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..