本文主要是介绍android 和 ios中实现类似C#的BackgroundWorker接口，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
移动应用为支持各种功能，大多采用了多线程技术。使用单独的线程执行某些任务，同时不影响界面的刷新，在线程执行过程中，可能需要通知一些信息给界面线程，在线程结束之后，需要告诉界面线程执行的结果，这是较为通用的一种线程执行方式。
在C#中，实现该功能的类是BackgroundWorker, 而在android和ios中，并无类似的封装好的类。通常在开发应用的时候需要考虑可移植性，存在为多种平台开发相同应用的情况，为简化不同平台应用的开发，编程需要考虑相同的逻辑结构。因此在android和ios实现与BackgroundWorker类似的功能和接口。
1.C#的BackgroundWorker
BackgroundWorker包含的主要属性和接口说明如下：
主要属性:
event DoWorkEventHandler DoWork; //线程的主体
event ProgressChangedEventHandler ProgressChanged; //线程运行过程中的消息
event RunWorkerCompletedEventHandler RunWorkerCompleted; //线程结束时的处理
主要函数：
void CancelAsync(); 取消线程的运行
void ReportProgress(int percentProgress, object userState); //报告线程的消息
void RunWorkerAsync(object argument); //开始执行线程
为了方面使用，可以将BackgroundWorker进行封装如下
public class StarBackgroundWorker{private BackgroundWorker m_worker;public StarBackgroundWorker(){m_worker = new BackgroundWorker();}public void CancelAsync(){m_worker.CancelAsync();}public void RunAsync(DoWorkEventHandler DoWork, object userState, ProgressChangedEventHandler ProgressChanged, RunWorkerCompletedEventHandler RunWorkerCompleted){m_worker.DoWork += DoWork;m_worker.WorkerSupportsCancellation = true;m_worker.RunWorkerCompleted += RunWorkerCompleted;if (ProgressChanged != null){m_worker.ProgressChanged += ProgressChanged;m_worker.WorkerReportsProgress = true;}m_worker.RunWorkerAsync(userState);}public void ReportProgress(int percentProgress, object userState){m_worker.ReportProgress(percentProgress, userState);}}
使用方法：
StarCoreBackgroundWorker myworker = new StarCoreBackgroundWorker();
myworker.RunAsync((object sender1, DoWorkEventArgs e1) =>{BackgroundWorker worker = sender1 as BackgroundWorker;//线程的主体},null,(object sender1, ProgressChangedEventArgs e1) =>{//--在界面线程中执行，可以刷新界面},(object sender1, RunWorkerCompletedEventArgs e1) =>{//--在界面线程中处理，线程运行结束后的处理}
);2.Android中实现类似BackgroundWorker的功能
Android中使用java编程，通常创建线程使用Thread和Runnable，线程与界面线程通信使用消息的方式，从界面线程中的handler获取一条消息结构，填充参数，使用sendMessage将消息发送给界面线程。界面线程的Handler获取消息队列中的消息进行处理。利用这些方式，可以实现类似c# BackgroundWorker功能
a. 封装Handler
由于采用Handler处理所有BackgroundWorker线程中的消息，为了区分不同的线程，需要线程在创建时进行登记。代码如下：
public class StarUIHander {static public Handler handler;static int InvokeTag = 0;static HashMap<Integer,HandlerCallBack> CallBackList;public interface HandlerCallBack {void Invoke(Message msg);}static int Register(HandlerCallBack CallBack){int Val = InvokeTag;CallBackList.put(InvokeTag,CallBack);InvokeTag ++;return Val;}static void Remove(int Which){CallBackList.remove(Which);}static void InitStarUIHander(){handler = new android.os.Handler() {public void handleMessage(Message msg) {HandlerCallBack CallBack = CallBackList.get(msg.what);if( CallBack != null )CallBack.Invoke(msg);}};CallBackList = new HashMap<Integer,HandlerCallBack>();}
}
在android应用主Activity中，调用InitStarUIHander初始化Handler，对于创建的线程，调用Register注册消息处理函数，获取标识，使用该标识发送消息时。
b. 实现BackgroundWorker功能
在实现BackgroundWorker之前，参照c#的定义，需要实现一些相关的接口。有以下几个：
CancellationTokenSource, ProgressChangedEventArgs, DoWorkEventArgs，RunWorkerCompletedEventArgs，具体代码可参考附件
public BackgroundWorker()
{//_dispatcher = this.Dispatcher;cts = new CancellationTokenSource();HandlerQueue = StarUIHander.Register(new StarUIHander.HandlerCallBack() {@Override public void Invoke(Message msg) {Object[] Para = (Object[])msg.obj;switch ((int)Para[0]) {case Message_ReportProgress:if (ProgressChanged != null ){ProgressChanged.Invoke(this,(ProgressChangedEventArgs)Para[1]);}break;case Message_OnRunWorkerCompleted:if (RunWorkerCompleted != null)RunWorkerCompleted.Invoke(this,(RunWorkerCompletedEventArgs)Para[1]);break;}}});
}
报告状态:
public void ReportProgress(int percentProgress, Object userState)
{if (ProgressChanged != null ){Message message = StarUIHander.handler.obtainMessage();message.what = HandlerQueue;message.obj = new Object[]{Message_ReportProgress,new ProgressChangedEventArgs(percentProgress,userState)};StarUIHander.handler.sendMessage(message);}
}
创建线程执行:
public void RunWorkerAsync(Object userState)
{final BackgroundWorker m_worker = this;if (DoWork != null){IsBusy = true;try {final DoWorkEventArgs args = new DoWorkEventArgs(userState);new Thread(new Runnable(){@Overridepublic void run() {DoWork.Invoke(m_worker, args);IsBusy = false;if (RunWorkerCompleted != null) {Message message = StarUIHander.handler.obtainMessage();message.what = HandlerQueue;message.obj = new Object[]{Message_OnRunWorkerCompleted, new RunWorkerCompletedEventArgs(args.Result, null, args.Cancel)};StarUIHander.handler.sendMessage(message);}}}).start();}catch (Exception ex) {IsBusy = false;if (RunWorkerCompleted != null) {Message message = StarUIHander.handler.obtainMessage();message.what = HandlerQueue;message.obj = new Object[]{Message_OnRunWorkerCompleted, new RunWorkerCompletedEventArgs(false, ex, false)};StarUIHander.handler.sendMessage(message);}}}
}
为了方面使用，将BackgroundWorker进行封装如下
public static class StarCoreBackgroundWorker{private BackgroundWorker m_worker;public StarCoreBackgroundWorker(){m_worker = new BackgroundWorker();}public void CancelAsync(){m_worker.CancelAsync();}public void RunAsync(DoWorkEventHandler DoWork, Object userState, ProgressChangedEventHandler ProgressChanged, RunWorkerCompletedEventHandler RunWorkerCompleted){m_worker.DoWork = DoWork;m_worker.WorkerSupportsCancellation = true;m_worker.RunWorkerCompleted = RunWorkerCompleted;if (ProgressChanged != null){m_worker.ProgressChanged = ProgressChanged;m_worker.WorkerReportsProgress = true;}m_worker.RunWorkerAsync(userState);}public void ReportProgress(int percentProgress, Object userState){m_worker.ReportProgress(percentProgress, userState);}} 使用方法：
StarBackgroundWorker myworker = new StarBackgroundWorker();
myworker.RunAsync(new DoWorkEventHandler() {public void Invoke(Object sender1, DoWorkEventArgs e1) {BackgroundWorker worker = sender1 as BackgroundWorker;//线程的主体}},null,new ProgressChangedEventHandler() {public void Invoke(Object sender1, ProgressChangedEventArgs e1) {//--在界面线程中执行，可以刷新界面}},new RunWorkerCompletedEventHandler() {public void Invoke(Object sender, RunWorkerCompletedEventArgs e) {//--在界面线程中处理，线程运行结束后的处理}});3. ios中实现类似BackgroundWorker的功能
ios创建线程可以使用NSThread，在界面线程中运行调用performSelectorOnMainThread函数；也可以使用GCD相关的函数，对多线程进行封装，可以实现类似c#的BackgroundWorker功能
a. 实现BackgroundWorker功能
与android类似，在实现BackgroundWorker之前，参照c#的定义，同样需要实现一些相关的接口。有以下几个：
CancellationTokenSource, ProgressChangedEventArgs, DoWorkEventArgs，RunWorkerCompletedEventArgs，具体代码可参考附件
定义接口:
typedef void(^ProgressChangedEventHandler)(id,ProgressChangedEventArgs*);
typedef void(^RunWorkerCompletedEventHandler)(id,RunWorkerCompletedEventArgs*);
typedef void(^DoWorkEventHandler)(id,DoWorkEventArgs*);实现BackgroundWorker
上报状态:
-(void)ReportProgress:(uint)percentProgress userState:(id)userState
{if (ProgressChanged != nil || ProgressChangedSelector != nil ){dispatch_async(dispatch_get_main_queue(),^{@try{if( ProgressChangedSelector == nil )ProgressChanged(self,[ProgressChangedEventArgs initProgressChangedEventArgs:percentProgress UserState:userState]);else{IMP imp = [SelectorController methodForSelector:ProgressChangedSelector];void (*func)(id, SEL, id, ProgressChangedEventArgs* ) = (void *)imp;func(SelectorController, ProgressChangedSelector, self, [ProgressChangedEventArgs initProgressChangedEventArgs:percentProgress UserState:userState]);}}@catch(NSException* e){}});}
}
异步执行
-(void)RunWorkerAsync:(id)userState
{if (DoWork != nil || DoWorkSelector != nil){@try {DoWorkEventArgs* args = [DoWorkEventArgs initDoWorkEventArgs:userState];dispatch_async(dispatch_get_global_queue(0, 0),^{if( DoWork != nil )DoWork(self,args);else if(DoWorkSelector != nil ){IMP imp = [SelectorController methodForSelector:DoWorkSelector];void (*func)(id, SEL, id, DoWorkEventArgs* ) = (void *)imp;func(SelectorController, DoWorkSelector, self,args);}dispatch_async(dispatch_get_main_queue(),^{if (RunWorkerCompleted != nil)RunWorkerCompleted(self,[RunWorkerCompletedEventArgs initRunWorkerCompletedEventArgs:args.Result Cancelled:args.Cancel]);else if(RunWorkerCompletedSelector != nil){IMP imp = [SelectorController methodForSelector:RunWorkerCompletedSelector];void (*func)(id, SEL, id, RunWorkerCompletedEventArgs* ) = (void *)imp;func(SelectorController, RunWorkerCompletedSelector, self,[RunWorkerCompletedEventArgs initRunWorkerCompletedEventArgs:args.Result Cancelled:args.Cancel]);}});});}@catch(NSException* e){dispatch_async(dispatch_get_main_queue(),^{if (RunWorkerCompleted != nil)RunWorkerCompleted(self,[RunWorkerCompletedEventArgs initRunWorkerCompletedEventArgs:e]);else if( RunWorkerCompletedSelector != nil ){IMP imp = [SelectorController methodForSelector:RunWorkerCompletedSelector];void (*func)(id, SEL, id, RunWorkerCompletedEventArgs* ) = (void *)imp;func(SelectorController, RunWorkerCompletedSelector, self,[RunWorkerCompletedEventArgs initRunWorkerCompletedEventArgs:e]);}});}}
}
b. 为了方面使用，将BackgroundWorker进行封装如下
-(void)RunAsync:(DoWorkEventHandler)DoWork userState:(id)userState ProgressChanged:(ProgressChangedEventHandler)ProgressChanged RunWorkerCompleted:(RunWorkerCompletedEventHandler)RunWorkerCompleted
{m_worker.DoWork = DoWork;m_worker.RunWorkerCompleted = RunWorkerCompleted;if (ProgressChanged != nil){m_worker.ProgressChanged = ProgressChanged;}[m_worker RunWorkerAsync:userState];
}-(void)ReportProgress:(uint)percentProgress userState:(id)userState
{[m_worker ReportProgress:percentProgress userState:userState];
}
使用方法：
StarBackgroundWorker* myworker = [StarBackgroundWorker initStarBackgroundWorker];[myworker RunAsync:^(id sender1, DoWorkEventArgs *e) {BackgroundWorker* worker = (BackgroundWorker*)sender1;} userState:nil ProgressChanged:^(id sender1, ProgressChangedEventArgs *e) {} RunWorkerCompleted:^(id sender1, RunWorkerCompletedEventArgs *e) {}}];4. 结束语
如果不考虑可移植性，可以直接使用android，ios，windows中定义的多线程方法开发应用，但由于不同平台采用的是不同语言，多线程实现接口和方式不同，会影响应用的逻辑结构，增加不同平台移植的工作量。基于线程执行过程，参考C#中的BackgroundWorker机制，在android和ios实现了类似的多线程机制，采用相同的框架结构，提供类似的接口，可以使多线程在不同平台具有相同的逻辑结构
上面的代码不完整，具体请参考附件
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