在保持自动布局约束的同时替换NSView

Question

我想NSView在保持约束的同时将一个替换为另一个视图.

我有一个superview,subview因为它的孩子和placeholder我正计划搬到subview的地方.但它似乎是代码

[[superview] replaceSubview:subview with:placeholder];

删除所有与之相关的约束subview并导致只删除subview.

如何将约束从一个视图"复制"到另一个视图？

Answer 1

这是我很久以前写的一些代码,用来做你要求的.

我的代码用于在同一个superview中交换两个NSView,但是您可以通过剥离不需要的位并按照谨慎的顺序添加和删除视图/约束来轻松地对其进行修改以进行替换.事实上,我在"代理"视图控制器类中有一个较短版本的代码,它完全符合你的要求,但我不能分享它,因为它是一个不属于我的专有项目.

我将告诉您,您需要做的是将约束从代理视图复制到新视图,然后将新视图添加到superview.之后,将代理的超级视图约束复制到新视图,并且只有在执行此操作后才从超级视图中删除代理视图.

- (void)swapView:(NSView*) source withView:(NSView*) dest persist:(BOOL) persist
{
    NSLog(@"swapping %@ with %@", source.identifier, dest.identifier);
    // !!!: adjust the "Auto Layout" constraints for the superview.
    // otherwise changing the frames is impossible. (instant reversion)
    // we could disable "Auto Layout", but let's try for compatibility

    // TODO: we need to either enforce that the 2 controls have the same superview
    // before accepting the drag operation
    // or modify this code to take two diffrent superviews into account

    // we are altering the constraints so iterate a copy!
    NSArray* constraints = [dest.superview.constraints copy];
    for (NSLayoutConstraint* constraint in constraints) {
        id first = constraint.firstItem;
        id second = constraint.secondItem;
        id newFirst = first;
        id newSecond = second;

        BOOL match = NO;
        if (first == dest) {
            newFirst = source;
            match = YES;
        }
        if (second == dest) {
            newSecond = source;
            match = YES;
        }
        if (first == source) {
            newFirst = dest;
            match = YES;
        }
        if (second == source) {
            newSecond = dest;
            match = YES;
        }
        if (match && newFirst) {
            [dest.superview removeConstraint:constraint];
            @try {
                NSLayoutConstraint* newConstraint = nil;
                newConstraint = [NSLayoutConstraint constraintWithItem:newFirst
                                                             attribute:constraint.firstAttribute
                                                             relatedBy:constraint.relation
                                                                toItem:newSecond
                                                             attribute:constraint.secondAttribute
                                                            multiplier:constraint.multiplier
                                                              constant:constraint.constant];
                newConstraint.shouldBeArchived = constraint.shouldBeArchived;
                newConstraint.priority = NSLayoutPriorityWindowSizeStayPut;
                [dest.superview addConstraint:newConstraint];
            }
            @catch (NSException *exception) {
                NSLog(@"Constraint exception: %@\nFor constraint: %@", exception, constraint);
            }
        }
    }
    [constraints release];

    NSMutableArray* newSourceConstraints = [NSMutableArray array];
    NSMutableArray* newDestConstraints = [NSMutableArray array];

    // again we need a copy since we will be altering the original
    constraints = [source.constraints copy];
    for (NSLayoutConstraint* constraint in constraints) {
        // WARNING: do not tamper with intrinsic layout constraints
        if ([constraint class] == [NSLayoutConstraint class]
            && constraint.firstItem == source) {
            // this is a source constraint. we need to copy it to the destination.
            NSLayoutConstraint* newConstraint = nil;
            newConstraint = [NSLayoutConstraint constraintWithItem:dest
                                                         attribute:constraint.firstAttribute
                                                         relatedBy:constraint.relation
                                                            toItem:constraint.secondItem
                                                         attribute:constraint.secondAttribute
                                                        multiplier:constraint.multiplier
                                                          constant:constraint.constant];
            newConstraint.shouldBeArchived = constraint.shouldBeArchived;
            [newDestConstraints addObject:newConstraint];
            [source removeConstraint:constraint];
        }
    }
    [constraints release];

    // again we need a copy since we will be altering the original
    constraints = [dest.constraints copy];
    for (NSLayoutConstraint* constraint in constraints) {
        // WARNING: do not tamper with intrinsic layout constraints
        if ([constraint class] == [NSLayoutConstraint class]
            && constraint.firstItem == dest) {
            // this is a destination constraint. we need to copy it to the source.
            NSLayoutConstraint* newConstraint = nil;
            newConstraint = [NSLayoutConstraint constraintWithItem:source
                                                         attribute:constraint.firstAttribute
                                                         relatedBy:constraint.relation
                                                            toItem:constraint.secondItem
                                                         attribute:constraint.secondAttribute
                                                        multiplier:constraint.multiplier
                                                          constant:constraint.constant];
            newConstraint.shouldBeArchived = constraint.shouldBeArchived;
            [newSourceConstraints addObject:newConstraint];
            [dest removeConstraint:constraint];
        }
    }
    [constraints release];

    [dest addConstraints:newDestConstraints];
    [source addConstraints:newSourceConstraints];

    // auto layout makes setting the frame unnecissary, but
    // we do it because its possible that a module is not using auto layout
    NSRect srcRect = source.frame;
    NSRect dstRect = dest.frame;
    // round the coordinates!!!
    // otherwise we will have problems with persistant values
    srcRect.origin.x = round(srcRect.origin.x);
    srcRect.origin.y = round(srcRect.origin.y);
    dstRect.origin.x = round(dstRect.origin.x);
    dstRect.origin.y = round(dstRect.origin.y);

    source.frame = dstRect;
    dest.frame = srcRect;

    if (persist) {
        NSString* rectString = NSStringFromRect(srcRect);
        [[_theme prefrences] setObject:rectString forKey:dest.identifier];
        rectString = NSStringFromRect(dstRect);
        [[_theme prefrences] setObject:rectString forKey:source.identifier];
    }
}

你可以放心地忽略你想象中的持久性.在我的情况下,我想实现iOS跳板功能(能够点按并按住按钮,它摇晃,让我将它拖到另一个按钮并交换位置,同时在启动之间保持不变)