iOS——添加基本的啓動畫面切換

添加從啓動畫面到運行的程序之間的平滑切換

最簡單的「啓動畫面切換」是從默認圖像淡出，而UI同時淡入。爲了讓默認圖像淡出屏幕，首先須要一個視圖，有它顯示這幅圖像，而後把這個視圖淡出。步驟以下：

建立一個可用於任何項目的簡單的視圖控制器，由它使用定製的啓動屏幕圖像，並定義一個執行淡出的-hide方法。
代碼以下：
XYSplashScreen.h

#import <UIKit/UIKit.h>
#import "XYSplashScreenDelegate.h"

@interface XYSplashScreen : UIViewController

@property (nonatomic, retain) UIImage *splashImage;
@property (nonatomic, assign) BOOL showsStatusBarOnDismissal;
@property (nonatomic, assign) IBOutlet id<XYSplashScreenDelegate> delegate;
- (void)hide;
@end

將委託單獨寫到一個頭文件裏
代碼以下
XYSplashScreenDelegate.h

#import <Foundation/Foundation.h>

@class XYSplashScreen;

@protocol XYSplashScreenDelegate <NSObject>
@optional
- (void) splashScreenDidAppear:(XYSplashScreen *)splashScreen;
- (void) splashScreenWillDisappear:(XYSplashScreen *)splashScreen;
- (void) splashScreenDidDisappear:(XYSplashScreen *)splashScreen;

@end

XYSplashScreen.m

#import "XYSplashScreen.h"

@interface XYSplashScreen ()

@end

@implementation XYSplashScreen

- (void)dealloc{
    
    [_splashImage release], _splashImage = nil;
    [super dealloc];
}

- (void)loadView{
    
    UIImageView *iv = [[UIImageView alloc] initWithImage:self.splashImage];
    iv.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    iv.contentMode = UIViewContentModeCenter;
    self.view = iv;
    [iv release];
}

- (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    SEL didAppearSelector = @selector(splashScreenDidAppear:);
    if ([[self delegate] respondsToSelector:didAppearSelector]) {
        [[self delegate] splashScreenDidAppear:self];
    }
    [self performSelector:@selector(hide) withObject:nil afterDelay:0];
}

- (void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    if ([[self delegate] respondsToSelector:@selector(splashScreenWillDisappear:)]) {
        [[self delegate] splashScreenWillDisappear:self];
    }
}

- (void)viewDidDisappear:(BOOL)animated{
    [super viewDidDisappear:animated];
    if ([[self delegate] respondsToSelector:@selector(splashScreenDidDisappear:)]) {
        [[self delegate] splashScreenDidDisappear:self];
    }
    self.splashImage = nil;
}

- (void)hide{
    if (self.showsStatusBarOnDismissal) {
        UIApplication *app = [UIApplication sharedApplication];
        [app setStatusBarHidden:NO withAnimation:UIStatusBarAnimationFade];
    }
    [self dismissViewControllerAnimated:YES completion:nil];
}

#pragma mark - getter 
- (UIImage *)splashImage{
    if (_splashImage == nil){
        self.splashImage = [UIImage imageNamed:@"Default.png"];
    }
    return _splashImage;
}

@end

-(void)loadView，將view屬性設置爲一個以居中的圖像充滿屏幕的圖像視圖。

-(UIImage *)splashImage,splashImage是能夠寫的，因此必要時咱們能夠定製切換圖像，這裏只是用Default.png做爲啓動圖像。

在appdelegate裏設置啓動畫面，代碼以下：
XYAppDelegate.h

#import <UIKit/UIKit.h>
#import "XYSplashScreen.h"

@class XYViewController;

@interface XYAppDelegate : UIResponder <UIApplicationDelegate,XYSplashScreenDelegate>

@property (strong, nonatomic) UIWindow *window;

@property (strong, nonatomic) XYViewController *viewController;

@property (strong, nonatomic) XYSplashScreen *splashScreen;

@end

XYAppDelegate.m

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    // Override point for customization after application launch.
    self.viewController = [[[XYViewController alloc] initWithNibName:@"XYViewController" bundle:nil] autorelease];
    //self.window.rootViewController = self.viewController;
    [self.window addSubview:self.viewController.view];
    
    self.splashScreen = [[[XYSplashScreen alloc] init] autorelease];
    self.splashScreen.showsStatusBarOnDismissal = YES;
    self.splashScreen.delegate = self;
    self.splashScreen.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
    [self.viewController presentViewController:self.splashScreen animated:NO completion:nil];
    
    [self.window makeKeyAndVisible];
    return YES;
}

並在XYAppDelegate.m添加委託方法：

- (void)splashScreenDidAppear:(XYSplashScreen *)splashScreen{
    NSLog(@"%s",__PRETTY_FUNCTION__);
}

- (void)splashScreenDidDisappear:(XYSplashScreen *)splashScreen{
    NSLog(@"%s",__PRETTY_FUNCTION__);
}

- (void)splashScreenWillDisappear:(XYSplashScreen *)splashScreen{
    NSLog(@"%s",__PRETTY_FUNCTION__);
    self.splashScreen = nil;
}

最後將啓動畫面的showStatusBarOnDismissal屬性設置爲YES，好了，這樣就啓動圖像的淡出效果就製做好了，

關於ipad的設備旋轉爲題，能夠設置一張，1024*1024像素的啓動圖像，這個大小足夠知足這兩個方向的最大屏幕尺寸，由於咱們的代碼可以讓圖像充滿屏幕並始終居中。

代碼下載：連接地址