Fragment生命周期及add、replace、remove、hide&show方法分析

转载自https://blog.csdn.net/u014699958/article/details/52996143
项目有一个Activity类和3个Fragment类。Activity 中放置3个按钮（实质TextView）可以切换到不同的Fragment上。下面将给出Activity 和Fragment的代码和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

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

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">

</RelativeLayout>

5 测试生命周期
(一) add 方法分析
1.启动app，log如图：

界面如下：

2.点击Fragment1，log如下:

界面如下：

3点击fragment2 log如下： (这里并没有触发fragment1的生命周期)

界面如下：

4点击fragment3 log如下：

界面如下：

5 在此时分为两次不同的操作：

5-1 测试返回
操作：点击返回键，此时应用已经退出。log如下：

5-2 home键测试
操作：（1）点击home键，app退到后台，log如下:

（2）点击应用图标重新打开app，log如下:

6 回退栈测试
再回到5-1 ，如果想要点击返回键回到上一个Fragment的话，那么就需要加入到会退栈。
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：执行 1.打开app,2.点击Fragment，3.点击Fragment2，4.点击Fragment3。
此时清空LogCat，再点击返回键Log如下：

此时界面回到Fragment2，而其他Fragment和Activity的生命周期是没有变化的。若再点击返回键将回到Fragment1界面，再点击返回键就是回到Activity界面了。

(二) replace方法分析
修改 MainActivity 的方法initListener如下：（主要是替换add为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.测试replace
操作：启动app，然后点击Fragment1，再点击Fragment2，log如下：

2.测试返回键
在上一步骤的基础上点击物理返回键Log如下：（应用程序已经退出了）

3.在（二）1的基础上点击home键，再重新打开app，log如下:

4．此时看下会退栈的情况。
修改 MainActivity 的方法initListener，主要是取消

// transaction.addToBackStack(null);
1
的注释。

操作：打开app，点击Fragment1，点击Fragment2，清空logCat，再点击返回键，此时log如下：

可见replace 是会销毁掉被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的点击事件。）

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();
}

}

@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：启动app ，log如下图，代码里面是先add Fragment2 再add Fragment1，此时显示的界面是Fragment1 的界面，然后点击TextView mFragment2Tv，界面切换到了Fragment2上，而log无任何的信息打印，可见hide &show 方法不触发Fragment生命周期，只影响它的显示。

(四) remove方法分析
在 (三)hide&show方法分析的代码基础上修改MainActivity 如下：
(其他代码不变，只修改为remove方法)

mFragment2Tv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
transaction = manager.beginTransaction();
transaction.remove(fragment1).show(fragment2);
transaction.commit();
}
});

启动app 时的log: