目前大多數(shù)APP的啟動圖片還是launchImage的形式，這張啟動圖片顯示的時間很短，大概不到0.5s左右，有時候我們啟動的時候一些初始化的步驟或者網(wǎng)絡不好的情況會花掉1~2s的時間，會造成很不好的體驗，網(wǎng)上有人說讓線程睡1s，但是這個睡眠過程中app不會做任何事，只是單純的延長了啟動圖片的時間。還有就是一些節(jié)假日app想要發(fā)布一些主題開屏，但是公司的輸求是不能在app中預留這些圖片，只能從網(wǎng)絡中獲取。
于是乎我有了余下的想法：
1>啟動時，下載一張圖片到launchImage中，然后用于下一次啟動。這樣的好處就是能做到無縫銜接，不會有過渡的過程。（這種方法不知道能不能實現(xiàn)）
2>launchImage放一張只帶有l(wèi)ogo的白色圖片，然后再app中放一張基本上能通用的圖片，主題開屏的圖片從網(wǎng)上下載。在app中放一張通用的開屏圖片是為了防止主題圖片沒有下載好用到的。從只有白色logo的啟動圖片到開屏圖的過渡時間在iphone7大概只有0.2s左右，5s大概是0.5s左右。放白色logo圖也就是為了過渡自然的效果，廢話不多說上代碼。
2.1>先初始化window,加載主控制器，在window上放的這張圖片的時間是3s，網(wǎng)絡基本還行的情況下，3s首頁的一些初始化、請求是基本能做完的。
self.window=[[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
self.window.backgroundColor = [UIColor whiteColor];
self.window.rootViewController = [[ALSRootViewController alloc] init];
[self.window makeKeyAndVisible];
ALSLaunchImageView *launchImageView = [[ALSLaunchImageView alloc] init];
[self.window addSubview:launchImageView];
[ALSLaunchImageView loadNewLaunchImage];
2.2> 初始化，用到的圖片是上一次啟動下載的，這也是為了使過渡時間盡可能的減小，第一次啟動用的是通用的那張開屏的圖片
- (instancetype)init
{
if (self = [super init]) {
CGSize viewSize = CGSizeMake(KScreenWidth, KScreenHeight);
//橫屏請設置成 @"Landscape"
NSString *viewOrientation = @"Portrait";
NSString *launchImageName;
NSArray* imagesDict = [[[NSBundle mainBundle] infoDictionary] valueForKey:@"UILaunchImages"];
for (NSDictionary* dict in imagesDict) {
CGSize imageSize = CGSizeFromString(dict[@"UILaunchImageSize"]);
if (CGSizeEqualToSize(imageSize, viewSize) && [viewOrientation isEqualToString:dict[@"UILaunchImageOrientation"]])
{
launchImageName = dict[@"UILaunchImageName"];
}
}
UIImage * bgImage = [UIImage imageNamed:launchImageName];
//將app里面的launchImage這張圖片渲染到自身背景色
self.backgroundColor = [UIColor colorWithPatternImage:bgImage];
self.frame = CGRectMake(0, 0, KScreenWidth, KScreenHeight);
NSString *saveDiretory = [NSString stringWithFormat:@"%@/image",[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES) lastObject]];
NSString *launchImagePath =[NSString stringWithFormat: @"%@/launchImage.png",saveDiretory];
NSData *launchImageData = [NSData dataWithContentsOfFile:launchImagePath];
UIImage *launchImage;
if (launchImageData) {//如果本地文件夾有下載的網(wǎng)絡圖片就用網(wǎng)絡的
launchImage = [UIImage imageWithData:launchImageData];
} else {//沒有就用放在APP里面的圖片
launchImage = [UIImage imageNamed:@"default_launchImage"];
}
//設置成圖片
UIImageView *launchImageView = [[UIImageView alloc] init];
//0 全屏 1 帶logo的屏
BOOL launchImageType = [ALSUserDefaults boolForKey:@"launchImageType"];
if (launchImageType) {
launchImageView.frame = CGRectMake(0, 0, KScreenWidth, KScreenHeight - KScreenWidth / 3);
} else {
launchImageView.frame = CGRectMake(0, 0, KScreenWidth, KScreenHeight);
}
//設置圖片，帶logo的需要剪裁
launchImageView.image = [self clipImage:launchImage targetSize:launchImageView.size];
[self addSubview:launchImageView];
//需要打開接收事件，不然會有穿透效果
self.userInteractionEnabled = YES;
//怕商品推送圖片過來時，啟動圖片在推送圖片的下面
self.layer.zPosition = 10;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
[self closeAddImgAnimation];
});
}
return self;
}
2.3>剪裁圖片
- (UIImage *)clipImage:(UIImage *)sourceImage targetSize:(CGSize)defineSize {
if(defineSize.height == KScreenHeight){
return sourceImage;
} else { //半屏 需要剪裁
CGSize imageSize = sourceImage.size;
CGFloat width = imageSize.width;
CGFloat targetWidth = defineSize.width;
CGFloat widthSacler = width / targetWidth;
CGFloat height = widthSacler * defineSize.height;
CGSize size = CGSizeMake(width, height);
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, size.width, size.height)];
[path addClip];
// 5.畫圖片
[sourceImage drawAtPoint:CGPointZero];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
}
2.4>下載圖片，是否全屏顯示由后臺決定的
+ (void)loadNewLaunchImage {
NSString *url = [baseStr stringByAppendingString:@"api/app/appScreensaverAction_search"];
[ALSHttpTool GetWithURL:url params:nil success:^(id json) {
ALSLog(@"%@",json);
if ([json[@"rs"] integerValue] == 200) {
NSInteger type = [json[@"content"][@"type"] integerValue];
[ALSUserDefaults setBool:type forKey:@"launchImageType"];
[[SDWebImageManager sharedManager] downloadImageWithURL:[NSURL URLWithString:json[@"content"][@"image"]] options:0 progress:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
if (image) {
NSFileManager *fm = [NSFileManager defaultManager];
NSString *saveDiretory = [NSString stringWithFormat:@"%@/image",[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES) lastObject]];
BOOL isDirectory ;
BOOL isExist = [fm fileExistsAtPath:saveDiretory isDirectory:&isDirectory];
if (!isExist) {
[fm createDirectoryAtPath:saveDiretory withIntermediateDirectories:NO attributes:nil error:nil];
}
//寫入圖片
NSString *savePath =[NSString stringWithFormat: @"%@/launchImage.png",saveDiretory];
NSData *imageData = UIImagePNGRepresentation(image);
[imageData writeToFile:savePath atomically:YES];
}
}];
}
} failure:^(NSError *error) {
}];
}
2.5>移除launchImage
-(void)closeAddImgAnimation
{
//這個比較自然，設置alpha比較舒服
[UIView animateWithDuration:0.3 animations:^{
self.alpha = 0;
} completion:^(BOOL finished) {
[self removeFromSuperview];
}];
}
開屏廣告也是差不多的，后臺獲取的圖片不能用于下一次，可能會有點延時。然后加一個跳過按鈕，讓圖片接受事件，大同小異，最主要的就是將放在app里面imageLaunch這張圖片渲染成背景色，以及圖片剪裁的處理
