[Java] AlertDialog

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"
    android:layout_gravity="center"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btnAlert"
        android:layout_width="200dp"
        android:layout_height="90dp"
        android:text="Alert"
        android:textSize="26dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

activity_main.xml

 

 

 

 

 

MainActivity.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    AlertDialog alertDialog;

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

        alertDialog = new AlertDialog.Builder(getApplicationContext())
                .setTitle("Title")
                .setMessage("Message")
                .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Toast.makeText(getApplicationContext(), "OK", Toast.LENGTH_SHORT).show();
                    }
                })
                .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Toast.makeText(getApplicationContext(), "Cancel", Toast.LENGTH_SHORT).show();
                    }
                })
                .setNeutralButton("Neutral", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Toast.makeText(getApplicationContext(), "Neutral", Toast.LENGTH_SHORT).show();
                    }
                })
                .create();

        Button btnAlert = findViewById(R.id.btnAlert);
        btnAlert.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                alertDialog.show();
            }
        });
    }

}

 

실행 결과

 

 

 

 

 

 

MainActivity.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    AlertDialog alertDialog;

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

        alertDialog = new AlertDialog.Builder(this)
                .setTitle("Title")
                .setMessage("Message")
                .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Toast.makeText(getApplicationContext(), "OK", Toast.LENGTH_SHORT).show();
                    }
                })
                .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Toast.makeText(getApplicationContext(), "Cancel", Toast.LENGTH_SHORT).show();
                    }
                })
                .setNeutralButton("Neutral", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Toast.makeText(getApplicationContext(), "Neutral", Toast.LENGTH_SHORT).show();
                    }
                })
                .create();

        Button btnAlert = findViewById(R.id.btnAlert);
        btnAlert.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                alertDialog.show();
            }
        });
    }

}

alertDialog = new AlertDialog.Builder(getApplicationContext()) 에서

alertDialog = new AlertDialog.Builder(this) 로 수정

 

실행 결과