added files via upload

Tweaks/FLEX/ViewHierarchy/FLEXImagePreviewViewController.m

@@ -0,0 +1,147 @@
+//
+//  FLEXImagePreviewViewController.m
+//  Flipboard
+//
+//  Created by Ryan Olson on 6/12/14.
+//  Copyright (c) 2020 FLEX Team. All rights reserved.
+//
+
+#import "FLEXImagePreviewViewController.h"
+#import "FLEXUtility.h"
+#import "FLEXColor.h"
+#import "FLEXResources.h"
+
+@interface FLEXImagePreviewViewController () <UIScrollViewDelegate>
+@property (nonatomic) UIImage *image;
+@property (nonatomic) UIScrollView *scrollView;
+@property (nonatomic) UIImageView *imageView;
+@property (nonatomic) UITapGestureRecognizer *bgColorTapGesture;
+@property (nonatomic) NSInteger backgroundColorIndex;
+@property (nonatomic, readonly) NSArray<UIColor *> *backgroundColors;
+@end
+
+#pragma mark -
+@implementation FLEXImagePreviewViewController
+
+#pragma mark Initialization
+
++ (instancetype)previewForView:(UIView *)view {
+    return [self forImage:[FLEXUtility previewImageForView:view]];
+}
+
++ (instancetype)previewForLayer:(CALayer *)layer {
+    return [self forImage:[FLEXUtility previewImageForLayer:layer]];
+}
+
++ (instancetype)forImage:(UIImage *)image {
+    return [[self alloc] initWithImage:image];
+}
+
+- (id)initWithImage:(UIImage *)image {
+    NSParameterAssert(image);
+    
+    self = [super init];
+    if (self) {
+        self.title = @"Preview";
+        self.image = image;
+        _backgroundColors = @[FLEXResources.checkerPatternColor, UIColor.whiteColor, UIColor.blackColor];
+    }
+    
+    return self;
+}
+
+
+#pragma mark Lifecycle
+
+- (void)viewDidLoad {
+    [super viewDidLoad];
+    
+    self.imageView = [[UIImageView alloc] initWithImage:self.image];
+    self.scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
+    self.scrollView.delegate = self;
+    self.scrollView.backgroundColor = self.backgroundColors.firstObject;
+    self.scrollView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
+    [self.scrollView addSubview:self.imageView];
+    self.scrollView.contentSize = self.imageView.frame.size;
+    self.scrollView.minimumZoomScale = 1.0;
+    self.scrollView.maximumZoomScale = 2.0;
+    [self.view addSubview:self.scrollView];
+    
+    self.bgColorTapGesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(changeBackground)];
+    [self.scrollView addGestureRecognizer:self.bgColorTapGesture];
+    
+    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc]
+        initWithBarButtonSystemItem:UIBarButtonSystemItemAction
+        target:self
+        action:@selector(actionButtonPressed:)
+    ];
+}
+
+- (void)viewDidLayoutSubviews {
+    [self centerContentInScrollViewIfNeeded];
+}
+
+
+#pragma mark UIScrollViewDelegate
+
+- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
+    return self.imageView;
+}
+
+- (void)scrollViewDidZoom:(UIScrollView *)scrollView {
+    [self centerContentInScrollViewIfNeeded];
+}
+
+
+#pragma mark Private
+
+- (void)centerContentInScrollViewIfNeeded {
+    CGFloat horizontalInset = 0.0;
+    CGFloat verticalInset = 0.0;
+    if (self.scrollView.contentSize.width < self.scrollView.bounds.size.width) {
+        horizontalInset = (self.scrollView.bounds.size.width - self.scrollView.contentSize.width) / 2.0;
+    }
+    if (self.scrollView.contentSize.height < self.scrollView.bounds.size.height) {
+        verticalInset = (self.scrollView.bounds.size.height - self.scrollView.contentSize.height) / 2.0;
+    }
+    self.scrollView.contentInset = UIEdgeInsetsMake(verticalInset, horizontalInset, verticalInset, horizontalInset);
+}
+
+- (void)changeBackground {
+    self.backgroundColorIndex++;
+    self.backgroundColorIndex %= self.backgroundColors.count;
+    self.scrollView.backgroundColor = self.backgroundColors[self.backgroundColorIndex];
+}
+
+- (void)actionButtonPressed:(id)sender {
+    static BOOL canSaveToCameraRoll = NO, didShowWarning = NO;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        if (UIDevice.currentDevice.systemVersion.floatValue < 10) {
+            canSaveToCameraRoll = YES;
+            return;
+        }
+        
+        NSBundle *mainBundle = NSBundle.mainBundle;
+        if ([mainBundle.infoDictionary.allKeys containsObject:@"NSPhotoLibraryUsageDescription"]) {
+            canSaveToCameraRoll = YES;
+        }
+    });
+    
+    UIActivityViewController *activityVC = [[UIActivityViewController alloc] initWithActivityItems:@[self.image] applicationActivities:@[]];
+    
+    if (!canSaveToCameraRoll && !didShowWarning) {
+        didShowWarning = YES;
+        NSString *msg = @"Add 'NSPhotoLibraryUsageDescription' to this app's Info.plist to save images.";
+        [FLEXAlert makeAlert:^(FLEXAlert *make) {
+            make.title(@"Reminder").message(msg);
+            make.button(@"OK").handler(^(NSArray<NSString *> *strings) {
+                [self presentViewController:activityVC animated:YES completion:nil];
+            });
+        } showFrom:self];
+    } else {
+        [self presentViewController:activityVC animated:YES completion:nil];
+    }
+}
+
+@end