List all files of a specific type

This is my FileFilter for audio files (you can change the list of extensions for your script).

package com.designfuture.music.util;

import java.io.File;
import java.io.FileFilter;
import java.io.FilenameFilter;
import java.util.ArrayList;

import com.designfuture.framework.util.LogHelper;

public class AudioFileFilter implements FileFilter {

    protected static final String TAG = "AudioFileFilter";
    /**
     * allows Directories
     */
    private final boolean allowDirectories;

    public AudioFileFilter( boolean allowDirectories) {
        this.allowDirectories = allowDirectories;
    }

    public AudioFileFilter() {
        this(true);
    }

    @Override
    public boolean accept(File f) {
        if ( f.isHidden() || !f.canRead() ) {
            return false;
        }

        if ( f.isDirectory() ) {
            return checkDirectory( f );
        }
        return checkFileExtension( f );
    }

    private boolean checkFileExtension( File f ) {
        String ext = getFileExtension(f);
        if ( ext == null) return false;
        try {
            if ( SupportedFileFormat.valueOf(ext.toUpperCase()) != null ) {
                return true;
            }
        } catch(IllegalArgumentException e) {
            //Not known enum value
            return false;    
        }
        return false; 
    }

    private boolean checkDirectory( File dir ) {
        if ( !allowDirectories ) {
            return false;
        } else {
            final ArrayList<File> subDirs = new ArrayList<File>();
            int songNumb = dir.listFiles( new FileFilter() {

                @Override
                public boolean accept(File file) {
                    if ( file.isFile() ) {
                        if ( file.getName().equals( ".nomedia" ) )
                            return false;

                        return checkFileExtension( file );
                    } else if ( file.isDirectory() ){
                        subDirs.add( file );
                        return false;
                    } else
                        return false;
                }
            } ).length;

            if ( songNumb > 0 ) {
                LogHelper.i(TAG, "checkDirectory: dir " + dir.toString() + " return true con songNumb -> " + songNumb );
                return true;
            }

            for( File subDir: subDirs ) {
                if ( checkDirectory( subDir ) ) {
                    LogHelper.i(TAG, "checkDirectory [for]: subDir " + subDir.toString() + " return true" );
                    return true;
                }
            }
            return false;
        }       
    }

    private boolean checkFileExtension( String fileName ) {
        String ext = getFileExtension(fileName);
        if ( ext == null) return false;
        try {
            if ( SupportedFileFormat.valueOf(ext.toUpperCase()) != null ) {
                return true;
            }
        } catch(IllegalArgumentException e) {
            //Not known enum value
            return false;    
        }
        return false; 
    }

    public String getFileExtension( File f ) {
        return getFileExtension( f.getName() );
    }

    public String getFileExtension( String fileName ) {
        int i = fileName.lastIndexOf('.');
        if (i > 0) {
            return fileName.substring(i+1);
        } else 
            return null;
    }

    /**
     * Files formats currently supported by Library
     */
    public enum SupportedFileFormat
    {
        _3GP("3gp"),
        MP4("mp4"),
        M4A("m4a"),
        AAC("aac"),
        TS("ts"),
        FLAC("flac"),
        MP3("mp3"),
        MID("mid"),
        XMF("xmf"),
        MXMF("mxmf"),
        RTTTL("rtttl"),
        RTX("rtx"),
        OTA("ota"),
        IMY("imy"),
        OGG("ogg"),
        MKV("mkv"),
        WAV("wav");

        private String filesuffix;

        SupportedFileFormat( String filesuffix ) {
            this.filesuffix = filesuffix;
        }

        public String getFilesuffix() {
            return filesuffix;
        }
    }

}

You must use FileFilter to get a filtered list of files and directories from a directory:

File[] files = dir.listFiles(new AudioFileFilter());

.

If you select some shared files, such as images or videos, use the library.

For any other types, you can try the regular iOS apache library.

Firstly,

dependencies {
    implementation 'commons-io:commons-io:2.5'
}

Then

val iterator = FileUtils.iterateFiles(
    Environment.getExternalStorageDirectory(),
    FileFilterUtils.suffixFileFilter("pdf"),
    TrueFileFilter.INSTANCE)
while (iterator.hasNext()) {
    val fileINeed = iterator.next()
    // do your job
}

As an example, I use the collection of PDF files. It will process sub-dictionaries automatically. Thus, the iterator contains all the PDF files of my device.

Its APIs are very flexible, powerful and easy to use. You can add many filters or rules to complete your XD assignment.