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Mono Android: Marquee Text View

November 11th, 2011

On mobile devices you have a limited set of real estate on the screen, often the text you need to display is to long to be shown.  You have several options, you can wrap it and take up additional vertical space, you ellipse it and expand it in a dialog, or you can scroll it marquee style to display it. Android supports all of these options, the one I chose to use for certain situations is marquee because its unobtrusive and can easily display the data to the user with zero interaction on their part.

There are some issues with the control unfortunately, one of them being the default behavior is to not marquee the text unless the TextView has focus.  The fix to this in Android is easy, inherit from TextView and override a couple of methods.  In Mono Android it was not so clear, I fussed with this for a while before diving into reflection to actually figure out how to get this to work.

Here is the code to allow a Marquee TextView in Mono Android:

C#
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public class MarqueeTextView : TextView
{
[Register(".ctor", "(Landroid/content/Context;)V", "")]
public MarqueeTextView(Context context)
: base(context) { }
public MarqueeTextView(IntPtr doNotUse)
: base(doNotUse) { }
[Register(".ctor", "(Landroid/content/Context;Landroid/util/AttributeSet;)V", "")]
public MarqueeTextView(Context context, IAttributeSet attrs)
: base(context, attrs) { }
[Register(".ctor", "(Landroid/content/Context;Landroid/util/AttributeSet;I)V", "")]
public MarqueeTextView(Context context, IAttributeSet attrs, int defStyle)
: base(context, attrs, defStyle) { }
protected override void OnFocusChanged(bool gainFocus, FocusSearchDirection direction, Android.Graphics.Rect previouslyFocusedRect)
{
if (gainFocus)
base.OnFocusChanged(gainFocus, direction, previouslyFocusedRect);
}
public override void OnWindowFocusChanged(bool hasWindowFocus)
{
if (hasWindowFocus)
base.OnWindowFocusChanged(hasWindowFocus);
}
public override bool IsFocused
{
get
{
return true;
}
}
}

Related posts:

  1. Mono Android: Working with SQLite
  2. Mono Android: Using Logcat Effectively
  3. Mono Android Linking (Xamarin)
  4. Mono Android Debugging
  5. InfiniteListView Mono Android

This entry was posted on Friday, November 11th, 2011 at 12:22 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

2 Comments

  1. Hugo says:
    February 12, 2012 at 4:59 pm

    Thanks for this Eric.. How can I register this control to use it in the xml layout? Regards!

  2. Eric Malamisura says:
    February 13, 2012 at 12:31 pm

    Hi Hugo,

    You do not need to register it, you can simple reference in your axml/xml layout files, but you do need to use the fully qualified name of the control. You need to use the namespace that java uses and not your .NET namespace, they are similar in Mono Droid but the distinct difference is in capitilization. It may be something like the following: myNamespace.Controls.MarqueeTextView, also Visual Studio will underline it as invalid because the XSD used for validation of the layoutfiles is unaware of this declaration, pay no attention to this, the only thing that should concern you is if it runs or not, pay very close attention to your LOGCAT output (see my other articles on how to set this up). You can also get your Java namespace from LogCat by simply running your application, or intentionally throwing an exception in your app and viewing the LOGCAT stack details.

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