networkActivityIndi​​catorVisible

Question

此代码与networkActivityIndi​​catorVisible一起使用是否正确？

- (void)viewWillAppear:(BOOL)animated {

    [super viewWillAppear:animated];

    UIApplication* app2 = [UIApplication sharedApplication]; 
    app2.networkActivityIndicatorVisible = YES; 
    [self loadSources];  // Loads data in table view
    app2.networkActivityIndicatorVisible = NO; 
}

张志贤

Answer 1

由于NetworkActivityIndicatorVisible可以在连接仍处于活动状态时从多个点进行设置,因此您需要跟踪启用/禁用连接的呼叫数.以下UIApplication类别仅使用静态变量:

// file UIApplication+NetworkActivity.h
@interface UIApplication (NetworkActivity)
- (void)showNetworkActivityIndicator;
- (void)hideNetworkActivityIndicator;
@end

// file UIApplication+NetworkActivity.m
#import "UIApplication+NetworkActivity.h"
static NSInteger activityCount = 0;
@implementation UIApplication (NetworkActivity)
- (void)showNetworkActivityIndicator {
    if ([[UIApplication sharedApplication] isStatusBarHidden]) return;
    @synchronized ([UIApplication sharedApplication]) {
        if (activityCount == 0) {
            [self setNetworkActivityIndicatorVisible:YES];
        }
        activityCount++;
    }
}
- (void)hideNetworkActivityIndicator {
    if ([[UIApplication sharedApplication] isStatusBarHidden]) return;
    @synchronized ([UIApplication sharedApplication]) {
        activityCount--;
        if (activityCount <= 0) {
            [self setNetworkActivityIndicatorVisible:NO];
            activityCount=0;
        }    
    }
}
@end

现在导入UIApplication+NetworkActivity.h您的客户端代码并调用

// on connection started:
[[UIApplication sharedApplication] showNetworkActivityIndicator];

// on connection finished:
[[UIApplication sharedApplication] hideNetworkActivityIndicator];

如果您担心指示灯只闪烁一秒钟,则不需要后台处理.只需调用,[self performSelector:@selector(loadSources) withObject:Nil afterDelay:0.1]以便UI线程有时间在阻止主线程之前启动网络指示器动画.

Answer 2

如果您还没有使用AFNetworking(https://github.com/AFNetworking/AFNetworking),您可以在AFNetworkingActivityIndi​​catorManager中查看他们的网络活动指示器实现.

如果您确实选择使用此库进行网络访问,则会自动为您处理网络活动指示.您需要做的就是在AppDelegate中进行一次调用以进行设置,他们会为您完成剩余的工作.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    [[AFNetworkActivityIndicatorManager sharedManager] setEnabled:YES];
}