CODEWITHSUNDEEP
androidxmllayoutview
I4004
I4004

Reputation: 145

Custom xml attributes without attrs.xml file

Recently I've faced with adding custom xml parameters to my views in xml layout. I know that I should use attrs.xml file for this purpose, but... I have found, that I can use custom parameters without any attrs.xml file at all. Can somebody explain this ? Is this a bug or is this a valid case ?

here is my custom view:

public class TestView extends View {

public TestView(final Context context, final AttributeSet attrs) {
    this(context, attrs, 0);
}

public TestView(final Context context, final AttributeSet attrs, final int defStyle) {
    super(context, attrs, defStyle);
    final String scheme = "http://red.com/ui/scheme";
    if (attrs != null) {
        Log.d("TestView", "custom param value: " + attrs.getAttributeValue(scheme, "cutom"));
    }
}

}

and here is the main layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:red="http://red.com/ui/scheme"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello" />

<com.red.ui.TestView 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="#ffAABBCC"
    red:cutom="customvalue"
    />

 </LinearLayout>

It is a simple scratch project, created by Android wizard.

Upvotes: 2

Views: 4350

Answers (2)

Sonam Daultani
Sonam Daultani

Reputation: 749

The custom attribute that you added is not available in R.java I think the main motto of making custom attributes is to use it at multiple places. But through this code we cann't accomplish the same scenario.

Here is the sample code - attrs.xml file

<?xml version="1.0" encoding="utf-8"?>
<resources>
 <declare-styleable name="MyLayout">
    <attr name="text" format="string" />
 </declare-styleable>
</resources>

I am changing main.xml to add the the text attribute

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:red="http://red.com/ui/scheme"
  xmlns:myapp="http://schemas.android.com/apk/res/com.psl"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical" >

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    myapp:text="Text String" />

<com.psl.TestView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="#ffAABBCC"
    myapp:text="My Special Text String"
    red:cutom="customvalue" />

</LinearLayout>

TestView.java -

public class TestView extends View {

public TestView(final Context context, final AttributeSet attrs) {
this(context, attrs, 0);
}

public TestView(final Context context, final AttributeSet attrs, final int defStyle) {
super(context, attrs, defStyle);
final String scheme = "http://red.com/ui/scheme";
if (attrs != null) {
    Log.d("TestView", "custom param value: " + attrs.getAttributeValue(scheme, "cutom"));
}

TypedArray a = context.obtainStyledAttributes(attrs,
        R.styleable.MyLayout);
CharSequence s = a.getString(R.styleable.MyLayout_text);
Log.d("MyTestView", "attrs param value: " + s.toString());
}
}

If you noticed after making the attr in attrs.xml. It is available everywhere. But the attr defined in xml itself through custom namespace is available only through the namespace that you have to define everywhere. May be its a bug because the attribute is getting added to some custom namespace and not in the application itself.

Upvotes: 4

Vinay W
Vinay W

Reputation: 10190

This is not a "bug" of course. This is how you use a custom view in your xml. refer to this : http://developer.android.com/guide/topics/ui/custom-components.html

Upvotes: 0

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