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Using the System class

The System class contains methods and properties that allow you to interact with the user's operating system and retrieve the current memory usage of the runtime. The methods and properties of the System class also allow you to listen for imeComposition events, instruct the runtime to load external text files using the user's current code page or to load them as Unicode, or set the contents of the user's clipboard.

Getting data about the user's system at run time​

By checking the System.totalMemory property, you can determine the amount of memory (in bytes) that the runtime is currently using. This property allows you to monitor memory usage and optimize your applications based on how the memory level changes. For example, if a particular visual effect causes a large increase in memory usage, you may want to consider modifying the effect or eliminating it altogether.

The System.ime property is a reference to the currently installed Input Method Editor (IME). This property allows you to listen for imeComposition events ( flash.events.IMEEvent.IME_COMPOSITION) by using the addEventListener() method.

The third property in the System class is useCodePage. When useCodePage is set to true, the runtime uses the traditional code page of the operating system to load external text files. If you set this property to false, you tell the runtime to interpret the external file as Unicode.

If you set System.useCodePage to true, remember that the traditional code page of the operating system must include the characters used in your external text file in order for the text to display. For example, if you load an external text file that contains Chinese characters, those characters cannot display on a system that uses the English Windows code page because that code page does not include Chinese characters.

To ensure that users on all platforms can view the external text files that are used in your application, you should encode all external text files as Unicode and leave System.useCodePage set to false by default. This way, the runtime interprets the text as Unicode.

Saving text to the clipboard​

The System class includes a method called setClipboard() that allows the Flash runtime to set the contents of the user's clipboard with a specified string. For security reasons, there is no Security.getClipboard() method, since such a method could potentially allow malicious sites to access the data last copied to the user's clipboard.

The following code illustrates how an error message can be copied to the user's clipboard when a security error occurs. The error message can be useful if the user wants to report a potential bug with an application.

private function securityErrorHandler(event:SecurityErrorEvent):void
{
    var errorString:String = "[" + event.type + "] " + event.text;
    trace(errorString);
    System.setClipboard(errorString);
}

Flash Player 10 and AIR 1.0​

You can use the Clipboard class to read and write clipboard data in response to a user event. In AIR, a user event is not required for code running in the application sandbox to access the clipboard.