src/main/java/de/pixart/messenger/utils/SerialSingleThreadExecutor.java


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package de.pixart.messenger.utils;

import android.os.Looper;
import android.util.Log;

import java.util.ArrayDeque;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

import de.pixart.messenger.Config;

public class SerialSingleThreadExecutor implements Executor {

    private final Executor executor = Executors.newSingleThreadExecutor();
	final ArrayDeque<Runnable> tasks = new ArrayDeque<>();
    protected Runnable active;
    private final String name;

    public SerialSingleThreadExecutor(String name) {
        this(name, false);
    }

    SerialSingleThreadExecutor(String name, boolean prepareLooper) {
        if (prepareLooper) {
            execute(Looper::prepare);
        }
        this.name = name;
    }

    public synchronized void execute(final Runnable r) {
        tasks.offer(() -> {
            try {
                r.run();
            } finally {
                scheduleNext();
            }
        });
        if (active == null) {
            scheduleNext();
        }
    }

    private synchronized void scheduleNext() {
        if ((active = tasks.poll()) != null) {
            executor.execute(active);
            int remaining = tasks.size();
            if (remaining > 0) {
                Log.d(Config.LOGTAG, remaining + " remaining tasks on executor '" + name + "'");
            }
        }
    }
}