UIButton设置框架不起作用？

Question

I have written the following code for my app:

self.PlayButton = [[UIButton alloc] init];

//Setup Play Button
[self.PlayButton setTranslatesAutoresizingMaskIntoConstraints:NO];
self.PlayButton.frame = CGRectMake(self.view.frame.size.width * 0.38, self.view.frame.size.height * 0.666, self.view.frame.size.width * 0.48, self.view.frame.size.height * 0.29);
[self.PlayButton setBackgroundImage:[UIImage imageNamed:@"PlayButton.png"] forState:UIControlStateNormal];
[self.PlayButton.layer setMagnificationFilter:kCAFilterNearest];
[self.PlayButton addTarget:self action:@selector(PlayButtonMethod) forControlEvents:(UIControlEvents)UIControlEventTouchUpInside]


[self.view addSubview:self.PlayButton];

But when this code it run rather than the image appearing in a rather specific location it simply appears in the top left hand corner of the view. Almost like it had been set

self.PlayButton.frame = CGRectMake(0, 0, self.view.frame.size.width * 0.48, self.view.frame.size.height * 0.29);

It's odd because the width and height is put in correctly but for whatever reason the position of the button set by the CGRectMake is not taken into account. Ive done a bit of research into creating UIButtons in code and fro what I've seen not only has this happened to no-one else the code have written is perfectly liable.

Any help would be appreciated. Thanks

Answer 1

Looks like ive found the fix: Removing this line of code fixed the issue for me.

[self.PlayButton setTranslatesAutoresizingMaskIntoConstraints:NO];

not 100% sure why this was causing the problem but it fixed it.

Answer 2

When creating UIButton s using the standard alloc init method doesn't actually create a button. The method for creating and initializing a UIButton is called buttonWithType: . This creates a UIButton of the specified type if you use alloc init it will not work correctly, see the Apple Documentation for UIButton .

So you need to change line

self.PlayButton = [[UIButton alloc] init];

to

self.PlayButton = [UIButton buttonWithType:UIButtonTypeCustom];

buttonWithType: allows you to pass in an enum of UIButtonType so it will accept any of the following values :

• UIButtonTypeCustom
• UIButtonTypeSystem
• UIButtonTypeDetailDisclosure
• UIButtonTypeInfoLight
• UIButtonTypeInfoDark
• UIButtonTypeContactAdd
• UIButtonTypeRoundedRect

If you don't pass it a UIButtonType the button will not be initialized as it will not know what type of button you want and it will not assume. Also check out the Apple Documentation for UIButtonType

Side Note

I'm just going to include this as a side note. Also have a read of the Apple Coding Conventions Documentation as I have noticed that you are using uppercase to start your variable names (ie PlayButton ). Variable names should start with lowercase (ie playButton ) and Class and Enum names should start with uppercase (ie UIViewController ). It's always good to stick to conventions as it makes you code more readable and maintainable so if another developer comes to modify your code it is easy for them or even yourself to read.