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android:src attrs for custom view

Is there a way to set default android attrs to the custom view, that would be available when defining this view in xml?. For example, I need to create CustomImageView that will be FrameLayout with ImageView and ProgressBar inside it. If I add such view in xml I want to set background or src of that view, for example. FrameLayout has no android:src attribute and it doesn't offer via Android Studio autocomplete window, can I make somehow Android Studio to know that this layout can process such attributes?

The trick is to put android:src in custom styleables, located at values/attrs.xml:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="MyView">
<attr name="android:src"/>
</declare-styleable>
</resources>
And having MyView class that is a descendant of a View, then in xml file we'd see this:

Android how to use app attribute for custom class options [duplicate]

I know it is possible to create custom UI element (by way of View or specific UI element extension). But is it possible to define new properties or attributes to newly created UI elements (I mean not inherited, but brand new to define some specific behavior I am not able to handle with default propertis or attributes)
e.g. element my custom element:
<com.tryout.myCustomElement
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Element..."
android:myCustomValue=<someValue>
/>
So is it possible to define MyCustomValue?
Thx

Yes. Short guide:
Create an attribute XML
Create a new XML file inside /res/values/attrs.xml, with the attribute and its type
<?xml version="1.0" encoding="UTF-8"?>
<resources>
<declare-styleable name="MyCustomElement">
<attr name="distanceExample" format="dimension"/>
</declare-styleable>
</resources>
Basically you have to set up one <declare-styleable /> for your view that contains all your custom attributes (here just one). I never found a full list of possible types, so you need to look at the source for one I guess. Types that I know are reference (to another resource), color, boolean, dimension, float, integer and string. They are pretty self-explanatory
Use the attributes in your layout
That works the same way you did above, with one exception. Your custom attribute needs its own XML namespace.
<com.example.yourpackage.MyCustomElement
xmlns:customNS="http://schemas.android.com/apk/res/com.example.yourpackage"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Element..."
customNS:distanceExample="12dp"
/>
Pretty straight forward.
Make use of the values you get passed
Modify the constructor of your custom view to parse the values.
public MyCustomElement(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.MyCustomElement, 0, 0);
try {
distanceExample = ta.getDimension(R.styleable.MyCustomElement_distanceExample, 100.0f);
} finally {
ta.recycle();
}
// ...
}
distanceExample is a private member variable in this example. TypedArray has lots of other things to parse other types of values.
And that's it. Use the parsed value in your View to modify it, e.g. use it in onDraw() to change the look accordingly.

In your res/values folder create attr.xml. There you can define your attribues:
<declare-styleable name="">
<attr name="myCustomValue" format="integer/boolean/whatever" />
</declare-styleable>
When you then want to use it in your layout file you have to add
xmlns:customname="http://schemas.android.com/apk/res/your.package.name"
and then you can use the value with customname:myCustomValue=""

Yes , you can.Just use <resource> tag.
like this:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="CodeFont" parent="#android:style/TextAppearance.Medium">
<item name="android:layout_width">fill_parent</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:textColor">#00FF00</item>
<item name="android:typeface">monospace</item>
</style>
</resources>
link from official website

how to get reference to color attribute defined in xml layouts?

Update: There were 2 custom attributes defined in CustomTextView.. If both are defined in xml it works fine.. If first is missing it does not give any value for 2nd also...
<com.mycompany.projectname.MyCustomView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:extraColor="?someColor"
/>
Here someColor is another color attr which varies for different themes..
I need value of extraColor custom attribute in MyCustomView class...
Currently obtaining it as below:
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CustomTextView, defStyleAttr, 0);
a.getColorStateList() does not work here...
CustomTextView defined as:
<declare-styleable name="CustomTextView">
<attr name="state" format="boolean" />
<attr name="extraColor" format="reference|color" />
</declare-styleable>
Update: There were 2 custom attributes defined in CustomTextView..
If both are defined in xml it works fine.. If first is missing it does not give any value for 2nd also...

Could you try that one..
a.getColor(R.styleable.CustomTextView_extraColor, Color.WHITE)

use only either reference or color
<declare-styleable name="CustomTextView">
<attr name="extraColor" format="reference" />
</declare-styleable>
And then if it is reference get it like,
a. getColorStateList(R.styleable.CustomTextView_extraColor);
if it is color then,
a. getColor(R.styleable.CustomTextView_extraColor, Color.WHITE);

In addition to what others have said, it looks like the naming is inconsistent (copy+paste error?): in most of the code you posted, your refer to a CustomTextView, but in the XML, you use MyCustomView.
Try changing your XML:
<com.mycompany.projectname.CustomTextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:extraColor="?someColor"
/>

Complex Attributes in Android Custom View XML

I've got a question on custom view XML-declarations.
I created my own View with the custom attributes as normal. Now I want to add more complex attributes like this: (This is non-working code)
<com.xxx.yyy.CustomTextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/customTextView1"
android:layout_marginBottom="22dp"
android:layout_toRightOf="#+id/buttonBlack"
android:text="TextView" >
<Animation
animation:property1="123"
animation:property2="456" />
<Animation
animation:property1="789"
animation:property2="012" >
</Animation>
</com.xxx.yyy.CustomTextView>
I didnt find a way to do this on my own but maybe someone has got an idea.
Thanks!
Edit:
I just solved the problem more or less nicely.
I created a new .xml file in my /res/xml folder called animations.xml
<animations>
<animation
name="Animation name 1"
float1="1.1"
float2="1.2"
integer1="11"
integer2="12" />
<animation
name="Animation name 2"
float1="2.1"
float2="2.2"
integer1="21"
integer2="22" />
</animations>
My custom view in attrs.xml contains an attribute which is used to reference the animations.xml file from above:
<declare-styleable name="MyTextView">
<attr name="animations" format="reference" />
</declare-styleable>
Now i parse the referenced .xml file in the constructor of the MyTextView as described here: http://thedevelopersinfo.com/2009/12/14/using-xml-file-resources-in-android/
Maybe this helps somebody at some time.

Unless CustomTextView extends ViewGroup (or has it in it's class hierarchy) and Animation is a custom view you've defined, this will not work. Only Views and ViewGroups are allowed in layout XML files (and some special tags defined by Android like include and merge), and only ViewGroup elements can have child elements.

You can add custom XML attributes to your custom view like this:
<resources>
<declare-styleable name="YourCustomClass">
<attr name="someCustomAnimationAttribute" format="reference" />
</declare-styleable>
<resources>
How you obtain it is described here:
http://developer.android.com/training/custom-views/create-view.html#applyattr
In your layout you have to declare a namespace:
xmlns:app="http://schemas.android.com/apk/res-auto"
and then use it like this:
<com.xxx.yyy.CustomTextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/customTextView1"
android:layout_marginBottom="22dp"
android:layout_toRightOf="#+id/buttonBlack"
android:text="TextView"
app:someCustomAnimationAttribute="#drawable/someAnimation">
That way you can supply those animations via XML instead of adding them as as child elements which is not possible.

How to create a simple custom View?

I would like to create an custom View on Android. I have tried to do it as simple as possible and created an almost empty class MyView and used it in my LinearLayout but the application fails on start with "Force Close". How can I do a simple custom View? According to Building Custom Components the View gets the size 100x100 if I don't override onMeasure().
public class MyView extends View {
public MyView(Context context) {
super(context);
}
}
And I use it in a LinearLayout with:
<view
class="com.example.MyView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.0" />
What am I doing wrong?
If I use the constructor that itemon suggest and the corresponding call to the superclass. Then the "Force Close" is gone, but my LinearLayout is broken, the components after MyView isn't shown.
Here is my main.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.0"
android:background="#f00"
android:text="Hello"
/>
<view
class="com.example.MyView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.0"
/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="0.0"
android:background="#00f"
android:text="World"
/>
</LinearLayout>

may be you could define another constructor method like this:
public MyView(Context context, AttributeSet attrs)
the android framework will try to build the UI with your view from the constructor above.

The Android Developer Guide has a section called Building Custom Components. Unfortunately, the discussion of XML attributes only covers declaring the control inside the layout file and not actually handling the values inside the class initialisation. The steps are as follows:
Declare attributes in values\attrs.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="MyCustomView">
<attr name="android:text"/>
<attr name="android:textColor"/>
<attr name="extraInformation" format="string" />
</declare-styleable>
</resources>
Notice the use of an unqualified name in the declare-styleable tag. Non-standard android attributes like extraInformation need to have their type declared. Tags declared in the superclass will be available in subclasses without having to be redeclared.
Create constructors
Since there are two constructors that use an AttributeSet for initialisation, it is convenient to create a separate initialisation method for the constructors to call.
private void init(AttributeSet attrs){
TypedArray a=getContext().obtainStyledAttributes(attrs,R.styleable.MyCustomView);
//Use a
Log.i("test",a.getString(R.styleable.MyCustomView_android_text));
Log.i("test",""+a.getColor(R.styleable.MyCustomView_android_textColor, Color.BLACK));
Log.i("test",a.getString(R.styleable.MyCustomView_android_extraInformation));
//Don't forget this
a.recycle();
}
R.styleable.MyCustomView is an autogenerated int[] resource where each element is the ID of an attribute. Attributes are generated for each property in the XML by appending the attribute name to the element name. Attributes can then be retrieved from the TypedArray using various get functions. If the attribute is not defined in the XML, then null is returned. Except, of course, if the return type is a primitive, in which case the second argument is returned.
If you don't want to retrieve all of the attributes, it is possible to create this array manually.The ID for standard android attributes are included in android.R.attr, while attributes for this project are in R.attr.
int attrsWanted[]=new int[]{android.R.attr.text, R.attr.textColor};
Please note that you should not use anything in android.R.styleable, as per this thread it may change in the future. It is still in the documentation as being to view all these constants in the one place is useful.
Use it in a layout files such as layout\main.xml
Include the namespace declaration
xmlns:app="http://schemas.android.com/apk/res/com.mycompany.projectname"
in the top level xml element.
<com.mycompany.projectname.MyCustomView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:text="Test text"
android:textColor="#FFFFFF"
app:extraInformation="My extra information";
/>
Reference the custom view using the fully qualified name.
Android LabelView Sample
If you want a complete example, look at the android label view sample.
LabelView.java
TypedArray a=context.obtainStyledAttributes(attrs, R.styleable.LabelView);
CharSequences=a.getString(R.styleable.LabelView_text);
attrs.xml
<declare-styleable name="LabelView">
<attr name="text"format="string"/>
<attr name="textColor"format="color"/>
<attr name="textSize"format="dimension"/>
</declare-styleable>
custom_view_1.xml
<com.example.android.apis.view.LabelView
android:background="#drawable/blue"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
app:text="Blue"app:textSize="20dp"/>
This is contained in a LinearLayout with a namespace attribute:
xmlns:app="http://schemas.android.com/apk/res/com.example.android.apis"