本文主要是介绍iOS NSTimer的用法-下载进度显示，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
NSTimer的作用就是以一定的时间间隔向目标对象发送特殊的消息。最常见的是用来控制下载进度条的显示。
创建一个 Timer
- + scheduledTimerWithTimeInterval: invocation: repeats:
- + (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti invocation:(NSInvocation *)invocation repeats:(BOOL)yesOrNo;
- + scheduledTimerWithTimeInterval: target: selector: userInfo: repeats:
- + (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(id)userInfo repeats:(BOOL)yesOrNo;
启动 Timer
- – fire
停止 Timer
- – invalidate
Timer设置
- – isValid
- – fireDate
- – setFireDate:
- – timeInterval
- – userInfo
有码有真相：
//
// AppDelegate.m
// TimerDemo
//
// Created by 李振杰 on 13-12-18.
// Copyright (c) 2013年 swplzj. All rights reserved.
//#import "AppDelegate.h"//最大下载时间
#define DOWNLOAD_TIMEOUT 60.0static int sec = 0;@interface AppDelegate ()
{NSTimer *_timer;
}@end@implementation AppDelegate- (void)dealloc
{[_window release];[super dealloc];
}- (void)initView
{//创建一个进度条：用于显示下载的进度UIProgressView *progress = [[UIProgressView alloc] initWithFrame:CGRectMake(20, 60, 220, 30)];[progress setBackgroundColor:[UIColor brownColor]];[progress setProgressViewStyle:UIProgressViewStyleBar];[progress setProgress:0];[progress setTag:0x123];[self.window addSubview:progress];
}//更新进度条
- (void)updateView
{sec++;UIProgressView *pro = (UIProgressView *)[self.window viewWithTag:0x123];if (pro) {[pro setProgress:sec / DOWNLOAD_TIMEOUT animated:YES];}if (sec > DOWNLOAD_TIMEOUT) {//这是唯一的方法：从NSRunLoop中移除创建的定时器[_timer invalidate];_timer = nil;}
}- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];// Override point for customization after application launch.[self initView];//在当前的runloop中添加一个定时器，每0.5s调用updateView函数一次_timer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(updateView) userInfo:nil repeats:YES];self.window.backgroundColor = [UIColor whiteColor];[self.window makeKeyAndVisible];return YES;
}@end
下载例子链接
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