Why It Only Show 2 Menu Icon On The Actionbar Even Though There Are Enough Space For 3?

I have 3 menu icons on the menu bar, but everytime it only shows 2 icons, the last one is in nowhere. my questions are: 1. there is enough space for 3 icons, why only 2 are shown?

Solution 1:

I have 3 menu icons on the menu bar

For the purposes of this answer, I am assuming that by "menu bar" you are referring to the action bar.

but everytime it only shows 2 icons, the last one is in nowhere

The last one is available by pressing the MENU button, for devices (or emulators) that have an off-screen MENU button.

there is enough space for 3 icons, why only 2 are shown?

Presumably because Android disagrees with your assessment of whether or not there is enough space for 3 icons.

if the system thinks the space is not enough for the 3rd icon, why doesn't it combine the 2nd and 3rd icon into an overflow menu?

I have no idea why you think forcing the 2nd icon -- which, by your admission, fits -- into the overflow menu would be a good idea. The 3rd menu item is in the overflow menu, which is accessed via the MENU button on devices that have one or a three-vertical-dots button on the action bar for devices that lack a MENU button.

Solution 2:

I encountered this same issue and resolved it by doing two things, although I think the main reason is the second item. I was using the Android Asset Studio to create icons for my Actionbar menu.

1. In Android Asset Studio, I set the icon to "trim".

2. In my menu/activity_main.xml definition file (or whatever you call your menu definition file) I defined my menu icons with android:showAsAction="always"

It looked something like this:

   <item android:id="@+id/menu_test"
     android:icon="@drawable/ic_menu_test"
     android:title="@string/menu_test"
     android:showAsAction="always" />