i want to add shadow effect in alert dialog box . [i want this type of shadow effect in my dialog box](https://i.stack.imgur.com/QelqE.png)
here i post 3 files first is style.xml second is theme.java or third file is demo\_bg.xml file.i already try like that

```
Style.xml 
 <style name="AppCompatAlertDialogStyle" parent="Theme.AppCompat.Light.Dialog.Alert">
        <item name="colorAccent">@color/bg_color</item>
        <item name="android:textColorPrimary">@color/colorBlack</item>
        <item name="android:background">@drawable/demo_bg</item>

    </style>

```

```html
theme.java

final AlertDialog.Builder builder =
                new AlertDialog.Builder(this, R.style.AppCompatAlertDialogStyle);
        builder.setMessage(R.string.wsdialogdata);
        builder.setPositiveButton("START", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialogInterface, int i) {
                Intent ii = new Intent(WelcomeFromActivity.this, Question1Activity.class);
                startActivity(ii);
            }
        });
        builder.show();

demo_bg.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <layer-list>
            <!-- SHADOW LAYER -->
            <item android:left="2dp" android:top="2dp">
                <shape>
                    <solid android:color="#66000000" />
                    <corners android:radius="35dip" />
                </shape>
            </item>
            <!-- CONTENT LAYER -->
            <item android:bottom="4dp" android:right="4dp">
                <shape>
                    <solid android:color="@color/btn_fb" />
                    <corners android:radius="40dip" />
                </shape>
            </item>
        </layer-list>
    </item>
</selector>
```