Button, TextView, Toast

1-1. MainActivity.java (익명 클래스 사용, 클래스 선언 없이 내부 클래스 사용, 메서드의 인자에서 익명의 클래스 사용)

package com.example.tutorial1;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Application;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;

public class MainActivity3 extends AppCompatActivity {

    Button testButton;
    TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);

        textView = (TextView) findViewById(R.id.textView);
        testButton = (Button) findViewById(R.id.testButton);
        testButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(getApplicationContext(), "테스트", Toast.LENGTH_SHORT).show();
                if(testButton.getText().equals("Button"))
                {
                    testButton.setText("clicked");
                    textView.setText("clicked");
                }
                else
                {
                    testButton.setText("Button");
                    textView.setText("Hello!");
                }
            }
        });
    }
}

1-2. MainActivity에 Event Listener 구현

package com.example.tutorial1;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Application;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import org.w3c.dom.Text;

public class MainActivity3 extends AppCompatActivity implements View.OnClickListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);
        Button testButton = (Button) findViewById(R.id.testButton);
        testButton.setOnClickListener(this);
    }
    @Override
    public void onClick(View v)
    {
        switch(v.getId())
        {
            case R.id.testButton:
                Toast.makeText(getApplicationContext(), "버튼클릭", Toast.LENGTH_SHORT).show();
                break;
        }
    }
}

 

2. activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity3">

    <Button
        android:id="@+id/testButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <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_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/testButton" />
</androidx.constraintlayout.widget.ConstraintLayout>