创建一个名为“ParallelTaskDispatcher”的Car设备类型的任务，用于演示ParallelTaskDispatcher任务分发器派发任务的使用。

修改ability_main.xml

修改ability_main.xml内容如下：

<?xml version="1.0" encoding="utf-8"?>
<DirectionalLayout
    xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:height="match_parent"
    ohos:width="match_parent"
    ohos:orientation="vertical">

    <Text
        ohos:id="$+id:text_start_parallel_task_dispatcher"
        ohos:height="match_parent"
        ohos:width="match_content"
        ohos:background_element="$graphic:background_ability_main"
        ohos:layout_alignment="horizontal_center"
        ohos:text="Start ParallelTaskDispatcher"
        ohos:text_size="50"
    />

</DirectionalLayout>

显示界面效果如下图1所示

自定义任务

MyTask是自定义的一个任务。该任务逻辑比较简单，只是模拟了一个耗时的操作。

package com.waylau.hmos.paralleltaskdispatcher;
 
 import ohos.hiviewdfx.HiLog;
 import ohos.hiviewdfx.HiLogLabel;
 
 import java.util.concurrent.TimeUnit;
 
 public class MyTask implements Runnable {
     private static final String TAG = MyTask.class.getSimpleName();
     private static final HiLogLabel LABEL_LOG =
             new HiLogLabel(HiLog.LOG_APP, 0x00001, TAG);
 
     private String taskName;
 
     public MyTask(String taskName) {
         this.taskName = taskName;
     }
 
     @Override
     public void run() {
         HiLog.info(LABEL_LOG, "before %{public}s run", taskName);
         int task1Result = getRandomInt();
         try {
             // 模拟一个耗时的操作
             TimeUnit.MILLISECONDS.sleep(task1Result);
         } catch (InterruptedException e) {
             e.printStackTrace();
         }
 
         HiLog.info(LABEL_LOG, "after %{public}s run, result is: %{public}s", taskName, task1Result);
     }
 
     // 返回随机整数
     private int getRandomInt() {
         // 获取[0, 1000)之间的int整数。方法如下：
         double a = Math.random();
         int result = (int) (a * 1000);
         return result;
     }
 
 }

这个耗时操作，是通过获取一个随机数，而后根据随机数执行线程sleep实现的。

执行任务派发

修改MainAbilitySlice，增加任务派发器相关的逻辑。

package com.waylau.hmos.paralleltaskdispatcher.slice;
 
 import com.waylau.hmos.paralleltaskdispatcher.MyTask;
 import com.waylau.hmos.paralleltaskdispatcher.ResourceTable;
 import ohos.aafwk.ability.AbilitySlice;
 import ohos.aafwk.content.Intent;
 import ohos.agp.components.Text;
 import ohos.app.dispatcher.Group;
 import ohos.app.dispatcher.TaskDispatcher;
 import ohos.app.dispatcher.task.TaskPriority;
 import ohos.hiviewdfx.HiLog;
 import ohos.hiviewdfx.HiLogLabel;
 
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
 
 public class MainAbilitySlice extends AbilitySlice {
     private static final String TAG = MainAbilitySlice.class.getSimpleName();
     private static final HiLogLabel LABEL_LOG =
             new HiLogLabel(HiLog.LOG_APP, 0x00001, TAG);
 
     @Override
     public void onStart(Intent intent) {
         super.onStart(intent);
         super.setUIContent(ResourceTable.Layout_ability_main);
 
         // 添加点击事件来触发
         Text textStartDispatcher =
                 (Text) findComponentById(ResourceTable.Id_text_start_parallel_task_dispatcher);
         textStartDispatcher.setClickedListener(listener -> startDispatcher());
     }
 
     // 指定任务排发
     private void startDispatcher() {
         String dispatcherName = "MyDispatcher";
 
         TaskDispatcher dispatcher = this.getContext().createParallelTaskDispatcher(dispatcherName, TaskPriority.DEFAULT);
 
         // 创建任务组
         Group group = dispatcher.createDispatchGroup();
 
         // 将任务1加入任务组
         dispatcher.asyncGroupDispatch(group, new MyTask("task1"));
 
         // 将与任务1相关联的任务2加入任务组
         dispatcher.asyncGroupDispatch(group, new MyTask("task2"));
 
         // task3必须要等任务组中的所有任务执行完成后才会执行
         dispatcher.groupDispatchNotify(group, new MyTask("task3"));
     }
 
 
     @Override
     public void onActive() {
         super.onActive();
     }
 
     @Override
     public void onForeground(Intent intent) {
         super.onForeground(intent);
     }
 }

上述代码，

l  Text增加了点击事件，以触发startDispatcher任务

l  startDispatcher方法中创建了ParallelTaskDispatcher任务派发器

l  创建了三个MyTask任务实例，这些任务都是一个任务组。

l  task1和task2通过asyncGroupDispatch方式异步派发。

l  task3通过groupDispatchNotify方式派发。groupDispatchNotify方式是需要等任务组中的所有任务执行完成后才会执行指定任务。

运行

运行应用后，点击2次界面文本“Start ParallelTaskDispatcher”以触发任务派发。此时，控制台输出如下：

01-15 11:29:18.180 15991-16685/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: before task1 run

01-15 11:29:18.181 15991-16686/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: before task2 run

01-15 11:29:18.338 15991-16686/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: after task2 run, result is: 157

01-15 11:29:18.974 15991-16685/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: after task1 run, result is: 793

01-15 11:29:18.976 15991-16744/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: before task3 run

01-15 11:29:19.248 15991-16744/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: after task3 run, result is: 269

01-15 11:29:22.499 15991-16946/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: before task1 run

01-15 11:29:22.500 15991-16947/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: before task2 run

01-15 11:29:22.666 15991-16947/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: after task2 run, result is: 166

01-15 11:29:23.203 15991-16946/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: after task1 run, result is: 704

01-15 11:29:23.204 15991-16995/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: before task3 run

01-15 11:29:23.750 15991-16995/com.waylau.hmos.paralleltaskdispatcher I 00001/MyTask: after task3 run, result is: 545

分别执行了两次，可以看到 task1和 taks2先后顺序是随机的，但task3一定是在task1和 taks2完成之后，才会执行。

源码

更多示例源码，见《跟老卫学HarmonyOS》   https://github.com/waylau/harmonyos-tutorial