Questions:-
I will make a score adding and resting the score to 0 example.To understand the basic concept of a view model first i will create a normal way to do the problem.
1. I used data binding concept here so for that i have used below line of code in app gradle file:-
dataBinding {
enabled = true
}
2. Now create the UI first, activity.main.xml-
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout 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">
<TextView
android:id="@+id/score"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_marginBottom="30dp"
android:text="0"
android:textSize="40sp" />
<Button
android:id="@+id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/score"
android:layout_centerHorizontal="true"
android:layout_marginBottom="20dp"
android:background="@color/colorAccent"
android:text="Start"
android:textColor="#ffffff" />
<Button
android:id="@+id/reset"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/start"
android:layout_centerHorizontal="true"
android:text="reset" />
</RelativeLayout>
</layout>
3. MainActivity.java
public class MainActivity extends AppCompatActivity {
private int num = 0;
private ActivityMainBinding binding;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
binding.start.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
addScore();
}
});
binding.reset.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
resetValue();
}
});
}
private void addScore() {
num++;
binding.score.setText(String.valueOf(num));
}
private void resetValue() {
num = 0;
binding.score.setText(String.valueOf(num));
}
}
----------------MainActivityViewModel.java-------------------
package com.example.androidviewmodelbasicex;
import androidx.lifecycle.ViewModel;
public class MainActivityViewModel extends ViewModel {
private Integer score = 0;
public Integer getScore() {
if (score == null)
score = 0;
return score;
}
public void setScore() {
score++;
}
public void resetScore() {
score = 0;
}
}
-----------------MainActivity.java------------------
package com.example.androidviewmodelbasicex;
import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.ViewModelProvider;
import androidx.lifecycle.ViewModelProviders;
import android.os.Bundle;
import android.view.View;
import com.example.androidviewmodelbasicex.databinding.ActivityMainBinding;
public class MainActivity extends AppCompatActivity {
private ActivityMainBinding binding;
private MainActivityViewModel viewModel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
viewModel = ViewModelProviders.of(this).get(MainActivityViewModel.class);
binding.score.setText(String.valueOf(viewModel.getScore()));
binding.start.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
viewModel.setScore();
binding.score.setText(String.valueOf(viewModel.getScore()));
}
});
binding.reset.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
viewModel.resetScore();
binding.score.setText(String.valueOf(viewModel.getScore()));
}
});
}
}
I will make a score adding and resting the score to 0 example.To understand the basic concept of a view model first i will create a normal way to do the problem.
1. I used data binding concept here so for that i have used below line of code in app gradle file:-
dataBinding {
enabled = true
}
2. Now create the UI first, activity.main.xml-
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<RelativeLayout 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">
<TextView
android:id="@+id/score"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_marginBottom="30dp"
android:text="0"
android:textSize="40sp" />
<Button
android:id="@+id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/score"
android:layout_centerHorizontal="true"
android:layout_marginBottom="20dp"
android:background="@color/colorAccent"
android:text="Start"
android:textColor="#ffffff" />
<Button
android:id="@+id/reset"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/start"
android:layout_centerHorizontal="true"
android:text="reset" />
</RelativeLayout>
</layout>
3. MainActivity.java
public class MainActivity extends AppCompatActivity {
private int num = 0;
private ActivityMainBinding binding;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
binding.start.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
addScore();
}
});
binding.reset.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
resetValue();
}
});
}
private void addScore() {
num++;
binding.score.setText(String.valueOf(num));
}
private void resetValue() {
num = 0;
binding.score.setText(String.valueOf(num));
}
}
############################
-----------------Same example viewModel--------------------------MainActivityViewModel.java-------------------
package com.example.androidviewmodelbasicex;
import androidx.lifecycle.ViewModel;
public class MainActivityViewModel extends ViewModel {
private Integer score = 0;
public Integer getScore() {
if (score == null)
score = 0;
return score;
}
public void setScore() {
score++;
}
public void resetScore() {
score = 0;
}
}
-----------------MainActivity.java------------------
package com.example.androidviewmodelbasicex;
import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.ViewModelProvider;
import androidx.lifecycle.ViewModelProviders;
import android.os.Bundle;
import android.view.View;
import com.example.androidviewmodelbasicex.databinding.ActivityMainBinding;
public class MainActivity extends AppCompatActivity {
private ActivityMainBinding binding;
private MainActivityViewModel viewModel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
viewModel = ViewModelProviders.of(this).get(MainActivityViewModel.class);
binding.score.setText(String.valueOf(viewModel.getScore()));
binding.start.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
viewModel.setScore();
binding.score.setText(String.valueOf(viewModel.getScore()));
}
});
binding.reset.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
viewModel.resetScore();
binding.score.setText(String.valueOf(viewModel.getScore()));
}
});
}
}
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