How to change shapedrawable color dynamically for TabHost background?

Question

I have a TabHost, where I use a shape xml to make it looks like this:

I define the TabHost background this way:

private void setTabColor(TabHost tabHost) {
    try {

        for (int i = 0; i < tabHost.getTabWidget().getChildCount(); i++) {
            tabHost.getTabWidget().getChildAt(i).setBackgroundResource(R.drawable.strib_tab);
        }

    } catch (ClassCastException e) {
    }
}

where strib_tab is:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/line_pressed" android:state_selected="true"/>
<item android:drawable="@drawable/line"/>
</selector>

and line_pressed is:

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <item>
        <shape android:shape="rectangle" >
            <stroke
                android:width="5dip"
                android:color="@color/blue_bg" />

            <padding
                android:bottom="0dip"
                android:left="0dip"
                android:right="0dip"
                android:top="0dip" />
        </shape>
    </item>
    <item
        android:bottom="5dp"
        android:top="0dp">
            <shape android:shape="rectangle" >
            <solid android:color="#FFFFFF" />
        </shape>
    </item>

</layer-list>

and line is:

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape>
            <solid android:color="@android:color/transparent" />
        </shape>
    </item>
</selector>

How can I change dynamically the color of the shape where the color is blue_bg in line_pressed ?

Answer 1

It seems you can't modify a StateListDrawable, however you can easily create a new one.

As for the LayerDrawable, it can be manipulated pretty easily.

Code speaks better, so here it is:

Resources r = getResources();

// Modify the LayerDrawable (line_pressed)
LayerDrawable ld = (LayerDrawable) r.getDrawable(R.drawable.line_pressed);
GradientDrawable gradient = (GradientDrawable) ld
            .findDrawableByLayerId(R.id.stroke);
// Set a custom stroke (width in pixels)
gradient.setStroke(5, Color.RED);

// Create a new StateListDrawable
StateListDrawable newStripTab = new StateListDrawable();
newStripTab.addState(new int[] { android.R.attr.state_selected }, ld);
newStripTab.addState(new int[0], r.getDrawable(R.drawable.line));

tabHost.getTabWidget().getChildAt(i).setBackgroundResource(newStripTab);

Notes:

• I used a custom line_pressed, so could find the specific layer easily:

  <layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
      <item android:id="@+id/stroke">
          <shape android:shape="rectangle" >
              <stroke
                  android:width="5dip"
                  android:color="#000" />
              ...
          </shape>
      </item>
      ...     
  </layer-list>
  

• This code is untested practically but should work or at least provide some insight in how to accomplish this.