Question

我有一个按钮，我正在尝试设置线程完成时的图像。我的代码似乎没有用，只是更改图像按钮，但这是为了练习并进行更大的事情。

目标：将b0的图像设置为button_x.png（在项目中找到）。

问题：按钮图像没有改变，如果我在故事板上找到的按钮与viewController按钮声明之间建立了连接，我的-[UIButton setImage:]: unrecognized selector sent to instance 0x8b4c270崩溃了。

谢谢。

ViewController.h：

@interface ViewController : UIViewController {
    IBOutlet UIButton *b0;
    Game *instanceOfGame;
}

@property (nonatomic, strong) UIButton *b0;
@property (nonatomic, strong) Game *instanceOfGame;

@end

ViewController.m：

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController
@synthesize instanceOfGame;
@synthesize b0;
static NSString *postName = @"123";


- (void)viewDidLoad
{
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(post:) name:postName object:nil];
    instanceOfGame = [[Game alloc] init];
    [instanceOfGame start];
}

- (void) post: (NSNotification *) result {
    NSNumber *str = [result object];
    if (str == 0) {
        [self.b0 performSelectorOnMainThread:@selector(setImage: ) withObject:[UIImage imageNamed:@"button_x.png"] waitUntilDone:NO];
    }

}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

Game.h：

#import <Foundation/Foundation.h>

    @interface Game : NSObject
    @property (nonatomic, strong) NSNumber *choice;
    @property (nonatomic, strong) NSNotificationCenter *ns;
    -(void) start;
    @end

Game.m：

#import "Game.h"

@implementation Game

NSNotificationCenter *ns;
@synthesize ns;
@synthesize choice;
static NSString *postName = @"123";

-(id) init {
    if (self = [super init]) {
        ns = [NSNotificationCenter defaultCenter];
    }
    return self;
}

-(void) start {
    [self performSelectorInBackground:@selector(loadData) withObject:Nil];
}

-(void) loadData {
    choice = 0;

    [ns postNotificationName:postName object:choice];
}

@end

Answer 1

@Colin Cornaby说写。

UIButton没有setImage方法。

您也可以使用相同的现有代码。只需更新以下行

[self.b0 performSelectorOnMainThread:@selector(setImage: ) withObject:[UIImage imageNamed:@"button_x.png"] waitUntilDone:NO];

作为

[self performSelectorOnMainThread:@selector(setImage: ) withObject:[UIImage imageNamed:@"ListDropDown.png"] waitUntilDone:NO];

然后定义方法setImage：

-(void)setImage:(UIImage *)img
{
    [self.bo setImage:img forState:UIControlStateNormal];
}

我希望它对你有用

Answer 2

UIButton没有setImage：函数，因此会抛出异常。

它确实有这个功能：

- (void)setImage:(UIImage *)image forState:(UIControlState)state

尝试更换：

[self.b0 performSelectorOnMainThread:@selector(setImage: ) withObject:[UIImage imageNamed:@"button_x.png"] waitUntilDone:NO];

使用GCD调用正确的函数完成类似的实现：

dispatch_async(dispatch_get_main_queue(), ^{
   [self.b0 setImage:[UIImage imageNamed:@"button_x.png"] forState:UIControlStateNormal];
});

Answer 3

试试这个，

if (str == 0) {
    dispatch_sync(dispatch_get_main_queue(), ^{
        [self.b0 setImage:[UIImage imageNamed:@"button_x.png"] forState:UIControlStateNormal];       
    });
}

目标C线程完成后设置图像

3 个答案: