基于网络的客户端开发技巧——第七篇后台上传

这里说的后台上传当然不是真的后台上传，只是在开启程序的情况下不影响操作的上传。基本的思想就是开启一个线程，不断的处理上传操作。这里用队列比较方便一些。主要做以下几步：第一步：实现一个自定义类，继承NSObject

@interface MinroadOperation : NSObject {

NSOperationQueue *operationQueue;

}

- (void)addOperation:(NSDictionary *)_dic;

- (void)reStartOperation:(NSDictionary *)_dic;

@property (retain,nonatomic) NSOperationQueue *operationQueue;

@end

@implementation MinroadOperation

@synthesize operationQueue;

- (id)init

{

self = [super init];

if (self) {

self.operationQueue = [[NSOperationQueue alloc] init];

[self.operationQueue setMaxConcurrentOperationCount:2];//设置同时进行的线程数量，建议为2。

}

return self;

}

- (void)addOperation:(NSDictionary *)_dic{//保存上传列表到nsuserdefaultsNSUserDefaults *userDefault = [NSUserDefaults standardUserDefaults];if ([userDefault valueForKey:@"upload"] == nil) {NSMutableDictionary *dic = [NSMutableDictionarydictionaryWithObjectsAndKeys:[NSMutableArrayarrayWithObject:_dic],@"upload",nil];[userDefault registerDefaults:dic];[userDefault synchronize];}else {NSArray *array = [userDefault valueForKey:@"upload"];NSMutableArray *arr = [[NSMutableArray alloc] initWithArray:array];[arr addObject:_dic];[userDefault setObject:arr forKey:@"upload"];[arr release];[userDefault synchronize];}//添加到队列NSInvocationOperation* theOp = [[NSInvocationOperation alloc] initWithTarget:selfselector:@selector(myTaskMethod:) object:_dic];[self.operationQueue addOperation:theOp];[theOp release];//更新UI}- (void)reStartOperation:(NSDictionary *)_dic{//从userdefaults读取数据，并添加到队列NSUserDefaults *userDefault = [NSUserDefaults standardUserDefaults];NSArray *array = [userDefault valueForKey:@"upload"];NSMutableArray *arr = [[NSMutableArray alloc] initWithArray:array];int i = (int)[arr indexOfObject:_dic];if (i == NSNotFound) {return;}NSMutableDictionary *dic = [NSMutableDictionary dictionaryWithDictionary:[arr objectAtIndex:i]];[dic setValue:[NSNumber numberWithInt:0] forKey:@"state"];//0 等待上传 1 上传中 2 失败[arr replaceObjectAtIndex:i withObject:dic];[userDefault setValue:arr forKey:@"upload"];[userDefault synchronize];NSInvocationOperation* theOp = [[NSInvocationOperation alloc] initWithTarget:selfselector:@selector(myTaskMethod:) object:dic];[self.operationQueue addOperation:theOp];[theOp release];//更新UI}- (void)myTaskMethod:(id)_obj{//实现上传方法//成功调用[self performSelectorOnMainThread:@selector(taskMethodDidFinish:) withObject:nil waitUntilDone:YES];//失败调用[self performSelectorOnMainThread:@selector(taskMethodDidFailed:) withObject:nil waitUntilDone:YES];}- (void)taskMethodDidFailed:(id)_obj{//失败的任务更改状态之后保存NSDictionary *tdic = [_obj retain];NSMutableDictionary *dic = [NSMutableDictionary dictionaryWithDictionary:tdic];[dic setValue:[NSNumber numberWithInt:1] forKey:@"state"];NSUserDefaults *userDefault = [NSUserDefaults standardUserDefaults];NSArray *array = [userDefault valueForKey:@"upload"];NSMutableArray *arr = [[NSMutableArray alloc] initWithArray:array];int _index = (int)[arr indexOfObject:dic];if (_index != NSNotFound) {NSMutableDictionary *tmp = [NSMutableDictionary dictionaryWithDictionary:[arr objectAtIndex:_index]];[tmp setValue:[NSNumber numberWithInt:2] forKey:@"state"];//0 等待上传 1 上传中 2 失败[arr replaceObjectAtIndex:_index withObject:tmp];}[userDefault setObject:arr forKey:@"upload"];[arr release];[userDefault synchronize];//更新UI}- (void)taskMethodDidFinish:(id)_obj{//成功的任务从userdefaults中删除NSDictionary *tdic = [_obj retain];NSMutableDictionary *dic = [NSMutableDictionary dictionaryWithDictionary:tdic];[dic setValue:[NSNumber numberWithInt:1] forKey:@"state"];NSUserDefaults *userDefault = [NSUserDefaults standardUserDefaults];NSArray *array = [userDefault valueForKey:@"upload"];NSMutableArray *arr = [[NSMutableArray alloc] initWithArray:array];int _index = (int)[arr indexOfObject:dic];if (_index != NSNotFound) {[arr removeObjectAtIndex:_index];}[userDefault setObject:arr forKey:@"upload"];[arr release];[userDefault synchronize];//更新UI}

- (void)dealloc{[operationQueue release];[super dealloc];}@end

第二步：在appdelegate中初始化一个MinroadOperation对象，添加的时候用addOperation(),重新开始的时候用reStartOperation()。第三步：在程序重新开启的时候启动队列。同时有一点不确认，就是从后台返回貌似队列会继续进行，也就是说进入后台的时候队列处在等待状态。需要注意的几点：1. NSInvocationOperation的cancel方法只是设置一个标识，在进入队列的时候判断是否为true,从而判断是否进行。如果想取消NSInvocationOperation，可以尝试继承它。2.避免无限重试。