What is the DisplayMetrics class ?

The DisplayMetrics class is used to get various information about the screen in android .The information that we can get are the following :

• DENSITY_DEVICE_STABLE : The density of the device in ppi read from the system settings , this density does not change.
• densityDpi : The user can change the display size in android , and set it to Small , Default , Large , Larger , Largest . This will affect the device density . densityDpi is the DENSITY_DEVICE_STABLE plus or minus the set display size.

• density : this is the densityDpi divided by the default density which is 160 ppi . So if we want to know how much a dp will be equal in pixels on this device , we can multiply the dp by the density.
• scaledDensity : this is the density multiplied by the set font size , which can be one of the following : small , normal , large , huge . So it will be the density multiplied by 0.85 , 1 , 1.15 , 1.3 . The scale density can be used to calculate how much an sp is equal in pixels , by multiplying the sp by the scalDensity .
• widthPixels : the device width in pixels
• heightPixels : the device height in pixels
• xdpi : the density of the device on the x axis . This is equal to DENSITY_DEVICE_STABLE
• ydpi : the density of the device on the y axis . This is equal to DENSITY_DEVICE_STABLE.

DisplayMetrics class an example

In this application we are using the DisplayMetrics class to get various information about the screen . The application is formed of a MainActivity.java file

package com.twiserandom.a002displaymetrics;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.DisplayMetrics;
import android.widget.TextView;


public class MainActivity extends AppCompatActivity {

    DisplayMetrics displayMetrics;
    TextView tvDisplayMetrics;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        //call the super method

        setContentView(R.layout.activity_main);
        // set the content view to the layout activity main

        tvDisplayMetrics = (TextView) findViewById(R.id.tvDisplayMetrics);

        displayMetrics = getResources().getDisplayMetrics();
        // Get the displayMetrics for the current device


        //width and height
        tvDisplayMetrics.append(String.format("widthPixels is : %d \n", displayMetrics.widthPixels));
        tvDisplayMetrics.append(String.format("heightPixels is : %d \n\n", displayMetrics.heightPixels));


        // DENSITY_DEVICE_STABLE : read from the system property
        tvDisplayMetrics.append(String.format("DENSITY_DEVICE_STABLE is : %d \n\n", DisplayMetrics.DENSITY_DEVICE_STABLE));


        // densitydpi :  DENSITY_DEVICE_STABLE ± display size [Small , Default , Large , Larger , Largest]
        // density  : ratio of densitydpi / 160
        tvDisplayMetrics.append(String.format("densityDpi (= DENSITY_DEVICE_STABLE ± display size [Small , Default , Large , Larger , Largest]) is : %d \n\n", displayMetrics.densityDpi));
        tvDisplayMetrics.append(String.format("density is densitydpi / 160 : %f \n\n", displayMetrics.density));


        // scaleDensity [ ratio of (densityDpi / 160) * fontScale ]
        tvDisplayMetrics.append(String.format("scaledDensity [ ratio of (densityDpi / 160) * [small :0.85 , normal 1 , large 1.15 , huge 1.3] ]: %f \n\n", displayMetrics.scaledDensity));


        tvDisplayMetrics.append(String.format("xdpi is : %f \n", displayMetrics.xdpi));
        tvDisplayMetrics.append(String.format("ydpi is : %f \n", displayMetrics.ydpi));


    }


}

, and of an activity_main.xml file .

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="5dp"
        android:layout_marginBottom="5dp"
        android:layout_weight="1"
        android:gravity="center"
        android:text="Display Metrics"
        android:textSize="20dp">


    </TextView>

    <TextView
        android:id="@+id/tvDisplayMetrics"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="5"
        android:padding="20dp"
        android:textSize="16dp">


    </TextView>

</LinearLayout>

This application is run on the nexus 4 smartphone .

When the display size is set to default , and the font size is set to normal , we have the following display metrics :

• widthPixels : 768
• heightPixels : 1184
• DENSITY_DEVICE_STABLE : 320
• densityDpi : 320
• denisy : 2
• scaleDensity : 2
• xdpi : 320
• ydpi : 320

so on this phone ,

• 1dp is equal to 1px multiplied by the density and is equal to 2 px.
• 1sp is equal to 1px multiplied the scaleDensity and is equal to 2px.

When the display size is set to Large , and the font size is set to normal , we have the following display metrics :

• widthPixels : 768
• heightPixels : 1174
• DENSITY_DEVICE_STABLE : 320
• densityDpi : 352
• denisy : 2.2
• scaleDensity : 2.2
• xdpi : 320
• ydpi : 320

so on this phone ,

• 1dp is equal to 1px multiplied by the density and is equal to 2.2 px.
• 1sp is equal to 1px multiplied the scaleDensity and is equal to 2.2px

When the display size is set to Default , and the font size is set to large , we have the following display metrics :

• widthPixels : 768
• heightPixels : 1184
• DENSITY_DEVICE_STABLE : 320
• densityDpi : 320
• denisy : 2.0
• scaleDensity : 2.3
• xdpi : 320
• ydpi : 320

so on this phone ,

• 1dp is equal to 1px multiplied by the density and is equal to 2.0 px.
• 1sp is equal to 1px multiplied the scaleDensity and is equal to 2.3 px.

When the display size is set to Larger , and the font size is set to largest , we have the following display metrics :

• widthPixels : 768
• heightPixels : 1165
• DENSITY_DEVICE_STABLE : 320
• densityDpi : 384
• denisy : 2.4
• scaleDensity : 3.12
• xdpi : 320
• ydpi : 320

so on this phone ,

• 1dp is equal to 1px multiplied by the density and is equal to 2.4 px.
• 1sp is equal to 1px multiplied the scaleDensity and is equal to 3.12 px.