视图的自动布局可隐藏子视图

Question

I have a UIViewController embedded in a Navigation Controller. I am using autolayout. In interface builder this is how the VC looks.

But when run in the simulator I get this:

With this error.

2016-08-10 16:51:17.077 My App[11797:7752671] Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) ( "<_UILayoutSupportConstraint:0x7fad72f7d6b0 V:[_UILayoutGuide:0x7fad72e5d1d0(64)]>", "<_UILayoutSupportConstraint:0x7fad72ffa6a0 V:|-(0)-[_UILayoutGuide:0x7fad72e5d1d0] (Names: '|':UIView:0x7fad72fe1b40 )>", "<_UILayoutSupportConstraint:0x7fad72fe2460 V:[_UILayoutGuide:0x7fad72e64760(0)]>", "<_UILayoutSupportConstraint:0x7fad72fe1470 _UILayoutGuide:0x7fad72e64760.bottom == UIView:0x7fad72fe1b40.bottom>", "", "", "", "")

Will attempt to recover by breaking constraint

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in may also be helpful.

I have rebuilt this view several times. I go up to Editor > Resolve Auto Layout Issues > "All Views" Reset to Suggested Constrains .

Which generates this:

I have even manually deleted all constrains and started over.

But nothing works.

I have nothing in the .m file that lays anything out or adjust sizes or locations. Nothing fancy is happening with this view. What am I doing wrong?

Answer 1

Editor > Resolve Auto Layout Issues > "All Views" Reset to Suggested Constrains almost never works correctly. So just avoid it.

When adding constraints, you need to specify four things for every item:

1. X location
2. Y location
3. Width
4. Height

There are creative ways to do this, so for you I would suggest you add these constraints to the Lookup Button:

• Horizontally in center
• Leading Space To Superview or Trailing Space to Superview (you do not need both)
• Height
• Top Space to Call Number

Your x location and width are satisfied by Horizontally in Center and Leading or Trailing Space. These two constraints center the button and give you equal space on either side of the button. The button will be as wide as the view minus the space on both sides. Setting the height obviously satisfies the height of the button and Top Space satisfies the y position of your button. Therefore you have easily satisfied x location, y location, width and height of the button, and you are done.

Answer 2

plz set your constraints as following image

Answer 3

You need to start over and think about constraints you are making. Think about what information is known, what sizes should not change. Tell this information to Auto Layout.

Your button is not appearing because Auto Layout does not known how to position it, it missing following numbers. Delete all constraints and start over with the following. Not you can change this numbers.

1. Txt Search.top = Top Layout Guide.bottom. This is yours, it is correct.
2. Txt Search.height = 20.0
3. Txt Search.leading = 0 with margin
4. Txt Search.trailing = 0 with margin
5. Lookup.top = Txt.Search.bottom + standard margin
6. Lookup.leading = 0 with margin
7. Lookup.trailing = 0 with margin
8. Lookup.height = 20.0

Answer 4

Reset to suggested constraints never solves your problem, it only hides the warning. You have to set the constraints that suits for your requirement. From your question, when you choose the option, Reset to suggested constraints, the autolayout will give a bottom layout constraint for the LOOK UP button,and it had too much of bottom constraint(which happens when you rest to suggested constraint), hence it is pushed up in the runtime.

You just need top and leading/ top and center horizontal constraint for your button corresponding to its above textfield along with height and width constraint. Remove the bototm constraint for your LOOK up button.