Android ViewPager片段生命周期

Question

I have a Document fragment which is inside viewpager and i use same Document fragment's instance in another part of application. My problem is that, in fragment i am registering a broadcast receiver, normally i am unregistering it onPause method in fragment. But fragments onPause method is not called when i switch another. So next fragment of viewpager i use new instance of Document fragment and i am creating new instance of receiver also. But onReceive method receiver calls viewpager's document fragment method. So when look at logcat i can see that i can not unregister receiver. How can i unregister receiver, can i get list of registered receviers?

Answer 1

Try to register and unregister Broadcast Receivers in the ViewPager's OnPageChangeListener . This listener contains 3 methods namely onPageScrollStateChanged(int state) , onPageScrolled(int position, float positionOffset, int positionOffsetPixels) and onPageSelected(int position) .

Use onPageScrolledStateChanged() method. It uses 3 states for monitoring the Fragments inside the ViewPager. Use SCROLL_STATE_DRAGGING for unregistering your BroadcastReceiver and SCROLL_STATE_SETTLING for registering your BroadcastReceiver.

Answer 2

也许您可以在片段中使用setUserVisibleHint（）方法...或另一个想法，在视图分页器上注册OnPageChangeListener，然后从此侦听器中手动调用方法以注销接收者...

Answer 3

Thank you all for your answers, as you said i implemented OnPageChangeListener and created a logic, it is working fine now. Thank you all again, i am posting the code:

   @Override
   public void onPageSelected(int position) {

       Fragment currentFragment = adapterViewPager.getRegisteredFragment(position);

       if(currentFragment.getClass()==Document.class){
           Log.i (AppConfig.TAG,"Current Fragment is Document");
           Document document = (Document)currentFragment;
           document.registerDownloadService();
       }
       if(lastFragment!=null && lastFragment.getClass()==Document.class){
           Log.i (AppConfig.TAG,"Previous Fragment is Document");
           Document document = (Document)lastFragment;
           document.unregisterDownloadService();
       }
       lastFragment = currentFragment;
   }