我正在处理一个android项目。我想在Android应用终止时推送通知。因此,我正在创建BroadcastReceiver和Service类。他们在工作。但是,我有一个问题。
这个问题是,当用户登录我的应用程序时;我用SharedPreferences破坏了这个值。但是,当我杀死应用程序时,此SharedPreferences取“ null”值。
java.lang.NullPointerException:尝试调用接口方法 'java.lang.String android.content.SharedPreferences.getString(java.lang.String, java.lang.String)”上的空对象引用
当我搜索时,人们说:“ editor.clear();”但这不起作用。我该怎么办?
我的登录类别:
public static SharedPreferences UserDetailsSP,
UserDetailsSP = getSharedPreferences("UserDetails", MODE_PRIVATE);
SharedPreferences.Editor UserDetailsPreferencessEdit = UserDetailsSP .edit();
UserDetailsPreferencessEdit.clear();
UserDetailsPreferencessEdit.putString("UserName", A);
UserDetailsPreferencessEdit.commit();
我用这个调用其他java类:
String a1 = Login.UserDetailsSP.getString("UserName","A");
答案 0 :(得分:0)
You this approach create a SessionManager class
public class AppPrefrences {
private static SharedPreferences mPrefs;
private static SharedPreferences.Editor mPrefsEditor;
public AppPrefrences(Context context)
{
int PRIVATE_MODE = 0;
pref = context.getSharedPreferences("UserDetails", PRIVATE_MODE);
editor = pref.edit();
editor.apply();
}
public static boolean isUserLoggedOut() {
return mPrefs.getBoolean("id_logged_in", false);
}
public static void setUserLoggedOut(Boolean value) {
mPrefsEditor.putBoolean("id_logged_in", value);
mPrefsEditor.commit();
}
public static String getUserName() {
return mPrefs.getString("userName", "");
}
public static void setUserName(String value) {
mPrefsEditor.putString("userName", value);
mPrefsEditor.commit();
}
public static void clearAllPreferences()
{
mPrefsEditor.clear();
mPrefsEditor.commit();
}
}
Inside your activity
AppPrefrences sess = new AppPrefrences(this);
sess.setUserName("A");
答案 1 :(得分:0)
您可以创建这样的共享首选项类:-
public class AppPrefrences {
private static SharedPreferences mPrefs;
private static SharedPreferences.Editor mPrefsEditor;
public static boolean isUserLoggedOut(Context ctx) {
mPrefs = PreferenceManager.getDefaultSharedPreferences(ctx);
return mPrefs.getBoolean("id_logged_in", true);
}
public static void setUserLoggedOut(Context ctx, Boolean value) {
mPrefs = PreferenceManager.getDefaultSharedPreferences(ctx);
mPrefsEditor = mPrefs.edit();
mPrefsEditor.putBoolean("id_logged_in", value);
mPrefsEditor.commit();
}
public static String getUserName(Context ctx) {
mPrefs = PreferenceManager.getDefaultSharedPreferences(ctx);
return mPrefs.getString("userName", "");
}
public static void setUserName(Context ctx, String value) {
mPrefs = PreferenceManager.getDefaultSharedPreferences(ctx);
mPrefsEditor = mPrefs.edit();
mPrefsEditor.putString("userName", value);
mPrefsEditor.commit();
}
public static void clearAllPreferences(Context ctx) {
mPrefs = PreferenceManager.getDefaultSharedPreferences(ctx);
mPrefsEditor = mPrefs.edit();
mPrefsEditor.clear();
mPrefsEditor.commit();
}
}
,当您登录您的应用程序时,请像下面这样设置值:-
setUserLoggedOut(YourActivity.class, false);
并在启动屏幕上设置如下检查:-
if (isUserLoggedOut(StartActivity.this)) {
startActivity(new Intent(StartActivity.this, LoginActivity.class));
finish();
} else {
startActivity(new Intent(StartActivity.this, MainActivity.class));
finish();
}