To Lecture Notes

IT 372 -- Apr 17, 2019

Review Questions

1. How does an Android App know which startup activity file to use?
   Ans: The startup activity has these tags between <activity> and </activity>:
   

   <intent-filter>
       <action android:name="android.intent.action.MAIN" />
       <category android:name="android.intent.category.LAUNCHER" />
   </intent-filter>
   

2. Give the hex color codes for these colors:
       red      Ans: #ff0000
       green   Ans: #008000
       purple  Ans: #800080
       teal     Ans: #008080
       gray     Ans: #808080
       silver   Ans: #c0c0c0
3. Trivia Question: Name three major universities whose names are colors.
   Hint: one of them is Navy.  Ans: There are actually three more: Brown, Siena, Auburn
4. Show six ways of setting the background color in a layout.
   Hint: Use this chart of hex color codes if you get stuck.
   Ans: The first three ways are in the layout, the last three are in the Java activity file:
   
   1. android:background="@android:black"
   2. android:background="0xc0ffc0"
   3. android:background="@color/lightGreen
   4. layout.setBackground(getResource( ).getColor(Color.GREEN));
   5. layout.setBackground(getResource( ).getColor(Color.parseColor("0xc0ffc0"));
   6. layout.setBackground(getResource( ).getColor(R.color.lightGreen));
5. Create an Android app with a button. When the button is pressed repeatedly, the background color of the linear layout cycles through three colors or your choice.
   Ans: See the ChangeColors Example.

Using Images

• Setting a background image:
  
  • Copy the background image, for example, image1.jpg into the app/res/drawable folder.
  • Add this attribute to the layout or widget:
    

    android:background="@drawable/image1"
    

• This attribute can be used to crop the background image so that it fits the layout:
  

  android:scaleType="centerCrop"
  

• Practice Problem 2: Add a background image to the layout in Practice Problem 1.

Multiactivity Apps and Intents

• Look at the SendMessage Example.