Error in Saving Realtime Database in my Firebase Account

Question

I've created an App where a user clicks on get Coins Buton, 10 Coins are added in the Texview. User has separate Login Interface. But when I integrated Firebase Realtime Saving Data, It gets Crash.

I want that whenever a User Clicks on getCoins button, Coins should be added in Text Field and these coins should also reflect in my Firebase Data.

Activity_Main Layout.

    <?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.v7.widget.Toolbar
        android:id="@+id/main_toolbar_id"
        android:layout_width="match_parent"
        android:background="@color/colorPrimary"
        android:layout_height="wrap_content">
    </android.support.v7.widget.Toolbar>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <Button
            android:id="@+id/btn"
            android:layout_width="200dp"
            android:layout_height="66dp"
            android:layout_gravity="center"
            android:gravity="center"
            android:text="GET COINS"
            android:textSize="20sp"
            android:textStyle="bold"
            android:layout_centerVertical="true"
            android:layout_centerHorizontal="true"
            />

        <TextView
            android:id="@+id/edittext"
            android:layout_width="317dp"
            android:layout_height="50dp"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:layout_gravity="center"
            android:layout_marginTop="124dp"
            android:gravity="center"
            android:text="COINS: 0"
            android:textSize="40sp"
            android:textStyle="bold" />


    </RelativeLayout>

</android.support.constraint.ConstraintLayout>

Main Activity Class



public class MainActivity extends AppCompatActivity {
    int CoinAmount = 0;
    private Toolbar mainToolbar;
    private  FirebaseAuth mAuth;
    String myStringData;
    Firebase myFirebase;
    TextView myEditText;
    Button btngetcoin;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        myStringData = myEditText.getText().toString();
        Firebase.setAndroidContext(this);

        myFirebase = new Firebase("https://xpensive-b5178.firebaseio.com");
        btngetcoin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Firebase myNewChild= myFirebase.child("PresentCoin");

            }
        });
        btngetcoin= (Button)findViewById(R.id.btn);
        myEditText = (TextView)findViewById(R.id.edittext);

        final RewardedVideoAd RewardAd = MobileAds.getRewardedVideoAdInstance(this);
        RewardAd.loadAd("ca-app-pub-3940256099942544/5224354917", new AdRequest.Builder().build());
        MobileAds.initialize(this);

        btngetcoin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(RewardAd.isLoaded()){
                    RewardAd.show();
                }else{
                    RewardAd.loadAd("ca-app-pub-3940256099942544/5224354917", new AdRequest.Builder().build());

                }
            }
        });
        RewardAd.setRewardedVideoAdListener(new RewardedVideoAdListener() {
            @Override
            public void onRewardedVideoAdLoaded() {

            }

            @Override
            public void onRewardedVideoAdOpened() {

            }

            @Override
            public void onRewardedVideoStarted() {

            }

            @Override
            public void onRewardedVideoAdClosed() {

            }

            @Override
            public void onRewarded(RewardItem rewardItem) {
                CoinAmount= CoinAmount +10;
                myEditText.setText("COINS: "+ CoinAmount);

            }

            @Override
            public void onRewardedVideoAdLeftApplication() {

            }

            @Override
            public void onRewardedVideoAdFailedToLoad(int i) {


            }

            @Override
            public void onRewardedVideoCompleted() {

            }
        });

Logcat Errors-

06-30 20:20:24.988 6074-6074/com.vikramgehlot.xpensive E/AndroidRuntime: FATAL EXCEPTION: main

   Process: com.vikramgehlot.xpensive, PID: 6074

   java.lang.RuntimeException: Unable to start activity ComponentInfo{com.vikramgehlot.xpensive/com.vikramgehlot.xpensive.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2687)

       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2753)

       at android.app.ActivityThread.access$1100(ActivityThread.java:186)

       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1609)

       at android.os.Handler.dispatchMessage(Handler.java:111)

       at android.os.Looper.loop(Looper.java:238)

       at android.app.ActivityThread.main(ActivityThread.java:6016)

       at java.lang.reflect.Method.invoke(Native Method)

       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:937)

       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:798)

    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

       at com.vikramgehlot.xpensive.MainActivity.onCreate(MainActivity.java:45)

       at android.app.Activity.performCreate(Activity.java:6466)

       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1113)

       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2640)

       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2753) 

       at android.app.ActivityThread.access$1100(ActivityThread.java:186) 

       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1609) 

       at android.os.Handler.dispatchMessage(Handler.java:111) 

       at android.os.Looper.loop(Looper.java:238) 

       at android.app.ActivityThread.main(ActivityThread.java:6016) 

       at java.lang.reflect.Method.invoke(Native Method) 

       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:937) 

       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:798)

I'm new to Stackoverflow. So I dont know how this all Works. Kindly Just Help @ADM — Vikram Gehlot, Jun 30 '18 at 10:11
When your application crashed, check for the exception log in Android studio. Copy and paste the error here. — Jayson Chacko, Jun 30 '18 at 10:47
@VikramGehlot The error says btngetcoin is null. See my answer below. — Jayson Chacko, Jul 01 '18 at 02:48

score 0 · Answer 1 · answered Jun 30 '18 at 10:52

If you want to save your data in firebase realtime database then you just need to do something like this

 mDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(mAuth.getCurrentUser().getUid());

Take the reference of your database and then just save it like this

mDatabase.child("Key").setValue(value);

or you can take a reference from this link https://firebase.google.com/docs/database/android/read-and-write

score 0 · Answer 2 · answered Jul 01 '18 at 02:47

The variable btngetcoin is not initialized with a reference to the button object you have. Move the following findViewById() code above your set setOnClickListener,

    myFirebase = new Firebase("https://xpensive-b5178.firebaseio.com");
    // you need to initialize this before attaching listener!!
    btngetcoin= (Button)findViewById(R.id.btn);

    btngetcoin.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Firebase myNewChild= myFirebase.child("PresentCoin");

        }
    });

Error in Saving Realtime Database in my Firebase Account

2 Answers2