// 第３回終了時のソース
// 文字コード　UTF-8、改行 CRLF

---------------------------------------------------------------
  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=".MainActivity">

    <TextView
        android:id="@+id/text1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="選んでください"
        android:textSize="30sp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button_A"
        android:text="グー"
        android:textSize="30sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toBottomOf="@id/text1"
        app:layout_constraintLeft_toLeftOf="parent" />

    <Button
        android:id="@+id/button_B"
        android:text="チョキ"
        android:textSize="30sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="20sp"
        app:layout_constraintTop_toBottomOf="@id/text1"
        app:layout_constraintLeft_toRightOf="@id/button_A" />

    <Button
        android:id="@+id/button_C"
        android:text="パー"
        android:textSize="30sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="20sp"
        app:layout_constraintTop_toBottomOf="@id/text1"
        app:layout_constraintLeft_toRightOf="@id/button_B" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_centerInParent="true"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/gu"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

    <Button
        android:id="@+id/button_Go"
        android:text="勝負！"
        android:textSize="40sp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@id/imageView"
        app:layout_constraintBottom_toBottomOf="parent" />


</androidx.constraintlayout.widget.ConstraintLayout>


---------------------------------------------------------------
  MainActivity.java
---------------------------------------------------------------

package com.example.janken01;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.ImageView;
import android.content.Intent;

import java.util.Random;

public class MainActivity extends AppCompatActivity {

    TextView txtView01;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btnA = (Button)findViewById(R.id.button_A); // グー
        Button btnB = (Button)findViewById(R.id.button_B); // チョキ
        Button btnC = (Button)findViewById(R.id.button_C); // パー
        Button btnGo = (Button)findViewById(R.id.button_Go); // 勝負ボタン
        txtView01 = (TextView)findViewById(R.id.text1);

        btnGo.setOnClickListener( new View.OnClickListener(){
            public void onClick( View view ){
                Intent intent = new Intent();
                intent.setClassName("com.example.janken01","com.example.janken01.FightActivity");
                startActivity(intent);
            }
        });
        btnA.setOnClickListener( new View.OnClickListener(){
            public void onClick( View view ){
                showResult(1);
                ImageView imageView = (ImageView) findViewById(R.id.imageView);
                imageView.setImageResource(R.drawable.gu);
            }
        });
        btnB.setOnClickListener( new View.OnClickListener(){
            public void onClick( View view ){
                showResult(2);
                ImageView imageView = (ImageView) findViewById(R.id.imageView);
                imageView.setImageResource(R.drawable.choki);
            }
        });
        btnC.setOnClickListener( new View.OnClickListener(){
            public void onClick( View view ){
                showResult(3);
                ImageView imageView = (ImageView) findViewById(R.id.imageView);
                imageView.setImageResource(R.drawable.pa);
            }
        });
    }
    public void showResult(int user){ // 勝敗を決めて表示する
        int b = 0;
        Random rnd = new Random();
        int c = rnd.nextInt(3) + 1; // 乱数 1 or 2 or 3
        if( c==1 ){ // コンピュータの手を表示
            txtView01.setText("コンピュータ：グー");
        }else if( c==2 ){
            txtView01.setText("コンピュータ：チョキ");
        }else{
            txtView01.setText("コンピュータ：パー");
        }
        if( user==c ){ // あいこだった
            return;
        }
        if( user==1 ){ // 勝敗を判別
            if( c==2 ) b=1; else b=0;
        }else if( user==2 ){
            if( c==3 ) b=1; else b=0;
        }else{
            if( c==1 ) b=1; else b=0;
        }

        if( b==1 ){

        }else{

        }

    }
}


---------------------------------------------------------------
  activity_fight.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=".FightActivity">

    <TextView
        android:id="@+id/text1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="FightActivityの画面"
        android:textSize="30sp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>


---------------------------------------------------------------
  FightActivity.java
---------------------------------------------------------------

package com.example.janken01;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class FightActivity extends AppCompatActivity {

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