Flex 4.x Spark组件获取TextArea的行数

To get the number of lines call the following code in the change event handler of a Text control, My text area control is called taControl.

var nLines:uint=taControl.mx_internal::getTextFlow().flowComposer.numLines;

if(nLines>3)
{
Alert.show("Maximum of three lines of text is allowed for a project Topic");
}

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或者：

txtArea.textFlow.flowComposer.numLines.toString();