AsyncTask任務優先級設置

在Android中，AsyncTask是一個用于執行后臺任務的輕量級類

1. 自定義一個Executor：

import java.util.concurrent.Executor;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class PriorityExecutor implements Executor {
    private static final int CORE_POOL_SIZE = 5;
    private static final int MAXIMUM_POOL_SIZE = 128;
    private static final int KEEP_ALIVE = 1;

    private final ThreadPoolExecutor threadPoolExecutor;

    public PriorityExecutor() {
        threadPoolExecutor = new ThreadPoolExecutor(
                CORE_POOL_SIZE,
                MAXIMUM_POOL_SIZE,
                KEEP_ALIVE,
                TimeUnit.SECONDS,
                new LinkedBlockingQueue<Runnable>());
    }

    @Override
    public void execute(final Runnable command) {
        if (command instanceof PriorityRunnable) {
            threadPoolExecutor.execute((PriorityRunnable) command);
        } else {
            threadPoolExecutor.execute(new PriorityRunnable(command, 0));
        }
    }
}

2. 創建一個實現Comparable接口的Runnable子類，用于設置任務優先級：

public class PriorityRunnable implements Runnable, Comparable<PriorityRunnable> {
    private final Runnable runnable;
    private final int priority;

    public PriorityRunnable(Runnable runnable, int priority) {
        this.runnable = runnable;
        this.priority = priority;
    }

    @Override
    public void run() {
        runnable.run();
    }

    @Override
    public int compareTo(PriorityRunnable another) {
        return Integer.compare(another.priority, this.priority);
    }
}

3. 使用自定義的PriorityExecutor執行AsyncTask：

PriorityExecutor priorityExecutor = new PriorityExecutor();

// 創建一個具有高優先級的任務
AsyncTask<Void, Void, Void> highPriorityTask = new AsyncTask<Void, Void, Void>() {
    // ...
};

// 創建一個具有低優先級的任務
AsyncTask<Void, Void, Void> lowPriorityTask = new AsyncTask<Void, Void, Void>() {
    // ...
};

// 使用自定義的PriorityExecutor執行任務
highPriorityTask.executeOnExecutor(priorityExecutor, (Void[]) null);
lowPriorityTask.executeOnExecutor(priorityExecutor, (Void[]) null);

通過這種方式，你可以為AsyncTask任務設置優先級。請注意，這種方法可能會影響應用程序的性能和響應時間，因此在使用時要謹慎。在大多數情況下，Android系統默認的線程池和任務調度策略已經足夠滿足需求。