Android: Showing Action Bar menu items depending on ViewPager

问题

I am having trouble getting the following piece of code to work out. I have a viewpager with 3 fragments, and I want a search icon to only show up on one. I started off trying to add the search function by the fragment, but the rendering of the menu item was slow when swiping to that page. I am now on the part to add the search icon to the activity, and then just hide or show depending on which viewpager page is active, but the following is not working:

public class MyApp extends FragmentActivity implements 
   FragmentTeams.FragmentNotification,ViewPager.OnPageChangeListener, 
      OnNavigationListener{

  ...

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);

    menuSearch = menu.findItem(R.id.menu_search);
    mSearchView = new SearchView(this);
    menuSearch.setActionView(mSearchView);
    menuSearch.setVisible(false);
    return true;
}

 @Override
public void onPageSelected(int pageNum) {

if(pageNum== 1){     
    ActionBar actionBar = MyApp.this.getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);     
        menuSearch.setVisible(true);
        invalidateOptionsMenu();

}else{           
    ActionBar actionBar = MyApp.this.getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);  
        menuSearch.setVisible(false);
        invalidateOptionsMenu();
    }
}

While the above does (appear to) create and hide the icon at onCreateOptionsMenu, it is not reenabled when moving to

 pageNum ==1

Can anyone give me some insight as to why this may be happening?

回答1:

invalidateOptionsMenu make the system calls the method onPrepareOptionsMenu, so you can override this method as follows:

public boolean onPrepareOptionsMenu(Menu menu) {
      int pageNum = getCurrentPage();
      if (pageNum == 1) {
         menu.findItem(R.id.menu_search).setVisible(true);

      }
      else {
         menu.findItem(R.id.menu_search).setVisible(false);
      }
   }

public void onPageSelected(int pageNum) {
    invalidateOptionsMenu();
}

回答2:

You can implement onCreateOptionsMenu() in your Fragment and set 'setHasOptionsMenu(true)' for the fragment

回答3:

a possible solution for this problem would be inflating your custom menu inside the activity hosts your ViewPager and getting a menu reference as below:

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
     getMenuInflater().inflate(R.menu.custom_menu, menu);
     customMenu = menu;
     return super.onCreateOptionsMenu(menu);
 }

after that you can easily hide/show the menu's items without any delay inside onPageSelected method as below:

 @Override
 public void onPageSelected(int position) {
  switch (position) {
        case 0: { 
           customMenu.getItem(0).setVisible(false);
           break;
        }
       case 1: { 
           customMenu.getItem(0).setVisible(true);
             break;
        }
     }

来源：https://stackoverflow.com/questions/13229893/android-showing-action-bar-menu-items-depending-on-viewpager

标签

android

android-actionbar

android-viewpager