UIPickerView 无法显示 JSON 数组数据

Question

这是我第一次做 iOS 应用，所以我可能不知道一些看似简单的东西。请耐心等待我=)

基本上，我需要用我的 JSON 数据填充我的 UIPickerView。我已经成功解析了我的 JSON 数据并提取了我需要的内容并将它们放入 NSMutableArray。当我第一次尝试使用 UIPickerView 时，我使用了硬编码数组，一切正常。现在，当我尝试用我的 JSON 数组替换硬编码数组时，我不断得到一个空 JSON 数组。它的工作方式似乎 UIPickerView 试图在我的 JSON 数组被填充之前拉出所有内容。

我已尝试按照本网站其他地方的建议重新加载 UIPickerView，但它也无法正常工作。

以下是我的部分代码：

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    dispatch_async(randomiserBgQ, ^{
        NSData* data = [NSData dataWithContentsOfURL:randomiserCatURL];
        [self performSelectorOnMainThread:@selector(fetchedData:) withObject:data waitUntilDone:YES];
    });
}



- (void)fetchedData:(NSData *)responseData{
        NSError* error;
        NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];

        NSArray* randomiserCat = [json objectForKey:@"categories"];
        self.randCatSel =[[NSMutableArray alloc] init];

        NSLog(@"categories: %@", randomiserCat);

      for (int i = 0; i < [randomiserCat count]; i++) {
            NSDictionary *dict = [randomiserCat objectAtIndex:i];
            NSString* parent = [dict objectForKey:@"name"];
            [self.randCatSel addObject:parent];
            NSArray* childrenArray = [dict objectForKey:@"children"];

            for (int i = 0; i < [childrenArray count]; i++) {
                NSDictionary* dict = [childrenArray objectAtIndex:i];
                NSString* children = [dict objectForKey:@"name"];
                [self.randCatSel addObject:children];
                NSArray* grandchildrenArray = [dict objectForKey:@"grandchildren"];

                for (int i = 0; i < [grandchildrenArray count]; i++) {
                    NSDictionary* dict = [grandchildrenArray objectAtIndex:i];
                    NSString* grandchildren = [dict objectForKey:@"name"];
                    [self.randCatSel addObject:grandchildren];
                }
            }
        }
}

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
   return 1;
}


- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent: (NSInteger)component
{
    return [self.randCatSel count];    
}

-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row   forComponent:(NSInteger)component
{
    return [self.randCatSel objectAtIndex:row];
}

如您所见，我尝试解析 JSON 数据的方式是，我使用了很长的方法，因为我在 JSON 数据中有几个级别的数组。如果有更快的方法（如 PHP 中的 foreach），请也指出正确的方向。

到目前为止，我的 UIPickerView 得到一个空的 randCatSel 数组（我假设它在填充之前加载它）。

Answer 1

你好，试试这个，

- (void)fetchedData:(NSData *)responseData
{
        NSError* error;
        NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData options:kNilOptions error:&error];

        NSArray* randomiserCat = [json objectForKey:@"categories"];
        self.randCatSel =[[NSMutableArray alloc] init];

        NSLog(@"categories: %@", randomiserCat);

      for (int i = 0; i < [randomiserCat count]; i++) {
            NSDictionary *dict = [randomiserCat objectAtIndex:i];
            NSString* parent = [dict objectForKey:@"name"];
            [self.randCatSel addObject:parent];
            NSArray* childrenArray = [dict objectForKey:@"children"];

            for (int i = 0; i < [childrenArray count]; i++) {
                NSDictionary* dict = [childrenArray objectAtIndex:i];
                NSString* children = [dict objectForKey:@"name"];
                [self.randCatSel addObject:children];
                NSArray* grandchildrenArray = [dict objectForKey:@"grandchildren"];

                for (int i = 0; i < [grandchildrenArray count]; i++) {
                    NSDictionary* dict = [grandchildrenArray objectAtIndex:i];
                    NSString* grandchildren = [dict objectForKey:@"name"];
                    [self.randCatSel addObject:grandchildren];
                }
            }
        }
    packerView=[[UIPickerView alloc] initWithFrame:CGRectMake(0, 280, 320, 200)];
packerView.delegate=self;
packerView.dataSource=self;
[self.view addSubview:packerView];

}
//add the picker view delegate and datasource in .h file. and set the frame as per your requirement.

希望这会对你有所帮助。

Answer 2

正如这里的好人所指出的，我所要做的就是在我的fetchedData 方法中重新加载UIPickerView。我之前把它放在viewDidLoad =/

[pickerViewObj reloadAllComponents];

其中 pickerViewObj 是你自己的 UIPickerView。