Question

如果登录为，我正在一个项目中下载一些文件成功，然后打开“主要活动”。如果不是这样，则不会登录也不下载文件并提示用户成功登录下载所需的文件。
失败后，如果用户输入正确的用户名和密码，则它应该同时下载文件并打开“主要活动”。但是，在在这种情况下，我的应用程序崩溃了。如果用户正确输入用户名和初次尝试输入密码时，应用程序运行平稳。
我有3个不同的LiveData对象，因此我可以借助MediatorLiveData观察所有对象，并根据情况调用下一个对象。错误输出：

E / Android运行时：致命异常：主要工艺：com.cesar.sertificar，PID：7482 java.lang.IllegalArgumentException：此源已经与其他观察者一起添加 在android.arch.lifecycle.MediatorLiveData.addSource（MediatorLiveData.java:89）在com.cesar.sertificar.ui.activity.login.LoginViewModel.handleFirstRunProcess（LoginViewModel.java:101）在com.cesar.sertificar.ui.activity.login.LoginActivity.doLogin（LoginActivity.java:68）在com.cesar.sertificar.ui.activity.login.LoginActivity.onClick（LoginActivity.java:88）在android.view.View.performClick（View.java:5214）在android.view.View $ PerformClick.run（View.java:20978）在android.os.Handler.handleCallback（Handler.java:739）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:145）在android.app.ActivityThread.main（ActivityThread.java:6134）在java.lang.reflect.Method.invoke（本机方法）在java.lang.reflect.Method.invoke（Method.java:372）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:1399）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:1194）

LoginViewModel.class

void handleFirstRunProcess() {
        mIsNetworkAvailable.setValue(isAnActiveConnection());
        mProcessResult.addSource(mIsNetworkAvailable, isNetworkAvailable -> {
            mProcessResult.removeSource(mIsNetworkAvailable);
            if (isNetworkAvailable == null) return;

            if (!isNetworkAvailable) {
                mProcessResult.setValue(new NetworkState(NetworkState.Status.FAILED,
                        getApplication().getString(R.string.first_run_network_warning)));
                return;

            }

            doLogin(); //First doLogin
        });

        mProcessResult.addSource(mIsLoginSuccessful, isLoginSuccessful -> {
            mProcessResult.removeSource(mIsLoginSuccessful);
            if (isLoginSuccessful == null) return;

            if (isLoginSuccessful.getStatus() == NetworkState.Status.FAILED) {
                mProcessResult.setValue(new NetworkState(NetworkState.Status.FAILED,
                        getApplication().getString(R.string.login_error)));
                return;
            }

            if (preferenceUtil.getBooleanData(Constants.FIRST_RUN_KEY, true)) {
                downloadEmptyRecipientForm(); //Second download form if first run
            } else {
                mProcessResult.setValue(NetworkState.LOADED); //Open an activity
            }
        });

        mProcessResult.addSource(mIsFormDownloadingSuccessful, isFormDownloaded -> {
            mProcessResult.removeSource(mIsFormDownloadingSuccessful);
            if (isFormDownloaded == null) {
                return;
            }

            if (isFormDownloaded.getStatus() == NetworkState.Status.FAILED) {
                mProcessResult.setValue(new NetworkState(NetworkState.Status.FAILED,
                        getApplication().getString(R.string.first_run_empty_form_error)));
                return;
            }

            mProcessResult.setValue(NetworkState.LOADED); //Third open an activity
            preferenceUtil.putBooleanData(Constants.FIRST_RUN_KEY, false);
        });
    }

Answer 1

我在ViewModel中遇到了同样的问题。似乎这是MediatorLiveData的内部限制。如果看到添加了相同类型的LiveData，则它希望具有相同的侦听器来使用它。我将只添加我的案例，并添加相同的错误类型（无错误，可以正常工作）。错误代码：

networkSum = new MediatorLiveData<>();
    networkSum.addSource(firstData, integer -> {
        if (integer == null) {
            firstIsFinished = false;
            errorInFirst = false;
        } else if (integer == SupportNetworkFunctions.STATUS_IN_PROGRESS) {
            networkSum.postValue(integer);
            firstIsFinished = false;
        } else if (integer == SupportNetworkFunctions.STATUS_FINISHED_WITH_ERROR) {
            firstIsFinished = true;
            errorInFirst = true;
            calculateFinished();
        } else {
            firstIsFinished = false;
            errorInFirst = false;
            calculateFinished();
        }
    });
    networkSum.addSource(secondData, integer -> {
        if (integer == null) {
            secondIsFinished = false;
            errorInSecond = false;
        } else if (integer == SupportNetworkFunctions.STATUS_IN_PROGRESS) {
            networkSum.postValue(integer);
            secondIsFinished = false;
        } else if (integer == SupportNetworkFunctions.STATUS_FINISHED_WITH_ERROR) {
            secondIsFinished = true;
            errorInSecond = true;
            calculateFinished();
        } else {
            secondIsFinished = false;
            errorInSecond = false;
            calculateFinished();
        }
    });

重构后：

networkSum = new MediatorLiveData<>();
    Observer<Integer> statusObserver = new Observer<Integer>() {
        @Override
        public void onChanged(@Nullable Integer integer) {
            if (integer != null) {

                if (integer == SupportNetworkFunctions.STATUS_IN_PROGRESS) {
                    networkSum.postValue(integer);
                } else if (integer == SupportNetworkFunctions.STATUS_FINISHED_WITH_ERROR) {
                    finishedItems++;
                    errorAppeared = true;
                    calculateFinished();
                } else {
                    finishedItems++;
                    calculateFinished();
                }
            }
        }
    };
    networkSum.addSource(firstData, statusObserver);
    networkSum.addSource(secondData, statusObserver);

多个调用的MediatorLiveData观察器错误

1 个答案: