CODEWITHSUNDEEP
androidfilesharedpreferences
Amir H
Amir H

Reputation: 1126

check if SharedPrefecences exists in Android

I want to check if I have save data in my shared preferences read the file, because if the file not exist and I do that my app wont work.

I search stack overflow and somebody offered to do this:

File f = new File(
"/data/data/your_application_package/shared_prefs/Name_of_your_preference.xml");
if (f.exists()){
    SharedPreferences prefs = getPreferences(MODE_PRIVATE);
    String restoredText = prefs.getString("text", null);
}
else
    Log.d("TAG", "Setup default preferences");

Now I don't know I use it correctly or not. and this is where I save my pref:

SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit();
editor.putString("text", showcountTv.getText().toString());
editor.apply();

Edited: Of course I know I can :

SharedPreferences prefs = getPreferences(MODE_PRIVATE);
String restoredText = prefs.getString("text", null);

but when I do that at the first time my app installed because I nothing have been saved , my program crashed.This is logcat:

06-19 09:53:25.794  20485-20485/com.pirisalavat.amirhossein.amir D/AndroidRuntime﹕ Shutting down VM
06-19 09:53:25.795  20485-20485/com.pirisalavat.amirhossein.amir E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.pirisalavat.amirhossein.amir, PID: 20485
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.pirisalavat.amirhossein.amir/com.pirisalavat.amirhossein.amir.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.toString()' on a null object reference
            at com.pirisalavat.amirhossein.amir.MainActivity.getdataformsharedpref(MainActivity.java:73)
            at com.pirisalavat.amirhossein.amir.MainActivity.onCreate(MainActivity.java:30)
            at android.app.Activity.performCreate(Activity.java:5990)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Upvotes: 1

Views: 209

Answers (3)

Rajat Mehra
Rajat Mehra

Reputation: 1482

Try this:

SharedPreferences prefs = getPreferences(MODE_PRIVATE);

if(prefs.contains("text")) {
   //data exists
} else {
   //data doesn't exist
}

Upvotes: 0

aga
aga

Reputation: 29416

There is a SharedPreferences method called contains which you can use for this purpose: 

if (getPreferences(MODE_PRIVATE).contains("text")) {
    // do something
}

And I don't recommend creating a File pointing to the SharedPreferences - you can't know for sure that this file will be created in the directory called "/data/data/your_application_package/shared_prefs" - there are plenty of vendors and each of them has plenty of devices, so this file can be contained somewhere else/its name will be different/etc. contains() will be enough.

Upvotes: 4

GGDev
GGDev

Reputation: 600

Why don't you just do this:

SharedPreferences prefs = getPreferences(MODE_PRIVATE);
String restoredText = prefs.getString("text", null);

if(restoredText == null) {
    //you don't have any saved data
} else {
    //you do have saved data so do something with it here
}

If restoredText is null then you know that no data has been saved.

Upvotes: 4

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