Enable changing handler's operation mode in run-time.

The handler had a bug when switching from async to sync, and vice-versa.

Because the handler variable was final, switching from async to sync would not free the retained memory. Also, and more importantly, if the handler was sync and then switched to async, a NPE would result because the handler was always null from before.

This is now fixed.

Author: Oriental Sensation

library/src/main/java/com/loopj/android/http/AsyncHttpResponseHandler.java

@@ -91,10 +91,10 @@ public abstract class AsyncHttpResponseHandler implements ResponseHandlerInterfa
 
     protected static final int BUFFER_SIZE = 4096;
 
-    private final Handler handler;
     public static final String DEFAULT_CHARSET = "UTF-8";
     private String responseCharset = DEFAULT_CHARSET;
-    private Boolean useSynchronousMode = false;
+    private Handler handler;
+    private boolean useSynchronousMode;
 
     private URI requestURI = null;
     private Header[] requestHeaders = null;
@@ -142,6 +142,21 @@ public boolean getUseSynchronousMode() {
 
     @Override
     public void setUseSynchronousMode(boolean value) {
+        // Test that a looper has been prepared prior to setting asynchronous mode.
+        if (value && null == Looper.myLooper()) {
+            value = false;
+            Log.i(LOG_TAG, "Current thread has not called Looper.prepare(). Forcing synchronous mode.");
+        }
+
+        // If using asynchronous mode.
+        if (value && handler == null) {
+            // Create a handler on current thread to submit tasks
+            handler = new ResponderHandler(this);
+        } else if (!value && handler != null) {
+            // TODO: Consider adding a flag to remove all queued messages.
+            handler = null;
+        }
+
         useSynchronousMode = value;
     }
 
@@ -163,19 +178,8 @@ public String getCharset() {
      * Creates a new AsyncHttpResponseHandler
      */
     public AsyncHttpResponseHandler() {
-	boolean missingLooper = null == Looper.myLooper();
-	// Try to create handler
-	if (!missingLooper)
-		handler = new ResponderHandler(this);
-	else {
-		// There is no Looper on this thread so synchronous mode should be used.
-		handler = null;
-		setUseSynchronousMode(true);
-		Log.i(LOG_TAG, "Current thread has not called Looper.prepare(). Forcing synchronous mode.");
-	}
-
-        // Init Looper by calling postRunnable without an argument.
-        postRunnable(null);
+        // Use asynchronous mode by default.
+        setUseSynchronousMode(true);
     }
 
     /**
@@ -314,7 +318,7 @@ protected void handleMessage(Message message) {
     }
 
     protected void sendMessage(Message msg) {
-        if (getUseSynchronousMode()) {
+        if (getUseSynchronousMode() || handler == null) {
             handleMessage(msg);
         } else if (!Thread.currentThread().isInterrupted()) { // do not send messages if request has been cancelled
             handler.sendMessage(msg);
@@ -328,9 +332,9 @@ protected void sendMessage(Message msg) {
      */
     protected void postRunnable(Runnable runnable) {
         if (runnable != null) {
-            if (getUseSynchronousMode()){
-		// This response handler is synchronous, run on current thread
-		runnable.run();
+            if (getUseSynchronousMode() || handler == null) {
+                // This response handler is synchronous, run on current thread
+                runnable.run();
             } else {
                 // Otherwise, run on provided handler
                 handler.post(runnable);
@@ -346,7 +350,15 @@ protected void postRunnable(Runnable runnable) {
      * @return Message instance, should not be null
      */
     protected Message obtainMessage(int responseMessageId, Object responseMessageData) {
-	return Message.obtain(handler, responseMessageId, responseMessageData);
+        Message msg;
+        if (handler == null) {
+            msg = Message.obtain();
+            msg.what = responseMessageId;
+            msg.obj = responseMessageData;
+        } else {
+            msg = Message.obtain(handler, responseMessageId, responseMessageData);
+        }
+        return msg;
     }
 
     @Override

library/src/main/java/com/loopj/android/http/ResponseHandlerInterface.java

@@ -104,7 +104,7 @@ public interface ResponseHandlerInterface {
     void setUseSynchronousMode(boolean useSynchronousMode);
 
     /**
-     * Can set, whether the handler should be asynchronous or synchronous
+     * Returns whether the handler is asynchronous or synchronous
      *
      * @return boolean if the ResponseHandler is running in synchronous mode
      */