怎么在Flutter中自定义Plugin

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怎么在Flutter中自定义Plugin？很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。

1.在Android Studio 中创建一个Flutter Plugin 项目，如下图

上图中你能看到项目描述中写到，如果需要暴露Andorid或iOS的API给开发者时，选择"Plugin"项目类型。这个项目我们命名为:flutter_native_log_plugin, 当我们完成创建项目后，有两个文件我们需要看一看，一个是位于android/src下的FlutterNativeLogPlugin.java，这段代码是用来和本地设备交互，然后将交互结果返回供flutter前端调用，如下所示：

packagecom.cube8.flutter_native_log_plugin;

importio.flutter.plugin.common.MethodCall;
importio.flutter.plugin.common.MethodChannel;
importio.flutter.plugin.common.MethodChannel.MethodCallHandler;
importio.flutter.plugin.common.MethodChannel.Result;
importio.flutter.plugin.common.PluginRegistry.Registrar;

/**FlutterNativeLogPlugin*/
publicclassFlutterNativeLogPluginimplementsMethodCallHandler{
/**Pluginregistration.*/
publicstaticvoidregisterWith(Registrarregistrar){
finalMethodChannelchannel=newMethodChannel(registrar.messenger(),
"flutter_native_log_plugin");
channel.setMethodCallHandler(newFlutterNativeLogPlugin());
}

@Override
publicvoidonMethodCall(MethodCallcall,Resultresult){
if(call.method.equals("getPlatformVersion")){
result.success("Android"+android.os.Build.VERSION.RELEASE);
}else{
result.notImplemented();
}
}
}

另一个 /lib/mian.dart文件，这段代码是主要用来和native代码交互，如下所示：

import'dart:async';

import'package:flutter/services.dart';

classFlutterNativeLogPlugin{
staticconstMethodChannel_channel=
constMethodChannel('flutter_native_log_plugin');

staticFuturegetplatformVersionasync{
finalStringversion=await_channel.invokeMethod('getPlatformVersion');
returnversion;
}
}

2.现在我们开始编写我们的Plugin.

在lib/flutter_native_log_plugin.dart 文件中，我们先创建一个新的方法，代码如下：

import'dart:async';

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

enumLog{DEBUG,WARNING,ERROR}

classFlutterNativeLogPlugin{
staticconstMethodChannel_channel=
constMethodChannel('flutter_native_log_plugin');

staticFutureprintLog(
{LoglogType,@requiredStringtag,@requiredStringmsg})async{
Stringlog="debug";
if(logType==Log.WARNING){
log="warning";
}elseif(logType==Log.ERROR){
log="error";
}else{
log="debug";
}

finalMapparams={
'tag':tag,
'msg':msg,
'logType':log
};

finalStringresult=await_channel.invokeMethod('printLog',params);

returnresult;
}
}

在Android端，我们将android/src下的FlutterNativePlugin.java改写如下：

packagecom.cube8.flutter_native_log_plugin;

importandroid.util.Log;

importio.flutter.plugin.common.MethodCall;
importio.flutter.plugin.common.MethodChannel;
importio.flutter.plugin.common.MethodChannel.MethodCallHandler;
importio.flutter.plugin.common.MethodChannel.Result;
importio.flutter.plugin.common.PluginRegistry.Registrar;

/**
*FlutterNativeLogPlugin
*/
publicclassFlutterNativeLogPluginimplementsMethodCallHandler{
/**
*Pluginregistration.
*/
publicstaticvoidregisterWith(Registrarregistrar){
finalMethodChannelchannel=newMethodChannel(registrar.messenger(),"flutter_native_log_plugin");
channel.setMethodCallHandler(newFlutterNativeLogPlugin());
}

@Override
publicvoidonMethodCall(MethodCallcall,Resultresult){
if(call.method.equals("printLog")){
Stringmsg=call.argument("msg");
Stringtag=call.argument("tag");
StringlogType=call.argument("logType");

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

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

3.测试plugin。当开发完了我们的plugin之后，我们需要测试这个新plugin是否可用，于是对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';

voidmain()=>runApp(MyApp());

classMyAppextendsStatefulWidget{
@override
_MyAppStatecreateState()=>_MyAppState();
}

class_MyAppStateextendsState{

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

voidprintLogs()async{
print(awaitFlutterNativeLogPlugin.printLog(
tag:"Debug",msg:"ThisisordinaryLog"));//defaultlogType
print(awaitFlutterNativeLogPlugin.printLog(
tag:"Debug",
msg:"ThisiswarningLog",
logType:Log.WARNING));//logType=warning
print(awaitFlutterNativeLogPlugin.printLog(
tag:"Debug",
msg:"ThisiserrorLog",
logType:Log.ERROR));//logType=error
print(awaitFlutterNativeLogPlugin.printLog(
tag:"Debug",
msg:"ThisisdebugLog",
logType:Log.DEBUG));//logType=debug
}

@override
Widgetbuild(BuildContextcontext){
returnMaterialApp(
home:Scaffold(
appBar:AppBar(
title:constText('Pluginexampleapp'),
),
body:Center(
child:RaisedButton(
child:Text("PrintLogs"),
onPressed:printLogs,
),
),
),
);
}
}

点击app中的按钮，控制台将看到如下输出，说明plugin可以顺利运行了。

4.最后一步就是将我们开发的plugin发布到dart pub供以后直接调用。打开控制台，需要确认定位到plugin项目的根目录，然后输入如下命令：