静态变量返回应用时返回null

Question

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，当我在 android 销毁并重新创建我的活动后尝试访问此变量时，它返回 null 并且应用程序崩溃：

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

我正在尝试保存变量状态：

@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);
}

为了恢复我的变量值，我尝试了两种不同的方法，但没有奏效：

@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");

}

和：

@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");
        }

在 onCreate 方法中，我的 savedInstance 不为空，但是当我尝试在 Log.d 中显示值时，它仍然崩溃。

Answer 1

几点：

1- static 不是 final，因此可以为 null，换句话说，请确保您将这些值设置为某个值。

2- super.onRestoreInstanceState(savedInstanceState); 应该在 protected void onRestoreInstanceState(Bundle savedInstanceState) 的开头而不是结尾调用。

Source (Look at the end of the page)

告诉我，干杯。