To Lecture Notes

IT 372 -- May 20, 2019

Exam Info

• Look at the Final Review Guide and the Final Exam Practice Questions on the Exam Info Page.

Practice Problems

1. Create a layout with a button that tests a LongClick Event Handler. Also attach a Click event handler to the button.
   Ans: Here are the XML layout file and the Java activity file. Toasts are shown by the LongClick and Click event handlers at two different y positions.
2. Research and test the SeekBar widget.
   Ans: Here are the XML layout file and the Java activity file. The SeekBar class is a class derived from ProgressBar, which represents a value by its horizontal position on the bar. This position is the progress attribute. Here are the relevant properties of the SeekBar:
   
   

   Attribute	Description
   progress	Value represented by the seek bar.
   min	Minimum progress value of seek bar
   max	Minimum progress value of seek bar

3. How do you change the image in an ImageView widget dynamically? Write an app to test this.
   Ans: See the ShowSuit Example.
4. Look at the Tourist Info Example that uses a ListView widget.

Setting the App Icon

This section will be discussed on May 27.

• To set the icon and label for an Android app, set the icon and label attributes in the application tag in the manifest:
  

  android:icon="@drawable/icon_name" 
  android:label="@string/app_name"
  

• Alternatively, an XML file that has drawing directions can be used for the icon. For example, here are the contents of the the default icon  file ic_launcher_background.xml:
  

  <?xml version="1.0" encoding="utf-8"?>
      <vector 
          xmlns:android=
              "http://schemas.android.com/apk/res/android"
          android:width="108dp"
          android:height="108dp"
          android:viewportWidth="108"
          android:viewportHeight="108">
  
      <path
          android:fillColor="#008577"
          android:pathData="M0,0h108v108h-108z" />
  
      <path
          android:fillColor="#00000000"
          android:pathData="M9,0L9,108"
          android:strokeWidth="0.8"
          android:strokeColor="#33FFFFFF" />
  
      <path
          android:fillColor="#00000000"
          android:pathData="M19,0L19,108"
          android:strokeWidth="0.8"
          android:strokeColor="#33FFFFFF" />
  
      <!-- 31 paths are omitted. -->
  
      <path
          android:fillColor="#00000000"
          android:pathData="M79,19L79,89"
          android:strokeWidth="0.8"
          android:strokeColor="#33FFFFFF" />
  
  </vector>
  

Themes

This section will be discussed on May 27.

• To set the theme for an app, set the theme attribute in the application tag in the manifest:
  

  android:theme="@style/AppTheme"
  

• The beginning of the styles.xml file in app/src/main/res/values:
  

  <resources>
  <!-- Base application theme. -->
  <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
      <!-- Customize your theme here. -->
      <item name="colorPrimary">@color/colorPrimary</item>
      <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
      <item name="colorAccent">@color/colorAccent</item>
  </style>
  </resources>
  

  The meanings of these color titles:
  
  • name="colorPrimary"   The color used in the app bar, the main color that "brands" the app.
  • name="colorPrimaryDark"   A darker variant of the main color, used for the status bar.
  • name="colorAccent"   the color of UI controls, such as EditText or RadioButton widgets.
• The colors.xml file, also in app/src/main/res/values.
  

  <?xml version="1.0" encoding="UTF-8"?>
  <resources>
      <color name="colorPrimary">#00BCD4</color>
      <color name="colorPrimaryDark">#660F09</color>
      <color name="colorAccent">#D81B60</color>
  </resources>
  

  These colors can be customized as desired.
• Alternatives to the default theme
  

  Theme.AppCompat.Light.DarkActionBar
  

  are

  Theme.AppCompat
  Theme.AppCompat.Light
  Theme.AppCompat.Light.NoActionBar
  Theme.AppCompat.NoActionBar