On 02/02/2012 05:27 PM, atcal wrote:
OK. So why is the documentation so misleading? View() is shown as a
public method in teh android documentation.
Not for me:
http://developer.android.com/reference/android/view/View.html
Public Constructors
View
<http://developer.android.com/reference/android/view/View.html#View%28android.content.Context%29>(Context
<http://developer.android.com/reference/android/content/Context.html>context)
Simple constructor to use when creating a view from code.
View
<http://developer.android.com/reference/android/view/View.html#View%28android.content.Context,%20android.util.AttributeSet%29>(Context
<http://developer.android.com/reference/android/content/Context.html>context,AttributeSet
<http://developer.android.com/reference/android/util/AttributeSet.html>attrs)
Constructor that is called when inflating a view from XML.
View
<http://developer.android.com/reference/android/view/View.html#View%28android.content.Context,%20android.util.AttributeSet,%20int%29>(Context
<http://developer.android.com/reference/android/content/Context.html>context,AttributeSet
<http://developer.android.com/reference/android/util/AttributeSet.html>attrs,
int defStyle)
Perform inflation from XML and apply a class-specific base style.
I don't see an argument-less View() here.
There is an argument-less constructor in the source:
https://github.com/android/platform_frameworks_base/blob/master/core/java/android/view/View.java#L3127
but it's access level is package, not public or protected, so
application code won't be able to use it.
Why is it not available to
a subclass? Are you seriously telling me that the explanation for this
is that I don't understand Java inheritance?
I'm seriously telling you that the snippet in your original email looked
like you used C++ constructor syntax, or something similar, and not Java
syntax.
( super(context) passes the compiler but then crashes out at run
time.
If you're trying to create a custom view, please refer to this:
http://developer.android.com/guide/topics/ui/custom-components.html
In particular, it says:
There is a form of the constructor that are called when the view is
created from code and a form that is called when the view is inflated
from a layout file. The second form should parse and apply any
attributes defined in the layout file.
The former is YourView(Context), the latter is YourView(Context,
AttributeSet)
Can anyone tell me the statement(s) I need to put in rather than
refer me to a crash course.
The link above should be a good start.
I've already spent several hours reading
the Oracle java course, so unless you have a specific course and
chapter in mind the suggestion isn't very helpful. )
I'll just put it here then:
The syntax for calling the base class constructor from a derived class
constructor, in Java, is:
class Derived extends Base {
public Derived(.. args here...)
{
super(... args here....);
}
}
and not:
class Derived extends Base {
public Derived(.. args here...)
{
Base(... args here....);
}
}
or:
class Derived extends Base {
public Derived(.. args here...) : Base (... args here... )
{
}
}
Why is this? Java doesn't have MI like C++, so it's not necessary to
explicitly specify which of the base classes you're referring to - just
"super" is unambiguous.
And actually, in C++, your original code snippet would be creating a
temporary View object on the stack, rather than initializing the base class.
-- Kostya
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