Flutter Show And Hide Text | Widget | Programmatically

We will learn how to show and hide text dynamically or programmatically in Flutter. You could also apply the same to any flutter widget.

Below is the complete code showing and hiding text on button click.

If you want to use, it just call DescriptionTextWidget() with an argument inside. The argument is expected to a long text. 

You also need to replace TextWidget with Text() widget and AppColors.. with any color you like.

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:shopping_app/components/colors.dart';
import 'package:shopping_app/uitls/app_dimensions.dart';
import 'package:shopping_app/widgets/text_widget.dart';
class DescriptionTextWidget extends StatefulWidget {
  final String text;

  DescriptionTextWidget({required this.text});

  @override
  _DescriptionTextWidgetState createState() => new _DescriptionTextWidgetState();
}

class _DescriptionTextWidgetState extends State<DescriptionTextWidget> {
  late String firstHalf;
  late String secondHalf;

  bool flag = true;
  double textHeight=Dimensions.screenSizeHeight/5.63;
  @override
  void initState() {
    super.initState();
    if (widget.text.length > textHeight) {
      firstHalf = widget.text.substring(0, textHeight.toInt());
      secondHalf = widget.text.substring(textHeight.toInt()+1, widget.text.length);
    } else {
      firstHalf = widget.text;
      secondHalf = "";
    }
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      margin:  EdgeInsets.only(bottom: Dimensions.margin80),
      child: secondHalf.isEmpty
          ? new TextWidget(size:16,text:firstHalf, color: AppColors.paraColor,height: 1.8,)
          : new Column(
        children: <Widget>[
          new TextWidget(size:16,height:1.8,text:flag ? (firstHalf + "...") : (firstHalf + secondHalf), color: AppColors.paraColor,),
          SizedBox(height: 5,),
          new InkWell(
            child: new Row(
              mainAxisAlignment: MainAxisAlignment.start,
              children: <Widget>[
                new TextWidget(
                  text: flag ? "show_more".tr : "show_less".tr,
                  color:AppColors.mainColor,
                  size: 14,
                ),
                Icon(flag?Icons.keyboard_arrow_down_outlined:Icons.keyboard_arrow_up_outlined, color: AppColors.mainColor,)
              ],
            ),
            onTap: () {
              setState(() {
                flag = !flag;
              });
            },
          ),
          SizedBox(height: 50,)

        ],
      ),
    );
  }
}

We use screen height as a standard to measure the text height. Here text height means how much of the screen the text should be visible

For the visible part we show the text. But we need to find the text length. 

If the text is too long, then we put part of it in the firstHalf variable and second part in secondHalf variable inside the initState() method.

Later inside the build() method, we just check if secondHalf is empty or not. If secondHalf is empty it means, the text is short and we can display it inside firstHalf.

If secondHalf is not empty, we show the text and the button in Column widget. We also need to toggle the condition using a bool variable.

We must use setState() to trigger the new build.

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