小编Yam*_*ion的帖子

我是 Kotlin 协程的新手，并试图了解监督。正如文档所说：

子节点的失败或取消不会导致主管作业失败，也不会影响其其他子节点。

好的，我已经为 JVM 编写了以下代码：

@JvmStatic
fun main(args: Array<String>) = runBlocking {
    val supervisorScope = CoroutineScope(Dispatchers.Default + SupervisorJob())

    // Coroutine #1
    supervisorScope.launch {
        println("Coroutine #1 start")
        delay(100)
        throw RuntimeException("Coroutine #1 failure")
    }

    // Coroutine #2
    supervisorScope.launch {
        for (i in 0 until 5) {
            println("Coroutine #2: $i")
            delay(100)
        }
    }

    supervisorScope.coroutineContext[Job]!!.children.forEach { it.join() }
}

这里一切都很好，Coroutine #1失败既不会影响父级，也不会影响Coroutine #2. 这就是监督的目的。输出与文档一致：

Coroutine #1 start
Coroutine #2: 0
Coroutine #2: 1
Exception in thread "DefaultDispatcher-worker-1" java.lang.RuntimeException: Coroutine …

问题是我尝试使用Dagger 2进行字段注入,但在运行时字段,应注入,始终是null.我也尝试使用MVVM模式.这是我的代码:

ProfileActivity.java:

@Override
protected void onStart() {
    super.onStart();
    Log.d(TAG, "ProfileActivity: onStart: ");

    final ProfileViewModel profileViewModel 
         = ViewModelProviders.of(this).get(ProfileViewModel.class);
    profileViewModel.init();
    profileViewModel.getUser().observe(this, new Observer<User>() {
        @Override
        public void onChanged(@Nullable User user) {
            if (user != null) {
                Log.d(TAG, "ProfileActivity: onStart: " + user.toString());
            } else {
                Log.d(TAG, "ProfileActivity: onStart: user == null");
            }
        }
    });
}

ProfileViewModel.java:

public class ProfileViewModel extends ViewModel {
    private LiveData<User> user;

    @Inject
    UserRepository userRepository;

    public ProfileViewModel() {
        Log.d(TAG, "ProfileViewModel: Constructor: ");
    }

    public void init() …