flutter 调用签字版

Flutter 可以通过调用原生代码来实现调用签字版的功能。具体实现步骤如下：

1. 首先在 Flutter 中编写调用签字版的 Dart 代码。

2. 接着，创建一个 Flutter 插件，用于与原生代码进行通信。

3. 在原生代码中实现调用签字版的功能，并将签字结果返回给 Flutter。

4. 最后，在 Flutter 中处理签字结果并进行相关操作。

代码示例：

在 Flutter 中调用签字版：

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

class SignaturePad extends StatefulWidget {
  @override
  _SignaturePadState createState() => _SignaturePadState();
}

class _SignaturePadState extends State<SignaturePad> {
  static const platform = const MethodChannel('signature_pad');

  Future<void> _showSignaturePad() async {
    try {
      final bool result = await platform.invokeMethod('showSignaturePad');
      if (result) {
        // 处理签字结果
      }
    } on PlatformException catch (e) {
      // 处理异常
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Signature Pad'),
      ),
      body: Center(
        child: RaisedButton(
          onPressed: _showSignaturePad,
          child: Text('Open Signature Pad'),
        ),
      ),
    );
  }
}

创建 Flutter 插件：

1. 在 Flutter 项目的根目录创建一个 `signature_pad` 文件夹，用于存放插件代码。

2. 在 `signature_pad/lib` 目录下创建 `signature_pad.dart` 文件，用于定义插件接口。

import 'dart:async';

import 'package:flutter/services.dart';

class SignaturePad {
  static const MethodChannel _channel = const MethodChannel('signature_pad');

  static Future<bool> showSignaturePad() async {
    final bool result = await _channel.invokeMethod('showSignaturePad');
    return result;
  }
}

3. 在 `signature_pad/android/src/main/kotlin/com/example/signature_pad/SignaturePadPlugin.kt` 文件中实现 Android 平台的签字功能：

class SignaturePadPlugin : FlutterPlugin, MethodCallHandler {
    private var activity: Activity? = null
    private var methodChannel: MethodChannel? = null

    companion object {
        const val CHANNEL_NAME = "signature_pad"
    }

    override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
        methodChannel = MethodChannel(binding.binaryMessenger, CHANNEL_NAME)
        methodChannel?.setMethodCallHandler(this)
    }

    override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
        methodChannel?.setMethodCallHandler(null)
        methodChannel = null
    }

    override fun onMethodCall(call: MethodCall, result: Result) {
        if (call.method == "showSignaturePad") {
            showSignaturePad(result)
        } else {
            result.notImplemented()
        }
    }

    private fun showSignaturePad(result: Result) {
        activity?.runOnUiThread {
            // 调用签字版界面，等待签字结果
            val signatureResult: Boolean = true // 签字结果
            result.success(signatureResult)
        }
    }
}

4. 在 `signature_pad/ios/Classes/SignaturePadPlugin.swift` 文件中实现 iOS 平台的签字功能：

public class SignaturePadPlugin: NSObject, FlutterPlugin {
    var methodChannel: FlutterMethodChannel?

    public static func register(with registrar: FlutterPluginRegistrar) {
        let channel = FlutterMethodChannel(name: "signature_pad", binaryMessenger: registrar.messenger())
        let instance = SignaturePadPlugin()
        instance.methodChannel = channel
        registrar.addMethodCallDelegate(instance, channel: channel)
    }

    public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
        if call.method == "showSignaturePad" {
            self.showSignaturePad(result: result)
        } else {
            result(FlutterMethodNotImplemented)
        }
    }

    private func showSignaturePad(result: @escaping FlutterResult) {
        // 调用签字版界面，等待签字结果
        let signatureResult = true // 签字结果
        result(signatureResult)
    }
}

在 Flutter 中调用插件：

import 'package:flutter/material.dart';
import 'package:signature_pad/signature_pad.dart';

class SignaturePadPage extends StatefulWidget {
  @override
  _SignaturePadPageState createState() => _SignaturePadPageState();
}

class _SignaturePadPageState extends State<SignaturePadPage> {
  Future<void> _showSignaturePad() async {
    bool result = await SignaturePad.showSignaturePad();
    if (result) {
      // 处理签字结果
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Signature Pad'),
      ),
      body: Center(
        child: RaisedButton(
          onPressed: _showSignaturePad,
          child: Text('Open Signature Pad'),
        ),
      ),
    );
  }
}