我正在做一個安卓項目。我想在 android 應(yīng)用程序被殺死時推送通知。所以，我正在創(chuàng)建 BroadcastReceiver 和 Service 類。他們在工作。但是，我有一個問題。這個問題是，當(dāng)用戶登錄我的應(yīng)用程序時；我用 SharedPreferences 存儲這個值。但是，當(dāng)我終止應(yīng)用程序時，此 SharedPreferences 取“空”值。java.lang.NullPointerException：嘗試在空對象引用上調(diào)用接口方法“java.lang.String android.content.SharedPreferences.getString(java.lang.String, java.lang.String)”當(dāng)我搜索時，人們說：“editor.clear();” 但它不起作用。我能做些什么？我的登錄類：public static SharedPreferences UserDetailsSP,UserDetailsSP = getSharedPreferences("UserDetails", MODE_PRIVATE);SharedPreferences.Editor UserDetailsPreferencessEdit = UserDetailsSP .edit();UserDetailsPreferencessEdit.clear();UserDetailsPreferencessEdit.putString("UserName", A);UserDetailsPreferencessEdit.commit();我用這個調(diào)用其他java類：String a1 = Login.UserDetailsSP.getString("UserName","A");
2 回答
侃侃爾雅
TA貢獻(xiàn)1801條經(jīng)驗 獲得超16個贊
您可以像這樣創(chuàng)建共享首選項類：-
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();
}
}
當(dāng)您登錄您的應(yīng)用程序時，請像這樣設(shè)置值：-
setUserLoggedOut(YourActivity.class, false);
并像這樣在啟動畫面上設(shè)置檢查：-
if (isUserLoggedOut(StartActivity.this)) {
startActivity(new Intent(StartActivity.this, LoginActivity.class));
finish();
} else {
startActivity(new Intent(StartActivity.this, MainActivity.class));
finish();
}
繁星coding
TA貢獻(xiàn)1797條經(jīng)驗 獲得超4個贊
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");
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