[안드로이드 스튜디오] 버튼 클릭하여 난수 생성

activity_main.xml 코드

<?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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="30dp"
        android:text="난수 :"
        android:gravity="center">
    </TextView>

    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="난수 생성"
        android:textSize="30dp"
        android:onClick="makeRandom">
    </Button>


</LinearLayout>

---

MainActivity.JAVA 코드

package com.example.random_num;

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

import androidx.appcompat.app.AppCompatActivity;

import java.util.Random;

public class MainActivity extends AppCompatActivity {
    private TextView tv; // 수정
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        tv = findViewById(R.id.textView); // 수정
    }

    public void makeRandom(View v) {
        Random rn = new Random();
        int num = rn.nextInt(100)+1;
        tv.setText("난수 : " + num);
    }

}