Overlapping Views in Android

Question

Is it possible to have overlapping views in Android? I would like to have an ImageView with a transparent png in the front and another view in the background.

edit:

This is what I have at the moment, the problem is that the image in the imageView is not transparent, the parts that should be transparent are just black.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:orientation="vertical"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/gallerylayout"
>
<Gallery android:id="@+id/overview"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    />

 <ImageView android:id="@+id/navigmaske"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:src="@drawable/navigmask"
    /> 

</RelativeLayout>

edit:

I got it to work, it was a theme file from another programmer on the team. Just changed this

<item name="android:background">#FF000000</item>

to this

<item name="android:background">#00000000</item>

Solution 1

Android handles transparency across views and drawables (including PNG images) natively, so the scenario you describe (a partially transparent ImageView in front of a Gallery) is certainly possible.

If you're having problems it may be related to either the layout or your image. I've replicated the layout you describe and successfully achieved the effect you're after. Here's the exact layout I used.

<RelativeLayout 
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/gallerylayout"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  <Gallery
    android:id="@+id/overview"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
  />
  <ImageView
    android:id="@+id/navigmaske"
    android:background="#0000"      
    android:src="@drawable/navigmask"
    android:scaleType="fitXY"
    android:layout_alignTop="@id/overview"
    android:layout_alignBottom="@id/overview"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
  />
</RelativeLayout>

Note that I've changed the parent RelativeLayout to a height and width of fill_parent as is generally what you want for a main Activity. Then I've aligned the top and bottom of the ImageView to the top and bottom of the Gallery to ensure it's centered in front of it.

I've also explicitly set the background of the ImageView to be transparent.

As for the image drawable itself, if you put the PNG file somewhere for me to look at I can use it in my project and see if it's responsible.

Solution 2

Also, take a look at FrameLayout, that's how the Camera's Gallery application implements the Zoom buttons overlay.

Solution 3

If you want to add you custom Overlay screen on Layout, you can create a Custom Linear Layout and get control of drawing and key events. You can my tutorial- Overlay on Android Layout- http://prasanta-paul.blogspot.com/2010/08/overlay-on-android-layout.html

Solution 4

Visible gallery changes visibility which is how you get the gallery over other view overlap. the Home sample app has some good examples of this technique.

Solution 5

The simples way arround is to put -40dp margin at the buttom of the top imageview

View more solutions

Comments

[Joe D'Andrea]

Nice! I tried setting an ImageView background to #0000 (and @android:color/transparent) … to no avail. If I try to fade it (alpha from 1.0 down to 0.0) it fades to black instead of fading to transparent. This is on Android 2.0.

[Joe D'Andrea]

A-ha! I was using LinearLayout. I changed it to Relative, then put the ImageView last. Now the fade "just works" … yay! Thanks tons for the code/tip. That cued me as to my goof.

[David]

Hi im using same xml layout coding but my transparent image is not displayed.It shows only black screen. Anything i want to add in my code.

[num1]

AbsoluteLayout is now depreciated. Nobody should use it anymore.

[class stacker]

Considering the functionality, I'd say FrameLayout should be preferred in general for such purposes, for the sake of the much lower layout overhead. However, for API < 11, FrameLayout can't handle the above combination of propagating the second child's height to the first child correctly, so RelativeLayout is your only option in this case; see here.

[class stacker]

Certainly a nice experiment, thank you for sharing the code. But this can simply be achieved with FrameLayout unless your specific scenario is affected by a pre-API 11 bug, see here, in which case you still can use RelativeLayout.

[class stacker]

I've always gone for FrameLayout which I find perfect for such purposes. However, I only now found out that prior to API 11, FrameLayout fails to propagate the maximum measured height to all of its children, see here. Hence, for supporting Android 2, one has to use RelativeLayout unless one goes for a predetermined height.