Transparent AlertDialog has black background

The problem is that AlertDialog builder is actually not good for designing transparent dialog and will and always have this black background which is actually a Theme for it, instead use the Dialog to create a transparent theme instead.

sample:

Dialog alertDialog = new Dialog(this);
alertDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
alertDialog.setContentView(R.layout.tabs);
alertDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
alertDialog.show();

Using Dialog does not require any theme manipulation for transparent background so it is basically easy.

In your R.layout.tabs,

Replace

<RelativeLayout
    android:layout_width="fill_parent"
    android:layout_height="match_parent"
    android:id="@+id/tabLayout"
    android:background="#000000ff">

with

<RelativeLayout
    android:layout_width="fill_parent"
    android:layout_height="match_parent"
    android:id="@+id/tabLayout"
    android:background="@android:color/transparent">

Have you tried using something like this:

<style name="CustomDialog" parent="@android:style/Theme.Translucent">
    <item name="android:windowBackground">@android:color/transparent</item>
    <item name="android:colorBackgroundCacheHint">@null</item>
    ...
</style>

EDIT

Try this in java code

dialog.getWindow().setBackgroundDrawable(new ColorDrawable(android.graphics.Color.TRANSPARENT));

Those who are having still problem creating custom transparent dialog or alert dialog, can use this combination. I also wanted to show custom background this is what worked for me.

getWindow().clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));

example:-

/**
 * alert dialog
 */

    public class ToolTipView extends AlertDialog {

        public ToolTipView(@NonNull Context context) {
            super(context);
            getWindow().clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
            getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
        }

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.dialog_tool_tip_view);
        }

    }