setBackgroundColor（drawable）！= android：background =（drawable）？

Question

I've got a custom drawable resource to display my items in a ListView, actually two because I wanted my results to have alternating background colors but both to respond to clicks by changing their color. The problem is even when assigning even one of these drawables to my LinearLayout container via the layout XML, it works fine, but via Java code it doesn't. So to be exact, this works:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/result_white"
android:id="@+id/result"
>

but this (in my ResultAdapter which extends ArrayAdapter) doesn't:

LinearLayout result = (LinearLayout) v.findViewById(R.id.result);
result.setBackgroundColor(R.drawable.result_white);

My final objective is of course to have alternating 'result_white' and 'result_ltgray' drawables for results so the first XML solution does not really satisfy my needs. What am I missing in the Java code please?

Answer 1

Well, assuming you are only using one-color backgrounds, you should use Colors instead since drawables can be shapes, gradients and more. Now, to actually use color, your code will look something like:

result.setBackgroundColor(mContext.getResources.getColor(R.color.result_white));

where mContext is the context, and you have a color (such as 0xFFFFFFFF) in your res/values/colors.xml file.

Also take a look at Color State Lists for changing colors when pressed / selected / etc

Answer 2

Thanks for your help guys, but what I needed to do is this:

result.setBackgroundResource(R.drawable.result_white);

This way I could easily implement this into my ResultAdapter for alternating results reacting to clicks with changing backgrounds:

LinearLayout result = (LinearLayout) v.findViewById(R.id.result);

        if (position % 2 == 0)
            result.setBackgroundResource(R.drawable.result_white);
        else
            result.setBackgroundResource(R.drawable.result_ltgray);

Answer 3

确保为R导入了正确的引用（对于android drawables为android.R，对于您自己的为your_app_path.R）。