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


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package de.pixart.messenger.utils;

import android.os.Looper;

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

public class SerialSingleThreadExecutor implements Executor {

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

    public SerialSingleThreadExecutor() {
        this(false);
    }

    public SerialSingleThreadExecutor(boolean prepareLooper) {
        if (prepareLooper) {
            execute(new Runnable() {
                @Override
                public void run() {
                    Looper.prepare();
                }
            });
        }
    }

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

    protected synchronized void scheduleNext() {
        if ((active = tasks.poll()) != null) {
            executor.execute(active);
        }
    }
}