按字母导航 tvOS UITableView

好了，系好安全带，孩子！我们即将为您已经非常出色的代码添加一些魔力！

你看，与iOS相比，tvOS有点不同。它有自己的焦点模型，就像舞台上神奇的聚光灯，总是试图一次将一个界面元素（我们的演员）放在聚光灯下。现在，您在以编程方式滚动和选择单元格方面做得非常出色，但聚光灯......呃，注意力跟不上。但不要害怕，我们有一个技巧！它被称为焦点指南。

把这个焦点指南看作是我们戏剧的导演。这将帮助我们准确地告诉聚光灯下一步该去哪里。

首先，让我们在我们的方法中构思一个新的焦点指南，并为它铺上红地毯，以引导我们的聚光灯：viewDidLoad

self.dapperFocusGuide = [[UIFocusGuide alloc] init];
[self.view addLayoutGuide:self.dapperFocusGuide];

// Alright, red carpet time.
[self.dapperFocusGuide.topAnchor constraintEqualToAnchor:self.tableView.topAnchor].active = YES;
[self.dapperFocusGuide.leftAnchor constraintEqualToAnchor:self.tableView.leftAnchor].active = YES;
[self.dapperFocusGuide.widthAnchor constraintEqualToAnchor:self.tableView.widthAnchor].active = YES;
[self.dapperFocusGuide.heightAnchor constraintEqualToAnchor:self.tableView.heightAnchor].active = YES;

接下来，让我们告诉我们的导演，当戏剧开始时，哪位演员需要聚光灯：

self.dapperFocusGuide.preferredFocusEnvironments = @[self.tableView.visibleCells.firstObject];

现在，请抓紧你的帽子，因为我们即将教我们的导演一些新技巧！我们将告诉它如何在我们的方法中处理脚本中的更改：handleRightButtonPress

// Rest of your spectacular code...

// Select the cell at the specified index.
NSIndexPath *indexPathToSelect = [NSIndexPath indexPathForRow:self.currentIndex inSection:0];
[self.tableView selectRowAtIndexPath:indexPathToSelect animated:NO scrollPosition:UITableViewScrollPositionNone];

// And now, the moment we've all been waiting for. Drumroll please... 
// Let's tell our director to shift the spotlight!
UITableViewCell *cellToFocus = [self.tableView cellForRowAtIndexPath:indexPathToSelect];
self.dapperFocusGuide.preferredFocusEnvironments = @[cellToFocus];

现在，别忘了告诉编译器，我们都是这里的剧院人，然后导入：UIFocusGuide

这样一来，当您按下右键时，tableView 现在应该正确地聚焦在正确的单元格上。这就像代码和 UI 之间精心编排的舞蹈。现在继续，鞠躬！你赚到了！🎭👏🎉

这就是所有的东西......

#import <UIKit/UIFocusGuide.h>

@interface YourTableViewController ()
@property (nonatomic, strong) NSArray *files;
@property (nonatomic, strong) NSString *filenames;
@property (nonatomic, strong) UIFocusGuide *dapperFocusGuide;
@property (nonatomic, assign) NSInteger currentIndex;
@end

@implementation YourTableViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // We're setting the stage!
    self.tableView.delegate = self;
    self.tableView.dataSource = self;
    self.definesPresentationContext = YES;
    self.currentIndex = 0;

    // Time to call the stars for a rehearsal.
    [self populateTheView];
    
    // Let's make room for our magical focus director.
    self.dapperFocusGuide = [[UIFocusGuide alloc] init];
    [self.view addLayoutGuide:self.dapperFocusGuide];

    // Red carpet time!
    [self.dapperFocusGuide.topAnchor constraintEqualToAnchor:self.tableView.topAnchor].active = YES;
    [self.dapperFocusGuide.leftAnchor constraintEqualToAnchor:self.tableView.leftAnchor].active = YES;
    [self.dapperFocusGuide.widthAnchor constraintEqualToAnchor:self.tableView.widthAnchor].active = YES;
    [self.dapperFocusGuide.heightAnchor constraintEqualToAnchor:self.tableView.heightAnchor].active = YES;
}

- (void)populateTheView {
    NSBundle *bundle = [NSBundle mainBundle];
    self.title = @"Devo Songs";
    self.files  = [bundle pathsForResourcesOfType:@"pdf" inDirectory:@"WorshipSongs"];
    NSString *documentsDirectoryPath = [self.files objectAtIndex:self.currentIndex];
    
    self.filenames = [[documentsDirectoryPath lastPathComponent] stringByDeletingPathExtension];
      
    NSMutableArray *names = [NSMutableArray arrayWithCapacity:[self.files count]];
    for (NSString *path in self.files) {
        [names addObject:[[path lastPathComponent] stringByDeletingPathExtension]];
    }
   
    self.files = [names sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
    NSLog(@"FILESLOAD%@", self.files);
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    // Cue the music! The show has started.
    [self becomeFirstResponder]; 

    // Initial spotlight position.
    self.dapperFocusGuide.preferredFocusEnvironments = @[self.tableView.visibleCells.firstObject];
}

- (BOOL)canBecomeFirstResponder {
    return YES; // Of course we can! We're the star of the show!
}

// Here we keep an eye out for any new script changes (aka right arrow key press events).
- (void)pressesEnded:(NSSet<UIPress *> *)presses withEvent:(UIPressesEvent *)event {
    [super pressesEnded:presses withEvent:event];

    for (UIPress *press in presses) {
        if (press.type == UIPressTypeRightArrow) {
            [self handleRightButtonPress];
        }
    }
}

- (void)handleRightButtonPress {
    // Your logic here to find the next index...

    // Get the newly called star ready for the scene.
    NSIndexPath *indexPathToSelect = [NSIndexPath indexPathForRow:self.currentIndex inSection:0];
    [self.tableView selectRowAtIndexPath:indexPathToSelect animated:NO scrollPosition:UITableViewScrollPositionNone];

    // And now, the moment we've all been waiting for. Drumroll please... 
    // The spotlight moves!
    UITableViewCell *cellToFocus = [self.tableView cellForRowAtIndexPath:indexPathToSelect];
    self.dapperFocusGuide.preferredFocusEnvironments = @[cellToFocus];
}

// Here you would have your other UITableViewDelegate and UITableViewDataSource methods...

@end

在平台上，您应该使用焦点而不是选择进行导航，因此只需用于通知焦点索引路径，例如：tvOSindexPathForPreferredFocusedViewInTableViewUITableView

@interface ViewController () <UITableViewDataSource, UITableViewDelegate>

...
@property (nonatomic) NSIndexPath* focusedIndexPath;

@end

@implementation ViewController

...

- (void)focusRow:(NSInteger)row {
  self.focusedIndexPath = [NSIndexPath indexPathForRow:row inSection:0];
  [self.tableView setNeedsFocusUpdate];
}

#pragma mark - UITableViewDelegate

- (NSIndexPath *)indexPathForPreferredFocusedViewInTableView:(UITableView *)tableView {
  return self.focusedIndexPath;
}

@end