vb.net barcode printing 16: Concurrency in Java

Generation Data Matrix ECC200 in Java 16: Concurrency

CHAPTER 16: Concurrency
Generate Data Matrix 2d Barcode In Java
Using Barcode creation for Android Control to generate, create Data Matrix 2d barcode image in Android applications.
www.OnBarcode.com
Barcode Drawer In Java
Using Barcode encoder for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
Figure 16 2. Adding a progress indicator
Making Quick Response Code In Java
Using Barcode encoder for Android Control to generate, create Denso QR Bar Code image in Android applications.
www.OnBarcode.com
Barcode Generator In Java
Using Barcode generation for Android Control to generate, create Barcode image in Android applications.
www.OnBarcode.com
With the progress indicator selected, use the Attributes Inspector to make sure that its Display When Stopped checkbox is turned off. Then switch to the Bindings Inspector, and configure a binding for its Animate attribute, binding to the app delegate with its isWorking key. Then select the Start button in your window, where we ll make a similar configuration. Bind the button s Enabled attribute to the app delegate s isWorking key, and this time add an NSNegateBoolean for the Value Transformer. Now, we re even more done with this. Save your changes, Build & Run, and you ll now see that when you click the Start button, it becomes disabled, and the circular progress indicator appears and starts spinning. When the work is done, the progress indicator disappears, and the button goes back to normal. Now let s take this just one step farther, and add a horizontal progress indicator, where a horizontal movement tells you that things are happening, such as you may see in a software installer. Our progress view will go from 0 to 4, each work-method upping the number a bit. Like the circular progress indicator, this will be configured entirely with Cocoa Bindings. Start off by adding a new instance variable and property called completed to our app delegate s .h and .m files:
Code 128 Code Set A Encoder In Java
Using Barcode maker for Android Control to generate, create USS Code 128 image in Android applications.
www.OnBarcode.com
GTIN - 13 Generator In Java
Using Barcode drawer for Android Control to generate, create EAN-13 image in Android applications.
www.OnBarcode.com
CHAPTER 16: Concurrency
Creating PDF-417 2d Barcode In Java
Using Barcode creation for Android Control to generate, create PDF 417 image in Android applications.
www.OnBarcode.com
Creating Leitcode In Java
Using Barcode generator for Android Control to generate, create Leitcode image in Android applications.
www.OnBarcode.com
// SlowWorkerAppDelegate.h // inside the @interface curly-braces: NSInteger completed; // after the @interface curly-braces: @property (assign) NSInteger completed; // SlowWorkerAppDelegate.m // inside the @implementation block @synthesize completed;
Scanning Data Matrix ECC200 In VB.NET
Using Barcode recognizer for .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Generating Data Matrix ECC200 In Java
Using Barcode drawer for Eclipse BIRT Control to generate, create Data Matrix ECC200 image in Eclipse BIRT applications.
www.OnBarcode.com
Next, add the following near the top of the doWork: method, to reset it as soon as the user hits the Start button:
GS1 DataBar Truncated Encoder In Visual Studio .NET
Using Barcode generator for Visual Studio .NET Control to generate, create DataBar image in Visual Studio .NET applications.
www.OnBarcode.com
Decode ANSI/AIM Code 39 In Visual C#.NET
Using Barcode scanner for Visual Studio .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
self.completed = 0;
European Article Number 13 Decoder In .NET Framework
Using Barcode recognizer for Visual Studio .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Encode Matrix In Visual Studio .NET
Using Barcode generation for ASP.NET Control to generate, create 2D Barcode image in ASP.NET applications.
www.OnBarcode.com
Each work-method now needs to increment this variable when they re done. Our first thought might be to add the following line to each work-method:
QR Code 2d Barcode Maker In Java
Using Barcode drawer for Java Control to generate, create Denso QR Bar Code image in Java applications.
www.OnBarcode.com
Drawing UCC-128 In Java
Using Barcode printer for Java Control to generate, create USS-128 image in Java applications.
www.OnBarcode.com
self.completed = self.completed + 1;
PDF-417 2d Barcode Printer In VS .NET
Using Barcode generation for Reporting Service Control to generate, create PDF417 image in Reporting Service applications.
www.OnBarcode.com
Code 128 Creator In Java
Using Barcode maker for Eclipse BIRT Control to generate, create Code128 image in Eclipse BIRT applications.
www.OnBarcode.com
However, this is where one of those sticky multi-threaded problems turns up. If you think about that line of code, you ll see that what really happens that it first grabs the current value of the completed property by calling [self completed], then adds one to it, and then stores the result back into the completed property by calling [self setCompleted:]. In a multi-threaded environment, this can lead to incorrect behavior. What if, for instance, two threads execute a line like this at about the same time Suppose the starting value of completed is 2. If both threads read the current value before either of the writes out their own result, each will add 1 to their own copy of the value, then each of them will write their local sum (3) back into the completed property, which ends up containing the value 3 instead of the correct value, 4. A way around this is to use Objective-C s @synchronized keyword, which lets us specify that a piece of code can only be run by one thread at a time. Enter the following method at the top of your app delegate s @implementation section:
Draw USS Code 39 In VS .NET
Using Barcode encoder for ASP.NET Control to generate, create Code-39 image in ASP.NET applications.
www.OnBarcode.com
Making Data Matrix In None
Using Barcode maker for Font Control to generate, create Data Matrix ECC200 image in Font applications.
www.OnBarcode.com
- (void)incrementCompleted { @synchronized(self) { self.completed = self.completed + 1; } }
What we re doing there is taking the same code we thought about earlier and wrapping it in a sort of a safe zone. The @synchronized keyword takes as its one argument an object which will be used to determine the scope of the synchronization limiting. Basically, any calls using the same value will each try to grab the same lock. If some other thread has already claimed it, the current thread has to wait until the other thread is done. In this case, because we re using self, any calls made to this method on the same instance will all try to acquire the same lock. We only have one instance of our app delegate, so this is in practice a global lock, but for our purposes that s okay. The coding we need to do in order for this to work is to just add this line to the end of each of the work-methods:
Copyright © OnBarcode.com . All rights reserved.