Question

我想通过在故事板中设计两个不同的界面来查看动画。当事件触发时，它会将自动布局约束（或帧）更改为目标布局。

有没有图书馆可以完成这项工作？如果不是，请阅读以下内容。

使用autolayout进行视图动画是一件容易的事。例如：

[self.view layoutIfNeeded];
[UIView animateWithDuration:5.0 animations:^{
    self.heightConstraint.constant = 200
    [self.view layoutIfNeeded];
}];

但是如果你想通过重置所有子视图的所有约束来改变整个布局，那么通过编程就不容易了。使用Interface Builder是使用相同视图对象构建完全不同的布局的更好选择。因为，

Interface Builder将在运行应用程序之前检查您的约束冲突。
这是“你所看到的就是你得到的东西（WYSIWYG）。”

这是我的想法：

在Interface Builder中设计控制器视图的布局（原始布局）。可以通过keypath或viewTag
将Interface Builder中的视图控制器复制为目标布局，根据需要更改所有框架和约束。
在运行时，当事件触发布局动画时，它会实例化目标布局的视图控制器。然后，它使用目标布局中的视图对象的约束（通过keypath或viewTag）替换呈现视图对象的约束。

这是我的代码：

// 1. Add the keypath `view` for the viewController. Use NSSet to remove duplicated keypaths or view tags.
NSSet *keySet = [NSSet setWithArray:[keypaths arrayByAddingObject:@"view"]];


// 2. Build the dictionaries to fetch corresponding view objects in the source and destination view controllers (presenting view and template view) by a specific key (a keypath or a view tag).
NSMutableDictionary *presentingViewsForKeypaths = [NSMutableDictionary dictionaryWithCapacity:[keypaths count]];
NSMutableDictionary *templateViewsForKeypaths = [NSMutableDictionary dictionaryWithCapacity:[keypaths count]];

[keySet enumerateObjectsUsingBlock:^(id key, BOOL *stop) {

    UIView *presentingViewForKeypath = nil;
    UIView *templateViewForKeypath = nil;

    // Fetch the view objects by the keypath or view tag.
    if ([key isKindOfClass:[NSString class]]) {
        presentingViewForKeypath = [self valueForKeyPath:key];
        templateViewForKeypath = [viewController valueForKeyPath:key];

    } else if ([key isKindOfClass:[NSNumber class]]) {
        presentingViewForKeypath = [self.view viewWithTag:[key integerValue]];
        templateViewForKeypath = [viewController.view viewWithTag:[key integerValue]];

    } else {
        NSString *errorMessage = [NSString stringWithFormat:@"keypath (%@) is not kind of NSString or NSNumber.", key];
        NSAssert(nil, errorMessage);
        NSLog(@"%@", errorMessage);
        return;
    }

    // The view objects should be found in both view controllers.
    if (!presentingViewForKeypath || !templateViewForKeypath) {
        NSString *errorMessage = [NSString stringWithFormat:@"KeynoteAnimation warning: keypath (%@) is not found.", key];
        NSAssert(nil, errorMessage);
        NSLog(@"%@", errorMessage);
        return;
    } else if (!templateViewForKeypath) {
        NSString *errorMessage = [NSString stringWithFormat:@"KeynoteAnimation warning: keypath (%@) is not found.", key];
        NSAssert(nil, errorMessage);
        NSLog(@"%@", errorMessage);
        return;
    }

    // Add the view objects to the corresponding dictionaries.
    presentingViewsForKeypaths[key] = presentingViewForKeypath;
    templateViewsForKeypaths[key] = templateViewForKeypath;
}];


// 3. Change the constraints of the view objects for the keys.
NSSet *presentingViewsForKeypathsSet = [NSSet setWithArray:[presentingViewsForKeypaths allValues]];
NSSet *templateViewsForKeypathsSet = [NSSet setWithArray:[templateViewsForKeypaths allValues]];
NSMutableArray *keysShouldUpdateItsViewFrame = [NSMutableArray array];

[keySet enumerateObjectsUsingBlock:^(id key, BOOL *stop) {

    NSLog(@"========= Remove constraints for Key: %@ ==========", key);

    __block BOOL didChangeAnyConstraint = NO;

    UIView *presentingView = presentingViewsForKeypaths[key];
    UIView *templateView = templateViewsForKeypaths[key];

    // Remove the original constraints for the view objects.
    [presentingView.constraints enumerateObjectsUsingBlock:^(NSLayoutConstraint *constraint, NSUInteger idx, BOOL *stop) {

        if ([presentingViewsForKeypathsSet containsObject:constraint.firstItem] &&
            ([presentingViewsForKeypathsSet containsObject:constraint.secondItem] || !constraint.secondItem)) {

            NSLog(@"detect constraint: %@\nFind: %@ (%x) -- %@ (%x)", constraint,  NSStringFromClass([constraint.firstItem class]), [constraint.firstItem hash], NSStringFromClass([constraint.secondItem class]), [constraint.secondItem hash]);

            [presentingView removeConstraint:constraint];

            didChangeAnyConstraint = YES;
        }

    }];

    NSLog(@"----------- Add constraints for Key: %@ -----------", key);

    // Add the new constraints for the view objects.
    [templateView.constraints enumerateObjectsUsingBlock:^(NSLayoutConstraint *constraint, NSUInteger idx, BOOL *stop) {

        if ([templateViewsForKeypathsSet containsObject:constraint.firstItem] &&
            ([templateViewsForKeypathsSet containsObject:constraint.secondItem] || !constraint.secondItem)) {
            NSLog(@"detect constraint: %@\nFind: %@ (%x) -- %@ (%x)", constraint, NSStringFromClass([constraint.firstItem class]), [constraint.firstItem hash], NSStringFromClass([constraint.secondItem class]), [constraint.secondItem hash]);

            if ([constraint isKindOfClass:NSClassFromString(@"NSIBPrototypingLayoutConstraint")]) {
                NSLog(@"|||||||||||||||||||| WARNING ||||||||||||||||");
                //return; // Return here to filter out this constraint.
            }

            // Create the new NSLayoutConstraint for the presenting view object.
            NSArray *firstItemKeys = [templateViewsForKeypaths allKeysForObject:constraint.firstItem];
            NSArray *secondItemKeys = [templateViewsForKeypaths allKeysForObject:constraint.secondItem];

            id firstItemKey = [firstItemKeys count]? firstItemKeys[0]:nil;
            id secondItemKey = [secondItemKeys count]? secondItemKeys[0]:nil;

            id firstItem = firstItemKey? presentingViewsForKeypaths[firstItemKey]:nil;
            id secondItem = secondItemKey? presentingViewsForKeypaths[secondItemKey]:nil;

            NSLog(@"params for new constraints: %@:%@(%x) => %@:%@(%x) for view: %@(%x)", firstItemKey, NSStringFromClass([firstItem class]), [firstItem hash], secondItemKey, NSStringFromClass([secondItem class]), [secondItem hash], NSStringFromClass([presentingView class]), [presentingView hash]);

            NSLayoutConstraint *newLayoutConstraint = [NSLayoutConstraint constraintWithItem:firstItem attribute:constraint.firstAttribute relatedBy:constraint.relation toItem:secondItem attribute:constraint.secondAttribute multiplier:constraint.multiplier constant:constraint.constant];

            [presentingView addConstraint:newLayoutConstraint];

            didChangeAnyConstraint = YES;
        }

    }];

    // Record the view object which doesn't have any layout constraint. It may change its frame set in the storyboard.
    if (!didChangeAnyConstraint) {
        [keysShouldUpdateItsViewFrame addObject:key];
    }       
}];


// Start Animation
[UIView animateWithDuration:1 delay:0 usingSpringWithDamping:1 initialSpringVelocity:1 options:0 animations:^{

    // Update the frame of the view objects which did not change its constraints (no constraint).
    [keysShouldUpdateItsViewFrame enumerateObjectsUsingBlock:^(id key, NSUInteger idx, BOOL *stop) {

        UIView *presentingView = presentingViewsForKeypaths[key];
        UIView *templateView = templateViewsForKeypaths[key];

        presentingView.frame = templateView.frame;

    }];

    [self.view layoutIfNeeded];

} completion:^(BOOL finished) {
    NSLog(@"finish.");
}];

添加新约束时，如果约束的类为NSIBPrototypingLayoutConstraint，它将崩溃并显示消息：当添加到视图时，约束的项必须是该视图的后代（或者视图本身）。如果在组装视图层次结构之前需要解析约束，则会崩溃。

我认为视图对象已经在视图层次结构中。我不知道如何解决这个问题。

如果过滤掉这些约束，它将不会更新布局，我不确定是否满足约束。

如何使用故事板中的另一个界面构建来刷新autolayout

0 个答案: