Determining the number of lines in a TextArea control in Flex

The following example shows how you can get the number of lines in a Flex TextArea control by using the getTextField() method (in the mx_internal namespace) and the numLines property.

Full code after the jump.

View MXML

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/05/08/determining-the-number-of-lines-in-a-textarea-control-in-flex/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Script>
        <![CDATA[
            import mx.utils.StringUtil;

            private function textArea_change(evt:Event):void {
                callLater(updateStats, [evt]);
            }

            private function updateStats(evt:Event):void {
                var nLines:uint = textArea.mx_internal::getTextField().numLines;
                var nChars:uint = textArea.length;
                var str:String = "{0} characters; {1} lines";
                panel.status = StringUtil.substitute(str,
                                    nChars,
                                    nLines);
            }
        ]]>
    </mx:Script>

    <mx:String id="str" source="lorem.txt" />

    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="width (%):">
                <mx:HSlider id="slider"
                        minimum="50"
                        maximum="100"
                        value="100"
                        liveDragging="true"
                        snapInterval="1"
                        tickInterval="10" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>

    <mx:Panel id="panel"
            percentWidth="{slider.value}"
            height="100%">
        <mx:TextArea id="textArea"
                htmlText="{str}"
                condenseWhite="true"
                width="100%"
                height="100%"
                change="textArea_change(event);"
                resize="textArea_change(event);" />
    </mx:Panel>

</mx:Application>

View source is enabled in the following example.

14 thoughts on “Determining the number of lines in a TextArea control in Flex

  1. Hi-

    how would I achieve this in an actionscript class? I have a class extending textArea and I’m trying to access the textField methods by using

    import mx.core.mx_internal; (right after the package definition)
    this.mx_internal::getTextField().numLines; (in a function)

    I get no warnings, but I still get a null object reference error when I debug:(

    help!

    -Randy

  2. Thanks, was trying to figure out how to reach the numLines by reading the docs and didn’t find anything of value. Thankfully this blogpost fixed that!
    (So odd this number isn’t exposed by default.)

  3. Johan,

    You can file an enhancement request to make the property public at http://bugs.adobe.com/flex/. That won’t guarantee that it will happen, but it will at least show Adobe there is interest.

    It may possibly have been made internal if it was “expensive” to calculate, so they didn’t want to expose it too easily. You could also try extending the TextArea control and making this value public in your custom component.

    Peter

  4. Hi,

    Can you please give me an example of how to assign “tabStops” format property to textarea control?

    Thanks,
    Karthik

  5. Karthik,

    Try something like the following:

    <?xml version="1.0" encoding="utf-8"?>
    <mx:Application name="TextArea_tabStops_test"
            xmlns:mx="http://www.adobe.com/2006/mxml"
            layout="vertical"
            verticalAlign="middle"
            backgroundColor="white">
    
        <mx:Script>
            <![CDATA[
                private function init1():void {
                    var tf:TextFormat = new TextFormat();
                    tf.tabStops = [100, 200, 300, 400];
    
                    textArea1.mx_internal::getTextField().setTextFormat(tf);
                }
    
                private function init3():void {
                    textArea3.htmlText = "<TEXTFORMAT TABSTOPS='100,200,300,400'><P>The quick<TAB/>brown fox<TAB/>jumps over<TAB/>the lazy<TAB/>dog.</P><P>The<TAB/>quick brown<TAB/>fox jumps<TAB/>over the<TAB/>lazy dog.</P></TEXTFORMAT>";
                }
    
                private function init4():void {
                    var tf:TextFormat = new TextFormat();
                    tf.tabStops = [100, 200, 300, 400];
    
                    textArea4.mx_internal::getTextField().defaultTextFormat = tf;
                    textArea4.text = "The quick\\tbrown fox\\tjumps over\\tthe lazy\\tdog.\\nThe\\tquick brown\\tfox jumps\\tover the\\tlazy dog.";
    
                    textArea4.validateNow();
                    trace(textArea4.htmlText);
                }
            ]]>
        </mx:Script>
    
        <mx:TextArea id="textArea1"
                condenseWhite="true"
                width="500"
                creationComplete="init1();">
            <mx:htmlText>
                <![CDATA[
                    <p>The quick<tab/>brown fox<tab/>jumps over<tab/>the lazy<tab/>dog.</p><p>The<tab/>quick brown<tab/>fox jumps<tab/>over the<tab/>lazy dog.</p>
                ]]>
            </mx:htmlText>
        </mx:TextArea>
    
        <mx:TextArea id="textArea2"
                condenseWhite="true"
                width="500">
            <mx:htmlText>
                <![CDATA[
                    <TEXTFORMAT TABSTOPS="100,200,300,400"><P>The quick<TAB/>brown fox<TAB/>jumps over<TAB/>the lazy<TAB/>dog.</P><P>The<TAB/>quick brown<TAB/>fox jumps<TAB/>over the<TAB/>lazy dog.</P></TEXTFORMAT>
                ]]>
            </mx:htmlText>
        </mx:TextArea>
    
        <mx:TextArea id="textArea3"
                condenseWhite="true"
                width="500"
                initialize="init3();" />
    
        <mx:TextArea id="textArea4"
                width="500"
                initialize="init4();" />
    
    </mx:Application>
    

    Peter

  6. Flex 3 has the textHeight property now which does the same. However it is still not correct when using HTML Text. I suppose it’s because of the html tags used in the text which are not part of the visible text. It would be great if there was a solution to solve that problem!

  7. Hi – im working on a project where i have to determin the number of lines and find the best fontsize in a multiline textarea.
    When i try to get the number of lines as you show above, I somethimes get wrong values. I can se in flex that its 2 lines, and numLines give me 3 lines.
    Any help of why this is happening? It happens even if a use callater after textchange or fontchange.

  8. Really helpful example, I can end my search here. But I want to find a string of particular line, I am using TextArea, and have wordWrap=true, so using above code I can find number of line, but not the string contain each line.

    Please help me.

    Thanks

  9. private function removeExcessLines():void
    {
    var numLines:int = this.textField.numLines;

    if( numLines > numLinesAllowed )
    {
    var lines:Array = ObjectUtil.copy( this.textField.text ) .split(“\r”);
    var lineCount:int = 0;
    var lineIndex:int = 0;
    var currentLine:String;
    this.textField.text = ”;

    while( lineCount 0 ) {
    this.textField.text += currentLine;
    lineCount++;

    if( lineCount == 1 ) {
    this.textField.text += ‘\r’;
    }

    if( lineCount == 2 ) {
    this.selectionBeginIndex = this.length;
    this.selectionEndIndex = this.length;
    }
    }
    lineIndex++;
    }
    }
    }

  10. Hi,

    That’s cool! Thanks.
    May I know how to limit characters per line instead in a textarea and to be able to save the value entered as it is, meaning the space and empty lines are included in the array?
    Been trying to figure that out.
    Thanks.

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