(1)View的Frame与Bounds区别
摘自 ios view的frame和bounds之区别（位置和大小）
UIView *view1 = [[UIView alloc] initWithFrame:CGRectMake(20, 20, 280, 250)];
[view1 setBounds:CGRectMake(-20, -20, 280, 250)];
view1.backgroundColor = [UIColor redColor];
[self.view addSubview:view1];//添加到self.view
UIView *view2 = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
view2.backgroundColor = [UIColor yellowColor];
[view1 addSubview:view2];//添加到view1上,[此时view1坐标系左上角起点为(-20,-20)]
