Added ROOM persistence library. The app now stores the last known cou…

app/build.gradle

@@ -40,4 +40,8 @@ dependencies {
     testImplementation 'junit:junit:4.+'
     androidTestImplementation 'androidx.test.ext:junit:1.1.2'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
+
+    //room
+    implementation "android.arch.persistence.room:runtime:1.1.1"
+    annotationProcessor "android.arch.persistence.room:compiler:1.1.1"
 }

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

@@ -1,14 +1,33 @@
 package com.geeks4ever.counter_app.model;
 
+import android.util.Log;
+
+import androidx.lifecycle.LiveData;
+import androidx.room.ColumnInfo;
+import androidx.room.Entity;
+import androidx.room.PrimaryKey;
+
+@Entity(tableName = "countmodel")
 public class CountModel {
 
+    @PrimaryKey
+    public int key;
+
+    @ColumnInfo(name = "count")
     private String count;
 
-    public String getCount() {
-        return count;
+    public CountModel(int key, String count){
+        this.key = key;
+        this.count = count;
     }
 
-    public void setCount(String count) {
-        this.count = count;
+    public String getCount(){
+        Log.e("db", "getCount"+this.count);
+        return this.count;
     }
+
+    public void setCount(String count){
+
+        Log.e("db", "setCount"+count);
+        this.count = count;}
 }

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

@@ -0,0 +1,22 @@
+package com.geeks4ever.counter_app.model.repository;
+
+import androidx.lifecycle.LiveData;
+import androidx.room.Dao;
+import androidx.room.Insert;
+import androidx.room.Query;
+import androidx.room.Update;
+
+import com.geeks4ever.counter_app.model.CountModel;
+
+import java.util.List;
+
+@Dao
+public interface CountDao {
+
+    @Query("Select * from countmodel where `key`= 0")
+    LiveData<List<CountModel>> getCount();
+
+    @Update
+    void setCount(CountModel count);
+
+}

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

@@ -0,0 +1,33 @@
+package com.geeks4ever.counter_app.model.repository;
+
+import android.content.Context;
+import android.util.Log;
+
+import androidx.room.Database;
+import androidx.room.Room;
+import androidx.room.RoomDatabase;
+
+import com.geeks4ever.counter_app.model.CountModel;
+
+import java.util.concurrent.Executors;
+
+@Database(entities = {CountModel.class}, version = 1, exportSchema = false)
+public abstract class CountDatabase extends RoomDatabase {
+
+    private static CountDatabase db;
+
+    public abstract CountDao countDao();
+
+    public static synchronized CountDatabase getInstance(Context context){
+
+        if(db == null){
+            Log.e("db", "created");
+            db = Room.databaseBuilder(context.getApplicationContext(),
+                    CountDatabase.class, "count_db")
+                    .fallbackToDestructiveMigration()
+                    .build();
+        }
+        return db;
+    }
+
+}

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

@@ -1,43 +1,54 @@
 package com.geeks4ever.counter_app.model.repository;
 
+import android.app.Application;
+import android.os.AsyncTask;
 import android.os.Handler;
+import android.os.Looper;
+import android.util.Log;
 
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.Observer;
 
 import com.geeks4ever.counter_app.model.CountModel;
 
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
 public class CountRepository {
 
-    public static CountRepository repository;
-    private final CountModel countModel;
+    private CountDao countDao;
+    private LiveData<List<CountModel>> countModelLiveData;
 
-    final MutableLiveData<CountModel> data = new MutableLiveData<>();
+    public CountRepository(Application application){
 
-    private CountRepository(){
-        countModel = new CountModel();
-        countModel.setCount("0");
-    }
+        countDao = CountDatabase.getInstance(application).countDao();
+        countModelLiveData = countDao.getCount();
 
-    //Singleton Implementation
-    public static CountRepository getInstance(){
+    }
 
+    public LiveData<List<CountModel>> getCount(){
+        return countModelLiveData;
+    }
 
-        if(repository == null)
-            repository = new CountRepository();
-        return repository;
+    public void setCount(int count){
+        new SetCountAsyncTask(countDao).execute(new CountModel(0, String.valueOf(count)));
     }
 
+    private static class SetCountAsyncTask extends AsyncTask<CountModel, Void, Void>{
 
-    public LiveData<CountModel> getCount(){
-        data.setValue(countModel);
-        return data;
-    }
+        private CountDao countDao;
 
-    public void setCount(int count){
+        private SetCountAsyncTask(CountDao countDao){
+            this.countDao = countDao;
+        }
 
-        countModel.setCount(String.valueOf(count));
-        data.postValue(countModel);
+        @Override
+        protected Void doInBackground(CountModel... countModels) {
+            countDao.setCount(countModels[0]);
+            return null;
+        }
     }
 
 }

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

@@ -12,7 +12,6 @@
 import com.geeks4ever.counter_app.R;
 import com.geeks4ever.counter_app.databinding.HomeScreenBinding;
 import com.geeks4ever.counter_app.viewmodel.CounterViewModel;
-import com.geeks4ever.counter_app.viewmodel.viewModelFactory;
 
 public class HomeScreen extends AppCompatActivity implements Listener {
 
@@ -28,7 +27,8 @@ protected void onCreate(Bundle savedInstanceState) {
 
         binding.setListeners(this);
 
-        viewModel = new ViewModelProvider(this, new viewModelFactory()).get(CounterViewModel.class);
+        viewModel = new ViewModelProvider(this, new ViewModelProvider
+                .AndroidViewModelFactory(getApplication())).get(CounterViewModel.class);
 
         count = viewModel.getCount();
 

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

@@ -1,37 +1,47 @@
 package com.geeks4ever.counter_app.viewmodel;
 
+import android.app.Application;
+import android.content.Context;
+
+import androidx.annotation.NonNull;
+import androidx.lifecycle.AndroidViewModel;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
 import androidx.lifecycle.Observer;
 import androidx.lifecycle.ViewModel;
 
 import com.geeks4ever.counter_app.model.CountModel;
+import com.geeks4ever.counter_app.model.repository.CountDatabase;
 import com.geeks4ever.counter_app.model.repository.CountRepository;
 
+import java.util.List;
 import java.util.Objects;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 
-public class CounterViewModel extends ViewModel {
+public class CounterViewModel extends AndroidViewModel {
 
     private final CountRepository countRepository;
 
     ExecutorService executorService;
 
     final MutableLiveData<String> count = new MutableLiveData<>();
-    final LiveData<CountModel> data;
 
-    public CounterViewModel() {
-        countRepository = CountRepository.getInstance();
-        data = countRepository.getCount();
-        data.observeForever( new Observer<CountModel>() {
+    public CounterViewModel(@NonNull Application application) {
+        super(application);
+
+        count.setValue("0");
+
+        countRepository = new CountRepository(application);
+        countRepository.getCount().observeForever( new Observer<List<CountModel>>() {
             @Override
-            public void onChanged(CountModel countModel) {
-                count.setValue(countModel.getCount());
+            public void onChanged(List<CountModel> countModel) {
+                count.setValue(countModel.get(0).getCount());
             }
         });
     }
 
+
     public LiveData<String> getCount(){
         return count;
     }