How to check an Android device is HDPI screen or MDPI screen?

I want to check this to fetch different images by internet. How to do that?

density = getResources().getDisplayMetrics().density;

// return 0.75 if it's LDPI
// return 1.0 if it's MDPI
// return 1.5 if it's HDPI
// return 2.0 if it's XHDPI
// return 3.0 if it's XXHDPI
// return 4.0 if it's XXXHDPI

You can check the screen density with:

switch (getResources().getDisplayMetrics().densityDpi) {
case DisplayMetrics.DENSITY_LOW:
    // ...
    break;
case DisplayMetrics.DENSITY_MEDIUM:
    // ...
    break;
case DisplayMetrics.DENSITY_HIGH:
    // ...
    break;
case DisplayMetrics.DENSITY_XHIGH:
    // ...
    break;
}

EDIT Be aware that as Android evolves, other values should be included in the switch cases. As of this edit, this includes DisplayMetrics.DENSITY_TV and DisplayMetrics.DENSITY_XXHIGH. Consult the docs for the latest info; I'm not going to bother maintaining this answer.

As of 2018, you can use the below method -

    public static String getDeviceDensityString(Context context) {
    switch (context.getResources().getDisplayMetrics().densityDpi) {
        case DisplayMetrics.DENSITY_LOW:
            return "ldpi";
        case DisplayMetrics.DENSITY_MEDIUM:
            return "mdpi";
        case DisplayMetrics.DENSITY_TV:
        case DisplayMetrics.DENSITY_HIGH:
            return "hdpi";
        case DisplayMetrics.DENSITY_260:
        case DisplayMetrics.DENSITY_280:
        case DisplayMetrics.DENSITY_300:
        case DisplayMetrics.DENSITY_XHIGH:
            return "xhdpi";
        case DisplayMetrics.DENSITY_340:
        case DisplayMetrics.DENSITY_360:
        case DisplayMetrics.DENSITY_400:
        case DisplayMetrics.DENSITY_420:
        case DisplayMetrics.DENSITY_440:
        case DisplayMetrics.DENSITY_XXHIGH:
            return "xxhdpi";
        case DisplayMetrics.DENSITY_560:
        case DisplayMetrics.DENSITY_XXXHIGH:
            return "xxxhdpi";
    }
}

But as @Ted pointed always consult the official docs before using

From the above answers, I combined them and created the below function:

    public static String getDeviceDensity(Context context){
    String deviceDensity = "";
    switch (context.getResources().getDisplayMetrics().densityDpi) {
        case DisplayMetrics.DENSITY_LOW:
            deviceDensity =  0.75 + " ldpi";
            break;
        case DisplayMetrics.DENSITY_MEDIUM:
            deviceDensity =  1.0 + " mdpi";
            break;
        case DisplayMetrics.DENSITY_HIGH:
            deviceDensity =  1.5 + " hdpi";
            break;
        case DisplayMetrics.DENSITY_XHIGH:
            deviceDensity =  2.0 + " xhdpi";
            break;
        case DisplayMetrics.DENSITY_XXHIGH:
            deviceDensity =  3.0 + " xxhdpi";
            break;
        case DisplayMetrics.DENSITY_XXXHIGH:
            deviceDensity =  4.0 + " xxxhdpi";
            break;
        default:
            deviceDensity = "Not found";
    }
    return deviceDensity;
}

Now, on which device you want to get the density information and which folder it will be used, just add the above method in that activity and add the below line in onCreate

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);

    Log.d("Screen Density: ", Helper.getDeviceDensity(this));

}

For React Native to check which size is currently of device

import { PixelRatio } from 'react-native';   
 switch(PixelRatio.get()) {
      case 1:
      return "mdpi";
      case 1.5:
      return "hdpi";
      case 2:
      return "xhdpi";
      case 3:
      return "xxhdpi";
      case 3.5:
      return "xxxhdpi";
    }

On some devices (mine is Galaxy Tab3), both density and densityDpi return strange values like 1.33(density), 213(densityDpi). So my solution is to add these flag :

> <item type="bool" > name="is_mdpi">[bool]</item>
<item > type="bool" > name="is_hdpi">[bool]</item>
<item > type="bool" > name="is_xhdpi">[bool]</item>
<item > type="bool" > name="is_xxhdpi">[bool]</item>

to 4 values.xml files, put these under corresponding res/values-[xxx]/ folders.

You should always check the interval not only break point values!

According to android documentation: https://developer.android.com/reference/android/util/DisplayMetrics

Check it like this in Kotlin:

    when {
                val density: Float = context?.resources?.displayMetrics?.density

                // ldpi
                (density <= 0.75f) -> mulFactor = 0.75f

                // mdpi
                (density >= 0.75f && density <= 1.0f) -> mulFactor = 1.0f

                // hdpi
                (density > 1.0f && density <= 1.5f) -> mulFactor = 1.5f

                // xhdpi
                (density > 1.5f && density <= 2.0f) -> mulFactor = 2.0f

                // xxhdpi
                (density > 2.0f && density <= 3.0f) -> mulFactor = 3.0f

                // xxxhdpi
                (density > 3.0f) -> mulFactor = 4.0f

         }
         return mulFactor;