java - 创建另一个任务时取消延迟的任务

Question

我目前有一个延迟任务，每当我点击一个按钮时它就会运行。单击按钮将 boolean 值切换为 true，7 秒后，延迟任务再次将其设置为 false。

但是，如果一个人多次单击该按钮， boolean 值将在打开和关闭之间切换，打开和关闭等等，因为延迟任务堆积如山。如果多次单击按钮而不是让所有延迟的任务相互堆积，是否有一种方法可以简单地延长延迟的任务？

假设延迟任务将等待 7 秒，然后在单击按钮后将 boolean 值从 true 切换为 false。我将如何更改代码，以便如果在延迟任务尚未执行时再次按下按钮，它会取消前一个并简单地执行下一个延迟任务(我将其用于服务器，因此简单地取消前一个任务可能并不意味着这是实际延迟的任务，但其他任务)？

@EventHandler
public void damage (EntityDamageEvent event) {
    Entity victim = event.getEntity();
    if (event instanceof EntityDamageByEntityEvent) {
        EntityDamageByEntityEvent edbeEvent = (EntityDamageByEntityEvent) event;
        if(edbeEvent.getDamager() instanceof Player && victim instanceof Player) {
            EntityDamageByEntityEvent edbeEvent1 = (EntityDamageByEntityEvent) event;
            Entity attacker = edbeEvent1.getDamager();
            //Checks if both players are humans and not NPCS.
            final Player player = (Player) victim;
            final Player player2 = (Player) attacker;
            //Saving the players as the variable Player.
            Damagelist.add(player);

            Damagelist.add(player2);
            //Adds both players to the hashmap to be used by other classes.
            isDamaged = true;
            //Toggles the boolean to true.
            int delay = plugin.getConfig().getInt("StunDuration") * 20;
            //The above line gets the delay time from the config.yml file.
            plugin.getServer().getScheduler().scheduleSyncDelayedTask(plugin, new Runnable() {
                public void run() {         

                    Damagelist.remove(player);
                    Damagelist.remove(player2);
                    //After an x amount of time, removes players from hashmap.
                    isDamaged = false;
                    playeradd = true;
                    //Toggles the booleans around.
                }
            }, delay);
        }
    }
}

Answer 1

为了确保该事件不会针对同一损坏事件运行后续次，您可以使用 isDamaged 变量来验证代码是否应该运行。

由于您在验证事件后将 isDamaged 设置为 true，您只需在事件中尽可能高地检查此值，如果它是 true然后从整个方法中返回，这将停止创建另一个计划任务。

如果您也想阻止玩家受到伤害，那么您也可以取消整个事件，然后再返回以传递给其他插件，在冷却期间不应访问任何伤害。

// End event, add setCancelled(true), and exit method if the isDamaged modifier is set to true
if (isDamaged) {
    event.setCancelled(true);
    return;
}

这是您修改后的代码以显示示例用法。

@EventHandler
public void damage (EntityDamageEvent event) {
    // Get the victim of the damage event.
    Entity victim = event.getEntity();

    // End event, add setCancelled(true), and exit method if the isDamaged modifier is set to true
    if (isDamaged) {
        event.setCancelled(true);
        return;
    }

    if (event instanceof EntityDamageByEntityEvent) {
        // Get the attacker of the event.
        EntityDamageByEntityEvent edbeEvent = (EntityDamageByEntityEvent) event;
        Entity attacker = edbeEvent.getDamager();

        // Continue only if both players are humans and not NPCS.
        if(edbeEvent.getDamager() instanceof Player && victim instanceof Player) {

            // Saving the players as the variable Player.
            final Player player = (Player) victim;
            final Player player2 = (Player) attacker;

            // Add both players to the hashmap to be used by other classes.
            Damagelist.add(player);
            Damagelist.add(player2);

            // Toggle to true.
            isDamaged = true;

            // Get delay time from the config.yml file.
            int delay = plugin.getConfig().getInt("StunDuration") * 20;

            // Setup delayed task to end cooldown set under StunDuration.
            plugin.getServer().getScheduler().scheduleSyncDelayedTask(plugin, new Runnable() {
                // Define task to be run by scheduler.
                public void run() {         
                    // After amount of time set by StunDuration, remove players from hashmap.
                    Damagelist.remove(player);
                    Damagelist.remove(player2);

                    // Toggle back to false;
                    isDamaged = false;
                    playeradd = true;
                }
            }, delay);
        }
    }
}