Flutter打印功能插件rare_print的使用

本篇文档将介绍如何在Flutter中使用rare_print插件来实现打印功能。该插件支持预览和纯指令打印，以避免因图片打印而导致的指令过多问题。

RarePrint

这是一个用于打印的渲染库。 支持预览，使用纯指令打印，避免因图片打印导致的指令过多问题。

目前支持的指令集：

• CPCL
• TSCL

打印Demo

以下是一个简单的打印示例：

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:rare_print/control_base.dart';
import 'package:rare_print/cpcl_canvas.dart';
import 'package:rare_print/io.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: PrintPage(),
    );
  }
}

class PrintPage extends StatefulWidget {
  [@override](/user/override)
  _PrintPageState createState() => _PrintPageState();
}

class _PrintPageState extends State<PrintPage> {
  late ControlBase control;

  [@override](/user/override)
  void initState() {
    super.initState();
    final demoXml = '<page width="880">...</page>';
    control = ControlBase.createForXml(demoXml);
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('打印Demo'),
      ),
      body: Center(
        child: ElevatedButton(
          onPressed: () {
            performPrinting();
          },
          child: Text('打印'),
        ),
      ),
    );
  }

  void performPrinting() async {
    var jsonData = json.decode(dataSource); // dataSource 是你的数据源字符串

    control.setDataSource(DataSource(jsonData));

    control.performLayout(BoxConstraints(maxWidth: 837));
    CPCLCanvas canvas = CPCLCanvas();
    canvas.pageSize = control.actualSize;
    canvas.reset();

    control.paint(canvas, Offset.zero);

    canvas.end();

    await io.send(canvas.buffer); // canvas.buffer 是指令
  }
}

预览Demo

以下是一个简单的预览示例：

import 'package:flutter/material.dart';
import 'package:rare_print/control_base.dart';
import 'package:rare_print/preview_widget.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: PreviewPage(),
    );
  }
}

class PreviewPage extends StatefulWidget {
  [@override](/user/override)
  _PreviewPageState createState() => _PreviewPageState();
}

class _PreviewPageState extends State<PreviewPage> {
  late ControlBase control;

  [@override](/user/override)
  void initState() {
    super.initState();
    final demoXml = '<page width="880">...</page>';
    control = ControlBase.createForXml(demoXml);
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('预览Demo'),
      ),
      body: Center(
        child: PreviewWidget(
          control: control,
        ),
      ),
    );
  }
}