Develop Reference

State selector for a custom button layout (i.e. LinearLayout)

I'm wondering if it's possible to build a custom button layout with different appearance depending on state so it acts like a button. For example, a LinearLayout with an ImageView and TextView, with these states.
When the button is in normal state, display image_normal.png and text in red.
When the button is pressed, display image_pressed.png, background red and text in white.
When the button is disabled, display image_disabled.png and text in grey.
Thank you!

Any view can have any background and any view can be made clickable, so there is nothing preventing you from having a LinearLayout with the background you described. It's worth noting that you don't need a LinearLayout to have an image next to text, you can use the fact that TextView supports drawables on any side of the text using the drawable[Left|Top|Right|Bottom] attributes.
If your question is about the syntax of a selector drawable, I would refer you to the documentation. Note that Android evaluates states top to bottom, so choose the order wisely. The last item should be the "default" state when none of the ones above apply. For the example you gave, you would probably have something like
<selector>
<item android:state_pressed="true" android:drawable="..." />
<item android:state_enabled="true" android:drawable="..." />
<item android:drawable="..." /> <!-- disabled -->
</selector>

Android: how add opacity on ImageButton click?

I thought to use OnTouchListener and tracking down and up events, setting then an alpha value, but I have to add this listener to all ImageButtons (they are really a lot). I wonder if there is a shortcut to achieve this result.

In case that when user click on button and this cause to change the opacity of that button you can do:
In your xml file on button declaration add this line:
android:onClick = "clickMethod"
and in the java file you need to implement the clickMethod,
public void clickMethod(View view)
{
// change opacity
}
so, if you want to do the same process(change button opacity) for each button, so in the xml file
for each button add the line
android:onClick="clickMethod"

If you want to give users better expirince when clicking ImageButton, I recommend you to use selection drawable as the background of your ImageButtons. It gives better user experience, then setting opacity while performing click and it’s really easy to achieve.
First you need to create in your drawable folder file with name f.e. image_button_selection.xml. In which you should define:
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_focused="true" android:state_pressed="false" android:drawable="#drawable/your_focused_background_drawable" />
<item android:state_pressed="true" android:drawable="#drawable/your_pressed_background_drawable " />
<item android:drawable="#android:color/transparent" />
</selector>
You should also put into drawable two png with alpha channel that will be displayed on focused button and pressed button. In this example they should be named respectively your_focused_background_drawable and your_pressed_background_drawable.
When you do this you should in every use of your ImageButton in xml use following statement:
android:background="#drawable/image_button_selection"

GridView item selector checked state not appearing

I have a GridView with a bunch of items that are being populated using a custom adapter. The grid view is set to CHOICE_MODE_MULTIPLE_MODAL in java, and I'm able to select things using the contextual action bar (all of this works fine).
I want the grid items to highlight when pressed and have a different highlight when selected (exactly the behavior you'll see in the Gallery app in ICS).
I have a selector which is being specified in the grid view XML like so: listSelector="#drawable/grid_item_selector". I have also specified android:drawSelectorOnTop="true". Here is the selector XML:
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="#drawable/grid_item_selected" android:state_activated="true"/>
<item android:drawable="#drawable/grid_item_selected" android:state_checked="true"/>
<item android:drawable="#drawable/grid_item_selected" android:state_selected="true"/>
<item android:drawable="#drawable/grid_item_pressed" android:state_pressed="true"/>
<item android:drawable="#android:color/transparent"/>
</selector>
The pressed state works perfectly. However, the checked/selected states never appear.
Even if I set an item to be checked in my java code, the checked state never appears.
I can't set the selector as the background of the grid items themselves because I need the selected state drawable to be the foreground, not the background.

The selector only shows on the thing that you're touching. Once you take your finger off it no longer displays.
So, what I've ended up doing is having a View at the bottom of the layout (so it appears on top) with a background set to a selector.
The selector only has anything for state_selected.
The OS handles the rest.
Not exactly the nicest, but it works...

Android Custom Button Pressed State

I am trying to change the appearance of an Android Button, but I can't get it to work. I use this code in "custom_button.xml" to handle the drawing of the button:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android" >
<item
android:drawable="#drawable/btn_normal"
/>
<item android:drawable="#drawable/btn_over"
android:state_pressed="true"/>
In my layout file I set the button's background to the custom_button drawable. The normal state works (the one that first appears), but when the button is pressed the image doesn't change. I double checked to make sure I am using different images and I am. Does anyone know why this isn't working?
Thanks!

Switch the order of the items (so pressed first, then neutral). Pressed or not, the top item is always true.

Button draws normal state after pressing

I'm new to Android and just starting the very basics. I implement my custom button skin using .9.png images for norma/focus/pressed states. It works fine, but I noticed that after a pressed the focussed button it visually "lost" focus and draws the normal state frame. I planned to use different state images to highloght what button is selected right now, but it seems that it would not work. I noticed also that the same happens with the default LAF button. Is it OK, or it's just emulator issue? What the good workaroud can be used?
Thanks

I think the following may help. I wanted to have one of the buttons in a list of button to be coloured differently, to highlight the fact you were already in that section.
My buttons android:background field was set to the following drawable (drawable/my_btn.xml)
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_pressed="true" android:drawable="#drawable/btn_pressed" />
<item android:state_focused="true" android:drawable="#drawable/btn_focused" />
<item android:state_selected="true" android:drawable="#drawable/btn_selected" />
<item android:drawable="#color/transparent" />
</selector>
You'll noticed i've got an item with the android:state_selected="true" attribute set.
Then in code you can have
Button mybtn = (Button)findViewById(R.id.my_btn_1);
mybtn.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
Button btn = (Button)findViewById(R.id.nav_secondary_1);
btn.setSelected(true);
}
});
I'm not sure if you can set the selected stat of a Button through a property in the xml. Not sure you would want to.
The order of the item's are also important as it can change the visibility of the other states. The current order will allow you to see the pressed and focused states. however, if you moved the selected item to the top you would find that your pressed and focused states would not be displayed.
I am not sure if you can combine the pressed, focused and selected states to allow for more customised graphics. I haven't tried it but the following would allow for more complicated state based graphical layouts.
<item android:state_selected="true" android:state_focused="true" android:drawable="#drawable/btn_selected_focused" />
Read up on Selectors here http://developer.android.com/guide/topics/resources/drawable-resource.html

This is the default behavior in touch mode, and you should not seek to tamper with it. This is how your users will expect for your app to behave. If you set the focus without touching the screen, such as when using the trackball that's available on most devices, it will indeed remain in focus, but in touch mode there's no visual representation for the state of having focus.