Observable / Observer Android

Question

EDIT please see Observer Observables implementing issue - It seems I was overriding methods that didn't need to be and not calling setChanged(); before notify();

I've been reading up on the Observer Pattern for keeping my UI up to date but I still can't see the use for it.. Even if in my particular object notifies my MainActivity then runs the update(); method I still wouldn't be able to use the Pet object to pull the update values as the object is created in Oncreate...and I just can't create a new object because then the variables will be different..this is my implementation and it doesn't seem to work.

Observer/MainActivity

package com.grim.droidchi;

import java.util.Observable;
import java.util.Observer;

import android.app.Activity;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.webkit.WebSettings.LayoutAlgorithm;
import android.webkit.WebView;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements Observer, OnClickListener {
    private static final String TAG = "VPET";
    private static final String APP_PREFS = "VPET";
    private static final int REQUEST_CODE = 1;
    Boolean isAlive = false;
    TextView happiness_display, health_display, hunger_display, level_display;
    Button PunchPet, UpdateHunger;
    public static Pet pet = new Renamon();

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

        SharedPreferences settings = getSharedPreferences("APP_PREFS",
                MODE_PRIVATE);

        WebView myWebView = (WebView) findViewById(R.id.pet_display);
        myWebView.loadUrl("file:///android_asset/renamon.gif");
        myWebView.setInitialScale(10000);
        myWebView.getSettings().setLayoutAlgorithm(LayoutAlgorithm.SINGLE_COLUMN);


        PunchPet = (Button) findViewById(R.id.PunchPet);
        UpdateHunger = (Button) findViewById(R.id.UpdateHunger);
        final TextView hunger_display = (TextView) findViewById(R.id.hunger_display);
        TextView happiness_display = (TextView) findViewById(R.id.happiness_display);
        TextView level_display = (TextView) findViewById(R.id.level_display);
        TextView health_display = (TextView) findViewById(R.id.health_display);

        hunger_display.setText(Integer.toString(pet.getHunger()));
        health_display.setText(Integer.toString(pet.getHP()));
        level_display.setText(Integer.toString(pet.getLVL()));
        happiness_display.setText(Integer.toString(pet.getHappy()));


        Intent intent = new Intent(this, Gameloop.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(
                getBaseContext(), REQUEST_CODE, intent, 0);

        AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
        alarmManager.setRepeating(AlarmManager.RTC_WAKEUP,
                System.currentTimeMillis() + (5 * 1000), 1800000, pendingIntent);
        // 1800000 ms = 30 mins

        pet.feed();
        pet.addObserver(this);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    protected void onPause() {


        super.onPause();
    }

    @Override
    public void update(Observable o, Object data) {

        hunger_display.setText(Integer.toString(pet.getHunger()));
        health_display.setText(Integer.toString(pet.getHP()));
        level_display.setText(Integer.toString(pet.getLVL()));
        happiness_display.setText(Integer.toString(pet.getHappy()));
        Log.d(TAG, "UPDATED FROM OBSERVER");

    }

    @Override
    public void onClick(View v) {
        if (v == PunchPet) {
            pet.setHP(500);
            Toast.makeText(getApplicationContext(), "PUNCHPET", Toast.LENGTH_SHORT).show();
            health_display.setText(Integer.toString(pet.getHP()));
    }else {

    }



    }

}

Observable/Pet

package com.grim.droidchi;

import java.util.Observable;
import java.util.Observer;
import java.util.Set;

import android.util.Log;

public class Pet extends Observable implements PetInterface {
    protected Set<Observer> observers;
    private static final String TAG = "VPET";
    private int Health = 100;
    @Override
    public void addObserver(Observer o) {
        observers.add(o); 
        super.addObserver(o);
    }

    @Override
    public void notifyObservers() {
        observers.notify();
        super.notifyObservers();
    }

    @Override
    public synchronized void deleteObserver(Observer o) {
        observers.remove(o);
        super.deleteObserver(o);
    }

    private int Happiness = 10;
    private int Level = 1;
    private int Hunger = 0;
    private int Exp = 0;
    private String Name;
    private Boolean isAlive = true;
    private Boolean isSick = false;

    public void setHP(int hp) {
        this.Health = hp;
        notifyObservers(hp);
    }

    public void setLVL(int lvl) {
        this.Level = lvl;
        notifyObservers(lvl);
    }

    public void setXP(int xp) {
        this.Exp = xp;
        notifyObservers(xp);
    }

    public void setHunger(int hunger) {
        this.Hunger = hunger;
        notifyObservers(hunger);
    }

    public void setHappy(int happy) {
        this.Happiness = happy;
        notifyObservers(happy);
    }

    public int getHP() {

        return Health;
    }

    public int getLVL() {

        return Level;
    }

    public int getXP() {

        return Exp;
    }

    public int getHunger() {

        return Hunger;
    }

    public int getHappy() {

        return Happiness;
    }

    public boolean isAlive() {
        return isAlive;

    }

    public boolean isSick() {
        return isSick;

    }

    @Override
    public void sleep() {
        // TODO Auto-generated method stub

    }

    @Override
    public void clean() {
        // TODO Auto-generated method stub

    }

    @Override
    public void feed() {
        Log.d(TAG, "FEEDING FROM INTERFACE THING");

    }

    @Override
    public void passtime() {

    }

}

Answer 1

First, I wouldn't recommend overriding addObserver or removeObserver in your observable object. The API does a really good job of implementing this (unless you want some specific functionality).

Second, the method notifyObservers() is overloaded so that you can pass it an object, IE notifyObservers(Object obj) . If you pass it your Pet , notifyObservers(this) , then you will have a reference to your Pet object that is being observed.

I think this is your question but please correct me if I am wrong.

EDIT : To clarify, my answer is contingent upon you using the Observable class in the Java API here .

Upon further review, you should already have a reference to the Pet object that called the update method of the Observer

Answer 2

Your pet is not accessible in other methods because its not defined at global level.

You should define Pet pet = new Renamon(); outside of onCreate method.