Hi ,
In previous posts , I have described the properties of View Model and Live Data . But if we use both together , that would be great for an individual application. So here I am going to share a demo where we can see that how both will work together .
Firstly I am creating one layout having one TextView inside , named view_model_layout.xml ->
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/textview7"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:textSize="25sp"
android:textColor="#085937"
android:textStyle="bold"
android:text="TextView" />
</RelativeLayout>
Now Let's create one view model class , named as : RandomNumViewModel.java :
And the Activity class will only be observe the changed value of mRandomNumber , let's have a look on Activity class, named ViewLiveDemoActivity.java:
Here you can see that , activity class only notify when variable value has been changed , and this is done by Live Data concept . If we rotate our device , then the value of variable will not be changed , this concept has been done by View Model . I have attached the screenshots for portrait and landscape modes for better understanding :
In previous posts , I have described the properties of View Model and Live Data . But if we use both together , that would be great for an individual application. So here I am going to share a demo where we can see that how both will work together .
Firstly I am creating one layout having one TextView inside , named view_model_layout.xml ->
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="@+id/textview7"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:textSize="25sp"
android:textColor="#085937"
android:textStyle="bold"
android:text="TextView" />
</RelativeLayout>
Now Let's create one view model class , named as : RandomNumViewModel.java :
package com.development.view_model_live_data;
import android.arch.lifecycle.MutableLiveData;
import android.arch.lifecycle.ViewModel;
import java.util.Random;
public class RandomNumViewModel extends ViewModel {
MutableLiveData mMutableLiveData;
public RandomNumViewModel() {
mMutableLiveData = new MutableLiveData<>();
}
private int[] items = new int[]{1, 2, 3, 44, 65, 87, 22, 65, 87, 22, 90, 63, 4, 8, 50};
private Random random = new Random();
/**
* mRandomNumber , this variable should retain its value,
* on configuration change
*/
private int mRandomNumber = 0;
/**
* used to create a random number from array
* @return
*/
public int createNumber(){
mRandomNumber = items[random.nextInt(items.length)];
return mRandomNumber;
}
/**
* used to get the random number
* @return
* @param txt
*/
/**
* Observe the random number
*/
public MutableLiveData getRandArrayElement(){
if(mRandomNumber == 0){
mRandomNumber = createNumber();
}
mMutableLiveData.setValue(mRandomNumber);
return mMutableLiveData;
}
}
package com.development.view_model_live_data;
import android.arch.lifecycle.Observer;
import android.arch.lifecycle.ViewModelProviders;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;
import com.development.R;
public class ViewLiveDemoActivity extends AppCompatActivity {
TextView txt;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_model_layout);
txt = (TextView)findViewById(R.id.textview7);
RandomNumViewModel randomNumViewModel = ViewModelProviders.of(this).get(RandomNumViewModel.class);
randomNumViewModel.getRandArrayElement().observe(this, new Observer() {
@Override
public void onChanged(@Nullable Object o) {
txt.setText(""+ o);
}
});
}
}
Portrait Mode
Landscape Mode
Here in above images you can see that the variable value remains same after the rotation of device . And this all has been done both using Live Data +View Model . You can take this code and run it by yourself . Happy Coding :)
