Ipad开发课程-Charpter3 代码实现窗口

15Aug

Posted by: 9 in: Iphone程序开发

到了这里,你应该可以通过拖来拖去搞定很多应用程序了,但是有些简单程序可以拖来拖去,高级的就不行了,呵呵不然满大街都是app程序了,还卖钱?送人估计都不要!有些时候我们需要一个动态的界面,比如游戏.

interface Builder可能比较容易,但是也容易让一些人脑袋晕忽忽的.因为我们经常有很多方法通过界面模式来创建一个程序,但是有时候这样有很多意想不到的结果.还有一些开发者发誓用代码写程序.

来,我们来用代码实现View窗口DynamicViews.rar

1.打开Xcode,建立一个View-based应用项目,DynamicViews

2.进入DynamicViewsViewController.m文件,编代码:

#import “DynamicViewsViewController.h”

@implementation DynamicViewsViewController

- (void)loadView {

//---create a UIView object---

UIView *view =

[[UIView alloc] initWithFrame:[UIScreen mainScreen].applicationFrame];

view.backgroundColor = [UIColor lightGrayColor];

//---create a Label view---

CGRect frame = CGRectMake(10, 15, 300, 20);

UILabel *label = [[UILabel alloc] initWithFrame:frame];

label.textAlignment = UITextAlignmentCenter;

label.backgroundColor = [UIColor clearColor];

label.font = [UIFont fontWithName:@“Verdana” size:20];

label.text = @“This is a label”;

label.tag = 1000;

//---create a Button view---

frame = CGRectMake(10, 70, 300, 50);

UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];

button.frame = frame;

[button setTitle:@“Click Me, Please!” forState:UIControlStateNormal];

button.backgroundColor = [UIColor clearColor];

button.tag = 2000;

[button addTarget:self

action:@selector(buttonClicked:)

forControlEvents:UIControlEventTouchUpInside];

[view addSubview:label];

[view addSubview:button];

self.view = view;

[label release];

}

-(IBAction) buttonClicked: (id) sender{

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@“Action invoked!”

message:@“Button clicked!” delegate:self

cancelButtonTitle:@“OK”

otherButtonTitles:nil];

[alert show];

[alert release];

}

@end

3.Ctrl+R,我们用代码实现了一个Label标签和一个按钮控件,点击按钮显示一个alert窗口显示一个消息.

它是怎么实现的呢?

你可以用loadView方法来创建你的程序窗口,这个方法只有在你运行程序的时候才会出现.

我们首先要使用的UIView对象,它能让我们创建一个或几个窗口:

//---create a UIView object---

UIView *view =[[UIView alloc] initWithFrame:[UIScreen mainScreen].applicationFrame];

//---set the background color to lightgray---

view.backgroundColor = [UIColor lightGrayColor];

接下来,我们在窗口中创建Label标签和设置它的显示:

//---create a Label view---

CGRect frame = CGRectMake(10, 15, 300, 20);

UILabel *label = [[UILabel alloc] initWithFrame:frame];

label.textAlignment = UITextAlignmentCenter;

label.backgroundColor = [UIColor clearColor];

label.font = [UIFont fontWithName:@“Verdana” size:20];

label.text = @“This is a label”;

label.tag = 1000;

tag标清是必须要设置的,这样在多窗口实现的时候我们才知道是哪个在运行.

我们再用buttonWithType:方法创建一个按钮,定义UIButtonTypeRoundedRect常量.这个方法将返回一个UIRoundedRectButton对象的值(这个是属于UIButton的之类).

//---create a Button view---

frame = CGRectMake(10, 70, 300, 50);

UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];

button.frame = frame;

[button setTitle:@“Click Me, Please!” forState:UIControlStateNormal];

button.backgroundColor = [UIColor clearColor];

button.tag = 2000;

定义buttonClicked:方法,实现按钮被敲击的返回值;

[button AddTarget:Self action:@selector(buttonClicked:) 

forControlEvents:UIControlEventTouchUpInside];

定义label和button视窗到早先我们创建的View视窗:

[view addSubview:label];

[view addSubview:button];

最后我们要对View对象赋值

self.view = view;

理解View窗口的层次结构

当一个窗口被创建或者添加的时候,应该是一个树形结构.如果要区别他们,我们需要修改UIButton对象:

//---create a Button view---

frame = CGRectMake(10, 30, 300, 50);

UIButton *button = [UIButton buttonWithType:UIButtonTypeRoundedRect];

button.frame = frame;

[button setTitle:@“Click Me, Please!”

forState:UIControlStateNormal];

button.backgroundColor = [UIColor clearColor];

button.tag = 2000;

[button addTarget:self

action:@selector(buttonClicked:)

forControlEvents:UIControlEventTouchUpInside];

当你现在运行程序的时候,你可以注意到按钮将label标签遮住了.

通过这个代码实现的两个控件显示:

[view addSubview:label];

[view addSubview:button];

在这两个控件被添加后,我们可以用恶心changeSubviewAtIndex:withSubviewAtIndex:方法交换控件的显示顺序:

[self.view addSubview:label];

[self.view addSubview:button];

[self.view exchangeSubviewAtIndex:1 withSubviewAtIndex:0];

[label release];

再次运行这个程序,我们可以看到两个标签显示顺序已经变换:

要定义每个已添加控件的顺序,你能通过定义tag值来确定:

[self.view addSubview:label];

[self.view addSubview:button];

[self.view exchangeSubviewAtIndex:1 withSubviewAtIndex:0];

for (int i=0; i<[self.view.subviews count]; ++i) {

UIView *view = [self.view.subviews objectAtIndex:i];

NSLog([NSString stringWithFormat:@“%d”, view.tag]);

}

接下来用UIView对象采用递归的方法进行定义:

-(void) printViews: (UIView *) view {

if ([view.subviews count] > 0){

for (int i=0; i<[view.subviews count]; ++i) {

UIView *v = [view.subviews objectAtIndex:i];

NSLog([NSString stringWithFormat:@“View index: %d Tag: %d”,i, v.tag]);

[self printViews:v];

}

} else

return;

}

想要对已经定义好的窗口中除以一个窗口,我们会用到removeFromSuperview方法.例如我们将label标签层除移:

[label removeFromSuperview];

本小节完!