Add XHR-based callbacks from Java to JavaScript.

framework/assets/js/phonegap.js.base

@@ -67,6 +67,9 @@ PhoneGap.addConstructor = function(func) {
 					}
 				}
             }
+            // Start listening for callbacks from Java
+            PhoneGap.JSCallback();
+
 			// all constructors run, now fire the deviceready event
 			var e = document.createEvent('Events'); 
 			e.initEvent('deviceready');
@@ -133,3 +136,48 @@ PhoneGap.run_command = function() {
     document.location = url;
 
 };
+
+/**
+ * Internal function that uses XHR to call into PhoneGap Java code and retrieve 
+ * any JavaScript code that needs to be run.  This is used for callbacks from
+ * Java to JavaScript.
+ */
+PhoneGap.JSCallback = function() {
+    var xmlhttp = new XMLHttpRequest();
+
+    // Callback function when XMLHttpRequest is ready
+    xmlhttp.onreadystatechange=function(){
+        if(xmlhttp.readyState == 4){
+
+            // If callback has JavaScript statement to execute
+            if (xmlhttp.status == 200) {
+
+                var msg = xmlhttp.responseText;
+                setTimeout(function() {
+                    try {
+                        var t = eval(msg);
+                    }
+                    catch (e) {
+                        console.log("JSCallback Error: "+e);
+                    }
+                }, 1);
+                setTimeout(PhoneGap.JSCallback, 1);
+            }
+
+            // If callback ping (used to keep XHR request from timing out)
+            else if (xmlhttp.status == 404) {
+                setTimeout(PhoneGap.JSCallback, 10);
+            }
+
+            // If error, restart callback server
+            else {
+                console.log("JSCallback Error: Request failed.");
+                CallbackServer.restartServer();
+                setTimeout(PhoneGap.JSCallback, 100);
+            }
+        }
+    }
+
+    xmlhttp.open("GET", "http://127.0.0.1:"+CallbackServer.getPort()+"/" , true);
+    xmlhttp.send();
+}

framework/src/com/phonegap/CompassListener.java

@@ -9,46 +9,97 @@ import android.hardware.SensorManager;
 import android.content.Context;
 import android.webkit.WebView;
 
+/**
+ * This class listens to the compass sensor and calls navigator.compass.setHeading(heading)
+ * method in Javascript every sensor change event it receives.
+ */
 public class CompassListener implements SensorEventListener{
-	WebView mAppView;
-	Context mCtx;
-	Sensor mSensor;	
+
+	public static int STOPPED = 0;
+	public static int STARTING = 1;
+    public static int RUNNING = 2;
+    public static int ERROR_FAILED_TO_START = 3;
 	
-	private SensorManager sensorManager;
+    WebView mAppView;					// WebView object
+    DroidGap mCtx;						// Activity (DroidGap) object
+
+    int status;							// status of listener
 	
+    private SensorManager sensorManager;// Sensor manager
+    Sensor mSensor;						// Compass sensor returned by sensor manager
+	
+	/**
+	 * Constructor.
+	 * 
+	 * @param appView
+	 * @param ctx			The Activity (DroidGap) object
+	 */
 	CompassListener(WebView appView, Context ctx)
 	{
-		mCtx = ctx;
-		mAppView = appView;		
-		sensorManager = (SensorManager) mCtx.getSystemService(Context.SENSOR_SERVICE);
+		this.mCtx = (DroidGap)ctx;
+		this.mAppView = appView;
+		this.sensorManager = (SensorManager) mCtx.getSystemService(Context.SENSOR_SERVICE);
 	}
 	
+    /**
+     * Start listening for compass sensor.
+     * 
+     * @return 			status of listener
+     */
+	public int start() {
 
-	public void start()
-	{
+		// Get accelerometer from sensor manager
 		List<Sensor> list = this.sensorManager.getSensorList(Sensor.TYPE_ORIENTATION);
-		if (list.size() > 0)
-		{
+
+        // If found, then register as listener
+		if (list.size() > 0) {
 			this.mSensor = list.get(0);
 			this.sensorManager.registerListener(this, this.mSensor, SensorManager.SENSOR_DELAY_NORMAL);
+            this.status = CompassListener.STARTING;
 		}
-		
+
+		// If error, then set status to error
+        else {
+            this.status = CompassListener.ERROR_FAILED_TO_START;
+        }
+        
+        return this.status;
 	}
 	
-	public void stop()
-	{
-		this.sensorManager.unregisterListener(this);
+    /**
+     * Stop listening to compass sensor.
+     */
+	public void stop() {
+        if (this.status != CompassListener.STOPPED) {
+        	this.sensorManager.unregisterListener(this);
+        }
+        this.status = CompassListener.STOPPED;
+	}
+	
+    /**
+     * Called when listener is to be shut down and object is being destroyed.
+     */
+	public void destroy() {
+		this.stop();
 	}
 	
 	public void onAccuracyChanged(Sensor sensor, int accuracy) {
-		// TODO Auto-generated method stub
-		
+		// TODO Auto-generated method stub	
 	}
 
-
+    /**
+     * Sensor listener event.
+     * 
+     * @param SensorEvent event
+     */
 	public void onSensorChanged(SensorEvent event) {
+
 		// We only care about the orientation as far as it refers to Magnetic North
 		float heading = event.values[0];
-		mAppView.loadUrl("javascript:navigator.compass.setHeading(" + heading + ")");
+
+		this.status = CompassListener.RUNNING;
+		
+		// TODO This is very expensive to process every event. Should this use polling from JS instead?
+        mCtx.sendJavascript("navigator.compass.setHeading(" + heading + ");");
 	}
 }

framework/src/com/phonegap/DroidGap.java

@@ -72,6 +72,7 @@ public class DroidGap extends Activity {
 	private CryptoHandler crypto;
 	private BrowserKey mKey;
 	private AudioHandler audio;
+    private CallbackServer callbackServer;
 
 	private Uri imageUri;
 	
@@ -185,10 +186,38 @@ public class DroidGap extends Activity {
     	if (accel != null) {
     		accel.destroy();
     	}
+    	if (launcher != null) {
+    		
+    	}
+    	if (mContacts != null) {
+    		
+    	}
+    	if (fs != null) {
+    		
+    	}
+    	if (netMan != null) {
+    		
+    	}
+    	if (mCompass != null) {
+    		mCompass.destroy();
+    	}
+    	if (crypto != null) {
+    		
+    	}
+    	if (mKey != null) {
+    		
+    	}
+    	if (audio != null) {
+    		
+    	}
+    	if (callbackServer != null) {
+    		callbackServer.destroy();
+    	}
     }
 
     private void bindBrowser(WebView appView)
     {
+        callbackServer = new CallbackServer();
     	gap = new Device(appView, this);
     	accel = new AccelBroker(appView, this);
     	launcher = new CameraLauncher(appView, this);
@@ -211,7 +240,7 @@ public class DroidGap extends Activity {
     	appView.addJavascriptInterface(crypto, "GapCrypto");
     	appView.addJavascriptInterface(mKey, "BackButton");
     	appView.addJavascriptInterface(audio, "GapAudio");
-    	
+        appView.addJavascriptInterface(callbackServer, "CallbackServer");
     	
     	if (android.os.Build.VERSION.RELEASE.startsWith("1."))
     	{
@@ -227,6 +256,25 @@ public class DroidGap extends Activity {
 	{
 		appView.loadUrl(url);
 	}
+    
+    /**
+     * Send JavaScript statement back to JavaScript.
+     * 
+     * @param message
+     */
+    public void sendJavascript(String statement) {
+    	System.out.println("DroidGap.sendResponse("+statement+")");
+    	this.callbackServer.sendJavascript(statement);
+    }
+    
+    /**
+     * Get the port that the callback server is listening on.
+     * 
+     * @return
+     */
+    public int getPort() {
+    	return this.callbackServer.getPort();
+    }
 	
 	
   /**