最近2天在學習CAAnimation，今天突發奇想，檢視隨手指觸控的實現。

 @interface ViewController (){
    UILabel *lab;
    CGPoint begin;
    //BOOL noL;
}

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    //檢視允許使用者互動  mark這點非常重要，不然不能讓觸控事件取到該檢視
    lab.userInteractionEnabled = YES;
}

-(void)loadView{
    [super loadView];
    lab = [[UILabel alloc]init];
    lab.frame = CGRectMake(120, 120, 100, 60);
    lab.backgroundColor = [UIColor redColor];
    //lab.text = @"咚咚咚";
    lab.tag = 1 ;
    [self.view addSubview:lab];
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch =  touches.anyObject;
    //NSLog(@"%@",touch.view);
    if(touch.view.tag==1){
        begin = [touch locationInView:lab];
        //NSLog(@"11");
    }
}
//
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
    UITouch *touch =  touches.anyObject;
    NSLog(@"%@",touch.view);
    if(touch.view.tag==1){
        CGPoint point = [touch locationInView:lab];
        //NSLog(@"11");
        //lab.center = point;

       //控制不讓檢視移動到螢幕外
        CGPoint newCenter = CGPointZero;
        if(point.x-begin.x>0){
            newCenter.x = MIN(self.view.bounds.size.width-lab.bounds.size.width/2, lab.center.x+(point.x-begin.x));
        }else{
            newCenter.x = MAX(lab.bounds.size.width/2, lab.center.x+(point.x-begin.x));
        }
        if(point.y-begin.y>0){
            newCenter.y = MIN(self.view.bounds.size.height-lab.bounds.size.height/2, lab.center.y+(point.y-begin.y));
        }else{
         newCenter.y = MAX(lab.bounds.size.height/2, lab.center.y+(point.y-begin.y));
        }

       //移動檢視
        lab.center = newCenter;
    }
    
    }

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end

整體來說還是比較容易實現的，就是幾個點需要注意

lab.userInteractionEnabled = YES;  這個坑了我半個小時，網上找了些資料發現的