Firebase connection issues

Question

The code below crashes my app before it gets a chance to run:

public class MainActivity extends AppCompatActivity {

    EditText txtname,txtage,txtphone,txtheight;
    Button btnsave;
    DatabaseReference reff;
    Schedule schedule;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        txtname=(EditText)findViewById(R.id.txtname);
        txtage=(EditText)findViewById(R.id.txtage);
        txtphone=(EditText)findViewById(R.id.txtphone);
        txtheight=(EditText)findViewById(R.id.txtheight);
        btnsave=(Button)findViewById(R.id.btnsave);
        schedule=new Schedule();
        reff=FirebaseDatabase.getInstance().getReference().child("Schedule");
        btnsave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                int agea=Integer.parseInt(txtage.getText().toString().trim());
                Float hit=         
                Float.parseFloat(txtheight.getText().toString().trim());
                Long phn=Long.parseLong(txtphone.getText().toString().trim());

                schedule.setName(txtname.getText().toString().trim());
                schedule.setAge(agea);
                schedule.setHt(hit);
                schedule.setPh(phn);
                reff.child("schedule1").setValue(schedule);
                Toast.makeText(MainActivity.this, "Data inserted successfully", 
                Toast.LENGTH_LONG).show();
            }
        });



        Toast.makeText(MainActivity.this, "Firebase connection Success", 
        Toast.LENGTH_LONG).show();
      }
}

I am new to Firebase and not sure where I am going wrong, the code runs when my reff = firebase line is commented out so there must be a problem with the way I am referencing, but obviously, the code does nothing without the connection to the database, if anyone could help.

Logs from crash as requested:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.notihng/com.example.notihng.MainActivity}: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.example.notihng. Make sure to call FirebaseApp.initializeApp(Context) first. 

at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2946) 

at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3081) 

at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 

at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 

at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 

at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1831) 

at android.os.Handler.dispatchMessage(Handler.java:106) 

at android.os.Looper.loop(Looper.java:201) 

at android.app.ActivityThread.main(ActivityThread.java:6806) 

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

at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547) 

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873) 

Caused by: java.lang.IllegalStateException: Default FirebaseApp is not initialized in this process com.example.notihng. Make sure to call FirebaseApp.initializeApp(Context) first. 

at com.google.firebase.FirebaseApp.getInstance(com.google.firebase:firebase-common@@16.0.4:240) 

at com.google.firebase.database.FirebaseDatabase.getInstance(com.google.firebase:firebase-database@@16.0.6:67) 

at com.example.notihng.MainActivity.onCreate(MainActivity.java:28) 

at android.app.Activity.performCreate(Activity.java:7210) 

at android.app.Activity.performCreate(Activity.java:7201) 

at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272) 

at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2926) 

... 11 more 

App Gradle File:

 apply plugin: 'com.android.application'
 apply plugin: 'com.google.gms.google-services'

 android {
     compileSdkVersion 28
     defaultConfig {
         applicationId "com.example.notihng"
         minSdkVersion 21
         targetSdkVersion 28
         versionCode 1
         versionName "1.0"
         testInstrumentationRunner 
 "android.support.test.runner.AndroidJUnitRunner"
     }
     buildTypes {
         release {
             minifyEnabled false
             proguardFiles getDefaultProguardFile('proguard-android- 
optimize.txt'), 'proguard-rules.pro'
         }
     }
 }

 dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
     implementation 'com.android.support:appcompat-v7:28.0.0'
     implementation 'com.android.support:support-v4:28.0.0'
     implementation 'com.android.support.constraint:constraint- 
      layout:1.1.3'
     implementation 'com.google.firebase:firebase-database:16.0.6'
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'com.android.support.test:runner:1.0.2'
     androidTestImplementation 
     'com.android.support.test.espresso:espresso- 
      core:3.0.2'
    }
    apply plugin: 'com.google.gms.google-services'

Answer 1

Got it working guys thanks for all the help. It was the dependencies in project gradle, when i changed them to classpath 'com.android.tools.build:gradle:3.3.1' classpath 'com.google.gms:google-services:3.0.0' It promted me to install new sdk files. Not sure if the default dependencies just werent working or the downloading files was the fix, but its working now anyways, thanks again.

Answer 2

The crash report clearly says the problem in your code.

Make sure to call FirebaseApp.initializeApp(Context) first

You need to initialize it first before using it like the following.

FirebaseApp.initializeApp(this);

In your build.gradle file, there are two declarations of adding the following plugin.

apply plugin: 'com.google.gms.google-services'

I would like to suggest you remove the first one. Keep the one at the end of your gradle file.