使用 LiveData 时无法进入 MainActivity

Question

我的启动画面没有布局文件。这是我试过的：

 public class SplashActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (!isNotAuthenticated()) {
            openLoginInActivity();
        } else {
            openMainActivity();
        }

        finish();
    }

    private void openMainActivity() {
        viewModel.idLiveData.observe(this, new Observer<String>() {
            @Override
            public void onChanged(String id) {
                Intent intent = new Intent(SplashActivity.this, MainActivity.class);
                intent.putExtra("id", id);
                startActivity(intent); //Go to MainActivity
            }
        });
    }
}

使用这段代码，我得到了这个错误：

2019-09-03 12:03:06.615 1871-1934/? E/ViewRootImpl[myapp]: Could not unlock surface
java.lang.IllegalArgumentException
    at android.view.Surface.nativeUnlockCanvasAndPost(Native Method)
    at android.view.Surface.unlockSwCanvasAndPost(Surface.java:382)
    at android.view.Surface.unlockCanvasAndPost(Surface.java:363)
    at android.view.ViewRootImpl.drawSoftware(ViewRootImpl.java:3451)
    at android.view.ViewRootImpl.draw(ViewRootImpl.java:3339)

如果我在 onChanged() 以外的意图下创建，一切正常。我添加了一条日志语句，但 onChanged 甚至没有被触发。那么我怎样才能移动到下一个 activity 而不出现那个错误呢？

编辑：

public class SplashViewModel extends ViewModel {
    private SplashRepository splashRepository;
    MutableLiveData<String> idLiveData;

    @Inject
    SplashViewModel(SplashRepository splashRepository) {
        this.splashRepository = splashRepository;
        idLiveData = splashRepository.addIdToLiveData();
    }
}

Answer 1

我如何在 Splash 中使用实时数据 Activity

class SplashActivity : BaseActivity<ActivitySplashBinding, SplashViewModel>() {
override val mViewModel: SplashViewModel by currentScope.inject()

override fun getLayoutResId(): Int {
    return R.layout.activity_splash
}

override fun initialization() {

}

override fun initializeObserver() {
    mViewModel.liveData.observe(this, Observer {
        if (it) {
            launchActivityWithFinish<LoginActivity>()
        }
    })
}}

这是我的 SplashViewModel

class SplashViewModel : BaseViewModel() {
val liveData = MutableLiveData<Boolean>()

init {
    viewModelScope.launch {
        delay(SPLASH_TIME_OUT)
        liveData.postValue(true)
    }
}}

我的飞溅Activity在java

public class SplashActivity1 extends BaseActivity<ActivitySplashBinding, SplashViewModel> {
@NotNull
@Override
protected SplashViewModel getMViewModel() {
    return new SplashViewModel();
}

@Override
public int getLayoutResId() {
    return R.layout.activity_splash;
}

@Override
public void initialization() {

}

@Override
public void initializeObserver() {
    getMViewModel().getLiveData().observe(this, aBoolean -> {
        if (aBoolean) {
            Intent intent = new Intent(SplashActivity1.this, MainActivity.class);
            intent.putExtra("id", "id");
            startActivity(intent); //Go to MainActivity
            finish();
        }
    });
}}

我的 SplashViewModel 在 Java

public class SplashViewModel extends BaseViewModel {

public MutableLiveData<Boolean> liveData = new MutableLiveData<>(false);

public SplashViewModel(){
    new Handler().postDelayed(() -> liveData.postValue(true),SPLASH_TIME_OUT);
}}

它在 Kotlin 和 Java 中都非常适合我

Answer 2

我以前也遇到过类似的导航问题。我通常通过在 onChanged 中验证参数（在您的情况下为 String id）不为 null 并在内部调用将 id 更改为 null 的视图模型方法来修复它们。

viewModel.idLiveData.observe(this, new Observer<User>() {
            @Override
            public void onChanged(String id) {
                if(id != null) {
                  viewModel.navigationDone();
                  Intent intent = new Intent(SplashActivity.this, MainActivity.class);
                  intent.putExtra("id", id);
                  startActivity(intent); //Go to MainActivity
                }
            }
        });

其中 navigationDone 是一个视图模型方法，例如：

void onNavigationDone() {
    idLiveData.setValue(null);
}

使用 LiveData 时无法进入 MainActivity

Cannot go to MainActivity when using LiveData

android

splash-screen

android-intent

android-studio

android-livedata