Android java: request multiple permission READ_EXTERNAL_STORAGE & WRITE_EXTERNAL_STORAGE

Minimum API 24 (Android 7.0) 

Note:

• Beginning with Android 4.4 (API level 19) it's no longer necessary for your app to request the WRITE_EXTERNAL_STORAGE permission to write to its own application-specific directories on external storage, which are provided by getExternalFilesDir(). However, the permission is required for API level 18 and lower. Example:
  File extDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
• If the permission is a runtime permission or special permission, and if your app is installed on a device that runs Android 6.0 (API level 23) or higher, you must request the runtime permission or special permission yourself.
• On devices that run Android 4.4 (API level 19) and higher, your app can interact with a documents provider, including external storage volumes and cloud-based storage, using the Storage Access Framework. This framework allows users to interact with a system picker to choose a documents provider and select specific documents and other files for your app to create, open, or modify.
• To support media file access on devices that run Android 9 (API level 28) or lower, declare the READ_EXTERNAL_STORAGE permission and set the maxSdkVersion to 28. See reference 1.
• If your app targets Android 10 (API level 29) or lower, you can temporarily opt out of scoped storage in your production app. If you target Android 10, however, you need to set the value of requestLegacyExternalStorage to true in your app's manifest file.
  

AndroidManifest.xml

...
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"
        android:maxSdkVersion="28"
        />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
        android:maxSdkVersion="28"
        />
...
    <!-- This attribute is "false" by default on apps targeting Android 10. -->
    <!-- android:requestLegacyExternalStorage="true" -->
    <application
        android:requestLegacyExternalStorage="true"
...

MainActivity.java

...
import static android.Manifest.permission.READ_EXTERNAL_STORAGE;
import static android.Manifest.permission.WRITE_EXTERNAL_STORAGE;
...
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);

        // android:maxSdkVersion="28" =  Build.VERSION_CODES.P
        if (android.os.Build.VERSION.SDK_INT <= Build.VERSION_CODES.P) {
            checkMyPermission();
        }
...    int MY_CODE_REQUEST = 123;
    /*
     * 1. check permission
     */
    private void checkMyPermission() {
        // Build.VERSION.SDK_INT >= 23
        // https://riptutorial.com/android/example/23932/multiple-runtime-permissions-from-same-permission-groups
        ArrayList<String> sPermissionRequest = new ArrayList<>();
        int myRead = ContextCompat.checkSelfPermission(getApplicationContext()
                , READ_EXTERNAL_STORAGE);
        int myWrite = ContextCompat.checkSelfPermission(getApplicationContext()
                , WRITE_EXTERNAL_STORAGE);
        if (myRead != PackageManager.PERMISSION_GRANTED) {
            sPermissionRequest.add(getString(R.string.s_permission_read_storage));
        }
        if (myWrite != PackageManager.PERMISSION_GRANTED) {
            sPermissionRequest.add(getString(R.string.s_permission_write_storage));
        }

        if (sPermissionRequest.size()>0) {
            // NOT Granted
            String[] sPermissions = new String[sPermissionRequest.size()];
            for (int i=0;i<sPermissionRequest.size();i++) {
                sPermissions[i]=sPermissionRequest.get(i);
            }
            //sLog.e("dedetok", "sPermissionRequest.size()>0 size "+sPermissions.length); // debug
            requestPermissions(sPermissions, MY_CODE_REQUEST);
        }
    }

    /*
     * 2. receive permission status
     */
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode==MY_CODE_REQUEST) {

            if (permissions.length>0) {
                ArrayList<String> myPermission = new ArrayList<>();
                for (int i=0;i<permissions.length;i++) {
                    //Log.e("dedetok", permissions[i]+" "+grantResults[i]); // debug
                    if (permissions[i].equals(getString(R.string.s_permission_read_storage)) &&
                            grantResults[i]!=PackageManager.PERMISSION_GRANTED) {
                        myPermission.add(READ_EXTERNAL_STORAGE);
                    }
                    if (permissions[i].equals(getString(R.string.s_permission_write_storage)) &&
                            grantResults[i]!=PackageManager.PERMISSION_GRANTED) {
                        myPermission.add(WRITE_EXTERNAL_STORAGE);
                    }
                }
                // Not granted, Request permissions on runtime

                String[] sRequestPermission = new String[myPermission.size()];
                for (int i=0;i<myPermission.size();i++) {
                    sRequestPermission[i] = myPermission.get(i);
                }

                //Log.e("dedetok", "requestCode==MY_CODE_REQUEST "+sRequestPermission.length); // debug
                requestPermissionLauncher.launch(sRequestPermission);
            }
        }
    }

    /*
     * 3. callback user permission
     * Register the permissions callback, which handles the user's response to the
     * system permissions dialog. Save the return value, an instance of
     * ActivityResultLauncher, as an instance variable.
     */
    private final ActivityResultLauncher<String[] > requestPermissionLauncher =
            registerForActivityResult(new ActivityResultContracts.RequestMultiplePermissions()
                    , new ActivityResultCallback() {
                        @Override
                        public void onActivityResult(Object objMap) {
                            //Log.e("dedetok", "onActivityResult "+o.toString()); // debug
                            if (objMap instanceof Map) {
                                StringBuilder mySB = new StringBuilder();
                                Map<String,Boolean> myMapPermission = (Map<String,Boolean>) objMap;
                                myMapPermission.forEach((permissionKey, permissionBoolean)->{
                                    //Log.e("dedetok", permissionKey+" "+READ_EXTERNAL_STORAGE+" "+permissionBoolean); // debug
                                    if (permissionKey.equals(READ_EXTERNAL_STORAGE) && !permissionBoolean) {
                                        mySB.append(READ_EXTERNAL_STORAGE+" ");
                                    }
                                    if (permissionKey.equals(WRITE_EXTERNAL_STORAGE) && !permissionBoolean) {
                                        mySB.append(WRITE_EXTERNAL_STORAGE+" ");
                                    }
                                });
                                //Log.e("dedetok", "mySB "+mySB.toString()); // debug
                                if (mySB.length()>0) {
                                    updateStatus(mySB.toString());
                                }
                            }
                        }
                    });

 References:

1. https://developer.android.com/training/data-storage/shared/documents-files
2. https://developer.android.com/training/permissions/declaring
3. https://developer.android.com/guide/topics/manifest/uses-permission-element
4. https://stackoverflow.com/questions/3093365/how-can-i-check-the-system-version-of-android
5. https://developer.android.com/training/data-storage/use-cases