Android 返回应用程序时，静态变量返回null

我有两个活动，第一个是LoginActivity，我有五个静态变量：

public static Login loginTargetApp;
public static Gateway gateway;
public static Login loginGateway;
public static OfflineUser offlineUser;
public static boolean isLoggedIn;

在我的第二个活动MainViewActivity中，在android销毁并重新创建我的活动后，当我尝试访问此变量时，它返回null，应用程序崩溃：

jsonTempDownload = new File(Constants.DEST_PATH_PARENT + File.separator
                    + LoginActivity.gateway.getUuidInstituicao() + Constants.JSON_TEMP_DOWNLOAD);

我试图通过以下方式保存变量状态：

@Override
protected void onSaveInstanceState(Bundle saveInstanceState) {

    saveInstanceState.putParcelable("loginTargetApp", LoginActivity.loginTargetApp);
    saveInstanceState.putParcelable("gateway", LoginActivity.gateway);
    saveInstanceState.putParcelable("loginGateway", LoginActivity.loginGateway);
    saveInstanceState.putParcelable("offlineUser", LoginActivity.offlineUser);

    saveInstanceState.putBoolean("isLoggedIn", LoginActivity.isLoggedIn);

    super.onSaveInstanceState(saveInstanceState);
}

为了恢复变量值，我尝试了两种不同的方法，但都不起作用：

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {

    super.onRestoreInstanceState(savedInstanceState);

    LoginActivity.loginTargetApp = savedInstanceState.getParcelable("loginTargetApp");
    LoginActivity.gateway = savedInstanceState.getParcelable("gateway");
    LoginActivity.loginGateway = savedInstanceState.getParcelable("loginGateway");
    LoginActivity.offlineUser = savedInstanceState.getParcelable("offlineUser");

    LoginActivity.isLoggedIn = savedInstanceState.getBoolean("isLoggedIn");

}

以及：

在onCreate方法中，我的savedInstance不是null，但当我尝试在Log.d中显示值时，它仍然崩溃。

两点：

1-

static

不是

final

，因此可以为null，换句话说，请确保您正在将这些值设置为某个值

2-

super.onRestoreInstanceState（savedInstanceState），

而不是结束时

---

让我知道，干杯。

当活动被销毁并重新创建时，您的静态变量将被重新初始化，但我正在saveInstanceState中保存它的状态，并在onRestoreInstanceState中重新分配。我的回答有帮助吗？您是对的，我尝试获取从未实例化的值时出错了，谢谢兄弟

@Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        Log.d(Constants.MAIN_VIEW_ACTIVITY, "----------------");
        Log.d(Constants.MAIN_VIEW_ACTIVITY, "Abrindo MainViewActivity...");
        Log.d(Constants.MAIN_VIEW_ACTIVITY, "----------------");

        if (savedInstanceState != null) {

            // Restore value of members from saved state

            LoginActivity.isLoggedIn = savedInstanceState.getBoolean("isLoggedIn");
            boolean isLoggedIn = savedInstanceState.getBoolean("isLoggedIn");
            Log.d(Constants.MAIN_VIEW_ACTIVITY, "VARIÁVEL NORMAL: " + isLoggedIn);
            Log.d(Constants.MAIN_VIEW_ACTIVITY, "VARIÁVEL ESTÁTICA: " + LoginActivity.isLoggedIn);

            LoginActivity.loginTargetApp = savedInstanceState.getParcelable("loginTargetApp");
            Login loginTargetApp = savedInstanceState.getParcelable("loginTargetApp");
            Log.d(Constants.MAIN_VIEW_ACTIVITY, "VARIÁVEL NORMAL: " + loginTargetApp.getEmailAndress());
            Log.d(Constants.MAIN_VIEW_ACTIVITY, "VARIÁVEL ESTÁTICA: " + LoginActivity.loginTargetApp.getEmailAndress());

            LoginActivity.gateway = savedInstanceState.getParcelable("gateway");
            LoginActivity.loginGateway = savedInstanceState.getParcelable("loginGateway");

            LoginActivity.offlineUser = savedInstanceState.getParcelable("offlineUser");
            OfflineUser offlineUser = savedInstanceState.getParcelable("offlineUser");
            Log.d(Constants.MAIN_VIEW_ACTIVITY, "VARIÁVEL NORMAL: " + offlineUser.getEmail());
            Log.d(Constants.MAIN_VIEW_ACTIVITY, "VARIÁVEL ESTÁTICA: " + LoginActivity.offlineUser.getEmail());

        } else {

            Log.d(Constants.MAIN_VIEW_ACTIVITY, "SAVED INSTANCE STATE IS NULL");
        }