Activity is displayed as a dialog box

1. Set the screen height and width.

// The window is aligned to the screen width
Window win = this.getWindow();
win.getDecorView().setPadding(0, 0, 0, 0);
WindowManager.LayoutParams lp = win.getAttributes();
lp.width = WindowManager.LayoutParams.MATCH_PARENT;
lp.height = WindowManager.LayoutParams.WRAP_CONTENT;
lp.gravity = Gravity.TOP;//Set the dialog box to be displayed on top
win.setAttributes(lp);

2. Set the style

<style name="dialogstyle">
  <!--Set the background of the dialog-->
  <item name="android:windowBackground">@android:color/transparent</item>
  <!--Set Dialog's windowFrame box to none-->
  <item name="android:windowFrame">@null</item>
  <!--Set No Title-->
  <item name="android:windowNoTitle">true</item>
  <!--Whether it floats above the activity-->
  <item name="android:windowIsFloating">true</item>
  <!--Is it translucent-->
  <item name="android:windowIsTranslucent">true</item>
  <!--Set the window content not to cover-->
  <item name="android:windowContentOverlay">@null</item>
  <!--Set animation, use Animation.Dialog--> here to let it inherit the system
  <item name="android:windowAnimationStyle">@android:style/Animation.Dialog</item>
  <!--Whether the background is blurred display-->
  <item name="android:backgroundDimEnabled">true</item>
 </style>

3. Apply styles

<activity android:name="com.lpl.topnews.ShowDialogActivity" android:theme="@style/dialogstyle" ></activity>