Analysis on the problem of switching interface Fragment being destroyed in "Viewpager+fragment" Viewpager

Viewpager switch Interface Fragment the problem of the destruction of the original link HTTP://WWW.CNBLOGS.COM/MONODIN/P/3866441.HTML1, the use of scene viewpager+fragment to achieve interface switching, Number of Interfaces >=3 2, Fragment life cycle, and activity life cycle comparison

3, the problem description according to said, only when fragment attached activity execution destroy will call Ondestoryview method, but the reality is: when the interface from 2 to 1, The fragment of the 3 interface actually goes the following process:

1-->onpause2-->onstop3-->ondestroyview

Then switch back from 1 to 2 or 3 o'clock, and the 3 interface corresponds to the fragment execution flow:

1-->oncreateview2-->onstart3-->onresume

Visible, interface 3 corresponding fragment is destroyed and recreated.

4. Cause analysis The default loading method for Viewpager is to cache the two interfaces that are adjacent to the current interface, that is, a maximum of three interface information, including the current interface. The non-adjacent interface information is released when the switch interface is sliding. Interface 2 is the current interface, interface 1 and 3 is the cache interface, when switching to 1 o'clock, interface 2 is still cached, interface 3 is destroyed and released, so there is a ondestroyview call. Switching from 1 to 2 or 3 o'clock, interface 3 was re-created, and then went through the Oncreateview process. 5. Solutions

• Scenario One: Set the number of cache interfaces for Viewpager

This scenario is suitable for situations where the number of interfaces is low, and avoiding too many cache interfaces leads to memory crunch. Method:

Mpager. Setoffscreenpagelimit (2);

Parameters: Int Limit-caches the number of interfaces on each side of the current interface

In the example above, the current interface is 1,limit = 2, which represents caching 2, 32 interfaces. This prevents the interface 3 from being destroyed.

• Scenario Two: Save state and restore

This scenario applies to situations where the available interface information can be implemented by state saving and recovery. Save the relevant information within the Ondestroyview method and restore the information settings within the Oncreateview method.

• Scenario three (recommended): Reuse of fragment Rootview

This scenario is suitable for common scenarios and is recommended for use. Step 1: Remove fragment Rootview from Viewpager within the Ondestroyview method

1 @Override2 public void Ondestroyview () {3     logutils.d (TAG, "-->ondestroyview"); 4     super. Ondestroyview (); 5     if (null! = Fragmentview) {6         ((ViewGroup) mfragmentview.getparent ()). Removeview (Mfragmentview); 7     }8}

Step 2: Reuse the Rootview within the Oncreateview method

1 @Override 2 public View Oncreateview (layoutinflater inflater, ViewGroup container, 3         Bundle savedinstancestate) {4< C3/>LOGUTILS.D (TAG, "-->oncreateview"); 5     if (null = = Mfragmentview) {6          Mfragmentview = inflater.inflate (R.layout.fragment, container, false); 7          Mlistview = (ListView) mfragmentview. Findviewbyid (R.id.mm_listview); 8          Mlistview.setadapter (madapter); 9          Mpbar = (ProgressBar) Mfragmentview.findviewbyid (r.id.pbar_mm_loading) ; ten          mpbar.setvisibility (view.visible);     }12     return mfragmentview; 14}

Analysis on the problem of switching interface Fragment being destroyed in "Viewpager+fragment" Viewpager