[Android/Java] Fragment간 값 전달

Demo

MainActivity.java

package com.sjcoding.myapplication;

import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity implements FragmentA.FragmentAListener, FragmentB.FragmentBListener {
    private FragmentA fragmentA;
    private FragmentB fragmentB;

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

        fragmentA = new FragmentA();
        fragmentB = new FragmentB();

        getSupportFragmentManager().beginTransaction()
                .replace(R.id.container_a, fragmentA)
                .replace(R.id.container_b, fragmentB)
                .commit();
    }

    @Override
    public void onInputASent(CharSequence input) {
        fragmentB.updateEditText(input);
    }

    @Override
    public void onInputBSent(CharSequence input) {
        fragmentA.updateEditText(input);
    }

}

Fragment A, B 파일 2개 같은 구조로 만들면됨

package com.sjcoding.myapplication;

import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;

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

public class FragmentA extends Fragment {
    private FragmentAListener listener;
    private EditText editText;
    private Button btnOk;
    
    public interface FragmentAListener {
        void onInputASent(CharSequence input);
    }

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

        editText = v.findViewById(R.id.eidt_text);
        btnOk = v.findViewById(R.id.btn_ok);
        btnOk.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                CharSequence input = editText.getText();
                listener.onInputASent(input);
            }
        });
        return v;
    }

    public void updateEditText(CharSequence newText) {
        editText.setText(newText);
    }

    @Override
    public void onAttach(@NonNull Context context) {
        super.onAttach(context);
        if(context instanceof FragmentAListener) {
            listener = (FragmentAListener) context;
        } else {
            throw new RuntimeException(context.toString() + " must implement FragmentAListener");
        }
    }

    @Override
    public void onDetach() {
        super.onDetach();
        listener = null;
    }
}

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"
    android:id="@+id/container"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <FrameLayout
        android:id="@+id/container_a"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <FrameLayout
        android:id="@+id/container_b"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
</LinearLayout>

fragment_a.xml,fragment_b.xml 둘다 같은 구조로 만들면됨

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:color/holo_green_dark"
    android:gravity="center"
    android:orientation="vertical">

    <EditText
        android:id="@+id/eidt_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/btn_ok"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ok" />


</LinearLayout>