location2025/lib/widget/gradually_print_text.dart

import 'dart:async';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';

class GraduallyPrintText extends StatefulWidget {
  const GraduallyPrintText({
    super.key,
    this.initTxt,
    required this.graduallyController,
    this.textStyle,
  });

  final TextStyle? textStyle;
  final GraduallyController graduallyController;
  final String? initTxt;

  @override
  State<GraduallyPrintText> createState() => _GraduallyPrintTextState();
}

typedef GraduallyTxtListener = void Function(String txt);

class GraduallyController {
  String graduallyTxt = '';
  int progressIndex = 0;
  Timer? appendTimer;
  bool? isAppendDone;
  bool? isShowDone;
  Duration printSpeed;

  GraduallyTxtListener? listener;
  VoidCallback? finishedListener;

  GraduallyController({this.printSpeed = const Duration(milliseconds: 60)});

  setGraduallyTxtListener(GraduallyTxtListener listener) {
    this.listener = listener;
  }

  setGraduallyFinishedListener(VoidCallback finishedListener) {
    this.finishedListener = finishedListener;
  }

  void clear() {
    appendTimer?.cancel();
    appendTimer = null;
    graduallyTxt = '';
    progressIndex = 0;
    isAppendDone = null;
    isShowDone = null;
    listener?.call(''); // 通知 UI 清空
  }

  append(String txt) {
    graduallyTxt += txt;
    _startAppend();
  }

  void _initAppend() {
    progressIndex = 0;
    isAppendDone = null;
    isShowDone = null;
    appendTimer = null;
  }

  appendDone() {
    isAppendDone = true;
    // debugPrint('GraduallyMdText: appendDone');
  }

  _startAppend() {
    if (appendTimer != null) {
      return;
    }
    _initAppend();
    appendTimer = Timer.periodic(printSpeed, (timer) {
      // debugPrint('GraduallyMdText-progressIndex: $progressIndex');
      if (progressIndex < graduallyTxt.length) {
        progressIndex += 1;
        listener?.call(graduallyTxt.substring(0, progressIndex));
      } else if (isAppendDone == true) {
        // debugPrint('GraduallyMdText: appendTimer done');
        dispose();
        finishedListener?.call();
      }
    });
  }

  dispose() {
    appendTimer?.cancel();
    isAppendDone = null;
    isShowDone = true;
    appendTimer = null;
  }
}

class _GraduallyPrintTextState extends State<GraduallyPrintText> {
  String mdTxt = '';

  @override
  void initState() {
    super.initState();
    mdTxt = widget.initTxt ?? '';
    widget.graduallyController.setGraduallyTxtListener((txt) {
      if (mounted) {
        setState(() {
          mdTxt = txt;
        });
      }
    });
  }

  @override
  void dispose() {
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return SelectionArea(
      child: Text(
        mdTxt,
        style: widget.textStyle,
      ),
    );
  }
}