[英]iOS Objective C ScrollView
我正在嘗試實現UIScrollView並使用Objective-C從Xcode中的圖像數組中加載圖像,UIScrollView中的每個圖像在縱向和橫向模式下都必須全屏顯示。我已經能夠使其工作在縱向模式下,但不在橫向模式下。 所有iOS設備尺寸均應為全屏顯示。 以下是我到目前為止編寫的代碼。 我的情節提要中有UIScrollView,一個按鈕和一個標簽。 任何答案或指向實現此目的的教程將不勝感激。 提前致謝。
CGRect screen = [[UIScreen mainScreen] bounds];
CGFloat widthInPixel = screen.size.width;
CGFloat heightInPixel = screen.size.height;
float increaseAmount = widthInPixel;
self.imageScrollView.contentMode = UIViewContentModeScaleAspectFit;
self.imageScrollView.pagingEnabled = YES;
[self.imageScrollView setAlwaysBounceVertical:NO];
[self.imageScrollView setAlwaysBounceHorizontal:NO];
imageViews = [[NSMutableArray alloc] init];
self.imageScrollView.clipsToBounds = YES;
NSInteger imageNumbers = [self.images count];
UIImageView *image;
for(NSInteger i = 0; i < imageNumbers; i++) {
CGFloat xOrigin = i * self.view.frame.size.width;
image = [[UIImageView alloc] initWithFrame:
CGRectMake(xOrigin, 0,
widthInPixel,
self.imageScrollView.frame.size.height)];
image.contentMode = UIViewContentModeScaleAspectFit;
image.clipsToBounds = YES;
image.image = self.images[i];
[image setAutoresizingMask:
UIViewAutoresizingFlexibleWidth |
UIViewAutoresizingFlexibleHeight];
[self.imageScrollView addSubview:image];
}
self.imageScrollView.contentSize = CGSizeMake(image.frame.size.width *
imageNumbers,
self.imageScrollView.frame.size.height);
您確實應該學習如何使用自動布局和約束。 使用您喜歡的搜索引擎並搜索ios auto layout tutorial
...,您會發現很多材料。
編輯:
在啟用分頁的情況下旋轉滾動視圖時,滾動偏移是一個固有的問題。 有關viewWillTransitionToSize
的實現,請參見下面的編輯。
但是,給您一個想法,這會做您想要的,包括在設備旋轉時自動調整大小:
//
// ViewController.m
// ScrollingImages
//
// Created by Don Mag on 7/19/18.
//
#import "ViewController.h"
@interface ViewController ()
@property (strong, nonatomic) IBOutlet UIScrollView *theScrollView;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSArray *images = @[@"a", @"b", @"c", @"d", @"e"];
[_theScrollView setPagingEnabled:YES];
[_theScrollView setAlwaysBounceVertical:NO];
[_theScrollView setAlwaysBounceHorizontal:NO];
// we'll use this to hold the most recently added view
UIImageView *prevImageView = nil;
for (int i = 0; i < images.count; i++) {
// create an image view with named image from array
UIImageView *v = [[UIImageView alloc] initWithImage:[UIImage imageNamed:images[i]]];
// we want to use auto-layout
v.translatesAutoresizingMaskIntoConstraints = NO;
// we want aspect-fit
v.contentMode = UIViewContentModeScaleAspectFit;
// add it to the scroll view
[_theScrollView addSubview:v];
// set width and height constraints equal to the scroll view
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeWidth
multiplier:1.0
constant:0.0] setActive:YES];
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeHeight
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeHeight
multiplier:1.0
constant:0.0] setActive:YES];
if (i == 0) { // if it's the first image
// add top constraint
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:0.0] setActive:YES];
// and leading constraint
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeLeading
multiplier:1.0
constant:0.0] setActive:YES];
} else {
// constrain leading to previous image view trailing
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:prevImageView
attribute:NSLayoutAttributeTrailing
multiplier:1.0
constant:0.0] setActive:YES];
// and top to previous image view top
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:prevImageView
attribute:NSLayoutAttributeTop
multiplier:1.0
constant:0.0] setActive:YES];
}
if (i == images.count - 1) { // if it's the last image
// add trailing constraint
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeTrailing
multiplier:1.0
constant:0.0] setActive:YES];
// and bottom constraint
[[NSLayoutConstraint
constraintWithItem:v
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:_theScrollView
attribute:NSLayoutAttributeBottom
multiplier:1.0
constant:0.0] setActive:YES];
}
// reference to most recently added view
prevImageView = v;
}
}
- (void) viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator {
[super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
// execute before rotation
// get the "index" of the current image in the scroll view
NSUInteger idx = (unsigned)(_theScrollView.contentOffset.x / _theScrollView.frame.size.width);
[coordinator animateAlongsideTransition:^(id _Nonnull context) {
// execute during rotation
// update the scroll view's contentOffset, based on the "index"
self.theScrollView.contentOffset = CGPointMake(idx * self.theScrollView.frame.size.width, 0);
} completion:^(id _Nonnull context) {
// execute after rotation (if additional code wanted)
}];
}
@end
您可以在此處下載一個有效的示例項目: https : //github.com/DonMag/ScrollingImages
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