Fragment生命週期及add、replace、remove、hide&show方法分析
最近做專案時,發現未能完全的理解Fragment的生命週期,以致在處理邏輯上踩到到了一些坑。所以花了點時間去分析,也順便整理下,下次再碰到Fragment時就可以避免一些坑了(大笑)。
專案有一個Activity類和3個Fragment類。Activity 中放置3個按鈕(實質TextView)可以切換到不同的Fragment上。下面將給出Activity 和Fragment的程式碼和layout。
1-1 Fragment1
public class Fragment1 extends Fragment {
final String TAG = " test Fragment1" ;
public Fragment1() {
// Required empty public constructor
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Log.d(TAG,"onAttach");
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG,"onCreate" );
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment1_layout, null);
Log.d(TAG,"onCreateView");
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.d(TAG,"onActivityCreated");
}
@Override
public void onStart() {
super.onStart();
Log.d(TAG,"onStart");
}
@Override
public void onResume() {
super.onResume();
Log.d(TAG,"onResume");
}
@Override
public void onPause() {
super.onPause();
Log.d(TAG,"onPause");
}
@Override
public void onStop() {
super.onStop();
Log.d(TAG,"onStop");
}
@Override
public void onDestroyView() {
super.onDestroyView();
Log.d(TAG,"onDestroyView");
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d(TAG,"onDestroy");
}
@Override
public void onDetach() {
super.onDetach();
Log.d(TAG,"onDetach");
}
}
1-2 fragment1_layout.xml
<?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="match_parent"
android:background="#888"
android:gravity="center">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="30sp"
android:text="Fragment1"/>
</LinearLayout>
2-1 Fragment2
public class Fragment2 extends Fragment {
final String TAG = " test Fragment2";
public Fragment2() {
// Required empty public constructor
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Log.d(TAG,"onAttach");
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG,"onCreate");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment2_layout, null);
Log.d(TAG,"onCreateView");
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.d(TAG,"onActivityCreated");
}
@Override
public void onStart() {
super.onStart();
Log.d(TAG,"onStart");
}
@Override
public void onResume() {
super.onResume();
Log.d(TAG,"onResume");
}
@Override
public void onPause() {
super.onPause();
Log.d(TAG,"onPause");
}
@Override
public void onStop() {
super.onStop();
Log.d(TAG,"onStop");
}
@Override
public void onDestroyView() {
super.onDestroyView();
Log.d(TAG,"onDestroyView");
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d(TAG,"onDestroy");
}
@Override
public void onDetach() {
super.onDetach();
Log.d(TAG,"onDetach");
}
}
2-2 fragment2_layout.xml
<?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="match_parent"
android:background="#888"
android:gravity="center">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="30sp"
android:text="Fragment2"/>
</LinearLayout>
3-1 Fragment3
public class Fragment3 extends Fragment {
final String TAG = " test Fragment3";
public Fragment3() {
// Required empty public constructor
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
Log.d(TAG,"onAttach");
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG,"onCreate");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment3_layout, null);
Log.d(TAG,"onCreateView");
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.d(TAG,"onActivityCreated");
}
@Override
public void onStart() {
super.onStart();
Log.d(TAG,"onStart");
}
@Override
public void onResume() {
super.onResume();
Log.d(TAG,"onResume");
}
@Override
public void onPause() {
super.onPause();
Log.d(TAG,"onPause");
}
@Override
public void onStop() {
super.onStop();
Log.d(TAG,"onStop");
}
@Override
public void onDestroyView() {
super.onDestroyView();
Log.d(TAG,"onDestroyView");
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d(TAG,"onDestroy");
}
@Override
public void onDetach() {
super.onDetach();
Log.d(TAG,"onDetach");
}
}
3-2 fragment3_layout.xml
<?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="match_parent"
android:background="#888"
android:gravity="center">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="30sp"
android:text="Fragment3"/>
</LinearLayout>
4-1 MainActivity
public class MainActivity extends Activity{
final String TAG = " test MainActivity";
TextView mFragment1Tv ;
TextView mFragment2Tv ;
TextView mFragment3Tv ;
FrameLayout mainll ;
FragmentManager manager ;
FragmentTransaction transaction;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.activity_main);
initView();
initListener();
initData();
Log.d(TAG,"onCreate");
}
private void initListener() {
mFragment1Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment1 fragment1= new Fragment1();
transaction = manager.beginTransaction();
transaction.add(R.id.main_ll, fragment1,"1");
transaction.commit();
}
});
mFragment2Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment2 fragment2= new Fragment2();
transaction = manager.beginTransaction();
transaction.add(R.id.main_ll, fragment2,"2");
transaction.commit();
}
});
mFragment3Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment3 fragment3= new Fragment3();
transaction = manager.beginTransaction();
transaction.add(R.id.main_ll, fragment3,"3");
transaction.commit();
}
});
}
private void initData() {
manager = getFragmentManager();
}
private void initView() {
mFragment1Tv = (TextView) findViewById(R.id.fragment1_tv);
mFragment2Tv = (TextView) findViewById(R.id.fragment2_tv);
mFragment3Tv = (TextView) findViewById(R.id.fragment3_tv);
mainll = (FrameLayout) findViewById(R.id.main_ll);
}
@Override
protected void onStart() {
super.onStart();
Log.d(TAG,"onCreate");
}
@Override
protected void onRestart() {
super.onRestart();
Log.d(TAG,"onRestart");
}
@Override
protected void onResume() {
super.onResume();
Log.d(TAG,"onResume");
}
@Override
protected void onPause() {
super.onPause();
Log.d(TAG,"onPause");
}
@Override
protected void onStop() {
super.onStop();
Log.d(TAG,"onStop");
}
@Override
protected void onDestroy() {
super.onDestroy();
Log.d(TAG,"onDestroy");
}
}
4-2 activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:id="@+id/index"
android:layout_width="match_parent"
android:layout_height="40dp"
android:orientation="horizontal">
<TextView
android:id="@+id/fragment1_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:background="#bbb"
android:text="Fragment1"
android:textSize="22sp" />
<TextView
android:id="@+id/fragment2_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:background="#bbb"
android:text="Fragment2"
android:textSize="22sp" />
<TextView
android:id="@+id/fragment3_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:background="#bbb"
android:text="Fragment3"
android:textSize="22sp" />
</LinearLayout>
<View
android:layout_below="@id/index"
android:layout_width="match_parent"
android:layout_height="1dp"
android:background="#aaa"/>
<LinearLayout
android:id="@+id/main_ll"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true">
</LinearLayout>
</RelativeLayout>
5 測試生命週期
(一) add 方法分析
1.啟動app,log如圖:
介面如下:
2.點選Fragment1,log如下:
介面如下:
3點選fragment2 log如下: (這裡並沒有觸發fragment1的生命週期)
介面如下:
4點選fragment3 log如下:
介面如下:
5 在此時分為兩次不同的操作:
5-1 測試返回
操作:點選返回鍵,此時應用已經退出。log如下:
5-2 home鍵測試
操作:(1)點選home鍵,app退到後臺,log如下:
(2)點選應用圖示重新開啟app,log如下:
6 回退棧測試
再回到5-1 ,如果想要點選返回鍵回到上一個Fragment的話,那麼就需要加入到會退棧。
修改 MainActivity 的方法initListener如下:
private void initListener() {
mFragment1Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment1 fragment1= new Fragment1();
transaction = manager.beginTransaction();
transaction.add(R.id.main_ll, fragment1,"1");
transaction.addToBackStack(null);
transaction.commit();
}
});
mFragment2Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment2 fragment2= new Fragment2();
transaction = manager.beginTransaction();
transaction.add(R.id.main_ll, fragment2,"2");
transaction.addToBackStack(null);
transaction.commit();
}
});
mFragment3Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment3 fragment3= new Fragment3();
transaction = manager.beginTransaction();
transaction.add(R.id.main_ll, fragment3,"3");
transaction.addToBackStack(null);
transaction.commit();
}
});
}
操作:執行 1.開啟app,2.點選Fragment,3.點選Fragment2,4.點選Fragment3。
此時清空LogCat,再點選返回鍵Log如下:
此時介面回到Fragment2,而其他Fragment和Activity的生命週期是沒有變化的。若再點選返回鍵將回到Fragment1介面,再點選返回鍵就是回到Activity介面了。
(二) replace方法分析
修改 MainActivity 的方法initListener如下:(主要是替換add為replace)
private void initListener() {
mFragment1Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment1 fragment1= new Fragment1();
transaction = manager.beginTransaction();
transaction.replace(R.id.main_ll, fragment1,"1");
//transaction.add(R.id.main_ll, fragment1,"1");
// transaction.addToBackStack(null);
transaction.commit();
}
});
mFragment2Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment2 fragment2= new Fragment2();
transaction = manager.beginTransaction();
transaction.replace(R.id.main_ll, fragment2,"2");
//transaction.add(R.id.main_ll, fragment2,"2");
// transaction.addToBackStack(null);
transaction.commit();
}
});
mFragment3Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Fragment3 fragment3= new Fragment3();
transaction = manager.beginTransaction();
transaction.replace(R.id.main_ll, fragment3,"3");
//transaction.add(R.id.main_ll, fragment3,"3");
//transaction.addToBackStack(null);
transaction.commit();
}
});
}
1.測試replace
操作:啟動app,然後點選Fragment1,再點選Fragment2,log如下:
2.測試返回鍵
在上一步驟的基礎上點選物理返回鍵Log如下:(應用程式已經退出了)
3.在(二)1的基礎上點選home鍵,再重新開啟app,log如下:
4.此時看下會退棧的情況。
修改 MainActivity 的方法initListener,主要是取消
// transaction.addToBackStack(null);
的註釋。
操作:開啟app,點選Fragment1,點選Fragment2,清空logCat,再點選返回鍵,此時log如下:
可見replace 是會銷燬掉被replace 的Fragment。
(三) hide &show方法分析。
修改 MainActivity如下:(在activity的oncreate中add Fragment1和Fragment2,修改mFragment2Tv的點選事件。)
public class MainActivity extends Activity{
final String TAG = "testFragment MainActivity";
TextView mFragment1Tv ;
TextView mFragment2Tv ;
TextView mFragment3Tv ;
FrameLayout mainll ;
FragmentManager manager ;
FragmentTransaction transaction;
Fragment1 fragment1;
Fragment2 fragment2;
Fragment3 fragment3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.activity_main);
initView();
initListener();
initData();
Log.d(TAG,"onCreate");
}
private void initListener() {
mFragment1Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
transaction = manager.beginTransaction();
transaction.add(R.id.main_ll, fragment1,"1");
transaction.commit();
}
});
mFragment2Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
transaction = manager.beginTransaction();
transaction.hide(fragment1).show(fragment2);
transaction.commit();
}
});
mFragment3Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
transaction = manager.beginTransaction();
transaction.replace(R.id.main_ll, fragment3,"3");
// transaction.add(R.id.main_ll, fragment3,"3");
transaction.addToBackStack(null);
transaction.commit();
}
});
}
private void initData() {
manager = getFragmentManager();
fragment1= new Fragment1();
fragment2= new Fragment2();
fragment3= new Fragment3();
transaction = manager.beginTransaction();
transaction.add(R.id.main_ll, fragment2,"2");
transaction.add(R.id.main_ll, fragment1,"1");
transaction.commit();
}
private void initView() {
mFragment1Tv = (TextView) findViewById(R.id.fragment1_tv);
mFragment2Tv = (TextView) findViewById(R.id.fragment2_tv);
mFragment3Tv = (TextView) findViewById(R.id.fragment3_tv);
mainll = (FrameLayout) findViewById(R.id.main_ll);
}
@Override
protected void onStart() {
super.onStart();
Log.d(TAG,"onStart");
}
@Override
protected void onRestart() {
super.onRestart();
Log.d(TAG,"onRestart");
}
@Override
protected void onResume() {
super.onResume();
Log.d(TAG,"onResume");
}
@Override
protected void onPause() {
super.onPause();
Log.d(TAG,"onPause");
}
@Override
protected void onStop() {
super.onStop();
Log.d(TAG,"onStop");
}
@Override
protected void onDestroy() {
super.onDestroy();
Log.d(TAG,"onDestroy");
}
}
操作:啟動app ,log如下圖,程式碼裡面是先add Fragment2 再add Fragment1,此時顯示的介面是Fragment1 的介面,然後點選TextView mFragment2Tv,介面切換到了Fragment2上,而log無任何的資訊列印,可見hide &show 方法不觸發Fragment生命週期,隻影響它的顯示。
(四) remove方法分析
在 (三)hide&show方法分析 的程式碼基礎上修改MainActivity 如下:
(其他程式碼不變,只修改為remove方法)
mFragment2Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
transaction = manager.beginTransaction();
transaction.remove(fragment1).show(fragment2);
transaction.commit();
}
});
啟動app 時的log:
此時點選Fragment2,log如下:
本以為分析下Fragment會很簡單,想不到分析Fragment+一篇文章 能耗那麼多時間,看來得加個滷蛋犒勞犒勞自己了(偷笑中…)