Make you App looked like a Dialog

To make your app looked like a dialog, you can use the Android pre-defined Theme.Dialog.

Modify AndroidManifest.xml, to add the code inside
android:theme="@android:style/Theme.Dialog"

example:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.AndroidDialog"
     android:versionCode="1"
     android:versionName="1.0">
   <uses-sdk android:minSdkVersion="4" />

   <application android:icon="@drawable/icon" android:label="@string/app_name">
       <activity android:name=".AndroidDialog"
                 android:label="@string/app_name"
                 android:theme="@android:style/Theme.Dialog">
           <intent-filter>
               <action android:name="android.intent.action.MAIN" />
               <category android:name="android.intent.category.LAUNCHER" />
           </intent-filter>
       </activity>

   </application>
</manifest>