动作栏，导航抽屉和片段后台管理

Question

I'm implementing the following tutorial in my app: Creating a Navigation Drawer .

My target is to implement the following behavior:

• Using one Activity
• 2 Fragments: FragmentA is always attached. FragmentB is attached when a button is clicked
• When the FragmentB is visible, the action bar home button is a back arrow that removes FragmentB from the backstack
• When the Fragment B is not visible the action bar button home button show the Drawer Layout.

How can I implement that transformation of the home button?

Thanks

Answer 1

There are some methods in the ActionBar class that may help you:

The following call will set the Home button icon to the "back" icon.

getActionBar().setDisplayOptions(ActionBar.DISPLAY_HOME_AS_UP);

Because the MenuItem's action is defined by onOptionsItemSelected() method, so you have to override it too, and check whether you click the home button or not. Actually, the navigation drawer will draw again so you will want to return true from that method to prevent the drawer to draw again.

@Override
public boolean onOptionsItemSelected(MenuItem item) {
     if (item.getId() == android.R.id.home) {
          // do what you want here
          return true; // prevent the drawer to draw again;
     }
     return super.onOptionsItemSelected(item);
}

To turn the home button back to its default "behavior", use the following call:

getActionBar().setDisplayShowHomeEnabled(true);

The last step is to check if your current fragment is the FragmentA (which will active the drawer draw the navigation fragment) or the FragmentB (which does not). You may want to add a global boolean variable to do them, and check the position of the navigation item.

I have included an example here, please check out:

Navigation Drawer example

Hope this help.