Fragment lifecycle Summary

Link: http://www.php100.com/html/it/biancheng/2015/0120/8419.html

Reference: http://blog.csdn.net/lmj623565791/article/details/37992017

FragmentIs an important component in Android. It is added in Android 3.0.

AboutFragmentI believe that all the developers I know should blurt out the following methods: onattach, oncreate, oncreateview,Onviewcreated, Onactivitycreated, onstart, onresume, onpause, onstop, ondestroyview, ondestroy, ondetach.

WhenFragmentIn a static way, that is, when other controls are set in the layout file, its lifecycle changes with the lifecycle of the activity. At this time, the method calling process of its life cycle is as follows:

1. When the layout page is displayed for the first time, the sequence of calling the lifecycle method is as follows:

2. When the screen of the phone is turned off or the screen of the phone is dimmed, the call sequence of its life cycle method is as follows:

3. When the mobile phone screen is unlocked again or the mobile phone screen is highlighted again, the sequence of calling the lifecycle method is as follows:

4.FragmentWhen you press the return key on the screen, the order of the life cycle method calls is as follows:

1 01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragA： onPause2 01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragA： onStop3 01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragA： onDestroyView4 01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragA： onDestroy5 01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragA： onDetach

However, when fragmentmanager is used for dynamic managementFragmentWhen it comes to addtobackstack, the presentation of its lifecycle is slightly complicated. But it is still not complicated to be incomprehensible.

Okay. Let's look at these questions.

First, we have rewritten twoFragmentThey overwrite their lifecycle methods and display the call of their methods by printing logs in their lifecycle methods.

The two classes are:

package com.yeepay.fraglifecircletest.frag;import android.app.Activity;import android.app.Fragment;import android.os.Bundle;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import com.yeepay.fraglifecircletest.R;public class FragA extends Fragment {    private static final String TAG = FragA.class.getSimpleName();    @Override    public void onAttach(Activity activity) {        super.onAttach(activity);        Log.i(TAG, "onAttach");    }    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Log.i(TAG, "onCreate");    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {        Log.i(TAG, "onCreateView");        return inflater.inflate(R.layout.fragment_test_a, null, false);    }    @Override    public void onViewCreated(View view, Bundle savedInstanceState) {        Log.i(TAG, "onViewCreated");        super.onViewCreated(view, savedInstanceState);    }    @Override    public void onDestroy() {        Log.i(TAG, "onDestroy");        super.onDestroy();    }    @Override    public void onDetach() {        Log.i(TAG, "onDetach");        super.onDetach();    }    @Override    public void onDestroyView() {        Log.i(TAG, "onDestroyView");        super.onDestroyView();    }    @Override    public void onStart() {        Log.i(TAG, "onStart");        super.onStart();    }    @Override    public void onStop() {        Log.i(TAG, "onStop");        super.onStop();    }    @Override    public void onResume() {        Log.i(TAG, "onResume");        super.onResume();    }    @Override    public void onPause() {        Log.i(TAG, "onPause");        super.onPause();    }    @Override    public void onActivityCreated(Bundle savedInstanceState) {        Log.i(TAG, "onActivityCreated");        super.onActivityCreated(savedInstanceState);    }}FragA.java

package com.yeepay.fraglifecircletest.frag;import android.app.Activity;import android.app.Fragment;import android.os.Bundle;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import com.yeepay.fraglifecircletest.R;public class FragB extends Fragment {    private static final String TAG = FragB.class.getSimpleName();    @Override    public void onAttach(Activity activity) {        super.onAttach(activity);        Log.i(TAG, "onAttach");    }    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Log.i(TAG, "onCreate");    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {        Log.i(TAG, "onCreateView");        return inflater.inflate(R.layout.fragment_test_b, null, false);    }    @Override    public void onViewCreated(View view, Bundle savedInstanceState) {        Log.i(TAG, "onViewCreated");        super.onViewCreated(view, savedInstanceState);    }    @Override    public void onDestroy() {        Log.i(TAG, "onDestroy");        super.onDestroy();    }    @Override    public void onDetach() {        Log.i(TAG, "onDetach");        super.onDetach();    }    @Override    public void onDestroyView() {        Log.i(TAG, "onDestroyView");        super.onDestroyView();    }    @Override    public void onStart() {        Log.i(TAG, "onStart");        super.onStart();    }    @Override    public void onStop() {        Log.i(TAG, "onStop");        super.onStop();    }    @Override    public void onResume() {        Log.i(TAG, "onResume");        super.onResume();    }    @Override    public void onPause() {        Log.i(TAG, "onPause");        super.onPause();    }    @Override    public void onActivityCreated(Bundle savedInstanceState) {        Log.i(TAG, "onActivityCreated");        super.onActivityCreated(savedInstanceState);    }}FragB.java

1. When we add Fraga in the following ways,

1 FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();2 fragA = new FragA();3                     fragmentTransaction.replace(R.id.frag_container, fragA, fragNames[0]);4 fragmentTransaction.commit();

Its lifecycle is displayed in the same way as the static settings in the layout file. You can check the above content.

2. When Fraga is displayed in the following way without addtobackstack,

@Override    public void onClick(View v) {        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();        switch (v.getId()) {            case R.id.button1:                if (fragA == null) {                    fragA = new FragA();                    fragmentTransaction.replace(R.id.frag_container, fragA, fragNames[0]);//                    fragmentTransaction.addToBackStack(fragNames[0]);                } else {                    Fragment fragment = fragmentManager.findFragmentByTag(fragNames[0]);                    fragmentTransaction.replace(R.id.frag_container, fragment, fragNames[0]);                }                break;            case R.id.button2:                if (fragB == null) {                    fragB = new FragB();                    fragmentTransaction.replace(R.id.frag_container, fragB, fragNames[1]);//                    fragmentTransaction.addToBackStack(fragNames[1]);                } else {                    Fragment fragment = fragmentManager.findFragmentByTag(fragNames[1]);                    fragmentTransaction.replace(R.id.frag_container, fragment, fragNames[1]);                }                break;            default:                break;        }        fragmentTransaction.commit();    }

The call sequence of Fraga lifecycle is:

At this point, if you click another button B, fragb will be displayed. the lifecycle of Fraga and fragb will be displayed as follows:

It can be seen that the call sequence of Fraga is onpause, onstop, ondestroyview, ondestroy, and ondetach. This indicates that Fraga has been completely abandoned by fragmentmanager and replaced by the full display of fragb. If you press the return key, the lifecycle of fragb will also be onpause, onstop, ondestroyview, ondestroy, and ondetach. This indicates thatFragmentIf the addtobackstack method is not called, The fragmentmanager is changed.FragmentIs not savedFragment.

3. We will replaceFragmentWhen addtobackstack is ready, its life cycle is displayed as follows:

replace FragA and addToBackStack########################################################################################01-13 17:08:43.359    3102-3102/com.yeepay.fraglifecircletest I/FragA： onAttach01-13 17:08:43.359    3102-3102/com.yeepay.fraglifecircletest I/FragA： onCreate01-13 17:08:43.359    3102-3102/com.yeepay.fraglifecircletest I/FragA： onCreateView01-13 17:08:43.359    3102-3102/com.yeepay.fraglifecircletest I/FragA： onViewCreated01-13 17:08:43.359    3102-3102/com.yeepay.fraglifecircletest I/FragA： onActivityCreated01-13 17:08:43.359    3102-3102/com.yeepay.fraglifecircletest I/FragA： onStart01-13 17:08:43.359    3102-3102/com.yeepay.fraglifecircletest I/FragA： onResume

It can be seen that there is no difference between calling the lifecycle method at this time and without addtobackstack.

Click "B" and use "fragb" to replace "Fraga". In this case, the call sequence of the Fraga and fragb Life Cycle methods is as follows:

and then replace FragB and addToBackStack&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragA： onPause01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragA： onStop01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragA： onDestroyView01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragB： onAttach01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragB： onCreate01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragB： onCreateView01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragB： onViewCreated01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragB： onActivityCreated01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragB： onStart01-13 17:08:46.959    3102-3102/com.yeepay.fraglifecircletest I/FragB： onResume

It can be seen that the Fraga life cycle method only calls ondestroyview, while ondestroy and ondetach are not called. This indicates that the Fraga interface has been destroyed, but fragmentmanager has not completely destroyed Fraga, fraga is still saved in fragmentmanager.

Click a and use Fraga to replace the currently displayed fragb. In this case, the call sequence of the Fraga and fragb Life Cycle methods is as follows:

and then replace FragA again&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&01-13 17:08:51.869    3102-3102/com.yeepay.fraglifecircletest I/FragB： onPause01-13 17:08:51.869    3102-3102/com.yeepay.fraglifecircletest I/FragB： onStop01-13 17:08:51.869    3102-3102/com.yeepay.fraglifecircletest I/FragB： onDestroyView01-13 17:08:51.869    3102-3102/com.yeepay.fraglifecircletest I/FragA： onCreateView01-13 17:08:51.869    3102-3102/com.yeepay.fraglifecircletest I/FragA： onViewCreated01-13 17:08:51.869    3102-3102/com.yeepay.fraglifecircletest I/FragA： onActivityCreated01-13 17:08:51.869    3102-3102/com.yeepay.fraglifecircletest I/FragA： onStart01-13 17:08:51.869    3102-3102/com.yeepay.fraglifecircletest I/FragA： onResume

It can be seen that the call sequence of fragb's life methods is the same as that of Fraga when fragb replaces Fraga. The function is to destroy only the view, but keep it.Fragment. At this time, Fraga calls are worth noting. At this time, Fraga is directly called from oncreateview, that is, it only creates a new view, but still usesFragmentStatus.

OK. At this time, is it true?FragmentAre you familiar with addtobackstack?

Okay, the last question. Is aboutFragmentCall the lifecycle method of show and hide during fragmentmanager management.

The call implementation method is as follows:

FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();        switch (v.getId()) {            case R.id.button1:                hideAllFrags(fragmentTransaction);                if (fragA == null) {                    fragA = new FragA();                    fragmentTransaction.add(R.id.frag_container, fragA, fragNames[0]);                    fragmentTransaction.addToBackStack(fragNames[0]);                } else {                    fragmentTransaction.show(fragA);                }                break;            case R.id.button2:                hideAllFrags(fragmentTransaction);                if (fragB == null) {                    fragB = new FragB();                    fragmentTransaction.add(R.id.frag_container, fragB, fragNames[1]);                    fragmentTransaction.addToBackStack(fragNames[1]);                } else {                    fragmentTransaction.show(fragB);                }                break;            default:                break;        }fragmentTransaction.commit();

If you are careful, you can find thatFragmentInstead of using replace. And directly addtobackstack. In fact, this can also be understood. You think, fragmentmanager must already exist in show or hide, or you need to add it if it does not exist.Fragment. This is what you need to pay attention to when using show and hide, that is, using the ADD and addtobackstack methods.

When you click a, Fraga calls the following order:

01-15 16:57:20.390    9225-9225/com.yeepay.fraglifecircletest I/hideAllFrags： hideAllFrags01-15 16:57:20.390    9225-9225/com.yeepay.fraglifecircletest I/FragA： onAttach01-15 16:57:20.390    9225-9225/com.yeepay.fraglifecircletest I/FragA： onCreate01-15 16:57:20.390    9225-9225/com.yeepay.fraglifecircletest I/FragA： onCreateView01-15 16:57:20.390    9225-9225/com.yeepay.fraglifecircletest I/FragA： onViewCreated01-15 16:57:20.390    9225-9225/com.yeepay.fraglifecircletest I/FragA： onActivityCreated01-15 16:57:20.390    9225-9225/com.yeepay.fraglifecircletest I/FragA： onStart01-15 16:57:20.390    9225-9225/com.yeepay.fraglifecircletest I/FragA： onResume

It can be seen that there is nothing different from the above.

Then, when you click "B", Fraga and fragb are called in the following sequence:

01-15 16:57:23.360    9225-9225/com.yeepay.fraglifecircletest I/hideAllFrags： hideAllFrags01-15 16:57:23.360    9225-9225/com.yeepay.fraglifecircletest I/FragB： onAttach01-15 16:57:23.360    9225-9225/com.yeepay.fraglifecircletest I/FragB： onCreate01-15 16:57:23.360    9225-9225/com.yeepay.fraglifecircletest I/FragB： onCreateView01-15 16:57:23.370    9225-9225/com.yeepay.fraglifecircletest I/FragB： onViewCreated01-15 16:57:23.370    9225-9225/com.yeepay.fraglifecircletest I/FragB： onActivityCreated01-15 16:57:23.370    9225-9225/com.yeepay.fraglifecircletest I/FragB： onStart01-15 16:57:23.370    9225-9225/com.yeepay.fraglifecircletest I/FragB： onResume

It can be seen that Fraga does not call the lifecycle method. This shows that the lifecycle of Fraga does not change when fragb is displayed. The lifecycle of fragb is the same as that of Fraga when you click a for the first time.

Then click A and B. The output log is as follows:

1 01-15 16:57:25.220    9225-9225/com.yeepay.fraglifecircletest I/hideAllFrags： hideAllFrags2 01-15 16:57:44.990    9225-9225/com.yeepay.fraglifecircletest I/hideAllFrags： hideAllFrags3 01-15 16:57:47.350    9225-9225/com.yeepay.fraglifecircletest I/hideAllFrags： hideAllFrags4 01-15 16:57:48.020    9225-9225/com.yeepay.fraglifecircletest I/hideAllFrags： hideAllFrags

This means that After Fraga and fragb are added to the backstack, their lifecycles no matter how they are shown or hide.

When the screen is locked or dimmed, and then unlocked or brightened, the call sequence of Fraga and fragb's lifecycle methods is as follows:

when screen is locked:###########################################################################################01-15 16:58:36.840    9225-9225/com.yeepay.fraglifecircletest I/FragA： onPause01-15 16:58:36.840    9225-9225/com.yeepay.fraglifecircletest I/FragB： onPause01-15 16:58:36.870    9225-9225/com.yeepay.fraglifecircletest I/FragA： onStop01-15 16:58:36.880    9225-9225/com.yeepay.fraglifecircletest I/FragB： onStopwhen screen is unlocked:##########################################################################################01-15 17:05:01.850    9225-9225/com.yeepay.fraglifecircletest I/FragA： onStart01-15 17:05:01.850    9225-9225/com.yeepay.fraglifecircletest I/FragB： onStart01-15 17:05:01.870    9225-9225/com.yeepay.fraglifecircletest I/FragA： onResume01-15 17:05:01.870    9225-9225/com.yeepay.fraglifecircletest I/FragB： onResume

We can see that twoFragmentOnpause, onstop, onstart, and onresume are all called. In addition, Fraga is called before fragb, which indicates that it is related to the order in which they are added to the backstack.

Fragment lifecycle Summary