iOS：只调用一次方法 [英] iOS : Call a method just one time

问题描述

您好我想知道如何才能调用一个方法只有一次在应用程序的生活...我的应用程序应该从服务器下载一些文件，我需要做一次;我的意思是每次安装只有一次

Hi I was wondering how can I call a method just for one time in application life ... My application should download some files from server and I need do it just for one time; I mean mean just one time per installation

这里是我的方法

//Download some images from server and save it into directory 

- (void) downloadCovers {

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    [self saveFile:@"mag1" ofType:@"png" fromURL:@"http://myweb.com/mag1.png" inDirectory:documentsDirectory];

}

，此方法将图像设置为UIButton BG：

and this method set images as UIButton BG :

  - (void)buttonsBGImage {

       UIImage * bgMag1 = [self loadImage:@"mag1" ofType:@"png" inDirectory:[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]];

        [mag1 setBackgroundImage:bgMag1 forState:UIControlStateNormal];
         NSLog(@"BG IS SET");

    }

推荐答案

标志作为NSUserDefaults键，并在您的downloadCovers方法中检查此NSUserDefault值。如果已设置，则不执行任何操作，否则下载文件并将标记设置为true。

Set a flag as a NSUserDefaults key and check for this NSUserDefault value in your downloadCovers method. If it is already set, do nothing, else download files and set the flag to true.

像这样：

-(void) downloadCovers {
BOOL downloaded = [[NSUserDefaults standardUserDefaults] boolForKey: @"downloaded"];
if (!downloaded) {
     //download code here
      [[NSUserDefaults standardUserDefaults] setBool:YES forKey: @"downloaded"];
    }
}

干杯

这篇关于iOS：只调用一次方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！