Added view, model and viewmodel structures with code that increments the counter when the floating action button is clicked via livedata.

Author: praveen

app/build.gradle

@@ -16,6 +16,10 @@ android {
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 
+    buildFeatures {
+        dataBinding true
+    }
+
     buildTypes {
         release {
             minifyEnabled false

app/src/main/AndroidManifest.xml

@@ -9,7 +9,7 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.CounterAppSimpleMVVMExample">
-        <activity android:name=".MainActivity">
+        <activity android:name=".view.HomeScreen">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
 

app/src/main/java/com/geeks4ever/counter_app/MainActivity.java

@@ -0,0 +1,14 @@
+package com.geeks4ever.counter_app.model;
+
+public class CountModel {
+
+    private String count;
+
+    public String getCount() {
+        return count;
+    }
+
+    public void setCount(String count) {
+        this.count = count;
+    }
+}

app/src/main/java/com/geeks4ever/counter_app/model/CountModel.java

@@ -0,0 +1,40 @@
+package com.geeks4ever.counter_app.model.repository;
+
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+
+import com.geeks4ever.counter_app.model.CountModel;
+
+public class CountRepository {
+
+    public static CountRepository repository;
+    private CountModel countModel;
+
+    final MutableLiveData<CountModel> data = new MutableLiveData<>();
+
+    private CountRepository(){
+        countModel.setCount("0");
+    }
+
+    //Singleton Implementation
+    public static CountRepository getInstance(){
+
+
+        if(repository == null)
+            repository = new CountRepository();
+        return repository;
+    }
+
+
+    public LiveData<CountModel> getCount(){
+        data.setValue(countModel);
+        return data;
+    }
+
+    public void setCount(int count){
+
+        countModel.setCount(String.valueOf(count));
+        data.postValue(countModel);
+    }
+
+}

app/src/main/java/com/geeks4ever/counter_app/model/repository/CountRepository.java

@@ -0,0 +1,36 @@
+package com.geeks4ever.counter_app.view;
+
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.databinding.DataBindingUtil;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.Observer;
+
+import android.os.Bundle;
+
+import com.geeks4ever.counter_app.R;
+import com.geeks4ever.counter_app.databinding.HomeScreenBinding;
+import com.geeks4ever.counter_app.viewmodel.CounterViewModel;
+
+public class HomeScreen extends AppCompatActivity {
+
+    private CounterViewModel viewModel;
+    private LiveData<String> count;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        HomeScreenBinding binding = DataBindingUtil.setContentView(this, R.layout.home_screen);
+        binding.setCount("0");
+
+        count = viewModel.getCount();
+
+        count.observe(this, new Observer<String>() {
+            @Override
+            public void onChanged(String s) {
+                binding.setCount(s);
+            }
+        });
+
+    }
+}

app/src/main/java/com/geeks4ever/counter_app/view/HomeScreen.java

@@ -0,0 +1,44 @@
+package com.geeks4ever.counter_app.viewmodel;
+
+import android.app.Application;
+
+import androidx.annotation.NonNull;
+import androidx.lifecycle.AndroidViewModel;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.Observer;
+
+import com.geeks4ever.counter_app.model.CountModel;
+import com.geeks4ever.counter_app.model.repository.CountRepository;
+
+import java.util.Objects;
+
+public class CounterViewModel extends AndroidViewModel {
+
+    private final CountRepository countRepository;
+
+    final MutableLiveData<String> count = new MutableLiveData<>();
+    final LiveData<CountModel> data;
+
+    public CounterViewModel(@NonNull Application application) {
+        super(application);
+
+        countRepository = CountRepository.getInstance();
+        data = countRepository.getCount();
+        data.observe(getApplication(), new Observer<CountModel>() {
+            @Override
+            public void onChanged(CountModel countModel) {
+                count.setValue(countModel.getCount());
+            }
+        });
+    }
+
+    public LiveData<String> getCount(){
+        return count;
+    }
+
+    public void IncrementCount(){
+        int countint = Integer.parseInt(Objects.requireNonNull(count.getValue()));
+        countRepository.setCount(countint+1);
+    }
+}

app/src/main/java/com/geeks4ever/counter_app/viewmodel/CounterViewModel.java

@@ -0,0 +1,5 @@
+<vector android:height="24dp" android:tint="#FFFFFF"
+    android:viewportHeight="24" android:viewportWidth="24"
+    android:width="24dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillColor="@android:color/white" android:pathData="M19,13h-6v6h-2v-6H5v-2h6V5h2v6h6v2z"/>
+</vector>

app/src/main/res/drawable/add_icon.xml

@@ -0,0 +1,50 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layout 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">
+
+    <data>
+
+        <variable
+            name="count"
+            type="String" />
+
+    </data>
+
+    <androidx.constraintlayout.widget.ConstraintLayout
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        tools:context=".view.HomeScreen">
+
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="click the Button to increase the counter"
+            app:layout_constraintBottom_toTopOf="@+id/count"
+            app:layout_constraintLeft_toLeftOf="parent"
+            app:layout_constraintRight_toRightOf="parent"
+            app:layout_constraintTop_toTopOf="parent" />
+
+        <TextView
+            android:id="@+id/count"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="@{count}"
+            android:textSize="30sp"
+            android:textColor="@color/black"
+            android:textStyle="bold"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintLeft_toLeftOf="parent"
+            app:layout_constraintRight_toRightOf="parent"
+            app:layout_constraintTop_toTopOf="parent" />
+
+        <com.google.android.material.floatingactionbutton.FloatingActionButton
+            android:layout_margin="16dp"
+            app:layout_constraintRight_toRightOf="parent"
+            app:layout_constraintBottom_toBottomOf="parent"
+            android:foreground="@drawable/add_icon"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"/>
+
+    </androidx.constraintlayout.widget.ConstraintLayout>
+</layout>