AS中級 値の受け渡し編②解説～Activityから別のActivityへ配列、List（コレクション）、オブジェクトを渡す～

Try1.の解答例

MainActivity.java

package com.example.arraytransition;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
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);

        int[] intArray = new int[]{3,7,5};

        Button nextBtn = findViewById(R.id.nextBtn);
        nextBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                intent.putExtra("array",intArray);
                startActivity(intent);
            }
        });


    }
}

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"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="int型の配列　{3,7,5}"
        android:layout_marginTop="60sp"/>

    <Button
        android:id="@+id/nextBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="次ページへ遷移"
        android:layout_marginTop="40sp"/>

</LinearLayout>

SecondActivity.java

package com.example.arraytransition;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

public class SecondActivity extends AppCompatActivity {

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

        Intent intent = getIntent();
        int[] intArrayTake = intent.getIntArrayExtra("array");

        TextView secondView = findViewById(R.id.secondView);
        String viewText = "{" + intArrayTake[0] + "," + intArrayTake[1]+"," + intArrayTake[2] + "}";
        secondView.setText(viewText);
    }
}

activity_second.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=".SecondActivity"
    android:gravity="center_horizontal">

    <TextView
        android:id="@+id/secondView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:layout_marginTop="160sp"/>

</LinearLayout>

Try2の解答例

MainActivity.java

package com.example.arraytransition2;

import androidx.appcompat.app.AppCompatActivity;

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

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

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

        ArrayList<Nameage> nameageList = new ArrayList<>();
        nameageList.add(new Nameage("yamada",29));
        nameageList.add(new Nameage("satou",34));
        nameageList.add(new Nameage("suzuki",67));

        TextView firstView = findViewById(R.id.firstView);
        StringBuilder firstStrBld = new StringBuilder();
        for(Nameage nameage:nameageList){
            firstStrBld.append(nameage.getName()).append(" ").append(nameage.getAge()).append("\n");
        }
        firstView.setText(firstStrBld.toString());

        Button nextBtn = findViewById(R.id.nextBtn);
        nextBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(MainActivity.this,SecondActivity.class);
                intent.putParcelableArrayListExtra("list",nameageList);
                startActivity(intent);
            }
        });


    }
}

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"
    android:orientation="vertical">

    <TextView
        android:id="@+id/firstView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <Button
        android:id="@+id/nextBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="次ページへ"/>

</LinearLayout>

SecondActivity.java

package com.example.arraytransition2;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

import java.util.ArrayList;

public class SecondActivity extends AppCompatActivity {

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

        Intent intent = getIntent();
        ArrayList<Nameage> arrayList = intent.getParcelableArrayListExtra("list");

        TextView secondView = findViewById(R.id.secondView);
        StringBuilder strBld = new StringBuilder();
        for(Nameage nameage:arrayList){
            strBld.append(nameage.getName()).append(" ").append(String.valueOf(nameage.getAge())).append("\n");
        }

        secondView.setText(strBld.toString());
    }
}

activity_second.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=".SecondActivity"
    android:gravity="center_horizontal">

    <TextView
        android:id="@+id/secondView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="80sp"/>

</LinearLayout>

Nameage.java

package com.example.arraytransition2;

import android.os.Parcel;
import android.os.Parcelable;

public class Nameage implements Parcelable {
    private String name;
    private int age;

    public Nameage(String name, int age) {
        this.name = name;
        this.age = age;
    }

    protected Nameage(Parcel in) {
        name = in.readString();
        age = in.readInt();
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(name);
        dest.writeInt(age);
    }

    @Override
    public int describeContents() {
        return 0;
    }

    public static final Creator<Nameage> CREATOR = new Creator<Nameage>() {
        @Override
        public Nameage createFromParcel(Parcel in) {
            return new Nameage(in);
        }

        @Override
        public Nameage[] newArray(int size) {
            return new Nameage[size];
        }
    };

    public String getName() { return name; }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

Try3の解答例

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