夜晚本来像用代码写一个Button按钮，但是出现问题：开始是这样创建的

- (void)viewDidLoad {         [super viewDidLoad];

   //初始化Button的位置大小     UIButton *writeButton = [[UIButton alloc] initWithFrame:CGRectMake(100.0f, 100.0f, 50.0f, 30.0f)];     //设置BUtton的形状，此处为圆角按钮     writeButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];     //设置Button名字，和他的状态，此处是一般的状态     [writeButton setTitle:@"代码按钮" forState:UIControlStateNormal];     //Button背景色     writeButton.backgroundColor = [UIColor redColor];     //Button的触摸事件     [writeButton addTarget:self action:@selector(buttonClicked) forControlEvents:UIControlEventTouchUpInside];     //把Button添加到视图之上     [self.view addSubview:writeButton]; } 

按照这个看似没问题，但是在模拟器上运行的时候，Button并没有出现，用模拟器分析显示Value stored to 'writeButton' during its initialization is never read(值存储到“writeButton”在其初始化是从来没有读过)

- (void)viewDidLoad {         [super viewDidLoad];     UIButton *writeButton = [[UIButton alloc] init];          CGRect frame = CGRectMake(100.0f, 100.0f, 50.0f, 30.0f);          writeButton.frame= frame;          writeButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];          [writeButton setTitle:@"代码按钮" forState:UIControlStateNormal];          writeButton.backgroundColor = [UIColor redColor];          [writeButton addTarget:self action:@selector(buttonClicked) forControlEvents:UIControlEventTouchUpInside];          [self.view addSubview:writeButton]; } 

这样写在模拟器上也没有显示Button

- (void)viewDidLoad {         [super viewDidLoad];     UIButton *writeButton = [[UIButton alloc] init];          CGRect frame = CGRectMake(100.0f, 100.0f, 100.0f, 30.0f);                   writeButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];          writeButton.frame= frame;           [writeButton setTitle:@"代码按钮" forState:UIControlStateNormal];          writeButton.backgroundColor = [UIColor redColor];          [writeButton addTarget:self action:@selector(buttonClicked) forControlEvents:UIControlEventTouchUpInside];          [self.view addSubview:writeButton]; } 

当这样写的时候才出现Button在模拟器视图上，于是啄么着是Button初始化frame时候，没有确定Button类型（此处是UIButtonTypeRoundedRect），

但是由product----》Analyze 又出现Value stored to 'writeButton' during its initialization is never read

再次修改

- (void)viewDidLoad {         [super viewDidLoad];               CGRect frame = CGRectMake(100.0f, 100.0f, 100.0f, 30.0f);     UIButton *writeButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];          //    writeButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];          writeButton.frame= frame;           [writeButton setTitle:@"代码按钮" forState:UIControlStateNormal];          writeButton.backgroundColor = [UIColor redColor];          [writeButton addTarget:self action:@selector(buttonClicked) forControlEvents:UIControlEventTouchUpInside];          [self.view addSubview:writeButton]; }

难道是因为不需要初始化吗？  这个问题暂时不能理解

  本文转自新风作浪 51CTO博客，原文链接：http://blog.51cto.com/duxinfeng/1208767，如需转载请自行联系原作者