factor and not divide.

Do this:

int dp = (int)(pixel*getResources().getDisplayMetrics().density);

来源：https://stackoverflow.com/questions/6465680/how-to-determine-the-screen-width-in-terms-of-dp-or-dip-at-runtime-in-android

标签

android

density-independent-pixel