AS中級 フラグメント編④問題＆解説 ～DialogFragmentを使ってみた～

MainActivity.java

package com.example.smapho5;

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.DialogFragment;


import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

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

        Button button = findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                DialogFragment dialogFragment = new MyDialogFragment();
                dialogFragment.show(getSupportFragmentManager(), "my_dialog");
            }
        });
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:gravity="center_horizontal">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="PUSH"/>

</LinearLayout>

myDialogFragment.java

package com.example.smapho5;

import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.DialogFragment;

public class MyDialogFragment extends DialogFragment {
    @NonNull
    @Override
    public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

        builder.setTitle("タイトル")
                .setMessage("ここに入力してください")
                .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {

                    }
                })
                .setNegativeButton("キャンセル",null)
                .setNeutralButton("あとで",null);

        return builder.create();
    }
}