需求: 在iOS 10中, 使用系統(tǒng)UISearchBar, 使搜索圖標(biāo)和placeholder在無文本時(shí)靠左顯示.

系統(tǒng)UISearchBar效果圖:

需求效果圖:

思路:

兩種方案:

• 找到UISearchBar上的放大鏡圖標(biāo), 修改Frame. 同時(shí)判斷在有無文本內(nèi)容更改placeholder的顏色.
• 利用UISearchBar的Text有值后, 放大鏡自動(dòng)靠左特性, 讓UISearchBar設(shè)置一個(gè)默認(rèn)的Text, 在點(diǎn)擊UISearchBar開始編輯后, 如果沒有值,設(shè)置Text為則@"", 同時(shí)還要根據(jù)狀態(tài)修改placeholderLabel的顏色.(太繁瑣, 不推薦!)

實(shí)現(xiàn)代碼:

@interface ViewController () <UISearchBarDelegate>

/** xib搜索框 */
@property (weak, nonatomic) IBOutlet UISearchBar *searchBar;
/** 搜索圖片(放大鏡) */
@property (nonatomic, weak) UIImageView *imgV;
@end
@implementation ViewController

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
    // 查找放大鏡圖片ImageView
    for (UIImageView *imgV in _searchBar.subviews.firstObject.subviews.lastObject.subviews) {
        if ([imgV isMemberOfClass:[UIImageView class]]) {
            imgV.frame = CGRectMake(8, 7.5, 13, 13);
            _imgV = imgV;
            [_imgV addObserver:self forKeyPath:@"frame" options:NSKeyValueObservingOptionNew context:nil];
        }
    }
    // 設(shè)置searchBar文本顏色
    [self updateSeachBar];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context
{
    // 修改放大鏡Frame前, 移除觀察者
    [_imgV removeObserver:self forKeyPath:@"frame"];
    // 修改Frame
    _imgV.frame = CGRectMake(8, 7.5, 13, 13);
    // 再次添加觀察者
    [_imgV addObserver:self forKeyPath:@"frame" options:NSKeyValueObservingOptionNew context:nil];
}
#pragma mark -UISearchBarDelegate代理方法
- (void)searchBarTextDidBeginEditing:(UISearchBar *)searchBar
{
    if ([searchBar.text isEqualToString:searchBar.placeholder]) {
        // 無文本時(shí), 顯示placeholder
        searchBar.text = @"";
    }
    // 獲取到UISearchBar中UITextField
    UITextField *searchField = [searchBar valueForKey:@"_searchField"];
    // 開始編輯要修改textColor顏色
    searchField.textColor = [UIColor blackColor];
    searchField.clearButtonMode = UITextFieldViewModeWhileEditing;
}
- (void)searchBarTextDidEndEditing:(UISearchBar *)searchBar
{
    [self updateSeachBar];
}
#pragma mark -根據(jù)文本內(nèi)容設(shè)置searchBar顏色及clearButtonMode
- (void)updateSeachBar
{
    if ([_searchBar.text isEqualToString:@""]) {// 文本內(nèi)容為空時(shí)
        UITextField *searchField = [_searchBar valueForKey:@"_searchField"];
        // 修改textColor為placeholderColor
        searchField.textColor = [searchField valueForKeyPath:@"_placeholderLabel.textColor"];
        searchField.text = searchField.placeholder;
        // 去除右側(cè)clearButton
        searchField.clearButtonMode = UITextFieldViewModeNever;
    }
}
- (void)dealloc
{
    // 移除觀察者
    [_searchBar removeObserver:self forKeyPath:@"frame"];
}