Mono for Android Resource Naming Convention

When you create a default Mono for Android project the included resource files are named using a mixture of uppercase and lowercase letters. Please, do NOT follow this naming convention because this is the cause of a variety of unresolved, mostly minor bugs. Instead name all your resource files using all lowercase letters and underscores. It is much safer to follow this practice as opposed to the one presented by Xamarin.

ActionBarSherlock with Mono for Android

3/7/2013 - I updated the blog post so everything should be current and relevant as of today. This was long overdue, sorry.

For instant gratification try downloading the Xamarin sample project. However this will most likely yield an outdated version of the ActionBarSherlock library.

Today I will explain how to bind the ActionBarSherlock Java library so that it can be used with Mono for Android. ActionBar compatibility is important since over 90% of Android users are still running a pre 3.0 platform. It's a luxury Java programmers have enjoyed for awhile now, which can finally be shared with fellow C# programmers.

The required steps are listed below:

Build the ActionBarSherlock Zip

1. First, if necessary, download and install the latest version of Eclipse along with the ADT Plugin.
2. Next, download the latest version of ActionBarSherlock. After the download finishes extract the library folder from archive.
3. Rename the library folder to actionbarsherlock. In this tutorial, the library folder has been renamed/moved to c:\downloads\actionbarsherlock.
4. Start Eclipse and create a new workspace. In this tutorial, I created a workspace located at c:\projects\actionbarsherlock.
5. Begin creating a new Android project by clicking File -> New -> Other -> Android -> Android Project From Existing Code. Click Next.
6. In the "Root Directory" field, browse to c:\downloads\actionbarsherlock. Check the "Copy projects into workspace" field. Click Finish.
7. Click Project -> Clean and wait for Eclipse to finish building the project. Exit Eclipse after the build is complete. If you encounter any compile errors ensure that you are targetting Java 6+.
8. Open Windows Explorer, and browse to c:\projects\actionbarsherlock\actionbarsherlock. Select the bin, assets, and res folders and add them to a new Zip file. Name the file actionbarsherlock.zip.
9. Now browse to c:\projects\actionbarsherlock\actionbarsherlock\libs and locate the file android-support-v4.jar. No action is required yet, but remember this file location for future use.
10. Later, both the actionbarsherlock.zip and android-support-v4.jar files will be copied into Visual Studio.

Create the Binding Library

1. Open Visual Studio and create a new JAR Bindings Library project (click File -> New -> Project -> Mono for Android -> Java Bindings Library). Name the project ActionBarSherlockBinding and click OK.
2. Click Project -> ActionBarSherlockBinding Properties and change the Target API level to 14+.
3. Add a reference to the Mono.Android.Support.v4 binding library by clicking Project -> Add Reference and switching to the .NET tab. Select the Mono.Android.Support.v4 library and click OK.
4. Now copy the actionbarsherlock.zip and android-support-v4.jar files (from the previous section) into the Jars folder of the ActionBarSherlockBinding project in Visual Studio.
5. In the properties pane, right click on the the actionbarsherlock.zip file and change the Build Action to "LibraryProjectZip". Next, right click on the android-support-v4.jar file and change the Build Action to "ReferenceJar".
6. Open the Metadata.xml file located under the the Transforms folder and replace all of its contents with the XML code below. Save and close the file when finished.
   

   <metadata>
   
     <!-- Don't bind internal packages/classes -->
     <remove-node path="/api/package[starts-with(@name, 'com.actionbarsherlock.internal')]" />
     
     <!-- Normalize the API, forced to use underscore to avoid name conflicts -->
     <attr path="/api/package[@name='android.support.v4.app']" name="managedName">Android.Support.V4.App</attr>
     <attr path="/api/package[@name='com.actionbarsherlock']" name="managedName">ActionBar_Sherlock</attr>
     <attr path="/api/package[@name='com.actionbarsherlock.app']" name="managedName">ActionBar_Sherlock.App</attr>
     <attr path="/api/package[@name='com.actionbarsherlock.view']" name="managedName">ActionBar_Sherlock.View</attr>
     <attr path="/api/package[@name='com.actionbarsherlock.widget']" name="managedName">ActionBar_Sherlock.Widget</attr>
   
   </metadata>
   

   Note: Additional documentation regarding this step can be found here. Lines 6-11 are trivial but line 4 is important.
   
   
7. Build the solution and verify that there are no errors. There will probably be some warnings but it should still build successfully.

Reference the Binding Library

1. In Visual Studio, add a new Android Application project to the existing solution (click File -> Add -> New Project -> Mono for Android -> Android Application). Name the project ActionBarSherlockDemo and click OK.
2. Click Project -> ActionBarSherlockDemo Properties and change the Target API level to 14+.
3. Add a reference to the binding library by clicking Project -> Add Reference and switching to the Projects tab. Select the ActionBarSherlockBinding project and click OK.
4. Also add a reference to the Mono.Android.Support.v4 binding library from the .NET tab of the Add Reference dialog.
5. Rebuild the solution and verify that there are no errors.

Extend the SherlockActivity Class

1. Open Activity1.cs and change it so that it inherits from the ActionBar_Sherlock.App.SherlockActivity class. Documentation for the ActionBarSherlock library is more or less equivalent to the native ActionBar API.
2. Items can be added to the ActionBar by creating a menu resource and overriding the OnCreateOptionsMenu method.
3. Generate the AndroidManifest.xml and then edit it and set the SDK and theme like this:

   <?xml version="1.0" encoding="utf-8"?>
   <manifest xmlns:android="http://schemas.android.com/apk/res/android" android:installLocation="internalOnly">
     <uses-sdk android:minSdkVersion="7" android:targetSdkVersion="14" />
     <application android:theme="@style/Theme.Sherlock" />
   </manifest>
   

4. Rebuild the solution, deploy to the emulator or device, and congratulations, you're finished!

---

By Request - An ActionBar Tab Example

This is a quick and dirty example of ActionBar tabs with Mono for Android using ActionBarSherlock. This code is only intended as a demonstration of basic concepts. Please refer to the official Android ActionBar documentation for best practices and for a more complete example.

using System;

using Android.OS;
using Android.Views;
using ActivityAttribute = Android.App.ActivityAttribute;
using ActionBarNavigationMode = Android.App.ActionBarNavigationMode;
using Android.Support.V4.App;
using ActionBar_Sherlock.App;
using Tab = ActionBar_Sherlock.App.ActionBar.Tab;

namespace ActionBarSherlockDemo
{
    [Activity(Label = "Tab Activity", MainLauncher = true)]
    public class TabActivity : SherlockFragmentActivity, ActionBar_Sherlock.App.ActionBar.ITabListener
    {
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            SetContentView(Resource.Layout.Main);

            SupportActionBar.NavigationMode = (int)ActionBarNavigationMode.Tabs;
            SupportActionBar.SetDisplayShowTitleEnabled(true);

            Tab tab = SupportActionBar.NewTab();
            tab.SetTag("TAB1");
            tab.SetText("TAB 1");
            tab.SetTabListener(this);
            SupportActionBar.AddTab(tab);
            
            tab = SupportActionBar.NewTab();
            tab.SetTag("TAB2");
            tab.SetText("TAB 2");
            tab.SetTabListener(this);
            SupportActionBar.AddTab(tab);
        }

        public void OnTabSelected(Tab tab, Android.Support.V4.App.FragmentTransaction ft)
        {
            string tag = tab.Tag.ToString();

            Fragment f = SupportFragmentManager.FindFragmentByTag(tag);
            if (f != null)
            {
                ft.Show(f);
                return;
            }

            if (tag == "TAB1")
                f = new TestFragment1();
            else if (tag == "TAB2")
                f = new TestFragment2();

            ft.Add(Resource.Id.fragmentPlaceholder, f, tag);
        }


        public void OnTabUnselected(Tab tab, Android.Support.V4.App.FragmentTransaction ft)
        {
            string tag = tab.Tag.ToString();

            Fragment f = SupportFragmentManager.FindFragmentByTag(tag);
            if (f != null)
            {
                ft.Hide(f);
                return;
            }
        }

        public void OnTabReselected(Tab tab, Android.Support.V4.App.FragmentTransaction ft)
        {
            //Do nothing
        }
    }

    public class TestFragment1 : Fragment
    {
        public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle bundle)
        {
            return inflater.Inflate(Resource.Layout.test1, container, false);
        }
    }

    public class TestFragment2 : Fragment
    {
        public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle bundle)
        {
            return inflater.Inflate(Resource.Layout.test2, container, false);
        }
    }
}

ThreadStaticAttribute

Possibly one of the coolest tricks I've learned in awhile, adding the ThreadStaticAttribute to your .NET static field makes it static but only visible or accessible within the context of the current executing thread. So there can be multiple threads executing at the same time, referencing the same thread-static field, but the value returned is potentially different for each individual thread. This allows you to easily share a static value between different classes / methods of a thread while still encapsulating it from other threads. Because of this it is slightly more insulated than a normal static field, and can be useful in some cases where you don't necessarily want to chain-pass an object as a parameter from method to method, especially if the parameter is passed across many different classes with method calls many layers deep.

Perhaps a good use case for the ThreadStaticAttribute is managing database transactions. Often you need to pass the Transaction object between different method calls, and frequently these method calls are divided into different classes. You can declare a separate class that holds a thread-static reference to the current Transaction which eliminates the need to chain pass it as a parameter between the different methods. Of course this is not strictly necessary anymore since the introduction of the TransactionScope class, but guess what, this is basically exactly how the TransactionScope class is implemented - the associated Transaction class maintains a thread-static reference to the current Transaction.

A word of warning though, be careful when using the ThreadStaticAttribute if you are not in complete control of the thread. Examples of potentially dangerous situations are Thread Pools, ASP .NET, and WCF. I'm not saying that you absolutely shouldn't use the ThreadStaticAttribute in these situations, but you need to be knowledgeable about the thread's lifecycle so as to avoid unexpected errors. In cases like these you need to handle when and if the thread is re-used, terminated, or if your code runs on different threads during different phases of its lifecycle. So, if you use the thread-static feature then do so wisely, cautiously, and test thoroughly. It's not a feature you should overuse or abuse, but occasionally it may be a good solution for some niche problem.

Below is an example of actually using the ThreadStaticAttribute:

[ThreadStatic]
private static string foo;

Warning: ThreadStaticAttribute fields are initialized in the static constructor which only executes once. In the example below the variable foo will only be initialized to "TEST" for the first thread, but the value will be null for subsequent threads.

[ThreadStatic]
private static string foo = "TEST";

To work around this problem trying using a property to access and initialize the ThreadStaticAttribute field:

[ThreadStatic]
private static string _foo;

public static string Foo
{
   get
   {
     return _foo ?? "TEST";
   }
}

Note: There's also something new in .NET 4.0 called ThreadLocal, which is similar to ThreadStatic but doesn't require the variable to be static. I may write a separate blog about it sometime in the future.

Links:

• http://blogs.msdn.com/b/jfoscoding/archive/2006/07/18/670497.aspx
• http://www.mahmutkus.com/post/18968396817/threadstatic-usage-can-be-your-enemy
• http://piers7.blogspot.com/2005/11/threadstatic-callcontext-and_02.html

How to Improve SyntaxHighlighter

SyntaxHighlighter is a javascript library that I use on this blog to colorize and display my code snippets. SyntaxHighlighter is a great tool and the author deserves a lot of respect, but the default "select all" and "copy and paste" functionality can be somewhat frustrating. For the last few days I've been troubleshooting various issues with the "select all" and "copy and paste" functionality. Depending on the configuration and the browser, sometimes it copies the text with non-breaking spaces which causes errors in certain IDEs. Other times it copies the text with the wrong indentation or with no line breaks at all.

Even the fact that you can quickly select all of the text is not immediately apparent; SyntaxHighlighter contains a "hidden" feature that allows double clicking the text to select all of it (of course the average user would never know this functionality existed). Finally, when it does select all of the text it copies it from its native, colorized form into a simple, monochrome textarea control that is created dynamically using some javascript magic. The performance can be a little slow, it may cause the view to randomly jump or scroll in Internet Explorer, and the transition just looks a little tacky.

Below is a script you can embed in the header section of your website or blog that will correct some of these problems. It changes the the default behavior of the "select all" operation and it also adds a button to the top-right corner that is clearly labelled "Select All" (you can still double click the text too).

If you use this script for Blogger, be sure to replace any ampersands with & and any less than signs with < and any greater than signs with >. If you don't do this you will get a cryptic error when you try to upload the html. Blogger requires these characters to be escaped since it uses XML.

<!-- jQuery -->
<script src='http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js' type='text/javascript'></script>

<!-- Syntax Highlighter Additions START -->
<link href='http://alexgorbatchev.com/pub/sh/current/styles/shCore.css' rel='stylesheet' type='text/css'/>
<link href='http://alexgorbatchev.com/pub/sh/current/styles/shThemeEclipse.css' rel='stylesheet' type='text/css'/>
<script src='http://alexgorbatchev.com/pub/sh/current/scripts/shCore.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushCSharp.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushJava.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushBash.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushCss.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushJScript.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushSql.js' type='text/javascript'></script>
<script src='http://alexgorbatchev.com/pub/sh/current/scripts/shBrushXml.js' type='text/javascript'></script>

<style>
.syntaxwrapper
{
 position: relative;
}

.syntaxwrapper .toolbar
{
 position: absolute;
 z-index: 10;
 right: -7px;
 top: -17px;
 width: 65px;
 height: 20px;
 line-height: 20px;
 text-align: center; 
 color: #777;
 font-family: arial;
 font-size: 12px;
 cursor: pointer;
}
</style>

<script language='javascript' type='text/javascript'>

 function selectAll(element)
 {
     if (window.getSelection && document.createRange)
     {
         var selection = window.getSelection();
         var range = document.createRange();
         range.selectNodeContents(element);
         selection.removeAllRanges();
         selection.addRange(range);
     }
     else if (document.body.createTextRange)
     {
         var range = document.body.createTextRange();
         range.moveToElementText(element);
         range.select();
     }
 }

 function customizeSyntaxHighlighter()
 {
     var syntax = $('.syntaxhighlighter');
     if (syntax.length == 0)
     {
         setTimeout(function() { customizeSyntaxHighlighter(); }, 100);
         return;
     }

     syntax.each(function(index)
     {
         var selector = $(this);
         var wrapper = $(document.createElement('div')).addClass('syntaxwrapper');
         var toolbar = $(document.createElement('div')).addClass('toolbar').html('Select All');
         var code = selector.find('.code').first();

         selector.wrap(wrapper).before(toolbar);

         toolbar.get(0).onclick = code.get(0).ondblclick =
         function()
         {
             selectAll(code.get(0));
             syntax.scrollLeft(0);
             return false;
         };

         code.find('.line').each(
         function(index)
         {
             //this hack seems to fix all versions of IE
             this.appendChild(document.createTextNode('\r'));
         });
     });
 }

 SyntaxHighlighter.config.bloggerMode = true;
 SyntaxHighlighter.defaults.toolbar = false;
 SyntaxHighlighter.defaults['quick-code'] = false;
 SyntaxHighlighter.all();
 customizeSyntaxHighlighter();
 
</script>
<!-- Syntax Highlighter Additions END -->

Here is the SyntaxHighlighter website:

http://alexgorbatchev.com/SyntaxHighlighter/

SNMP Introduction: Communicating with your Router

"Simple Network Management Protocol (SNMP) is an Internet-standard protocol for managing devices on IP networks. Devices that typically support SNMP include routers, switches, servers, workstations, printers, modem racks, and more. It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention." - Wikipedia

Below is a Java code snippet which uses the 3rd party library snmp4j to communicate with a router. In this example we obtain the name of the router and the current data usage. Before executing the code confirm that your router supports SNMP and that it is enabled. Also verify that the SNMP read and write community is set to "public". These are configurable values that can be updated from within your router's administrative application.

Note that the OID variables contain long and cryptic numeric values. These values can be obtained using a free SNMP browser such as iReasoning's MIB Browser. When using an SNMP browser you must supply your router's IP address and SNMP port (usually 161) to connect to your router. Once connected you can browse through the different properties as a tree structure and obtain any of the numeric values for the OIDs.

import java.io.*;
import org.snmp4j.*;
import org.snmp4j.mp.*;
import org.snmp4j.smi.*;
import org.snmp4j.transport.*;

public class SnmpClient
{
 public static final OID sysNameOID = new OID(".1.3.6.1.2.1.1.5.0");
 public static final OID ifNumberOID = new OID(".1.3.6.1.2.1.2.1.0");
 public static final OID ifOutOctetsOID = new OID(".1.3.6.1.2.1.2.2.1.16.1");
 public static final OID ifInOctetsOID = new OID(".1.3.6.1.2.1.2.2.1.10.1");
 
 private String address;
 private Snmp snmp;
 
 public static void main(String[] arg)
 {
  try
  {
   //Create a client with the router's IP Address and SNMP port (161 is default)
   SnmpClient client = new SnmpClient("udp:192.168.0.1/161");
   
   //Get the router's name
   String name = client.getAsString(sysNameOID);
   
   //Display the router's name
   System.out.println("ROUTER'S NAME: " + name);
   
   //Update the router's name (sysName is one of the few properties that are writable)
   client.setAsString(sysNameOID, "TEST");
   
   //I had to read this property before reading the other data usage properties
   client.getAsInt(ifNumberOID);
   
   //Get total number of bytes sent since last router reboot
   int bytesSent = client.getAsInt(ifOutOctetsOID);
   
   //Get total number of bytes received since last router reboot
   int bytesReceived = client.getAsInt(ifInOctetsOID);
   
   //Calculate total number of bytes sent and received
   int bytesTotal = bytesSent + bytesReceived;
   
   //Display combined total data usage in megabytes
   System.out.println("DATA USAGE: " + (bytesTotal / 1024 / 1024) + " MB");
  }
  catch (Exception e)
  {
   e.printStackTrace();
  }
 }
 
 public SnmpClient(String address) throws IOException
 {
  this.address = address;
  start();
 }

 private void start() throws IOException
 {
  DefaultUdpTransportMapping transport = new DefaultUdpTransportMapping();
  snmp = new Snmp(transport);
  transport.listen();
 }
 
 public void stop() throws IOException
 {
  snmp.close();
 }
 
 private Target createTarget()
 {
  Address targetAddress = GenericAddress.parse(address);
  CommunityTarget target = new CommunityTarget();
  target.setCommunity(new OctetString("public"));
  target.setAddress(targetAddress);
  target.setRetries(3);
  target.setTimeout(1500);
  target.setVersion(SnmpConstants.version1);
  return target;
 }
 
 private PDU createGetPDU(OID oid)
 {
  PDU pdu = new PDU();
  pdu.setType(PDU.GET);
  pdu.add(new VariableBinding(oid));   
  return pdu;
 }
 
 public Variable get(OID oid) throws IOException
 {
  PDU response = snmp.send(createGetPDU(oid), createTarget()).getResponse();
  if (response != null && response.size() > 0)
  {
   return response.get(0).getVariable();
  }
  throw new IOException("Unable to obtain response from server");
 }
 
 public String getAsString(OID oid) throws IOException
 {
  return get(oid).toString();
 }
 
 public int getAsInt(OID oid) throws IOException
 {
  return get(oid).toInt();
 }
 
 private PDU createSetPDU(OID oid, Variable value)
 {
  PDU pdu = new PDU();
  pdu.setType(PDU.SET);
  pdu.add(new VariableBinding(oid, value));
  return pdu;
 } 
 
 public void set(OID oid, Variable value) throws IOException
 {
  snmp.send(createSetPDU(oid, value), createTarget());
 }
 
 public void setAsString(OID oid, String value) throws IOException
 {
  set(oid, new OctetString(value));
 }
 
 public void setAsInt(OID oid, int value) throws IOException
 {
  set(oid, new Integer32(value));
 }
}

Search SQL Server Column Names

Below is a short T-SQL code snippet that demonstrates how to search for some text in all the column names in all the tables in a SQL Server database.

declare @SEARCHTEXT varchar(256)
set @SEARCHTEXT = 'TEXT YOU WANT TO SEARCH FOR'
select t.table_name,
c.column_name,
c.data_type,
c.character_maximum_length
from information_schema.tables t
inner join information_schema.columns c
on c.table_name = t.table_name
where c.column_name like '%' + @SEARCHTEXT + '%'
order by t.table_name, c.column_name

Search SQL Server Stored Procedures and Functions

Below is a short T-SQL code snippet that demonstrates how to search for some text in all the stored procedures and functions in a SQL Server database.

DECLARE @SEARCHTEXT VARCHAR(256)
SET @SEARCHTEXT = 'TEXT YOU WANT TO SEARCH FOR'
SELECT ROUTINE_NAME
FROM INFORMATION_SCHEMA.ROUTINES
WHERE OBJECT_DEFINITION(OBJECT_ID(ROUTINE_NAME)) LIKE '%' + @SEARCHTEXT + '%'
ORDER BY ROUTINE_NAME