How can I generate random number in a given range in Android?

This example demonstrates how do I generate random number in a given range on android.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
   xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context=".MainActivity">
   <Button
      android:id="@+id/btn_generate"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_below="@id/et_max"
      android:layout_centerVertical="true"
      android:layout_centerHorizontal="true"
      android:text="GENERATE" />
   <EditText
      android:id="@+id/et_min"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_alignParentTop="true"
      android:layout_centerHorizontal="true"
      android:ems="10"
      android:hint="Minimum"
      android:inputType="number"/>
   <EditText
      android:id="@+id/et_max"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_below="@id/et_min"
      android:layout_centerHorizontal="true"
      android:ems="10"
      android:hint="Maximum"
      android:inputType="number"/>
   <TextView
      android:id="@+id/tv_output"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_below="@id/btn_generate"
      android:textSize="30dp"
      android:layout_centerHorizontal="true"
      android:hint="Output"
      android:text="" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.java

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import java.util.Random;
public class MainActivity extends AppCompatActivity {
   EditText et_min, et_max;
   Button btn_generate;
   TextView tv_output;
   Random r;
   int min, max, output;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      r = new Random();
      et_min = (EditText)findViewById(R.id.et_min);
      et_max = (EditText)findViewById(R.id.et_max);
      btn_generate = (Button)findViewById(R.id.btn_generate);
      tv_output = (TextView)findViewById(R.id.tv_output);
      btn_generate.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            String tempMin, tempMax;
            tempMin = et_min.getText().toString();
            tempMax = et_max.getText().toString();
            if (!tempMin.equals("") &&!tempMax.equals("")){
               min = Integer.parseInt(tempMin);
               max = Integer.parseInt(tempMax);
               if (max > min){
                  output = r.nextInt((max - min) +1) + min;
                  tv_output.setText("" + output);
               }
            }
         }
      });
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run  icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen −

Click here to download the project code.