我的方法是在开始时将所有按钮设置centerX
为超级视图centerX
。
IBOutletCollection(UIButton) NSArray *allButtons;
//3 buttons' references
IBOutletCollection(NSLayoutConstraint) NSArray *allButtonCenterConstraints;
//buttons' centerX constraints' references
然后在 viewDidAppear:
int t = arc4random() %3;// one of the 3 cases you will need
if (t == 0) {//if you want all 3 buttons appears
//all buttons shown
NSLayoutConstraint *c1 = allButtonCenterConstraints[0];//first button's centerX reference.
NSLayoutConstraint *c2 = allButtonCenterConstraints[2];//third button's centerX reference.
c1.constant = -self.view.frame.size.width*0.25;//push left
c2.constant = +self.view.frame.size.width*0.25;//push right
}
else if (t == 1)
{
//two buttons shown;
[allButtons[0] setHidden:YES];// close the one you dont need
NSLayoutConstraint *c1 = allButtonCenterConstraints[1];
NSLayoutConstraint *c2 = allButtonCenterConstraints[2];
c1.constant = -self.view.frame.size.width*0.125;
c2.constant = +self.view.frame.size.width*0.125;
}
else
{
//close 2 buttons
[allButtons[0] setHidden:YES];
[allButtons[1] setHidden:YES];
}
[self.view layoutIfNeeded];
如果需要某些东西取决于按钮的宽度,则可以根据按钮的宽度设置常数。
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