Multi-thread implementation solution in iOS and multi-thread solution in ios

Multi-thread implementation solution in iOS and multi-thread solution in ios

What is a main thread?

After an iOS program runs, a thread is enabled by default, which is called "main thread" or "UI thread"

 

Main functions of the main thread

1. Display/refresh the UI

2. Process UI events (such as click events, scroll events, and drag events)

 

Usage of the main thread

1. Do not place time-consuming operations in the main thread

2. Time-consuming operations will be stuck in the main thread, seriously affecting the smoothness of the UI

 

, Put time-consuming operations in the main thread, the task will be executed in the serial order, after clicking the button in the fifth second, the interface will be stuck for 5 seconds

Because the time-consuming operation has not been completed, you cannot immediately respond to the button clicking

 

 

1. Use of pthread

void *run(void *parme) {        NSLog(@"%@",[NSThread currentThread]);            for (int i = 0; i < 100000; i++) {        NSLog(@"%d",i);    }    return NULL;    }- (IBAction)btnClick:(id)sender {        pthread_t thread;    pthread_create(&thread, NULL, run, NULL);    }

 

2. Use of NSThread

-(Void) touchesBegan :( NSSet <UITouch *> *) touches withEvent :( UIEvent *) event {[self createThread3];} // method for creating the first event-(void) createThread1 {// you need several threads to alloc several NSThread * threads = [[NSThread alloc] initWithTarget: self selector: @ selector (run :) object: @ "first"]; thread. name = @ "one_thread"; [thread start] ;}// method 2-(void) createThread2 {[NSThread detachNewThreadSelector: @ selector (run :) toTarget: self withObject: @ "second"];} // method 3-(void) createThread3 {[self defined mselectorinbackground: @ selector (run :) withObject: @ "third"];} -(void) run :( NSString *) param {NSLog (@ "______ % @ _____ % @", param, [NSThread currentThread]);}

 

3. Use of GCD

-(Void) touchesBegan :( NSSet <UITouch *> *) touches withEvent :( UIEvent *) event {[self syncMain];} /** synchronization function + main column */-(void) syncMain {dispatch_queue_t queue = dispatch_get_main_queue (); NSLog (@ "syncMain ---- begin "); // Add the task to the queue dispatch_sync (queue, ^ {NSLog (@ "1 ---- % @", [NSThread currentThread]) ;}); dispatch_sync (queue, ^ {NSLog (@ "2 ---- % @", [NSThread currentThread]);}); dispatch_sync (queue, ^ {NSLog (@ "3 ---- % @", [NSThread currentThread]) ;}); NSLog (@ "syncMain ---- end") ;}/ ** asynchronous Function + main queue column */-(void) asyncMain {// asynchronous functions won't open threads when used in the main queue column // get the serial queue dispatch_queue_t queue = dispatch_get_main_queue (); // Add the task to the queue dispatch_async (queue, ^ {NSLog (@ "1 ---- % @", [NSThread currentThread]);}); dispatch_async (queue, ^ {NSLog (@ "2 ---- % @", [NSThread currentThread]);}); dispatch_async (queue, ^ {NSLog (@ "3 ---- % @", [NSThread currentThread]);} /** synchronous Function + Serial queue: New threads are not enabled and tasks are executed in the current thread */-(void) syncSerial {// create a serial queue dispatch_queue_t queue = dispatch_queue_create ("com.520.queue", DISPATCH_QUEUE_SERIAL); // Add the task to the queue dispatch_sync (queue, ^ {NSLog (@ "1 ---- % @", [NSThread currentThread]);}); dispatch_sync (queue, ^ {NSLog (@ "2 ---- % @", [NSThread currentThread]);}); dispatch_sync (queue, ^ {NSLog (@ "3 ---- % @", [NSThread currentThread]);} /** asynchronous Function + Serial queue: New threads are enabled, but tasks are serialized. After a task is executed, the next task is executed. */-(void) asyncSerial {// create a serial queue dispatch_queue_t queue = dispatch_queue_create ("com.5?queue", DISPATCH_QUEUE_SERIAL); // Add the task to the queue dispatch_async (queue, ^ {NSLog (@ "1 ---- % @", [NSThread currentThread]);}); dispatch_async (queue, ^ {NSLog (@ "2 ---- % @", [NSThread currentThread]);}); dispatch_async (queue, ^ {NSLog (@ "3 ---- % @", [NSThread currentThread]);} /** synchronous Function + concurrent queue: no thread is enabled. */-(void) syncConcurrent {// obtain the global concurrent queue dispatch_queue_t queue = dispatch_get_global_queue (queue, 0 ); // Add the task to the queue dispatch_async (queue, ^ {NSLog (@ "1 ---- % @", [NSThread currentThread]) ;}); dispatch_async (queue, ^ {NSLog (@ "1 ---- % @", [NSThread currentThread]);}); dispatch_async (queue, ^ {NSLog (@ "1 ---- % @", [NSThread currentThread]);}/** asynchronous Function + concurrent queue: Multiple Threads can be enabled at the same time */-(void) asycConcurrent {// create a queue // The first parameter is the tag equivalent to the name // The second parameter for serial or parallel transmission // dispatch_queue_t queue = dispatch_queue_create ("img. download ", DISPATCH_QUEUE_CONCURRENT); // obtain the global concurrent queue dispatch_queue_t queue = dispatch_get_global_queue (queue, 0); // Add the task to the queue dispatch_async (queue, ^ {for (int I = 0; I <10; I ++) {NSLog (@ "1 ---- % @", [NSThread currentThread]) ;}}); // Add the task to the queue dispatch_async (queue, ^ {for (int I = 0; I <10; I ++) {NSLog (@ "2 ---- % @", [NSThread currentThread]) ;}}); // Add the task to the queue dispatch_async (queue, ^ {for (int I = 0; I <10; I ++) {NSLog (@ "3 ---- % @", [NSThread currentThread]) ;}});}View Code

When using GCD, there are two main steps:

1. Custom task

2. Add the task to the queue

 

It is also necessary to distinguish between synchronous, asynchronous, parallel, and serial.

Synchronous Asynchronization: determines whether to enable new threads.

Parallel serial: affects the execution of tasks.