iOS小技巧

键盘透明：  

textField.keyboardAppearance = UIKeyboardAppearanceAlert;

状态栏的网络活动风火轮是否旋转：

[UIApplication sharedApplication].networkActivityIndicatorVisible ， 默认值是 NO 。 

.截取屏幕图片：

// 创建一个基于位 图的图形上下文并指定大小为CGSizeMake(200,400)
UIGraphicsBeginImageContext(CGSizeMake(,));  

//renderInContext  呈现接受者及其子范围到 指定的上下文
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    // 返回 一个基于当前图形上下文的图片
 UIImage *aImage = UIGraphicsGetImageFromCurrentImageContext();
  // 移除栈顶 的基于当前位图的图形上下文
UIGraphicsEndImageContext();
// 以 png 格式 返回指定图片的数据
imageData = UIImagePNGR epresentation(aImage); 

更改cell选中的背景： 

UIView *myview = [[UIView alloc] init];
   myview.frame = CGRectMake(, , , );
   myview.backgroundColor = [UIColorcolorWithPatternImage:[UIImage imageNamed:@"0006.png"]];
   cell.selectedBackgroundView = myview;

.显示图片：

CGRect myImageRect = CGRectMake(0.0f, 0.0f, 320.0f, 109.0f);
UIImageView *myImage = [[UIImageView alloc] initWithFrame:myImageRect];
[myImage setImage:[UIImage imageNamed:@"myImage.png"]];
myImage.opaque = YES; //opaque 是否透明
[self.view addSubview:myImage];

能让图片适应框的大小（beta）

NSString*imagePath = [[NSBundle mainBundle] pathForResource:@"XcodeCrash"ofType:@"png"];
    UIImage *image = [[UIImage alloc]initWithContentsOfFile:imagePath];
        UIImage *newImage= [image transformWidth:.f height:.f];
    UIImageView *imageView = [[UIImageView alloc]initWithImage: newImage];
         [newImagerelease];
    [image release];
    [self.view addSubview:imageView];

  实现点击图片进行跳转的代码：（生成一个带有背景图片的button，给button绑定想要的事件）

UIButton *imgButton=[[UIButton alloc]initWithFrame:CGRectMake(, , , )];
[imgButton setBackgroundImage:(UIImage *)[self.imgArray objectAtIndex:indexPath.row] forState:UIControlStateNormal];
imgButton.tag=[indexPath row];
[imgButton addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchUpInside];  

.第二种方法：在背景图片上添加Tap事件，相应单击处理。这种方法，很好代替了button方式，但是如果UI上没有背景图片，这种方法又回到到第一种山寨的方法行列中。

// 添加带有处理时间的背景图片 

UIImageView *backView = [[UIImageView alloc] initWithFrame:CGRectMake(, , self.view.bounds.size.width, self.view.bounds.size.height)];  

    backView.image = [UIImage imageNamed:@"small3.png"];  

    backView.userInteractionEnabled = YES;  

    UITapGestureRecognizer *singleTouch = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(dismissKeyboard:)];  

    [backView addGestureRecognizer:singleTouch];  

    backView.tag = ;  

    [self.view addSubview:backView];  

-(void)dismissKeyboard:(id)sender{  

    [text resignFirstResponder];  

}