public class MainActivity extends Activity
{
    private Button defaultbutton = null;
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final LinearLayout layout = (LinearLayout) findViewById(R.id.layout);
        //默认皮肤
        defaultbutton = (Button)findViewById(R.id.defaultButton);
        defaultbutton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v)
            {
                layout.setBackgroundResource(R.drawable.netskin);
            }
        });
        //为其他皮肤添加点击按钮
        ArrayList<PackageInfo> skinList = getAllSkin();
        for (int i = 0; i < skinList.size(); i++)
        {
            try
            {
                final Context context = createPackageContext(skinList.get(i).packageName,
                        Context.CONTEXT_IGNORE_SECURITY);
                Button btn = new Button(this);
                btn.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
                btn.setText(context.getText(R.string.app_name));
                btn.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View v)
                    {
                        layout.setBackgroundDrawable(context.getResources().getDrawable(R.drawable.netskin));
                    }
                });
                layout.addView(btn);
            }
            catch (NameNotFoundException e)
            {
                e.printStackTrace();
            }
        }
    }

    /**
     * 获取所有已安装的皮肤主题
     *
     * @return
     */
    private ArrayList<PackageInfo> getAllSkin()
    {
        ArrayList<PackageInfo> skinList = new ArrayList<PackageInfo>();
        List<PackageInfo> packs = getPackageManager().getInstalledPackages(0);
        for (PackageInfo p : packs)
        {
            if (isSkinPackage(p.packageName))
            {
                skinList.add(p);
            }
        }
        return skinList;
    }

    /**
     * 判断是否是皮肤主题
     *
     * @param packageName
     * @return
     */
    private boolean isSkinPackage(String packageName)
    {
        // 自己制作的皮肤主题包名 例如：sunlight.skin0 sunlight.skin1等等
        String rex = "sunlight.skin\\w";
        Pattern pattern = Pattern.compile(rex);
        Matcher matcher = pattern.matcher(packageName);
        return matcher.find();
    }
}

main.xml

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

    <Button
        android:id="@+id/defaultButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="默认皮肤" />

</LinearLayout>