Android Sharedpreference 检查用户是否已经登录

Question

I want to check if the user is logged in or not by checking if Their ID is null or not. if the ID is null then start loginActivity , if not then carry on.

I make a separate class for my sharedpreference and have imported it, declared it. however the program returned Nullpointer Error when I run it. My intention was exactly to check whether the string id is null or not.

FYI: at the moment, there is no user logged in, so the App should run the LoginActivity becauase getMyID() should return null and therefore run the condition

Please tell me where did I make mistake and how should I do it instead

my setter and getter for ID in sharedpreference:

public void setMyID(String myID) {
    editor.putString(MYUSERID, myID);
    editor.commit();
}

public String getMyID() {
    return pref_global.getString(MYUSERID, null);
}

This is my mainactivity file

public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
setTitle("Selamat Datang");

myContext = this;
mAuth = FirebaseAuth.getInstance();
mFirebaseAnalytics = FirebaseAnalytics.getInstance(myContext);

checkLoginState();

}

public void checkLoginState(){
    if(prefManager.getMyID() == null ){
        Intent intent = new Intent(MainActivity.this, LoginActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
        startActivity(intent);
        finish();
    }
}

Answer 1

I think default value parameter of getString(MYUSERID, "default value") is non null type, you just need to set it to another non null string. Hope it help.

Answer 2

When pulling data from sharedPreferences, you can try entering "" instead of entering the default value as null. I am sharing the sample code below;

public String getMyID() {
   return pref_global.getString(MYUSERID, "");
}


public void checkLoginState(){
if(prefManager.getMyID() == ""){
    Intent intent = new Intent(MainActivity.this, LoginActivity.class);
    intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
    startActivity(intent);
    finish();
}

}