How to write an image file in external storage with runtime permission in android?

This example demonstrates How to write an image file in external storage with runtime permission in 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"?>
<LinearLayout 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"
   android:orientation = "vertical">
   <Button
      android:id = "@+id/save"
      android:text = "save"
      android:layout_width = "wrap_content"
      android:layout_height = "wrap_content" />
</LinearLayout>
In the above code, we have taken a button. When user click on button, it will store data in external storage.
Step 3 − Add the following code to src/MainActivity.java
package com.example.andy.myapplication;

import android.annotation.TargetApi;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.File;
import java.io.FileOutputStream;

public class MainActivity extends AppCompatActivity {
   private static final int PERMISSION_REQUEST_CODE = 100;
   Button save;
   Bitmap bitmap;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      Drawable drawable = getResources().getDrawable(R.drawable.mario);
      bitmap = ((BitmapDrawable)drawable).getBitmap();
      save = findViewById(R.id.save);
      save.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            String state = Environment.getExternalStorageState();
            if (Environment.MEDIA_MOUNTED.equals(state)) {
               if (Build.VERSION.SDK_INT > = 23) {
                  if (checkPermission()) {
                     String path = Environment.getExternalStorageDirectory().toString();
                     File file = new File(path, "UniqueFileName"+".jpg");
                     if (!file.exists()) {
                        Log.d("path", file.toString());
                        try {
                           FileOutputStream fos = new FileOutputStream(file);
                           bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
                           fos.flush();
                           fos.close();
                        } catch (Exception e) {
                           e.printStackTrace();
                        }
                     }
                  } else {
                     requestPermission(); // Code for permission
                  }
               } else {
                  String path = Environment.getExternalStorageDirectory().toString();
                  File file = new File(path, "UniqueFileName"+".jpg");
                  if (!file.exists()) {
                     Log.d("path", file.toString());
                     FileOutputStream fos = null;
                     try {
                        fos = new FileOutputStream(file);
                        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
                        fos.flush();
                        fos.close();
                     } catch (java.io.IOException e) {
                        e.printStackTrace();
                     }
                  }
               }
            }
         }
      });
   }
   
   private boolean checkPermission() {
      int result = ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.WRITE_EXTERNAL_STORAGE);
      if (result = = PackageManager.PERMISSION_GRANTED) {
         return true;
      } else {
         return false;
      }
   }

   private void requestPermission() {
      if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, android.Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
         Toast.makeText(MainActivity.this, "Write External Storage permission allows us to save files. Please allow this permission in App Settings.", Toast.LENGTH_LONG).show();
      } else {
         ActivityCompat.requestPermissions(MainActivity.this, new String[]{android.Manifest.permission.WRITE_EXTERNAL_STORAGE}, PERMISSION_REQUEST_CODE);
      }
   }

   @Override
   public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
      switch (requestCode) {
         case PERMISSION_REQUEST_CODE:
          if (grantResults.length > 0 && grantResults[0] = = PackageManager.PERMISSION_GRANTED) {
            Log.e("value", "Permission Granted, Now you can use local drive .");
          } else {
            Log.e("value", "Permission Denied, You cannot use local drive .");
          }
          break;
      }
   }
}
Step 4 − Add the following code to manifest.xml
<?xml version = "1.0" encoding = "utf-8"?>
<manifest xmlns:android = "http://schemas.android.com/apk/res/android"
   package = "com.example.andy.myapplication">
   <uses-permission android:name = "android.permission.WRITE_EXTERNAL_STORAGE"/>
   <uses-permission android:name = "android.permission.READ_EXTERNAL_STORAGE"/>
   <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 –
In the above result, click on save button to store image in external storage as shown below –
Click here to download the project code