Lecture 19 Microsoft’s Approach 1 – .NET
Mobile Framework part 2
Rob Pooley rjp@macs.hw.ac.uk
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{
Class Form1 static void Main()
{
Application.Run(new Form1());
} private void menuItem2_Click(object sender, System.EventArgs e)
{
Application.Exit();
}
}
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MyNewForm mynewformForm = new MyNewForm (); mynewformForm.ShowDialog();
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• Let's demonstrate setting a control's value by altering a text label.
The sequence of events is:
1. Create a new instance of the Form that contains the control (but don't display it).
2. Change the property corresponding to the text label of the control.
3. Display the Form.
• Assume we have added a text label called label1 to the new Form, and we can do all that with some code like this:
MyNewForm mynewformForm = new MyNewForm(); mynewformForm.label1.Text = "Hello World"; mynewformForm.ShowDialog();
• The only thing to remember is that the label1 property, by default, will be private so the code for the main Form won't be able to see it.
• You get around this by setting it to Public
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Note The size of the Form is not important as the Pocket PC will always expand it to fill the screen.
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• If you are creating a new Form that acts as a dialog box, you should also add some way for the user to close it, such as a new button with code like the following attached: private void button1_Click(object sender,
System.EventArgs e)
{ this.Close();
}
• The new Form will have a close button in the top right for the user to click
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• tabs provide access to multiple pages all stored on one dialog.
• These can be very useful if your application has a lot of settings for the user to work through.
• Use the TabPage Collection to add and rename new tab pages.
• Each page is a like a blank form to which you add controls.
• Treat each tab page as a Form, and place the controls on it as you see fit.
• The Pocket PC will look after displaying the pages and controls
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• All the common features Windows Forms in the .NET Framework are present in .NET Compact
Framework. These features are differently implemented in a separate manner to make them more efficient for size and performance.
• Supported are:
• Common controls such as:
– Buttons
– Listboxes
– Tree-views
– Listviews
– Combo boxes
– Textboxes
– Picture boxes
– Scroll bars
– Labels
• Bitmaps
• Pens
• Brushes
• Colors
• Drawing
• Fonts
• Support for Forms
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• The System.Net.Sockets namespace is used to provide an interface to access the transport layer of protocol stacks.
• Multiple protocols can be exposed through this class.
• In addition, .NET Compact Framework provides additional classes that simplify common developer tasks encapsulating much of the necessary code that is common across all TCP client/server applications.
• Some of these are:
– TCPListener
– TCPClient
– UDPClient
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• HttpWebRequest and HttpWebResponse classes provide a rich HTTP client.
• These classes also support many of the standard mechanisms for encryption and authentication such as
SSL/TLS and basic HTTP authentication.
• Other Web requests can be implemented using other protocols such as:
– WebRequest interface
– WebResponse interface
– IwebRequestCreate interface
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• The System.Threading
namespace provides classes and interfaces that enable multithreaded programming.
• In addition to classes for synchronizing thread activities and access to data ( Mutex , Monitor , Interlocked ,
AutoResetEvent , and so on), this namespace includes a
– ThreadPool class that allows you to use a pool of system-supplied threads, and a
– Timer class that executes callback methods on thread pool threads.
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using System; using System.Threading;
// Simple threading scenario: Start a static method running
// on a second thread. public class ThreadExample
{
// The ThreadProc method is called when the thread starts.
// It loops ten times, writing to the console and yielding
// the rest of its time slice each time, and then ends. public static void ThreadProc() {
}
} for (int i = 0; i < 10; i++) {
Console.WriteLine("ThreadProc: {0}", i);
// Yield the rest of the time slice.
Thread.Sleep(0); public static void Main() {
Console.WriteLine("Main thread: Start a second thread.");
// The constructor for the Thread class requires a
ThreadStart
// delegate that represents the method to be executed on the
// thread. C# simplifies the creation of this delegate.
Thread t = new Thread(new
ThreadStart(ThreadProc));
// Start ThreadProc. On uniprocessor, thread does not get
// any processor time until the main thread yields.
//Uncomment
// Thread.Sleep that follows t.Start() to see the difference. t.Start();
//Thread.Sleep(0); for (int i = 0; i < 4; i++) {
Console.WriteLine("Main thread: Do some work.");
Thread.Sleep(0);
}
Console.WriteLine("Main thread: Call Join(), to wait until ThreadProc ends."); t.Join();
Console.WriteLine("Main thread: ThreadProc.Join has returned. Press Enter to end program.");
Console.ReadLine();
}
}
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• Problems
– Palm OS is the most cumbersome to program
– Palm OS uses C/C++
– Palm OS and .NET
Compact are both specific to certain kinds of device
– J2ME requires a JVM
(KVM or CVM)
– J2ME is not really compatible with J2SE
• Benefits
– Palm OS is available for many PDAs
– J2ME is the most portable
– J2ME has wireless features as standard
– J2ME uses Java
– .NET is higher level
– .NET supports XML
– .NET supports several languages
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