iPhone開發之UIActionSheet

UIActionSheet是iOS開發中實現警告框的重要的類，在很多情況下都要用到，先來一睹其芳容：

 

實現步驟如下：

一、爲了讓控制器類充當操作表的委託，控制器類需要遵從UIActionSheetDelegate協議。

@interface UIActionSheetDemoViewController : UIViewController <UIActionSheetDelegate>{

}

二、生成UIActionSheet並顯示。

UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Are you sure?"
                                                         delegate:self 
                                                cancelButtonTitle:@"No way!" 
                                           destructiveButtonTitle:@"Yes, I'm sure." 
                                                otherButtonTitles:@"Button One", @"Button Two", nil];
[actionSheet showInView:self.view];
[actionSheet release];

三、點擊按鈕後的事件。

- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
    NSLog(@"%i", buttonIndex);
    if (buttonIndex == actionSheet.cancelButtonIndex) {
        return;
    }
    switch (buttonIndex) {
        case 0: {
            NSLog(@"Item 1 Selected");
            break;
        }
        case 1: {
            NSLog(@"Item 2 Selected");
            break;
        }
        case 2: {
            NSLog(@"Item 3 Selected");
            break;
        }
    }
}

代碼樣例請下載：http://download.csdn.net/detail/flyter/4274695 

 

 

下面說說如何動態地添加UIActionSheet按鈕。

 

一、UIActionSheet的通常實現方法：

- (void)testActionSheetStatic {
    UIActionSheet *sheet = [[UIActionSheet alloc] initWithTitle:@"Static UIActionSheet"
                                                       delegate:self
                                              cancelButtonTitle:@"Cancel"
                                         destructiveButtonTitle:nil
                                              otherButtonTitles:@"Item A", @"Item B", @"Item C", nil];
    [sheet showFromRect:view.bounds inView:view animated:YES];
    [sheet release];
}

 

 

二、 如果事先知道各個按鈕並且再也不會改變的情況下，這樣的實現是OK的。但如果我要在運行時改變應該怎麼辦呢？動態添加按鈕看起來應該也很簡單，不要init函數中指定而在之後添加可以了，如下代碼就展示了這點。

- (void)testActionSheetDynamic {
    // 創建時僅指定取消按鈕
    UIActionSheet *sheet = [[UIActionSheet alloc] initWithTitle:@"Dynamic UIActionSheet"
                                                       delegate:self
                                              cancelButtonTitle:@"Cancel"
                                         destructiveButtonTitle:nil
                                              otherButtonTitles:nil];
    // 逐個添加按鈕（比如可以是數組循環）
    [sheet addButtonWithTitle:@"Item A"];
    [sheet addButtonWithTitle:@"Item B"];
    [sheet addButtonWithTitle:@"Item C"];
    [sheet showFromRect:view.bounds inView:view animated:YES];
    [sheet release];
}

 

        運行下就發現問題很明顯——取消按鈕是在視圖的頂部，而標準做法是顯示在底部。怎麼解決呢？如果在init函數中添加取消按鈕就無法解決了。最後找到了一種將取消按鈕也動態添加。

- (void)testActionSheetDynamic {
    // 創建時不指定按鈕
    UIActionSheet *sheet = [[UIActionSheet alloc] initWithTitle:@"Dynamic UIActionSheet"
                                                       delegate:self
                                              cancelButtonTitle:nil
                                         destructiveButtonTitle:nil
                                              otherButtonTitles:nil];
    // 逐個添加按鈕（比如可以是數組循環）
    [sheet addButtonWithTitle:@"Item A"];
    [sheet addButtonWithTitle:@"Item B"];
    [sheet addButtonWithTitle:@"Item C"];

    // 同時添加一個取消按鈕
    [sheet addButtonWithTitle:@"Cancel"];
    // 將取消按鈕的index設置成我們剛添加的那個按鈕，這樣在delegate中就可以知道是那個按鈕
     sheet.cancelButtonIndex = sheet.numberOfButtons-1;
    [sheet showFromRect:view.bounds inView:view animated:YES];
    [sheet release];
}

 

        這樣取消按鈕就顯示在底部並且行爲也符合預期了。

        對我來說現在剩下的最大一個疑問就是destructive按鈕到底是什麼（Apple文檔也沒有清晰地說明這點）？一些實驗結果也表明它實際上和 取消按鈕並無區別，只不過它有一個紅色背景而不是黑色的。所有如果在上例中改變destructiveButtonIndex而不是 cancelButtonIndex，就可以看到標有“取消”的按鈕有紅色背景了。

 

三、出於完整性的考慮，和上述代碼相匹配的delegate代碼如下：

- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
    if (buttonIndex == actionSheet.cancelButtonIndex) {
        return;
    }
    switch (buttonIndex)
    {
        case 0: {
            NSLog(@"Item A Selected");
            break;
        }
        case 1: {
            NSLog(@"Item B Selected");
            break;
        }
        case 2: {
            NSLog(@"Item C Selected");
            break;
        }
    }
}

 

最後說說如何自定義一個UIActionSheet類。

 

一、自定義CustomActionSheet類。

CustomActionSheet類繼承UIActionSheet，具體的實現如下所示：

（1）CustomActionSheet.h頭文件：

#import <UIKit/UIKit.h>

@interface CustomActionSheet : UIActionSheet {
    UIToolbar* toolBar;
    UIView* view;
}

@property(nonatomic,retain)UIView* view;
@property(nonatomic,retain)UIToolbar* toolBar;

-(id)initWithHeight:(float)height WithSheetTitle:(NSString*)title;

@end

（2）CustomActionSheet.m實現文件：

#import "CustomActionSheet.h"

@implementation CustomActionSheet

@synthesize view;
@synthesize toolBar;

-(id)initWithHeight:(float)height WithSheetTitle:(NSString*)title{
    self = [super init];
    if (self) {
        int theight = height - 40;
        int btnnum = theight/50;
        for(int i=0; i<btnnum; i++){
            [self addButtonWithTitle:@" "];
        }
        toolBar = [[UIToolbar alloc] initWithFrame:CGRectMake(0, 0, 320, 44)];
        toolBar.barStyle = UIBarStyleBlackOpaque;
        UIBarButtonItem *titleButton = [[UIBarButtonItem alloc] initWithTitle:title 
                                                                        style:UIBarButtonItemStylePlain 
                                                                       target:nil 
                                                                       action:nil];
        
        UIBarButtonItem *rightButton = [[UIBarButtonItem alloc] initWithTitle:@"Done" 
                                                                        style:UIBarButtonItemStyleDone 
                                                                       target:self
                                                                       action:@selector(done)];

        UIBarButtonItem *leftButton  = [[UIBarButtonItem alloc] initWithTitle:@"Cancel" 
                                                                        style:UIBarButtonItemStyleBordered 
                                                                       target:self 
                                                                       action:@selector(docancel)];

        UIBarButtonItem *fixedButton  = 
            [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace 
                                                          target:nil 
                                                          action:nil];
		
        NSArray *array = 
            [[NSArray alloc] initWithObjects:leftButton,fixedButton,titleButton,fixedButton,rightButton,nil];
        [toolBar setItems: array];
        [titleButton release];
        [leftButton release];
        [rightButton release];
        [fixedButton release];
        [array release];
        [self addSubview:toolBar];
        view = [[UIView alloc] initWithFrame:CGRectMake(0, 44, 320, height-44)];
        view.backgroundColor = [UIColor groupTableViewBackgroundColor];
        [self addSubview:view];
    }
    return self;
}

-(void)done{
    [self dismissWithClickedButtonIndex:0 animated:YES];
}

-(void)docancel{
    [self dismissWithClickedButtonIndex:0 animated:YES];
}

-(void)dealloc{
    [view release];
    [super dealloc];
}

@end

二、利用自定義的CustomActionSheet類顯示提示框。

-(IBAction)doClick:(id)sender{
    CustomActionSheet* sheet = [[CustomActionSheet alloc] initWithHeight:284.0f 
                                                          WithSheetTitle:@"自定義ActionSheet"];
    UILabel* label = [[UILabel alloc] initWithFrame:CGRectMake(0,50, 320, 50)];
    label.text = @"這裏是要自定義放的控制";
    label.backgroundColor = [UIColor clearColor];
    label.textAlignment = UITextAlignmentCenter;
    [sheet.view addSubview:label];

    [sheet showInView:self.view];
    [sheet release];
}

演示：

 

代碼樣例請下載：http://download.csdn.net/detail/flyter/4274763