Fragment끼리 데이터 전송

Fragment에선 findViewById가 바로 작동이 안됨 findViewById앞에 view를 붙여야 함

 

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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">

    <FrameLayout
        android:id="@+id/framelayout"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

    </FrameLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

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xml 파일 생성

1. res 폴더 > layout 폴더 우클릭 > File name: fragment_1 >

Root element: androidx.constraintlayout.widget.ConstraintLayout

2. design 탭에서 작업

TextView 생성 > Button 생성

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fragment_1.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">

    <TextView
        android:id="@+id/tv_frag1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="100dp"
        android:text="프래그먼트 1"
        android:textSize="36sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_move"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="프래그먼트 2로 이동"
        app:layout_constraintEnd_toEndOf="@+id/tv_frag1"
        app:layout_constraintStart_toStartOf="@+id/tv_frag1"
        app:layout_constraintTop_toBottomOf="@+id/tv_frag1" />
</androidx.constraintlayout.widget.ConstraintLayout>

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xml 파일 복사 후 붙여넣기

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fragment_2.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">

    <TextView
        android:id="@+id/tv_frag2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="100dp"
        android:text="프래그먼트 2"
        android:textSize="36sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_move"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="프래그먼트 1로 이동"
        app:layout_constraintEnd_toEndOf="@+id/tv_frag2"
        app:layout_constraintStart_toStartOf="@+id/tv_frag2"
        app:layout_constraintTop_toBottomOf="@+id/tv_frag2" />
</androidx.constraintlayout.widget.ConstraintLayout>

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MainActivity.java

package com.example.fragmentbundle;

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

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        Fragment1 fragment1 = new Fragment1();
        transaction.replace(R.id.framelayout, fragment1);
        transaction.commit(); // 저장
    }
}

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java 파일 생성

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Fragment1.java

package com.example.fragmentbundle;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentTransaction;

public class Fragment1 extends Fragment {

    private View view;
    private TextView tv_frag1;
    private Button btn_move;
    private String result;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_1, container, false);

        tv_frag1 = view.findViewById(R.id.tv_frag1);
        btn_move = view.findViewById(R.id.btn_move);

        if (getArguments() != null) { // null : 빈 값
            result = getArguments().getString("fromFrag2"); // 프래그먼트 1로 부터 setArguments된 데이터를 받아옴
            tv_frag1.setText(result);
        }

        btn_move.setOnClickListener(new View.OnClickListener() { // 프래그먼트 2로 이동
            @Override
            public void onClick(View view) {
                Bundle bundle = new Bundle(); // 무언가를 담을 준비를 할 수 있는 보따리 or 꾸러미 같은 느낌
                bundle.putString("fromFrag1","khon 프래그먼트 1");
                FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
                Fragment2 fragment2 = new Fragment2();
                fragment2.setArguments(bundle);
                transaction.replace(R.id.framelayout, fragment2);
                transaction.commit(); // 저장
            }
        });

        return view;
    }


}

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java 파일 복사 후 붙여넣기

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Fragment2.java

package com.example.fragmentbundle;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentTransaction;

public class Fragment2 extends Fragment {

    private View view;
    private TextView tv_frag2;
    private Button btn_move;
    private String result;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_2, container, false);

        tv_frag2 = view.findViewById(R.id.tv_frag2);
        btn_move = view.findViewById(R.id.btn_move);

        if (getArguments() != null) { // null : 빈 값
            result = getArguments().getString("fromFrag1"); // 프래그먼트 1로 부터 setArguments된 데이터를 받아옴
            tv_frag2.setText(result);
        }

        btn_move.setOnClickListener(new View.OnClickListener() { // 프래그먼트 2로 이동
            @Override
            public void onClick(View view) { // 프래그먼트 1로 이동
                Bundle bundle = new Bundle(); // 무언가를 담을 준비를 할 수 있는 보따리 or 꾸러미 같은 느낌
                bundle.putString("fromFrag2","khon 프래그먼트 2");
                FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
                Fragment1 fragment1 = new Fragment1();
                fragment1.setArguments(bundle);
                transaction.replace(R.id.framelayout, fragment1);
                transaction.commit(); // 저장
            }
        });

        return view;
    }


}