133自动滚动到被选中单元格（扩展知识：滚动到头部和底部）

效果如下：

ViewController.h

1 #import <UIKit/UIKit.h>
2
3 @interface ViewController : UITableViewController
4 @property (strong, nonatomic) NSMutableArray *mArrDataSource;
5
6 @end

ViewController.m

  1 #import "ViewController.h"
  2
  3 @interface ViewController ()
  4 - (void)layoutUI;
  5 - (UIBarButtonItem *)barButtonItemForToolbar:(NSString *)title selectorName:(NSString *)selectorName;
  6 - (void)scrollToTopDidPush:(UIBarButtonItem *)sender;
  7 - (void)scrollToSelectedRowDidPush:(UIBarButtonItem *)sender;
  8 - (void)scrollToBottomDidPush:(UIBarButtonItem *)sender;
  9 @end
 10
 11 @implementation ViewController
 12 #define kRowCount 64
 13
 14 - (void)viewDidLoad {
 15     [super viewDidLoad];
 16
 17     [self layoutUI];
 18 }
 19
 20 - (void)didReceiveMemoryWarning {
 21     [super didReceiveMemoryWarning];
 22     // Dispose of any resources that can be recreated.
 23 }
 24
 25 - (void)viewDidAppear:(BOOL)animated {
 26     [super viewDidAppear:animated];
 27
 28     [self.navigationController setNavigationBarHidden:NO animated:animated];
 29     [self.navigationController setToolbarHidden:NO animated:animated];
 30 }
 31
 32 - (void)layoutUI {
 33     _mArrDataSource = [[NSMutableArray alloc] initWithCapacity:kRowCount];
 34     for (NSUInteger i=0; i<kRowCount; i++) {
 35         [_mArrDataSource addObject:[NSNumber numberWithUnsignedInteger:i]];
 36     }
 37     [self.tableView setAllowsSelection:YES]; //设置在普通状态中，是否允许选中；默认值为YES
 38     [self.tableView setAllowsSelectionDuringEditing:YES]; //设置在编辑状态中，是否允许选中；默认值为YES
 39
 40     self.navigationItem.title = @"自动滚动到被选中单元格";
 41     UIBarButtonItem *barBtnScrollToTop = [self barButtonItemForToolbar:@"滚动到头部" selectorName:@"scrollToTopDidPush:"];
 42     UIBarButtonItem *barBtnScrollToSelectedRow = [self barButtonItemForToolbar:@"滚动到被选中单元格" selectorName:@"scrollToSelectedRowDidPush:"];
 43     UIBarButtonItem *barBtnScrollToBottom = [self barButtonItemForToolbar:@"滚动到底部" selectorName:@"scrollToBottomDidPush:"];
 44     self.toolbarItems = @[barBtnScrollToTop, barBtnScrollToSelectedRow, barBtnScrollToBottom];
 45 }
 46
 47 - (UIBarButtonItem *)barButtonItemForToolbar:(NSString *)title selectorName:(NSString *)selectorName {
 48     UIBarButtonItem *barBtnItem = [[UIBarButtonItem alloc] initWithTitle:title
 49                                                                    style:UIBarButtonItemStyleDone
 50                                                                   target:self
 51                                                                   action:NSSelectorFromString(selectorName)];
 52     return barBtnItem;
 53 }
 54
 55 - (void)scrollToTopDidPush:(UIBarButtonItem *)sender {
 56     [self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0]
 57                           atScrollPosition:UITableViewScrollPositionTop
 58                                                       animated:YES];
 59 }
 60
 61 - (void)scrollToSelectedRowDidPush:(UIBarButtonItem *)sender {
 62     [self.tableView scrollToNearestSelectedRowAtScrollPosition:UITableViewScrollPositionNone
 63                                                       animated:YES];
 64
 65     /*
 66      typedef NS_ENUM(NSInteger, UITableViewScrollPosition) {
 67      UITableViewScrollPositionNone,
 68      UITableViewScrollPositionTop,
 69      UITableViewScrollPositionMiddle,
 70      UITableViewScrollPositionBottom
 71      };                // scroll so row of interest is completely visible at top/center/bottom of view
 72      */
 73 }
 74
 75 - (void)scrollToBottomDidPush:(UIBarButtonItem *)sender {
 76     [self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:(kRowCount - 1) inSection:0]
 77                           atScrollPosition:UITableViewScrollPositionBottom
 78                                   animated:YES];
 79 }
 80
 81 #pragma mark - TableView
 82 - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {
 83     return @"列表";
 84 }
 85
 86 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
 87     return 1;
 88 }
 89
 90 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
 91     return kRowCount;
 92 }
 93
 94 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
 95     static NSString *cellIdentifier = @"cellIdentifier";
 96     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
 97     if (!cell) {
 98         cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
 99     }
100
101     NSInteger row = indexPath.row;
102     cell.textLabel.text = [_mArrDataSource[row] stringValue];
103
104     return cell;
105 }
106
107 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
108
109 }
110
111 @end

AppDelegate.h

1 #import <UIKit/UIKit.h>
2
3 @interface AppDelegate : UIResponder <UIApplicationDelegate>
4 @property (strong, nonatomic) UIWindow *window;
5 @property (strong, nonatomic) UINavigationController *navigationController;
6
7 @end

AppDelegate.m

 1 #import "AppDelegate.h"
 2 #import "ViewController.h"
 3
 4 @interface AppDelegate ()
 5 @end
 6
 7 @implementation AppDelegate
 8
 9 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
10     _window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
11     ViewController *viewController = [[ViewController alloc] init];
12     _navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];
13     _window.rootViewController = _navigationController;
14     //[_window addSubview:_navigationController.view]; //当_window.rootViewController关联时，这一句可有可无
15     [_window makeKeyAndVisible];
16     return YES;
17 }
18
19 - (void)applicationWillResignActive:(UIApplication *)application {
20 }
21
22 - (void)applicationDidEnterBackground:(UIApplication *)application {
23 }
24
25 - (void)applicationWillEnterForeground:(UIApplication *)application {
26 }
27
28 - (void)applicationDidBecomeActive:(UIApplication *)application {
29 }
30
31 - (void)applicationWillTerminate:(UIApplication *)application {
32 }
33
34 @end