เมื่อเรียก Fragment ไว้หลายอัน เวลากดปุ่ม Back ย้อนกลับ จะย้อนกลับตามลำดับ Stack

สร้าง Fragment ขึ้นมาใหม่ชื่อ FirstFragment, SecondFragment และ ThirdFragment
ไฟล์ที่เกี่ยวข้อง
- activity_main.xml
- MainActivity.java
- fragment_first.xml
- FirstFragment.java
- fragment_second.xml
- SecondFragment.java
- fragment_third.xml
- ThirdFragment.java
activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity"> <GridLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:layout_marginBottom="10dp"> <Button android:id="@+id/button1" android:text="Fragment 1" android:textSize="16sp" /> <Button android:id="@+id/button2" android:text="Fragment 2" android:textSize="16sp" /> <Button android:id="@+id/button3" android:text="Fragment 3" android:textSize="16sp" /> </GridLayout> <Button android:id="@+id/buttonClose" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:layout_marginBottom="10dp" android:text="Close Current Fragment" android:textAllCaps="false" android:textSize="18sp" /> <FrameLayout android:id="@+id/frameLayout" android:layout_width="match_parent" android:layout_height="match_parent" /> </LinearLayout>
MainActivity.java
package com.phaisarn.myapplication; import androidx.appcompat.app.AppCompatActivity; import androidx.fragment.app.Fragment; import androidx.fragment.app.FragmentManager; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.Toast; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final FirstFragment f1 = new FirstFragment(); final SecondFragment f2 = new SecondFragment(); final ThirdFragment f3 = new ThirdFragment(); final FragmentManager fragMan = getSupportFragmentManager(); Button button1 = findViewById(R.id.button1); Button button2 = findViewById(R.id.button2); Button button3 = findViewById(R.id.button3); Button buttonClose = findViewById(R.id.buttonClose); button1.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { replaceFragment(f1); } }); button2.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { replaceFragment(f2); } }); button3.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { replaceFragment(f3); } }); buttonClose.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { fragMan.popBackStack(); Toast.makeText(getApplication(), "popBackStack", Toast.LENGTH_SHORT).show(); } }); fragMan.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() { @Override public void onBackStackChanged() { if (fragMan.getBackStackEntryCount() == 0) { finish(); //close activity } } }); } private void replaceFragment(Fragment fragment) { getSupportFragmentManager() .beginTransaction() .replace(R.id.frameLayout, fragment) .addToBackStack(null) .commit(); } }
บรรทัดที่ 54 เมื่อมีการกดปุ่ม buttonClose
ไม่ว่าจะมี fragment
ให้ปิดหรือไม่ ก็จะทำการ Toast
ออกมา
บรรทัดที่ 61 เมื่อจำนวน fragment
ใน BackStack
เท่ากับ 0
ก็ให้ปิด Activity
นี้เลย
fragment_first.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#cde" android:orientation="vertical" tools:context=".FirstFragment"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:layout_margin="30dp" android:text="Fragment #1" android:textSize="20sp" /> </LinearLayout>
FirstFragment.java
package com.phaisarn.myapplication; import android.os.Bundle; import androidx.fragment.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; /** * A simple {@link Fragment} subclass. */ public class FirstFragment extends Fragment { public FirstFragment() { // Required empty public constructor } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment return inflater.inflate(R.layout.fragment_first, container, false); } }
fragment_second.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#ebe" android:orientation="vertical" tools:context=".SecondFragment"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:layout_margin="30dp" android:text="Fragment #2" android:textSize="20sp" /> </LinearLayout>
SecondFragment.java
package com.phaisarn.myapplication; import android.os.Bundle; import androidx.fragment.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; /** * A simple {@link Fragment} subclass. */ public class SecondFragment extends Fragment { public SecondFragment() { // Required empty public constructor } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment return inflater.inflate(R.layout.fragment_second, container, false); } }
fragment_third.xml
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#fbb" android:orientation="vertical" tools:context=".ThirdFragment"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center_horizontal" android:layout_margin="30dp" android:text="Fragment #3" android:textSize="20sp" /> </LinearLayout>
ThirdFragment.java
package com.phaisarn.myapplication; import android.os.Bundle; import androidx.fragment.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; /** * A simple {@link Fragment} subclass. */ public class ThirdFragment extends Fragment { public ThirdFragment() { // Required empty public constructor } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment return inflater.inflate(R.layout.fragment_third, container, false); } }