iOS

#import "FeedBackViewController.h"#import <Masonry.h>#define KCColor(r,g,b) [UIColor colorWithRed:r/255.0 green:g/255.0 blue:b/255.0 alpha:1]//颜色宏定义#define KCGrayColor KCColor(204,204,204)#define KCGreenColor KCColor(32,153,133)#define KCWhiteColor KCColor(250,249,245)@interface FeedBackViewController () <UITextViewDelegate, UINavigationControllerDelegate>@property (nonatomic, strong) UITextView *feedBackTextView;@property (nonatomic, strong) UIButton *commitButton;@property (nonatomic, strong) UILabel *placeHolderLabel;@property (nonatomic, strong) UILabel *stringLengthLabel;@end@implementation FeedBackViewController#pragma mark ------------------------------life circle------------------------------------ (void)viewDidLoad {    [super viewDidLoad];    [self initFeedBackText];    [self initButton];    // Do any additional setup after loading the view.}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}#pragma mark -----------------------------private method----------------------------------(void) initFeedBackText{    _feedBackTextView = [[UITextView alloc] init];    self.feedBackTextView.delegate = self;    _feedBackTextView.backgroundColor = [UIColor whiteColor];    _feedBackTextView.font = [UIFont systemFontOfSize:14];    self.automaticallyAdjustsScrollViewInsets = NO;    [self.view addSubview:self.feedBackTextView];    [self.feedBackTextView mas_makeConstraints:^(MASConstraintMaker *make) {        make.size.mas_equalTo(CGSizeMake([UIScreen mainScreen].bounds.size.width, 150));        make.top.equalTo(self.view.mas_top).offset(64);        make.centerX.equalTo(self.view.mas_centerX);    }];    _placeHolderLabel = [[UILabel alloc] init];    _placeHolderLabel.text = @"欢迎留下您的反馈";    _placeHolderLabel.textColor = KCGrayColor;    _placeHolderLabel.font = [UIFont systemFontOfSize:14];    self.placeHolderLabel.userInteractionEnabled = NO;    [self.view addSubview:self.placeHolderLabel];    [self.placeHolderLabel mas_makeConstraints:^(MASConstraintMaker *make) {        make.left.equalTo(self.view.mas_left).offset(16);        make.top.equalTo(self.feedBackTextView.mas_top).offset(16);    }];_stringLengthLabel = [[UILabel alloc] init];    _stringLengthLabel.textColor = KCGrayColor;    _stringLengthLabel.text = @"100";    _stringLengthLabel.font = [UIFont systemFontOfSize:12];    [self.view addSubview:self.stringLengthLabel];    [self.stringLengthLabel mas_makeConstraints:^(MASConstraintMaker *make) {        make.right.equalTo(self.view.mas_right).offset(-16);        make.bottom.equalTo(self.feedBackTextView.mas_bottom).offset(-10);    }];}-(void) initButton{    _commitButton = [[UIButton alloc] init];    [_commitButton setTitle:@"提交" forState:UIControlStateNormal];    [_commitButton setTitleColor:KCWhiteColor forState:UIControlStateNormal];    _commitButton.titleLabel.font = [UIFont systemFontOfSize:17];    _commitButton.backgroundColor = KCGrayColor;    _commitButton.layer.cornerRadius = 7;    self.commitButton.userInteractionEnabled = NO;    [self.commitButton addTarget:self action:@selector(commitButtonClicked) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:self.commitButton];    [self.commitButton mas_makeConstraints:^(MASConstraintMaker *make) {        make.size.mas_equalTo(CGSizeMake(320, 40));        make.top.equalTo(self.feedBackTextView.mas_bottom).offset(174);        make.centerX.equalTo(self.view.mas_centerX);    }];}#pragma mark -----------------------------textView  delegate-----------------------------------(void) textViewDidChange:(UITextView *)textView{    self.placeHolderLabel.hidden = YES;    self.commitButton.backgroundColor = KCGreenColor;    self.commitButton.userInteractionEnabled = YES;    self.stringLengthLabel.text = [NSString stringWithFormat:@"%lu", (unsigned long)(100 - textView.text.length)];    if (textView.text.length >= 100) {        textView.text = [textView.text substringToIndex:100];        self.stringLengthLabel.text = @"0";    }    if (textView.text.length == 0) {        self.placeHolderLabel.hidden = NO;        self.commitButton.userInteractionEnabled = NO;        self.commitButton.backgroundColor = KCGrayColor;    }}@end

参考：http://blog.csdn.net/yj_sail/article/details/52254278