【Android】Android Architecture Components のViewModel試してみた

Posted by takaaki On 12月 01, 2018 0 Comment

Android Architecture Components のViewModel

只今、Android Architecture Componentsを勉強しています。ViewModelを試してみたので、備忘録がわりにメモします。

以下は、ViewModelの値をチェックして、
空だったら：テキストをセット→テキストをTextViewにセットする。
それ以外：テキストをTextViewにセットする。
というものです。

build.gradleにライブラリ追加

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    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'

    //Add the library.
    implementation "android.arch.lifecycle:extensions:1.1.1"
}

dependencies {

implementation fileTree(dir: 'libs', include: ['*.jar'])

implementation 'com.android.support:appcompat-v7:28.0.0'

implementation 'com.android.support.constraint:constraint-layout:1.1.3'

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'

//Add the library.

implementation "android.arch.lifecycle:extensions:1.1.1"

}

ViewModel作成

package com.kussuue.testviewmodel;

import android.arch.lifecycle.ViewModel;

public class MainViewModel extends ViewModel {

    private String message = "";

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

package com.kussuue.testviewmodel;

import android.arch.lifecycle.ViewModel;

public class MainViewModel extends ViewModel {

private String message = "";

public String getMessage() {

return message;

}

public void setMessage(String message) {

this.message = message;

}

Activityに反映

package com.kussuue.testviewmodel;

import android.arch.lifecycle.ViewModelProviders;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // ViewModel get the instance via ViewModelProviders.
        MainViewModel mainViewModel = ViewModelProviders.of(this).get(MainViewModel.class);

        // Get the TextView reference.
        TextView textView = findViewById(R.id.textView);

        if (mainViewModel.getMessage().isEmpty()){
            mainViewModel.setMessage("Merry Christmas!!");
            textView.setText(mainViewModel.getMessage());

        } else {
            textView.setText(mainViewModel.getMessage());

        }
    }
}

package com.kussuue.testviewmodel;

import android.arch.lifecycle.ViewModelProviders;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

// ViewModel get the instance via ViewModelProviders.

MainViewModel mainViewModel = ViewModelProviders.of(this).get(MainViewModel.class);

// Get the TextView reference.

TextView textView = findViewById(R.id.textView);

if (mainViewModel.getMessage().isEmpty()){

mainViewModel.setMessage("Merry Christmas!!");

textView.setText(mainViewModel.getMessage());

} else {

textView.setText(mainViewModel.getMessage());

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>

</android.support.constraint.ConstraintLayout>