Data Binding with theme attributes

问题

I am trying out the new Android Databinding Library and I wanted to set the background color of ToolBar using a binding. By default the color should be colorPrimary (from the theme).

Before I was using DataBinding, my toolBar looked like

 <android.support.v7.widget.Toolbar
        android:id="@+id/mainToolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        />

After adding a binding, I wanted to set its background to colorPrimary if no color is bound - I'm using ternary operator for this (as mentioned in the guide) - but it causes an error, as theme attributes also have a "?" operator before their names. The compiler thinks I'm starting a new ternary operation.

<data>
    <variable name="toolBarBackgroundColor" type="int"/>
</data>
...
<android.support.v7.widget.Toolbar
        android:id="@+id/mainToolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="@{toolBarBackgroundColor!=0? toolBarBackgroundColor: ?attr/colorPrimary }"
        />

So is there a way I can access theme attributes inside a binding operation? Thanks!

Edit

I know I can get the colorPrimary attribute programmatically and bind it through java code. But I'm just wondering if there's an Xml-based solution for this or not.

回答1:

The answer is a bit late, but maybe it helps someone.

For accessing theme attributes in data binding, you can use this:

(imagine that clickable is Boolean variable)

android:background="@{clickable ? android.R.attr.selectableItemBackground : android.R.color.transparent}"

No additional binding adapters or another things needed.

回答2:

Finding a way using data-binding? Here is what I have done with test. First, create a custom binding adapter method:

@BindingAdapter({"app:customPrimaryBackground"})
public static void setCustomPrimaryBackground(View v, int resId) {
    TypedValue typedValue = new TypedValue();
    Context context = v.getContext();
    if (resId == 0) {
        context.getTheme().resolveAttribute(R.attr.colorPrimary, typedValue, true);
        v.setBackgroundResource(typedValue.resourceId);
    } else {
        // Check the given resource ID is a color or drawable
        context.getResources().getValue(resId, typedValue, true);
        Drawable drawable;
        if (typedValue.type >= TypedValue.TYPE_FIRST_COLOR_INT && typedValue.type <= TypedValue.TYPE_LAST_COLOR_INT) {
            // It's a color
            drawable = new ColorDrawable(typedValue.data);
        } else {
            drawable = ContextCompat.getDrawable(context, resId);
        }

        v.setBackground(drawable);
    }
}

Second, your binding xml layout:

<data>
    <variable name="toolBarBackgroundColor" type="int"/>
</data>
...
<android.support.v7.widget.Toolbar
        android:id="@+id/mainToolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        app:customPrimaryBackground="@{toolBarBackgroundColor}"
/>

来源：https://stackoverflow.com/questions/31235519/data-binding-with-theme-attributes

标签

android

data-binding

android-theme