objective-c - 如何使用 UIKeyCommand

Question

当用户按下硬件键盘上的向下箭头时，我试图在表格视图中选择一行。现在，我只是想打印一个日志，我似乎无法让它工作。根据其他类似问题的答案，这是我到目前为止所拥有的：

- (NSArray *)keyCommands {
UIKeyCommand *downArrowKeyCommand = [UIKeyCommand keyCommandWithInput:UIKeyInputDownArrow
                                                        modifierFlags:0
                                                               action:@selector(hardwareKeyboardDownArrowPressed)];

return @[downArrowKeyCommand];
}

- (BOOL)canBecomeFirstResponder {
return YES;
}

- (void)hardwareKeyboardDownArrowPressed {

NSLog(@"Down arrow pressed on external keyboard");

}

感谢所有帮助！

Answer 1

我不知道你的具体错误；可能是您没有(id)sender在方法中添加 a 。我想出了如何做到这一点。我将在下面添加我的代码：

- (BOOL)canBecomeFirstResponder {
    return YES;
}

- (NSArray *)keyCommands {
    return @[[UIKeyCommand keyCommandWithInput:UIKeyInputDownArrow modifierFlags:0 action:@selector(moveDownOneRow:) discoverabilityTitle:@"Select row down"],
             [UIKeyCommand keyCommandWithInput:UIKeyInputUpArrow modifierFlags:0 action:@selector(moveUpOneRow:) discoverabilityTitle:@"Select row up"]];
}

- (void)moveDownOneRow:(id)sender {
    NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];

    if (indexPath == nil) {
        indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
    } else {
        if ((indexPath.row + 1) < [self.tableView numberOfRowsInSection:0]) {
            indexPath = [NSIndexPath indexPathForRow:indexPath.row+1 inSection:0];
        }
    }

    [self.tableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionMiddle];
}

- (void)moveUpOneRow:(id)sender {
    NSIndexPath *indexPath = [self.tableViewindexPathForSelectedRow];

    if (indexPath == nil) {
        indexPath = [NSIndexPath indexPathForRow:([self.tableView numberOfRowsInSection:0]-1) inSection:0];
    } else {
        if ((indexPath.row - 1) >= 0) {
            indexPath = [NSIndexPath indexPathForRow:indexPath.row-1 inSection:0];
        }
    }

    [self.tableView selectRowAtIndexPath:indexPath animated:YES scrollPosition:UITableViewScrollPositionMiddle];
}