【Demo 0003】支持交互的应用
本章学习要点
1. 接触更多UI控件(UIImageView, UIButton, UILabel)
2. 掌握控件事件处理过程
一、构建需求
1. 统计用户点击按钮次数
2. 应用简捷易用，美观大方
二、创建工程
1. XCode 》File 》Projects (Cmd + Shift + N)
2. IOS 》User Interface 》Empty Application
3. Product Name: Demo0003 Device: iPhone
三、编写代码
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
// Override point for customization after application launch.
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
CGSize screenSize = [[UIScreen mainScreen] bounds].size;
// add imageview
UIImage*image= [UIImage imageNamed:@"login.jpg"];
CGRect imageRect= CGRectMake((screenSize.width - image.size.width)/2, 80, image.size.width, image.size.height);
UIImageView*imageView= [[[UIImageView alloc] initWithImage:image] autorelease];
[imageView setFrame:imageRect];
[self.window addSubview:imageView];
// add label
CGRect labelRect= CGRectMake(0, imageRect.origin.y + imageRect.size.height + 50, screenSize.width, 30);
UILabel *label= [[[UILabel alloc] initWithFrame:labelRect] autorelease];
label.tag= 1;
label.text= @"你还没有点击哟";
label.font= [UIFont systemFontOfSize:15];
label.textColor= [UIColor blueColor];
label.textAlignment= NSTextAlignmentCenter;
[self.window addSubview:label];
// add button
int buttonWidth= 120;
int left= (screenSize.width - buttonWidth) / 2;
int top= labelRect.origin.y + labelRect.size.height + 20;
CGRect buttonRect= CGRectMake(left, top, buttonWidth, 40);
UIButton*button= [UIButtonbuttonWithType:UIButtonTypeRoundedRect];
[button setFrame:buttonRect];
[button setTitle:@"点击我"forState:UIControlStateNormal];
[button addTarget:self action:@selector(tapButton:) forControlEvents:UIControlEventTouchUpInside];
[self.window addSubview:button];
returnYES;
}
- (void) tapButton:(id)sender
{
static long tapCount = 0;
UILabel*label= (UILabel*)[self.window viewWithTag:1];
label.text= [NSString stringWithFormat:@"你己点我%ld次了", ++tapCount];
}
代码解说：
1. 代码中分别创建了三个控件(UIImageView, UILabel, UIButton), 并设置控件的相关属性；
2. 在创建UIButton时，不是通过alloc之后再init的方式， 而是使用UIButtonWithType:类创建
UIButton*button= [UIButtonbuttonWithType:UIButtonTypeRoundedRect];
3. 为button对象加入TouchUpInside事件, 并关联tapButton事件，
[button addTarget:self action:@selector(tapButton:) forControlEvents:UIControlEventTouchUpInside];
4. 当用户点击button后，系统将调用tapButton事件，在此事件消息中我们创建了一个静态变量，每点击一次变量加1，最后显示到Label控件中;
5. 值的一提的是在tapButton事件消息中的，我们通过tag来获取获取的label控件对象
UILabel*label= (UILabel*)[self.window viewWithTag:1];
创建时设定了label tag属性值:
UILabel *label= [[[UILabel alloc] initWithFrame:labelRect] autorelease];
label.tag= 1;
三、测试程序
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