The document discusses several Java concepts including packages, access modifiers, encapsulation, getters and setters, and anonymous classes. It provides the following key points: 1. Packages provide a mechanism for grouping related types together in a unique namespace and common conventions for naming packages include using the domain name reversed plus the program name. 2. Access modifiers like private, default/package, protected, and public control the visibility of declarations. 3. Encapsulation is the idea that an object should not reveal details it does not intend to support. Getters and setters are a common example of encapsulation in Java. 4. The document provides an example of creating a Contact class with fields,

1. More Java: Encapsulation, Getters, Setters,
Anonymous Class
1
CS300

2. Java Packages
 Provide a mechanism for grouping related
types together in a universally unique
namespace.
 java.lang
 Java.util
 How to name a package?
 Domain name reversed
 Ex. domain android.com will be package com.android
 Plus name of the program
 Ex. com.android.notepad
CS300
2

3. Access Modifiers
 Keywords that modify the visibility of the
declarations to which they are applied
 Private: most restrictive. Not visible outside the
block that contains it.
 Default or package access: next most restrictive.
Visible only from other classes in package.
 Protected: permits all default access rights plus
access from within any subtype.
 Public: allows access from anywhere.
CS300
3

4. Encapsulation
 The idea that an object should never reveal
details about itself that it does not intend to
support.
 Getters and Setters:
 Common example of encapsulation in Java
CS300
4

5. Getters and Setters example
 Create a class Contact that extends
Comparable<Contact>:
 Fields: name, age, email
 Create constructor with arguments: name, age,
email
 Create getters and setters for all three fields
 Create method compareTo to sort contacts by e-
mail
 Test
CS300
5

6. Anonymous Class
 Callback: your code needs to be notified
when something in the UI changes.
 Ex. a button is pushed and we need to change
state, new data has arrived from the network and
it needs to be displayed
 Java provides idiom to pass blocks in code
 Anonymous classes are a handy tool for
expressing many kinds of code blocks.
CS300
6

7. 7
Without anonymous class With anonymous class
public class myDataModel{
//Callback class
private class keyHandler implements
View.onKeyListener {
public boolean onKey(View v,
int keyCode, KeyEvent event) {
handleKey(v, keyCode,
event);
}
}
/* @param view in the view we model */
public myDataModel(View view){
view.setOnKeyListener(new
KeyHandler())
}
/** Handle a key event **/
void handleKey(View v, int keyCode,
KeyEvent event){
// key handling code goes here …
}
}
public class myDataModel{
/* @param view in the view we model */
public myDataModel(View view) {
view.setOnKeyListener(
// this is an anonymous class!!
new View.OnKeyListener() {
public boolean onKey(View v, int
keyCode, KeyEvent event) {
handleKey(v, keyCode,
event);
}
} );
/** Handle a key event **/
void handleKey(View v, int keyCode,
KeyEvent event){
// key handling code goes here …
}
}
CS300

8. References
 Programming Android by Zigurd Mednieks,
Laird Dornin, G. Blake Meike, Masumi
Nakamura
CS300
8

9. Install ADT and AVD
 http://developer.android.com/sdk/index.html#d
ownload
 If you already have eclipse use an Existing IDE
option
CS300
9

10. Install notes
 Don’t forget to configure the ADT (Eclipse,
Window, Preferences, Android)
 Do not forget to set an AVD target (run
configuration)
 Do not forget to assign SD memory
 Check devices: use the proper one
CS300
10

11. Hello Android!!
 New android project
 Delete activity_main.xml
 Right click layout -> create new xml. Choose
relative layout
 Configure resolution: samsung nexus 4 inch
screen, 480-by-800
 Create AVD
CS300
11

12. Hello Android!!
 Drawables:
 Hdpi: high density
 Mdpi: medium density
 Ldpi: low density
 Xhdpi: extra high
 Change ID property for relative layout
 +: create new variable with name
 Change BG property
 RGB color map
CS300
12

13. Hello Android!!
 Add a TextView
 Configure text property: create a new string
resource (good practice)
 R.String: name
 String: content
 Configure text size:
 Dp: density independent pixel
 Configure layout margin top
 Text color: #00F
 Text Style: bold
CS300
13

14. Hello Android!!
 Add image view
 Create new drawable: be careful with names! No
hyphens allowed
 Change:
 Id
 Layout below: put it under your textview
 Layout center horizontal
 Src: do not forget to add your image in a drawable
directory
CS300
14