[Android Studio] Fragment

Fragment

 

Fragment는 Activity 내에 생성되는, UI 구성을 여러 개의 모듈 단위로 작성할 수 있도록 해주는 기능이다. 또한, 한번 작성된 Fragment는 여러 Activity에서 재사용이 가능하므로 UI 구성에 소요되는 작업량을 많은 부분을 감소시킬 수 있다.

 

xml : main

 

<?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">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:text="메인" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="메뉴"
        app:layout_constraintEnd_toEndOf="parent" />

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="411dp"
        android:layout_height="364dp"
        android:layout_below="@+id/button"
        android:layout_marginTop="92dp"
        app:layout_constraintTop_toTopOf="parent"
        tools:layout_editor_absoluteX="0dp">

    </FrameLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

 

java : main

 

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

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

public class MainActivity extends AppCompatActivity {
    // 프레그먼트는  xml레이아웃 파일 하나랑 자바소스 파일 하나로 정의
    Fragment fragment1;
    Fragment2 fragment2;
    Fragment3 fragment3;

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

        // 프레그먼트는 뷰와 다르게 context를 매개변수로 넣을 필요 없음
        fragment1 = new Fragment();
        fragment2 = new Fragment2();
        fragment3 = new Fragment3();

        Button button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                // 프레그먼트 추가할 때 여러 명령을 한꺼번에 쓸 수 있으므로 beginTransaction 사용
                // fragment1를 R.id.container에 넣음 (add 또는 replace, replace는 기존에있던걸 대체해줌)
                // transaction 안에서 수행되는 것이므로 마지막에 꼭 commit을 해줘야 실행됨
                getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment1).commit(); /* 프레그먼트 매니저가 프레그먼트를 담당 */
            }
        });

        Button button3 = findViewById(R.id.button3);
        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment2).commit();/* 프레그먼트 매니저가 프레그먼트를 담당 */
            }
        });
    }

    // 프레그먼트와 프레그먼트끼리 직접 접근 하지않음. 프레그먼트와 액티비티가 접근함
    public void onFragmentChange(int index){
        if(index == 0 ){
            getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment1).commit();
        }else if(index == 1){
            getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment2).commit();
        }else if(index == 2){
            getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment3).commit();
        }
    }
}

 

xml : fragment1

 

<?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"
    android:background="@android:color/holo_blue_bright"
    android:orientation="vertical">

    <TextView
        android:id="@+id/fragment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="프레그먼트1"
        android:textSize="45dp" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="3"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/fragment" />

    <Button
        android:id="@+id/button7"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="64dp"
        android:text="2"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/fragment" />

</androidx.constraintlayout.widget.ConstraintLayout>

 

java : Fragment1

 

package com.example.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 androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

public class Fragment extends Fragment {
    MainActivity activity;
    
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
	// 이 메소드가 호출될 때 프레그먼트가 액티비티 위에 올라와 있으므로 getActivity 메소드로 액티비티 참조 가능
        activity = (MainActivity) getActivity();
    }

    @Override
    public void onDetach() {
        super.onDetach();
	// 더이상 액티비티 참초 안됨
        activity = null;
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
	// 프레그먼트 메인을 인플레이트해주고 컨테이너에 붙이는 작업
        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_main , container, false);
        Button button = rootView.findViewById(R.id.button1);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                activity.onFragmentChange(2);
            }
        });

        Button button2 = rootView.findViewById(R.id.button7);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                activity.onFragmentChange(1);
            }
        });
        return rootView;
    }
}

 

xml : fragment2

 

<?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"
    android:background="@android:color/holo_purple"
    android:orientation="vertical">

    <TextView
        android:id="@+id/fragment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="프레그먼트2"
        android:textSize="45dp" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="1"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/fragment" />

    <Button
        android:id="@+id/button8"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="3"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/fragment" />

</androidx.constraintlayout.widget.ConstraintLayout>

 

java : Fragment2

 

package com.example.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 androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

public class Fragment2 extends Fragment {
    MainActivity activity;

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        activity = (MainActivity) getActivity();
    }

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

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_menu, container, false);
        Button button = rootView.findViewById(R.id.button2);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                activity.onFragmentChange(0);
            }
        });

        Button button2 = rootView.findViewById(R.id.button8);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                activity.onFragmentChange(2);
            }
        });
        return rootView;
    }
}

 

xml : fragment3

 

<?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"
    android:background="@color/teal_700"
    android:orientation="vertical">

    <TextView
        android:id="@+id/fragment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="프레그먼트3"
        android:textSize="45dp" />

    <Button
        android:id="@+id/button4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="96dp"
        android:text="2"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.273"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/fragment" />

    <Button
        android:id="@+id/button9"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="96dp"
        android:layout_marginEnd="72dp"
        android:text="1"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/fragment" />

</androidx.constraintlayout.widget.ConstraintLayout>

 

java : Fragment3

 

package com.example.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 androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

public class Fragment3 extends Fragment {
    MainActivity activity;

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        activity = (MainActivity) getActivity();
    }

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

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_menu2, container, false);
        Button button = rootView.findViewById(R.id.button4);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                activity.onFragmentChange(1);
            }
        });

        Button button2 = rootView.findViewById(R.id.button9);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                activity.onFragmentChange(0);
            }
        });
        return rootView;
    }
}