recursive file observer.

RecursiveFileObserver

import android.os.FileObserver;

import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.Stack;

/**
 * Created by zhengxiaoyong on 2018/3/20.
 */
public abstract class RecursiveFileObserver extends FileObserver {

    private List<SingleFileObserver> mFileObservers;
    private String mPath;
    private int mMask;

    public RecursiveFileObserver(String path) {
        this(path, ALL_EVENTS);
    }

    public RecursiveFileObserver(String path, int mask) {
        super(path, mask);
        mPath = path;
        mMask = mask;
    }

    @Override
    public synchronized void startWatching() {
        if (mFileObservers != null)
            return;

        mFileObservers = new ArrayList<>();

        Stack<String> stack = new Stack<>();
        stack.push(mPath);

        File file;
        String path;
        File[] files;
        while (!stack.empty()) {
            path = stack.pop();
            mFileObservers.add(new SingleFileObserver(path, mMask));

            file = new File(path);
            files = file.listFiles();
            if (files == null)
                continue;

            for (int i = 0; i < files.length; i++) {
                if (files[i] == null)
                    continue;
                if (files[i].isDirectory()
                        && files[i].exists()
                        && !files[i].getName().equals(".")
                        && !files[i].getName().equals("..")) {
                    stack.push(files[i].getPath());
                }
            }
        }

        for (int i = 0; i < mFileObservers.size(); i++) {
            mFileObservers.get(i).startWatching();
        }
    }

    @Override
    public synchronized void stopWatching() {
        if (mFileObservers == null)
            return;

        for (int i = 0; i < mFileObservers.size(); i++) {
            mFileObservers.get(i).stopWatching();
        }

        mFileObservers.clear();
        mFileObservers = null;
    }

    private final class SingleFileObserver extends FileObserver {

        private String mPath;

        SingleFileObserver(String path, int mask) {
            super(path, mask);
            mPath = path;
        }

        @Override
        public void onEvent(int event, String path) {
            String finalPath = mPath + "/" + path;
            RecursiveFileObserver.this.onEvent(event, finalPath);
        }
    }

}