iPhone開發之UIScrollView初步
今天我們初步介紹以一下iPhone開發中的UIScrollView。顧名思義，UIScrollView就是可以滾動的視圖，常常用在圖檔顯示（縮放，滾動等），文本顯示等，是一個非常有用的控件。今天我們的例子很簡單：在頂部有一個文本框和一個按鈕，在文本框中輸入數字，點選按鈕，就會在下方的UIScrollView中出現相應數目的按鈕，超出一屏的部分用垂直滾動條顯示。這個例子我們用兩種方法實作。并且我們都不使用Interface Builder來畫界面，完全手工寫代碼完成。下面開始吧：
方法1：
1.
建立一個View-based Application，名稱是Scroll
2.
修改 ScrollViewController.h 如下：
//
// ScrollViewController.h
// Scroll
// Created by HuTao on 8/21/12.
// Copyright __MyCompanyName__ 2012. All rights reserved.
#import <UIKit/UIKit.h>
@interface ScrollViewController : UIViewController<UIScrollViewDelegate>
{
UITextField * textFieldNumber;
UIButton * btnStart;
UIScrollView * scrollView;
NSMutableArray * btnArray;
}
@property (retain, nonatomic) UITextField * textFieldNumber;
@property (retain, nonatomic) UIButton * btnStart;
@property (retain, nonatomic) UIScrollView * scrollView;
@property (retain, nonatomic) NSMutableArray * btnArray;;
-(IBAction)btnStartAction:(id)sender;
-(IBAction)btnAlert:(id)sender;
@end
修改 ScrollViewController.m
如下：
// ScrollViewController.m
#import "ScrollViewController.h"
@implementation ScrollViewController
@synthesize textFieldNumber;
@synthesize btnStart;
@synthesize scrollView;
@synthesize btnArray;
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad
[super viewDidLoad];
self.view.backgroundColor = [UIColor yellowColor];
int widthOut = self.view.frame.size.width;
int widthIn = widthOut - 20;
btnArray = [[NSMutableArray alloc] init];
//聲明一個 UITextField
textFieldNumber = [[UITextField alloc] initWithFrame:CGRectMake(10, 10, widthIn - 70, 30)];
textFieldNumber.backgroundColor = [UIColor whiteColor];
textFieldNumber.borderStyle = UITextBorderStyleRoundedRect;
[self.view addSubview:textFieldNumber];
//聲明一個 UIButton
btnStart = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[btnStart setTitle:@"開始" forState:UIControlStateNormal];
btnStart.frame = CGRectMake(widthIn - 50, 10, 60, 30);
[btnStart addTarget:self action:@selector(btnStartAction:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:btnStart];
//聲明一個 UIScrollView
scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 50, widthOut, self.view.frame.size.height - 50)];
scrollView.backgroundColor = [UIColor redColor];
//任意劃動
scrollView.pagingEnabled = NO;
//劃動過程中顯示水準滾動條(如果有)
scrollView.showsHorizontalScrollIndicator = YES;
//劃動過程中顯示垂直滾動條(如果有)
scrollView.showsVerticalScrollIndicator = YES;
//點選頂部的狀态欄滾動到首
scrollView.scrollsToTop = YES;
scrollView.delegate = self;
[self.view addSubview:scrollView];
-(IBAction)btnStartAction:(id)sender
[textFieldNumber resignFirstResponder];
int i;
UIButton * button;
for(i=0; i<[btnArray count]; ++i)
{
button = (UIButton *)[btnArray objectAtIndex:i];
//先删除所有按鈕(删除後按鈕自然不可見)
[button removeFromSuperview];
}
[btnArray removeAllObjects];
int number = [textFieldNumber.text intValue];
for(i=0; i<number; ++i)
button = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[button setTitle:[NSString stringWithFormat:@"%d", i] forState:UIControlStateNormal];
button.frame = CGRectMake(10, 10 + i * 40, self.view.frame.size.width - 20, 30);
[button addTarget:self action:@selector(btnAlert:) forControlEvents:UIControlEventTouchUpInside];
[btnArray addObject:button];
[scrollView addSubview:button];
//設定UIScrollView中要滾動的視窗大小(很重要)
scrollView.contentSize = CGSizeMake(self.view.frame.size.width, number * 40 + 10);
-(IBAction)btnAlert:(id)sender
UIButton * btn = (UIButton *)sender;
NSString * str = [NSString stringWithFormat:@"您按下了 %@ 鍵", btn.currentTitle];
UIAlertView * alterview = [[UIAlertView alloc] initWithTitle:@"" message:str delegate:nil cancelButtonTitle:nil otherButtonTitles:@"确定", nil];
[alterview show];
[alterview release];
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
NSLog(@"scrollViewDidScroll");
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
NSLog(@"scrollViewWillBeginDragging");
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
NSLog(@"scrollViewDidEndDragging");
- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
NSLog(@"scrollViewWillBeginDecelerating");
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
NSLog(@"scrollViewDidEndDecelerating");
- (BOOL)scrollViewShouldScrollToTop:(UIScrollView *)scrollView
NSLog(@"scrollViewShouldScrollToTop");
return YES;
- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView
NSLog(@"scrollViewDidScrollToTop");
- (void)viewDidUnload
textFieldNumber = nil;
btnStart = nil;
scrollView = nil;
btnArray = nil;
- (void)dealloc
[super dealloc];
[textFieldNumber release];
[btnStart release];
[scrollView release];
[btnArray release];
說明：
在 Interface Builder 中，我們使用連線來關聯控件與IBAction，用代碼完成的話則是：
addTarget:(id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents
其中action是@selector(actionFunction:)，一定不要忘記最後的冒号！
要使用 UIScrollView，則必須實作 UIScrollViewDelegate，該Delegate定義如下：
@protocol UIScrollViewDelegate<NSObject>
@optional
- (void)scrollViewDidScroll:(UIScrollView *)scrollView; // any offset changes
- (void)scrollViewDidZoom:(UIScrollView *)scrollView __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_2); // any zoom scale changes
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView; // called on start of dragging (may require some time and or distance to move)
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate; // called on finger up if user dragged. decelerate is true if it will continue moving afterwards
- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView; // called on finger up as we are moving
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView; // called when scroll view grinds to a halt
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView; // called when setContentOffset/scrollRectVisible:animated: finishes. not called if not animating
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView; // return a view that will be scaled. if delegate returns nil, nothing happens
- (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(UIView *)view __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_3_2); // called before the scroll view begins zooming its content
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale; // scale between minimum and maximum. called after any 'bounce' animations
- (BOOL)scrollViewShouldScrollToTop:(UIScrollView *)scrollView; // return a yes if you want to scroll to the top. if not defined, assumes YES
- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView; // called when scrolling animation finished. may be called immediately if already at top
有幾個是比較重要的：
scrollViewDidScroll：scrollView隻要在滾動就會觸發該方法（無論是被使用者拖動還是在拖動後scrollView由于慣性繼續滾動一點距離）
scrollViewWillBeginDragging：scrollView被使用者拖動前就會觸發該方法
scrollViewDidEndDragging：scrollView被使用者拖動結束後就會觸發該方法
scrollViewWillBeginDecelerating：scrollView在拖動後繼續滾動前就會觸發該方法
scrollViewDidEndDecelerating：scrollView在拖動後繼續滾動後停止就會觸發該方法
scrollViewShouldScrollToTop：傳回YES或NO，表示是否支援使用者點選螢幕頂端的狀态條後scrollView滾動到頂端（預設YES）
scrollViewDidScrollToTop：使用者點選螢幕頂端的狀态條後scrollView滾動到頂端後會觸發該方法（scrollViewShouldScrollToTop如果傳回NO，則該方法不會被觸發）
UIScrollView的常用屬性如下：
scrollView.pagingEnabled = NO;
//劃動過程中顯示水準滾動條(如果有)
scrollView.showsHorizontalScrollIndicator = YES;
//劃動過程中顯示垂直滾動條(如果有)
scrollView.showsVerticalScrollIndicator = YES;
//點選頂部的狀态欄滾動到首
scrollView.scrollsToTop = YES;
scrollView.delegate = self;
scrollView.contentSize = CGRect
pagingEnabled：是否以整數倍的UIScrollView大小滾動（如果是用于圖檔類的UIScrollView，該值應該設定為YES，如果是用于顯示文本類的UIScrollView或者類似與本例的允許使用者滾動到任意位置的情況時應該設定為NO）
contentOffset：UIScrollView中content的左上角坐标
contentSize：UIScrollView中content的大小，該值與UIScrollView的大小決定滾動條的長短
decelerating：UIScrollView在拖動放手後是否仍在由于慣性繼續滾動中
dragging：UIScrollView是否正在被使用者拖動
showsHorizontalScrollIndicator：是否顯示水準滾動條
showsVerticalScrollIndicator：是否顯示垂直滾動條
另外例子中還介紹了如何用代碼（而不是Interface Builder）建立GUI控件，可以看看。
運作結果：
初始界面：
輸入20，按開始鍵，生成了20個UIButton：
劃動螢幕，出現滾動條：
點選任意一個按鈕：
輸入小一點的數字：
Console輸出結果如下：
下面介紹方法2：
和方法1類似，不過建立一個 Window-based Application，名稱是Scroll2：
建立一個基于UIView的子類，名稱是ScrollView
3.
修改 Scroll2AppDelegate.m 如下：
// Scroll2AppDelegate.m
// Scroll2
#import "Scroll2AppDelegate.h"
#import "ScrollView.h"
@implementation Scroll2AppDelegate
@synthesize window;
#pragma mark -
#pragma mark Application lifecycle
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
//注意這裡的坐标，是除去了頂部的狀态欄之後的剩餘部分
ScrollView * view = [[ScrollView alloc] initWithFrame:CGRectMake(0, 20, 320, 460)];
[window addSubview:view];
[window makeKeyAndVisible];
[window release];
方法1我們用的是UIViewController，方法2我們直接用了UIView，都是可以的。
修改 ScrollView.h
// ScrollView.h
// Copyright 2012 __MyCompanyName__. All rights reserved.
@interface ScrollView : UIView<UIScrollViewDelegate>
方法2實作了UIScrollViewDelegate的是UIView，而不是方法1中的UIViewController，都是可以的
修改 ScrollView.m
// ScrollView.m
@implementation ScrollView
- (id)initWithFrame:(CGRect)frame
if ((self = [super initWithFrame:frame]))
self.backgroundColor = [UIColor yellowColor];
int widthOut = self.frame.size.width;
int widthIn = widthOut - 20;
btnArray = [[NSMutableArray alloc] init];
//聲明一個 UITextField
textFieldNumber = [[UITextField alloc] initWithFrame:CGRectMake(10, 10, widthIn - 70, 30)];
textFieldNumber.backgroundColor = [UIColor whiteColor];
textFieldNumber.borderStyle = UITextBorderStyleRoundedRect;
[self addSubview:textFieldNumber];
//聲明一個 UIButton
btnStart = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[btnStart setTitle:@"開始" forState:UIControlStateNormal];
btnStart.frame = CGRectMake(widthIn - 50, 10, 60, 30);
[btnStart addTarget:self action:@selector(btnStartAction:) forControlEvents:UIControlEventTouchUpInside];
[self addSubview:btnStart];
//聲明一個 UIScrollView
scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 50, widthOut, self.frame.size.height - 50)];
scrollView.backgroundColor = [UIColor redColor];
//任意劃動
scrollView.pagingEnabled = NO;
//劃動過程中顯示水準滾動條(如果有)
scrollView.showsHorizontalScrollIndicator = YES;
//劃動過程中顯示垂直滾動條(如果有)
scrollView.showsVerticalScrollIndicator = YES;
//點選頂部的狀态欄滾動到首
scrollView.scrollsToTop = YES;
scrollView.delegate = self;
[self addSubview:scrollView];
return self;
button.frame = CGRectMake(10, 10 + i * 40, self.frame.size.width - 20, 30);
scrollView.contentSize = CGSizeMake(self.frame.size.width, number * 40 + 10);
我們将初始化代碼放在了[UIView initWithFrame]中，注意到我們在Scroll2AppDelegate.m中調用了initWithFrame方法，傳入了一個CGRect的視窗大小。總的來說，方法1中的self.view.xxx隻要改成方法2中的self.xxx就可以了。由此可見iPhone開發的靈活性。對于一個界面，即可以使用UIViewController（内包含一個UIView，就像方法1），也可以直接使用UIView（方法2），很友善。
運作結果與方法1完全一樣，故不在贅述。
最後我把兩種方法的完整代碼一起打包上傳上來了：
<a href="http://download.csdn.net/detail/htttw/4516528">http://download.csdn.net/detail/htttw/4516528</a>
本文轉自夏雪冬日部落格園部落格，原文連結：http://www.cnblogs.com/heyonggang/p/3497472.html，如需轉載請自行聯系原作者