用Flutter開發(fā)自定義Plugin的方法示例

更新時間：2019年06月16日 10:39:52 作者：zyangdev

這篇文章主要介紹了用Flutter開發(fā)自定義Plugin的方法示例，小編覺得挺不錯的，現(xiàn)在分享給大家，也給大家做個參考。一起跟隨小編過來看看吧

當你在開發(fā)flutter應用的時候，有時會需要調(diào)用native的api，往往遇到flutter并沒有相應的package，這時候flutter plugin就開始發(fā)揮作用了，這篇文章將會講解開發(fā)一個簡單flutter plugin的步驟和方法，好了，讓我們開始動手吧。

1.在Android Studio 中創(chuàng)建一個Flutter Plugin 項目，如下圖

上圖中你能看到項目描述中寫到，如果需要暴露Andorid或iOS的API給開發(fā)者時，選擇"Plugin"項目類型。
這個項目我們命名為:flutter_native_log_plugin, 當我們完成創(chuàng)建項目后，有兩個文件我們需要看一看，一個是位于android/src下的FlutterNativeLogPlugin.java，這段代碼是用來和本地設備交互，然后將交互結(jié)果返回供flutter前端調(diào)用，如下所示：

package com.cube8.flutter_native_log_plugin;

import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
import io.flutter.plugin.common.MethodChannel.Result;
import io.flutter.plugin.common.PluginRegistry.Registrar;

/** FlutterNativeLogPlugin */
public class FlutterNativeLogPlugin implements MethodCallHandler {
 /** Plugin registration. */
 public static void registerWith(Registrar registrar) {
  final MethodChannel channel = new MethodChannel(registrar.messenger(), 
    "flutter_native_log_plugin");
  channel.setMethodCallHandler(new FlutterNativeLogPlugin());
 }

 @Override
 public void onMethodCall(MethodCall call, Result result) {
  if (call.method.equals("getPlatformVersion")) {
   result.success("Android " + android.os.Build.VERSION.RELEASE);
  } else {
   result.notImplemented();
  }
 }
}

另一個 /lib/mian.dart文件，這段代碼是主要用來和native代碼交互，如下所示：

import 'dart:async';

import 'package:flutter/services.dart';

class FlutterNativeLogPlugin {
 static const MethodChannel _channel =
   const MethodChannel('flutter_native_log_plugin');

 static Future<String> get platformVersion async {
  final String version = await _channel.invokeMethod('getPlatformVersion');
  return version;
 }
}

2.現(xiàn)在我們開始編寫我們的Plugin.

在lib/flutter_native_log_plugin.dart 文件中，我們先創(chuàng)建一個新的方法，代碼如下：

import 'dart:async';

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

enum Log { DEBUG, WARNING, ERROR }

class FlutterNativeLogPlugin {
 static const MethodChannel _channel =
   const MethodChannel('flutter_native_log_plugin');

 static Future<String> printLog(
   {Log logType, @required String tag, @required String msg}) async {
  String log = "debug";
  if (logType == Log.WARNING) {
   log = "warning";
  } else if (logType == Log.ERROR) {
   log = "error";
  } else {
   log = "debug";
  }

  final Map<String, dynamic> params = <String, dynamic>{
   'tag': tag,
   'msg': msg,
   'logType': log
  };

  final String result = await _channel.invokeMethod('printLog', params);

  return result;
 }
}

在Android端，我們將android/src下的FlutterNativePlugin.java改寫如下：

package com.cube8.flutter_native_log_plugin;

import android.util.Log;

import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.MethodChannel.MethodCallHandler;
import io.flutter.plugin.common.MethodChannel.Result;
import io.flutter.plugin.common.PluginRegistry.Registrar;

/**
 * FlutterNativeLogPlugin
 */
public class FlutterNativeLogPlugin implements MethodCallHandler {
  /**
   * Plugin registration.
   */
  public static void registerWith(Registrar registrar) {
    final MethodChannel channel = new MethodChannel(registrar.messenger(), "flutter_native_log_plugin");
    channel.setMethodCallHandler(new FlutterNativeLogPlugin());
  }

  @Override
  public void onMethodCall(MethodCall call, Result result) {
    if (call.method.equals("printLog")) {
      String msg = call.argument("msg");
      String tag = call.argument("tag");
      String logType = call.argument("logType");

      if (logType.equals("warning")) {
        Log.w(tag, msg);
      } else if (logType.equals("error")) {
        Log.e(tag, msg);
      } else {
        Log.d(tag, msg);
      }

      result.success("Logged Successfully!");
    } else {
      result.notImplemented();
    }
  }
}

3.測試plugin。當開發(fā)完了我們的plugin之后，我們需要測試這個新plugin是否可用，于是對example/lib的main.dart文件作如下修改：

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

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

class MyApp extends StatefulWidget {
 @override
 _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

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

 void printLogs() async {
  print(await FlutterNativeLogPlugin.printLog(
    tag: "Debug", msg: "This is ordinary Log")); // default logType
  print(await FlutterNativeLogPlugin.printLog(
    tag: "Debug",
    msg: "This is warning Log",
    logType: Log.WARNING)); // logType = warning
  print(await FlutterNativeLogPlugin.printLog(
    tag: "Debug",
    msg: "This is error Log",
    logType: Log.ERROR)); // logType = error
  print(await FlutterNativeLogPlugin.printLog(
    tag: "Debug",
    msg: "This is debug Log",
    logType: Log.DEBUG)); // logType = debug
 }

 @override
 Widget build(BuildContext context) {
  return MaterialApp(
   home: Scaffold(
    appBar: AppBar(
     title: const Text('Plugin example app'),
    ),
    body: Center(
     child: RaisedButton(
      child: Text("PrintLogs"),
      onPressed: printLogs,
     ),
    ),
   ),
  );
 }
}