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steveliles/Foreground.java

Created April 20, 2014 15:30
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Revisions

  1. steveliles created this gist Apr 20, 2014.
    155 changes: 155 additions & 0 deletions Foreground.java
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,155 @@
    package com.sjl.util;

    import android.app.Activity;
    import android.app.Application;
    import android.content.Context;
    import android.os.Bundle;
    import android.os.Handler;
    import android.util.Log;

    import java.util.List;
    import java.util.concurrent.CopyOnWriteArrayList;

    public class Foreground implements Application.ActivityLifecycleCallbacks {

    public static final long CHECK_DELAY = 500;
    public static final String TAG = Foreground.class.getName();

    public interface Listener {

    public void onBecameForeground();

    public void onBecameBackground();

    }

    private static Foreground instance;

    private boolean foreground = false, paused = true;
    private Handler handler = new Handler();
    private List<Listener> listeners = new CopyOnWriteArrayList<Listener>();
    private Runnable check;

    /**
    * Its not strictly necessary to use this method - _usually_ invoking
    * get with a Context gives us a path to retrieve the Application and
    * initialise, but sometimes (e.g. in test harness) the ApplicationContext
    * is != the Application, and the docs make no guarantees.
    *
    * @param application
    * @return an initialised Foreground instance
    */
    public static Foreground init(Application application){
    if (instance == null) {
    instance = new Foreground();
    application.registerActivityLifecycleCallbacks(instance);
    }
    return instance;
    }

    public static Foreground get(Application application){
    if (instance == null) {
    init(application);
    }
    return instance;
    }

    public static Foreground get(Context ctx){
    if (instance == null) {
    Context appCtx = ctx.getApplicationContext();
    if (appCtx instanceof Application) {
    init((Application)appCtx);
    }
    throw new IllegalStateException("Foreground is not initialised and cannot obtain the Application object");
    }
    return instance;
    }

    public static Foreground get(){
    if (instance == null) {
    throw new IllegalStateException("Foreground is not initialised - invoke at least once with parameterised init/get");
    }
    return instance;
    }

    public boolean isForeground(){
    return foreground;
    }

    public boolean isBackground(){
    return !foreground;
    }

    public void addListener(Listener listener){
    listeners.add(listener);
    }

    public void removeListener(Listener listener){
    listeners.remove(listener);
    }

    @Override
    public void onActivityResumed(Activity activity) {
    paused = false;
    boolean wasBackground = !foreground;
    foreground = true;

    if (check != null)
    handler.removeCallbacks(check);

    if (wasBackground){
    Log.i(TAG, "went foreground");
    for (Listener l : listeners) {
    try {
    l.onBecameForeground();
    } catch (Exception exc) {
    Log.e(TAG, "Listener threw exception!", exc);
    }
    }
    } else {
    Log.i(TAG, "still foreground");
    }
    }

    @Override
    public void onActivityPaused(Activity activity) {
    paused = true;

    if (check != null)
    handler.removeCallbacks(check);

    handler.postDelayed(check = new Runnable(){
    @Override
    public void run() {
    if (foreground && paused) {
    foreground = false;
    Log.i(TAG, "went background");
    for (Listener l : listeners) {
    try {
    l.onBecameBackground();
    } catch (Exception exc) {
    Log.e(TAG, "Listener threw exception!", exc);
    }
    }
    } else {
    Log.i(TAG, "still foreground");
    }
    }
    }, CHECK_DELAY);
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {}

    @Override
    public void onActivityStarted(Activity activity) {}

    @Override
    public void onActivityStopped(Activity activity) {}

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {}

    @Override
    public void onActivityDestroyed(Activity activity) {}
    }