iOS 线程并在主线程上更改 UI

Question

我有以下 AcceptCallBack 方法，并希望在该方法运行时添加一个 UIActivityIndi​​cator，因此 [mvc performSelectorOnMainThread:@selector(invoke) withObject:nil waitUntilDone:YES] ;。 invoke 是改变 UI 的方法。然后我用这行 [mvc performSelectorOnMainThread:@selector(hide) withObject:nil waitUntilDone:YES]; 删除 UIActivityIndi​​cator。然而，似乎发生的是 invoke 仅在 AcceptCallBack 完成执行时被调用。 AcceptCallBack 和 invoke 不是在两个不同的线程上运行，因此允许它们同时运行吗？

void AcceptCallBack(
                CFSocketRef socket,
                CFSocketCallBackType type,
                CFDataRef address,
                const void *data,
                void *info)
{
NSLog(@"Start Receiving...");

MasterViewController* mvc = (__bridge MasterViewController*)info;
[mvc performSelectorOnMainThread:@selector(invoke) withObject:nil waitUntilDone:YES];

CFReadStreamRef readStream = NULL;
CFWriteStreamRef writeStream = NULL;
CFIndex bytes;
UInt8 buffer[8192];
UInt8 * fileData;
UInt8 recv_len = 0;

/* The native socket, used for various operations */
CFSocketNativeHandle sock = *(CFSocketNativeHandle *) data;

/* Create the read and write streams for the socket */
CFStreamCreatePairWithSocket(kCFAllocatorDefault, sock,
                             &readStream, &writeStream);

if (!readStream || !writeStream) {
    close(sock);
    fprintf(stderr, "CFStreamCreatePairWithSocket() failed\n");
    return;
}

CFReadStreamOpen(readStream);
CFWriteStreamOpen(writeStream);


bool headerRead = false;
int dataWritten = 0;
NSMutableString* filename = NULL;


NSMutableString * header = [[NSMutableString alloc] init];

while (true) {
    memset(buffer, 0, sizeof(buffer));
    bytes = CFReadStreamRead(readStream, buffer, sizeof(buffer));

    recv_len += bytes;

    if (bytes < 0) {
        fprintf(stderr, "CFReadStreamRead() failed: %d\n", (int)bytes);
        close(sock);
        return;
    }
    if (bytes == 0) {
        break;
    }

    if (!headerRead) {
        for (int b=0; b<bytes; b++) {
            if (buffer[b] == '\n') {
                headerRead = true;
                NSLog(@"Header is: %@", header);

                NSArray *listItems = [header componentsSeparatedByString:@":"];
                filename = [[NSMutableString alloc] init];
                [filename appendString:[listItems objectAtIndex:2]];
                [filename replaceOccurrencesOfString:@"/" withString:@"" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [filename length])];
                fileData = (UInt8*)malloc(sizeof(UInt8) * [[listItems objectAtIndex:3] intValue]);

                b++;
                memcpy(fileData, buffer + b, bytes - b);
                dataWritten = bytes - b;

                break;
            } else {
                [header appendFormat:@"%c", buffer[b]];
            }

        }
    } else {
        memcpy(fileData + dataWritten, buffer, bytes);
        dataWritten += bytes;
    }

}



NSString* docFile = [NSTemporaryDirectory() stringByAppendingPathComponent:filename];

NSData * outputData = [[NSData alloc] initWithBytes:fileData length:dataWritten];
if ([outputData writeToFile:docFile atomically:false] == YES) {
    NSLog(@"File received and successfully written out to file------------------------------");

    MasterViewController * thing = (__bridge MasterViewController*)info;

    [thing restClient:NULL loadedFile:docFile];

    NSString *destDir = @"/Slide2Me/";
    [[thing restClient] uploadFile:filename toPath:destDir
                     withParentRev:nil fromPath:docFile];
    [mvc performSelectorOnMainThread:@selector(hide) withObject:nil waitUntilDone:YES];




} else {
    NSLog(@"Failed to write received data to file");
}

编辑所以我最终为了得到我想要的结果所做的是将上面的所有代码放在 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0) 中，并将它与我想在主线程上进行的更改夹在一起，就像这样。 ...

void AcceptCallBack(
                    CFSocketRef socket,
                    CFSocketCallBackType type,
                    CFDataRef address,
                    const void *data,
                    void *info)
{


NSLog(@"Start Receiving...");

MasterViewController* mvc = (__bridge MasterViewController*)info;

[mvc performSelectorOnMainThread:@selector(invoke) withObject:nil waitUntilDone:YES];


dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT,0), ^{
      [the code above];

});

[mvc performSelectorOnMainThread:@selector(hide) withObject:nil waitUntilDone:YES];
}

Answer 1

您可以使用 GCD 使其成为多线程，并在指标启动和停止时发出信号。performSelector...将在函数完成时执行..并且它没有说明如何调用 AcceptCallBack 方法，我猜它已经在主线程上了。如果是，则需要在另一个线程中调用 AcceptCallback 并使用以下代码在主线程上执行“调用”方法。

dispatch_async(dispatch_get_main_queue(), ^{
    <do work here>
});

http://developer.apple.com/library/ios/#documentation/General/Conceptual/ConcurrencyProgrammingGuide/OperationQueues/OperationQueues.html#//apple_ref/doc/uid/TP40008091-CH102-SW1

编辑:

我会这样做

static dispatch_queue_t processing_queue;
static dispatch_queue_t request_processing_queue() {
    if (processing_queue == NULL) {
        processing_queue = dispatch_queue_create("com.xxx.processing", 0);
    }
    return processing_queue;
}

void AcceptCallBack(
                    CFSocketRef socket,
                    CFSocketCallBackType type,
                    CFDataRef address,
                    const void *data,
                    void *info)
{

    __block MasterViewController* mvc = (__bridge MasterViewController*)info;

    dispatch_async(processing_queue(), ^{

       dispatch_async(dispatch_get_main_queue(), ^{
            [mvc invoke];
        });


       ..... < Do AcceptCallback Code Here >


       dispatch_async(dispatch_get_main_queue(), ^{
            [mvc hide];
        });

    });

}

警告:这只是伪代码..