Obj-C- 在不重新加载整个 collectionView 的情况下更新 UICollectionView 数据？
Obj-C- Update UICollectionView data without reloading entire collectionView?
我有一个 UICollectionView，当单元格被选中时，它们会变成用户选择的颜色。绘制完整图片：颜色由用户从色轮 (UIImageView) 中选择，并带有点击手势。
就是说，当用户在选择 3 个单元格并将它们变为绿色后点击一种新颜色，比如紫色（并重置定义的 rString、bString 和 gString...）时，我想重新加载它们的颜色使用而不擦除 Collection View 中最初选择的 3 个绿色单元格。我怎样才能做到这一点？
请参阅下面的代码。
ViewController.m
@interface ViewController () {
CGPoint lastPoint;
NSInteger rString;
NSInteger bString;
NSInteger gString;
UIColor *colour;
}
@property (strong, nonatomic, nullable) NSIndexPath *trackingCellIndexPath;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.ringCollectionView.allowsMultipleSelection = YES;
UITapGestureRecognizer * tapRecognizer = [[UITapGestureRecognizer alloc]
initWithTarget:self action:@selector(tapGesture:)];
[self.colorWheel addGestureRecognizer:tapRecognizer];
self.colorWheel.userInteractionEnabled = YES;
}
- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"RingCollectionViewCell" forIndexPath:indexPath];
if (!cell.selectedBackgroundView) {
cell.selectedBackgroundView = [[UIView alloc] initWithFrame:cell.bounds];
cell.selectedBackgroundView.backgroundColor = [UIColor grayColor];
} else {
cell.selectedBackgroundView = [[UIView alloc] initWithFrame:cell.bounds];
cell.selectedBackgroundView.backgroundColor = [UIColor colorWithRed:rString/255.0 green:gString/255.0 blue:bString/255.0 alpha:1.0];
}
if ((indexPath.row >=9 && indexPath.row <=14) || ((indexPath.row >=17 && indexPath.row < 23) || (indexPath.row >=25 && indexPath.row <=30) || (indexPath.row >=33 && indexPath.row <=38))) {
NSLog(@"NOT AVAILABLE SORRY");
cell.backgroundColor = [UIColor whiteColor];
[cell setUserInteractionEnabled:NO];
}
return cell;
}
-(void)tapGesture:(UITapGestureRecognizer *)recognizer {
CGPoint location = [recognizer locationInView:recognizer.view];
CGPoint p = { round(location.x), round(location.y) };
_colorView.backgroundColor = [self colorInViewAtPoint:p];
UIColor *mylovelycolor = [self colorInViewAtPoint:p];
const CGFloat *components = CGColorGetComponents(mylovelycolor.CGColor);
NSLog(@"Red: %f", components[0]);
NSLog(@"Green: %f", components[1]);
NSLog(@"Blue: %f", components[2]);
NSLog(@"Alpha: %f", CGColorGetAlpha(mylovelycolor.CGColor));
int red = components[0] * 255;
int green = components[1] * 255;
int blue = components[2] * 255;
NSString *red1 = [@(red) stringValue];
NSString *green1 = [@(green) stringValue];
NSString *blue1 = [@(blue) stringValue];
NSInteger redInt = [red1 integerValue];
NSInteger greenInt = [green1 integerValue];
NSInteger blueInt = [blue1 integerValue];
rString = [red1 integerValue];
bString = [blue1 integerValue];
gString = [green1 integerValue];
self.redValue.text = red1;
self.greenValue.text = green1;
self.blueValue.text = blue1;
NSMutableString *str1 = [NSMutableString string];
for(NSInteger numberCopy = redInt; numberCopy > 0; numberCopy >>= 1)
{
[str1 insertString:((numberCopy & 1) ? @"1" : @"0") atIndex:0];
}
NSMutableString *str2 = [NSMutableString string];
for(NSInteger numberCopy = greenInt; numberCopy > 0; numberCopy >>= 1)
{
[str2 insertString:((numberCopy & 1) ? @"1" : @"0") atIndex:0];
}
NSMutableString *str3 = [NSMutableString string];
for(NSInteger numberCopy = blueInt; numberCopy > 0; numberCopy >>= 1)
{
[str3 insertString:((numberCopy & 1) ? @"1" : @"0") atIndex:0];
}
self.binaryString = [NSString stringWithFormat:@" %@ %@ %@", str1, str2, str3];
}
您需要在数据模型中跟踪用户select编辑的颜色。
在 cellForItemAtIndexPath 中，您想将单元格的背景颜色（或您正在使用的任何元素）设置为 数据元素 颜色。
当用户select编辑了一个或多个单元格并点击您的“colorWheel”时，更新您的数据模型，然后直接设置单元格元素或重新加载这些单元格。
这是一个非常简单的例子...
MyDataObject.h
//
// MyDataObject.h
//
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@interface MyDataObject : NSObject
@property (strong, nonatomic) UIColor *userColor;
@end
NS_ASSUME_NONNULL_END
MyDataObject.m
//
// MyDataObject.m
//
#import "MyDataObject.h"
@implementation MyDataObject
@end
MyCollectionViewCell.h
//
// MyCollectionViewCell.h
//
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@interface MyCollectionViewCell : UICollectionViewCell
@property (strong, nonatomic) UILabel *label;
@end
NS_ASSUME_NONNULL_END
MyCollectionViewCell.m
//
// MyCollectionViewCell.m
//
#import "MyCollectionViewCell.h"
@implementation MyCollectionViewCell
- (instancetype)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self commonInit];
}
return self;
}
- (instancetype)initWithCoder:(NSCoder *)coder
{
self = [super initWithCoder:coder];
if (self) {
[self commonInit];
}
return self;
}
- (void)commonInit {
_label = [UILabel new];
_label.textAlignment = NSTextAlignmentCenter;
_label.backgroundColor = [UIColor colorWithWhite:0.9 alpha:1.0];
_label.translatesAutoresizingMaskIntoConstraints = NO;
[self.contentView addSubview:_label];
UILayoutGuide *g = [self.contentView layoutMarginsGuide];
[NSLayoutConstraint activateConstraints:@[
[_label.widthAnchor constraintEqualToAnchor:g.widthAnchor multiplier:0.8],
[_label.heightAnchor constraintEqualToAnchor:g.heightAnchor multiplier:0.8],
[_label.centerXAnchor constraintEqualToAnchor:g.centerXAnchor],
[_label.centerYAnchor constraintEqualToAnchor:g.centerYAnchor],
]];
self.contentView.layer.borderColor = [UIColor yellowColor].CGColor;
}
- (void)setSelected:(BOOL)selected {
[super setSelected:selected];
self.contentView.layer.borderWidth = selected ? 2 : 0;
}
@end
MyTestViewController.h
//
// MyTestViewController.h
//
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@interface MyTestViewController : UIViewController <UICollectionViewDataSource, UICollectionViewDelegate>
@end
NS_ASSUME_NONNULL_END
MyTestViewController.m
//
// MyTestViewController.m
//
#import "MyTestViewController.h"
#import "MyCollectionViewCell.h"
#import "MyDataObject.h"
@interface MyTestViewController ()
{
NSMutableArray <MyDataObject *>*myCellData;
UICollectionView *collectionView;
}
@end
@implementation MyTestViewController
- (void)viewDidLoad {
[super viewDidLoad];
UICollectionViewFlowLayout *fl = [UICollectionViewFlowLayout new];
fl.itemSize = CGSizeMake(50, 50);
fl.scrollDirection = UICollectionViewScrollDirectionHorizontal;
collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:fl];
collectionView.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:collectionView];
UILayoutGuide *g = [self.view safeAreaLayoutGuide];
[NSLayoutConstraint activateConstraints:@[
[collectionView.leadingAnchor constraintEqualToAnchor:g.leadingAnchor constant:20.0],
[collectionView.trailingAnchor constraintEqualToAnchor:g.trailingAnchor constant:-20.0],
[collectionView.heightAnchor constraintEqualToConstant:240.0],
[collectionView.centerYAnchor constraintEqualToAnchor:g.centerYAnchor],
]];
// a few color views to tap, and an
// "Instructions" label
UILabel *label = [UILabel new];
label.text = @"Tap a color to change the selected cells:";
UIStackView *stack = [UIStackView new];
NSArray *colors = @[
[UIColor redColor],
[UIColor greenColor],
[UIColor blueColor],
[UIColor systemYellowColor],
[UIColor systemTealColor],
];
for (UIColor *c in colors) {
UIView *v = [UIView new];
v.backgroundColor = c;
UITapGestureRecognizer *t = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(gotTap:)];
[v addGestureRecognizer:t];
[stack addArrangedSubview:v];
}
stack.spacing = 20.0;
stack.distribution = UIStackViewDistributionFillEqually;
label.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:label];
stack.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:stack];
[NSLayoutConstraint activateConstraints:@[
[stack.leadingAnchor constraintEqualToAnchor:g.leadingAnchor constant:20.0],
[stack.trailingAnchor constraintEqualToAnchor:g.trailingAnchor constant:-20.0],
[stack.bottomAnchor constraintEqualToAnchor:g.bottomAnchor constant:-20.0],
[stack.heightAnchor constraintEqualToConstant:40.0],
[label.leadingAnchor constraintEqualToAnchor:g.leadingAnchor constant:20.0],
[label.trailingAnchor constraintEqualToAnchor:g.trailingAnchor constant:-20.0],
[label.bottomAnchor constraintEqualToAnchor:stack.topAnchor constant:-4.0],
]];
collectionView.dataSource = self;
collectionView.delegate = self;
collectionView.allowsMultipleSelection = YES;
[collectionView registerClass:MyCollectionViewCell.class forCellWithReuseIdentifier:@"c"];
// create 50 objects for our data
myCellData = [NSMutableArray new];
for (int i = 0; i < 50; i++) {
MyDataObject *obj = [MyDataObject new];
obj.userColor = [UIColor redColor];
[myCellData addObject:obj];
}
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return myCellData.count;
}
- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
// dequeue a cell
MyCollectionViewCell *c = (MyCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"c" forIndexPath:indexPath];
// get the data object
MyDataObject *obj = (MyDataObject *)[myCellData objectAtIndex:indexPath.item];
// set cell's contentView.backgroundColor to the data object's .userColor
c.contentView.backgroundColor = obj.userColor;
// set the cell's label text
c.label.text = [NSString stringWithFormat:@"%ld", indexPath.item];
return c;
}
- (void)gotTap:(UITapGestureRecognizer *)g {
if (collectionView.indexPathsForSelectedItems.count == 0) {
UIAlertController * alert = [UIAlertController
alertControllerWithTitle:@"Error"
message:@"No cells are selected!"
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* okButton = [UIAlertAction
actionWithTitle:@"OK"
style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action) {
}];
[alert addAction:okButton];
[self presentViewController:alert animated:YES completion:nil];
return;
}
UIView *v = g.view;
if (v) {
// get the background color from the tapped view
UIColor *color = v.backgroundColor;
// loop through selected cells
for (NSIndexPath *p in collectionView.indexPathsForSelectedItems) {
// update the object in our data
[myCellData objectAtIndex:p.item].userColor = color;
// get a reference to the cell
MyCollectionViewCell *c = (MyCollectionViewCell *)[collectionView cellForItemAtIndexPath:p];
// set its background color
c.contentView.backgroundColor = color;
// if we want to auto-deselect the cells
[collectionView deselectItemAtIndexPath:p animated:YES];
}
}
}
@end
所以，
- 我们的数据对象只有一个 属性：
userColor
- 我们的单元格 class 有一个居中的标签
- 我们的控制器
- 创建水平滚动集合视图
- 创建一个包含 50 个数据对象的数组，默认
userColor 为红色
- 从
添加 5 个颜色视图到 select
当一个单元格被 selected 时，它会用黄色勾勒出来。当点击颜色视图时，我们：
- 更新当前 selected 单元格的数据模型
- 设置当前 selected 单元格的 contentView 的背景颜色
- deselect 当前 selected 单元格
看起来像这样：
然后我们 select 单元格 5、9、14:
点击绿色视图：
然后我们 select 单元格 16、17、18：
点击蓝色视图：
然后我们稍微滚动一下 select 单元格 17、21、24、25、26：
点击黄色视图：
等等。
我有一个 UICollectionView，当单元格被选中时，它们会变成用户选择的颜色。绘制完整图片：颜色由用户从色轮 (UIImageView) 中选择，并带有点击手势。
就是说，当用户在选择 3 个单元格并将它们变为绿色后点击一种新颜色，比如紫色（并重置定义的 rString、bString 和 gString...）时，我想重新加载它们的颜色使用而不擦除 Collection View 中最初选择的 3 个绿色单元格。我怎样才能做到这一点？
请参阅下面的代码。
ViewController.m
@interface ViewController () {
CGPoint lastPoint;
NSInteger rString;
NSInteger bString;
NSInteger gString;
UIColor *colour;
}
@property (strong, nonatomic, nullable) NSIndexPath *trackingCellIndexPath;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.ringCollectionView.allowsMultipleSelection = YES;
UITapGestureRecognizer * tapRecognizer = [[UITapGestureRecognizer alloc]
initWithTarget:self action:@selector(tapGesture:)];
[self.colorWheel addGestureRecognizer:tapRecognizer];
self.colorWheel.userInteractionEnabled = YES;
}
- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath
{
UICollectionViewCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"RingCollectionViewCell" forIndexPath:indexPath];
if (!cell.selectedBackgroundView) {
cell.selectedBackgroundView = [[UIView alloc] initWithFrame:cell.bounds];
cell.selectedBackgroundView.backgroundColor = [UIColor grayColor];
} else {
cell.selectedBackgroundView = [[UIView alloc] initWithFrame:cell.bounds];
cell.selectedBackgroundView.backgroundColor = [UIColor colorWithRed:rString/255.0 green:gString/255.0 blue:bString/255.0 alpha:1.0];
}
if ((indexPath.row >=9 && indexPath.row <=14) || ((indexPath.row >=17 && indexPath.row < 23) || (indexPath.row >=25 && indexPath.row <=30) || (indexPath.row >=33 && indexPath.row <=38))) {
NSLog(@"NOT AVAILABLE SORRY");
cell.backgroundColor = [UIColor whiteColor];
[cell setUserInteractionEnabled:NO];
}
return cell;
}
-(void)tapGesture:(UITapGestureRecognizer *)recognizer {
CGPoint location = [recognizer locationInView:recognizer.view];
CGPoint p = { round(location.x), round(location.y) };
_colorView.backgroundColor = [self colorInViewAtPoint:p];
UIColor *mylovelycolor = [self colorInViewAtPoint:p];
const CGFloat *components = CGColorGetComponents(mylovelycolor.CGColor);
NSLog(@"Red: %f", components[0]);
NSLog(@"Green: %f", components[1]);
NSLog(@"Blue: %f", components[2]);
NSLog(@"Alpha: %f", CGColorGetAlpha(mylovelycolor.CGColor));
int red = components[0] * 255;
int green = components[1] * 255;
int blue = components[2] * 255;
NSString *red1 = [@(red) stringValue];
NSString *green1 = [@(green) stringValue];
NSString *blue1 = [@(blue) stringValue];
NSInteger redInt = [red1 integerValue];
NSInteger greenInt = [green1 integerValue];
NSInteger blueInt = [blue1 integerValue];
rString = [red1 integerValue];
bString = [blue1 integerValue];
gString = [green1 integerValue];
self.redValue.text = red1;
self.greenValue.text = green1;
self.blueValue.text = blue1;
NSMutableString *str1 = [NSMutableString string];
for(NSInteger numberCopy = redInt; numberCopy > 0; numberCopy >>= 1)
{
[str1 insertString:((numberCopy & 1) ? @"1" : @"0") atIndex:0];
}
NSMutableString *str2 = [NSMutableString string];
for(NSInteger numberCopy = greenInt; numberCopy > 0; numberCopy >>= 1)
{
[str2 insertString:((numberCopy & 1) ? @"1" : @"0") atIndex:0];
}
NSMutableString *str3 = [NSMutableString string];
for(NSInteger numberCopy = blueInt; numberCopy > 0; numberCopy >>= 1)
{
[str3 insertString:((numberCopy & 1) ? @"1" : @"0") atIndex:0];
}
self.binaryString = [NSString stringWithFormat:@" %@ %@ %@", str1, str2, str3];
}
您需要在数据模型中跟踪用户select编辑的颜色。
在 cellForItemAtIndexPath 中，您想将单元格的背景颜色（或您正在使用的任何元素）设置为 数据元素 颜色。
当用户select编辑了一个或多个单元格并点击您的“colorWheel”时，更新您的数据模型，然后直接设置单元格元素或重新加载这些单元格。
这是一个非常简单的例子...
MyDataObject.h
//
// MyDataObject.h
//
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@interface MyDataObject : NSObject
@property (strong, nonatomic) UIColor *userColor;
@end
NS_ASSUME_NONNULL_END
MyDataObject.m
//
// MyDataObject.m
//
#import "MyDataObject.h"
@implementation MyDataObject
@end
MyCollectionViewCell.h
//
// MyCollectionViewCell.h
//
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@interface MyCollectionViewCell : UICollectionViewCell
@property (strong, nonatomic) UILabel *label;
@end
NS_ASSUME_NONNULL_END
MyCollectionViewCell.m
//
// MyCollectionViewCell.m
//
#import "MyCollectionViewCell.h"
@implementation MyCollectionViewCell
- (instancetype)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self commonInit];
}
return self;
}
- (instancetype)initWithCoder:(NSCoder *)coder
{
self = [super initWithCoder:coder];
if (self) {
[self commonInit];
}
return self;
}
- (void)commonInit {
_label = [UILabel new];
_label.textAlignment = NSTextAlignmentCenter;
_label.backgroundColor = [UIColor colorWithWhite:0.9 alpha:1.0];
_label.translatesAutoresizingMaskIntoConstraints = NO;
[self.contentView addSubview:_label];
UILayoutGuide *g = [self.contentView layoutMarginsGuide];
[NSLayoutConstraint activateConstraints:@[
[_label.widthAnchor constraintEqualToAnchor:g.widthAnchor multiplier:0.8],
[_label.heightAnchor constraintEqualToAnchor:g.heightAnchor multiplier:0.8],
[_label.centerXAnchor constraintEqualToAnchor:g.centerXAnchor],
[_label.centerYAnchor constraintEqualToAnchor:g.centerYAnchor],
]];
self.contentView.layer.borderColor = [UIColor yellowColor].CGColor;
}
- (void)setSelected:(BOOL)selected {
[super setSelected:selected];
self.contentView.layer.borderWidth = selected ? 2 : 0;
}
@end
MyTestViewController.h
//
// MyTestViewController.h
//
#import <UIKit/UIKit.h>
NS_ASSUME_NONNULL_BEGIN
@interface MyTestViewController : UIViewController <UICollectionViewDataSource, UICollectionViewDelegate>
@end
NS_ASSUME_NONNULL_END
MyTestViewController.m
//
// MyTestViewController.m
//
#import "MyTestViewController.h"
#import "MyCollectionViewCell.h"
#import "MyDataObject.h"
@interface MyTestViewController ()
{
NSMutableArray <MyDataObject *>*myCellData;
UICollectionView *collectionView;
}
@end
@implementation MyTestViewController
- (void)viewDidLoad {
[super viewDidLoad];
UICollectionViewFlowLayout *fl = [UICollectionViewFlowLayout new];
fl.itemSize = CGSizeMake(50, 50);
fl.scrollDirection = UICollectionViewScrollDirectionHorizontal;
collectionView = [[UICollectionView alloc] initWithFrame:CGRectZero collectionViewLayout:fl];
collectionView.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:collectionView];
UILayoutGuide *g = [self.view safeAreaLayoutGuide];
[NSLayoutConstraint activateConstraints:@[
[collectionView.leadingAnchor constraintEqualToAnchor:g.leadingAnchor constant:20.0],
[collectionView.trailingAnchor constraintEqualToAnchor:g.trailingAnchor constant:-20.0],
[collectionView.heightAnchor constraintEqualToConstant:240.0],
[collectionView.centerYAnchor constraintEqualToAnchor:g.centerYAnchor],
]];
// a few color views to tap, and an
// "Instructions" label
UILabel *label = [UILabel new];
label.text = @"Tap a color to change the selected cells:";
UIStackView *stack = [UIStackView new];
NSArray *colors = @[
[UIColor redColor],
[UIColor greenColor],
[UIColor blueColor],
[UIColor systemYellowColor],
[UIColor systemTealColor],
];
for (UIColor *c in colors) {
UIView *v = [UIView new];
v.backgroundColor = c;
UITapGestureRecognizer *t = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(gotTap:)];
[v addGestureRecognizer:t];
[stack addArrangedSubview:v];
}
stack.spacing = 20.0;
stack.distribution = UIStackViewDistributionFillEqually;
label.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:label];
stack.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:stack];
[NSLayoutConstraint activateConstraints:@[
[stack.leadingAnchor constraintEqualToAnchor:g.leadingAnchor constant:20.0],
[stack.trailingAnchor constraintEqualToAnchor:g.trailingAnchor constant:-20.0],
[stack.bottomAnchor constraintEqualToAnchor:g.bottomAnchor constant:-20.0],
[stack.heightAnchor constraintEqualToConstant:40.0],
[label.leadingAnchor constraintEqualToAnchor:g.leadingAnchor constant:20.0],
[label.trailingAnchor constraintEqualToAnchor:g.trailingAnchor constant:-20.0],
[label.bottomAnchor constraintEqualToAnchor:stack.topAnchor constant:-4.0],
]];
collectionView.dataSource = self;
collectionView.delegate = self;
collectionView.allowsMultipleSelection = YES;
[collectionView registerClass:MyCollectionViewCell.class forCellWithReuseIdentifier:@"c"];
// create 50 objects for our data
myCellData = [NSMutableArray new];
for (int i = 0; i < 50; i++) {
MyDataObject *obj = [MyDataObject new];
obj.userColor = [UIColor redColor];
[myCellData addObject:obj];
}
}
- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
return myCellData.count;
}
- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
// dequeue a cell
MyCollectionViewCell *c = (MyCollectionViewCell *)[collectionView dequeueReusableCellWithReuseIdentifier:@"c" forIndexPath:indexPath];
// get the data object
MyDataObject *obj = (MyDataObject *)[myCellData objectAtIndex:indexPath.item];
// set cell's contentView.backgroundColor to the data object's .userColor
c.contentView.backgroundColor = obj.userColor;
// set the cell's label text
c.label.text = [NSString stringWithFormat:@"%ld", indexPath.item];
return c;
}
- (void)gotTap:(UITapGestureRecognizer *)g {
if (collectionView.indexPathsForSelectedItems.count == 0) {
UIAlertController * alert = [UIAlertController
alertControllerWithTitle:@"Error"
message:@"No cells are selected!"
preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* okButton = [UIAlertAction
actionWithTitle:@"OK"
style:UIAlertActionStyleDefault
handler:^(UIAlertAction * action) {
}];
[alert addAction:okButton];
[self presentViewController:alert animated:YES completion:nil];
return;
}
UIView *v = g.view;
if (v) {
// get the background color from the tapped view
UIColor *color = v.backgroundColor;
// loop through selected cells
for (NSIndexPath *p in collectionView.indexPathsForSelectedItems) {
// update the object in our data
[myCellData objectAtIndex:p.item].userColor = color;
// get a reference to the cell
MyCollectionViewCell *c = (MyCollectionViewCell *)[collectionView cellForItemAtIndexPath:p];
// set its background color
c.contentView.backgroundColor = color;
// if we want to auto-deselect the cells
[collectionView deselectItemAtIndexPath:p animated:YES];
}
}
}
@end
所以，
- 我们的数据对象只有一个 属性：
userColor - 我们的单元格 class 有一个居中的标签
- 我们的控制器
- 创建水平滚动集合视图
- 创建一个包含 50 个数据对象的数组，默认
userColor为红色 - 从 添加 5 个颜色视图到 select
当一个单元格被 selected 时，它会用黄色勾勒出来。当点击颜色视图时，我们：
- 更新当前 selected 单元格的数据模型
- 设置当前 selected 单元格的 contentView 的背景颜色
- deselect 当前 selected 单元格
看起来像这样：
然后我们 select 单元格 5、9、14:
点击绿色视图：
然后我们 select 单元格 16、17、18：
点击蓝色视图：
然后我们稍微滚动一下 select 单元格 17、21、24、25、26：
点击黄色视图：
等等。