【iOS开发-43】万能的transform注意事项，以及viewWithTag以及.png后缀可以省略的一些知识

注意事项：

（1）图片如果是png格式的话，在代码中可以省略后缀。

（2）可以给控件一个tag值，然后用viewWithTag获取这个控件。

（3）transform的上下左右移动是按照它的上下左右边框垂直的方向移动的，即如果你把控件旋转了，那么上下左右就不是传统的上下左右，而是斜着的上下左右。

（4）transform可以实现上下左右旋转缩放等效果，但它是相对于一个位置而言的，如果相对位置不变，则相当于只生效一次，而如果每次都把改变后的位置重新设置为新的相对位置，则每次都会生效。即代码中，有两种方法。

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    //创建一个btn，里面是图像
    UIButton *btnImg=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnImg.frame=CGRectMake(130, 120, 100, 100);
    //如果是.png的图像，可以省略.png后缀
    [btnImg setBackgroundImage:[UIImage imageNamed:@"hi"] forState:UIControlStateNormal];
    //增加一个tag，用于后续获取这个btnImg
    btnImg.tag=1;
    [self.view addSubview:btnImg];
    
    //创建上下左右、左右旋转、放大缩小按钮
    UIButton *btnUp=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnUp.frame=CGRectMake(80, 400, 20, 20);
    [btnUp setTitle:@"上" forState:UIControlStateNormal];
    [btnUp addTarget:self action:@selector(up) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnUp];
    
    UIButton *btnDown=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnDown.frame=CGRectMake(80, 460, 20, 20);
    [btnDown setTitle:@"下" forState:UIControlStateNormal];
    [btnDown addTarget:self action:@selector(down) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnDown];
    
    UIButton *btnLeft=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnLeft.frame=CGRectMake(50, 430, 20, 20);
    [btnLeft setTitle:@"左" forState:UIControlStateNormal];
    [btnLeft addTarget:self action:@selector(left) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnLeft];
    
    UIButton *btnRight=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnRight.frame=CGRectMake(110, 430, 20, 20);
    [btnRight setTitle:@"右" forState:UIControlStateNormal];
    [btnRight addTarget:self action:@selector(right) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnRight];
    
    UIButton *btnRoLeft=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnRoLeft.frame=CGRectMake(150, 430, 40, 20);
    [btnRoLeft setTitle:@"左转" forState:UIControlStateNormal];
    [btnRoLeft addTarget:self action:@selector(roLeft) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnRoLeft];
    
    UIButton *btnRoRight=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnRoRight.frame=CGRectMake(200, 430, 40, 20);
    [btnRoRight setTitle:@"右转" forState:UIControlStateNormal];
    [btnRoRight addTarget:self action:@selector(roRight) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnRoRight];
    
    UIButton *btnBig=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnBig.frame=CGRectMake(250, 430, 40, 20);
    [btnBig setTitle:@"放大" forState:UIControlStateNormal];
    [btnBig addTarget:self action:@selector(big) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnBig];
    
    UIButton *btnSmall=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    btnSmall.frame=CGRectMake(300, 430, 40, 20);
    [btnSmall setTitle:@"缩小" forState:UIControlStateNormal];
    [btnSmall addTarget:self action:@selector(small) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btnSmall];
    
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

//只有一个按钮的时候，就没必要传递这个按钮参数过来
-(void)up{
    //用viewWithTag获取UIView对象，如果我们知道具体是哪种UIView，可以强制转换一下
    UIButton *btnImg1=(UIButton *)[self.view viewWithTag:1];
    //以下语句是向上移动10，但按钮只生效一次，因为它相当于赋值ty=-10，且它的移动只相对于最原始位置，所以相对于的那个原始位置不变，而且ty=-10不变，则不再移动
    //要么每次点击按钮改变ty的值，要么用不断改变它相对于的位置，即把最新的位置设置为它的相对于的位置
    //btnImg1.transform=CGAffineTransformMakeTranslation(0, -10);
    btnImg1.transform=CGAffineTransformTranslate(btnImg1.transform, 0, -10);
}
-(void)down{
    //同理，如下
    UIButton *btnImg1=(UIButton *)[self.view viewWithTag:1];
    btnImg1.transform=CGAffineTransformTranslate(btnImg1.transform, 0, 10);
}
-(void)left{
    //同理，如下
    UIButton *btnImg1=(UIButton *)[self.view viewWithTag:1];
    btnImg1.transform=CGAffineTransformTranslate(btnImg1.transform, -10, 0);
}
-(void)right{
    //同理，如下
    UIButton *btnImg1=(UIButton *)[self.view viewWithTag:1];
    btnImg1.transform=CGAffineTransformTranslate(btnImg1.transform, 10, 0);
}
-(void)roLeft{
    UIButton *btnImg1=(UIButton *)[self.view viewWithTag:1];
    //同样，第一句只能点击生效1次，且用的是弧度制的数字,pi/4
    //btnImg1.transform=CGAffineTransformMakeRotation(-M_PI_4);
    btnImg1.transform=CGAffineTransformRotate(btnImg1.transform, -M_PI_4);
}
-(void)roRight{
    //同理
    UIButton *btnImg1=(UIButton *)[self.view viewWithTag:1];
    btnImg1.transform=CGAffineTransformRotate(btnImg1.transform, M_PI_4);
}
-(void)big{
    UIButton *btnImg1=(UIButton *)[self.view viewWithTag:1];
    //同样，第一句只能点击生效1次，且用的是弧度制的数字,pi/4
    //btnImg1.transform=CGAffineTransformMakeScale(1.2, 1.2);
    btnImg1.transform=CGAffineTransformScale(btnImg1.transform, 1.2, 1.2);
}
-(void)small{
    //同理
    UIButton *btnImg1=(UIButton *)[self.view viewWithTag:1];
    btnImg1.transform=CGAffineTransformScale(btnImg1.transform, 0.8, 0.8);
}

@end

结果：