Java Objects in Activities: Android Programming смотреть онлайн

Demonstration/guide on how to use custom plain-old Java objects inside an Activity.
Java code and outline are in this description (below).

Ideas:
---------------------------------------------
- Separate the UI from the Business Logic (BL)
- BL plain java
- UI code (Android) calls BL objects.

Steps:
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1. Design and implement BL (Java classes).
2. Instantiate BL object in UI code.
3. Call BL object from UI code (client)

enum:
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A set of possible values.
Example:
public enum Emotion {TIRED, HAPPY, SAD};



Example:
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PetRock: Generate get/set
public class PetRock {
public enum Emotion {TIRED, HAPPY, SAD};
private Emotion currentEmotion = Emotion.TIRED;

public Emotion getCurrentEmotion() {
return currentEmotion;
}

public void setCurrentEmotion(Emotion currentEmotion) {
this.currentEmotion = currentEmotion;
}

@Override
public String toString() {
return "I'm feeling " + currentEmotion.toString() + ".";
}
}


UI:
- Label for status
- 2 Buttons for Happy/Sad to change state and update UI
Function to setup each button, then refactor to one function.

public class MainActivity extends Activity {
private PetRock rocky = new PetRock();

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

setupEmotionButton(R.id.btnHappy, Emotion.HAPPY);
setupEmotionButton(R.id.btnSad, Emotion.SAD);
updateUI();
}

private void setupEmotionButton(int buttonId, final Emotion newEmotion) {
Button button = (Button) findViewById(buttonId);
button.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View arg0) {
rocky.setCurrentEmotion(newEmotion);
updateUI();
}
});
}

private void updateUI() {
TextView textView = (TextView) findViewById(R.id.txtRockyFeeling);
String feeling = rocky.toString();

textView.setText(feeling);
}

}