Android: Added a virtual backButtonPressed() method to JUCEApplicationBase which can be overridden to be informed when the back button is pressed on a device.

modules/juce_core/native/java/JuceAppActivity.java

@@ -630,6 +630,7 @@ public class JuceAppActivity   extends Activity
         //==============================================================================
         private native void handleKeyDown (long host, int keycode, int textchar);
         private native void handleKeyUp (long host, int keycode, int textchar);
+        private native void handleBackButton (long host);
 
         public void showKeyboard (String type)
         {
@@ -657,8 +658,14 @@ public class JuceAppActivity   extends Activity
                 case KeyEvent.KEYCODE_VOLUME_UP:
                 case KeyEvent.KEYCODE_VOLUME_DOWN:
                     return super.onKeyDown (keyCode, event);
+                case KeyEvent.KEYCODE_BACK:
+                {
+                    handleBackButton (host);
+                    return true;
+                }
 
-                default: break;
+                default:
+                    break;
             }
 
             handleKeyDown (host, keyCode, event.getUnicodeChar());

modules/juce_events/messages/juce_ApplicationBase.h

@@ -188,6 +188,13 @@ public:
                                      const String& sourceFilename,
                                      int lineNumber) = 0;
 
+    //==============================================================================
+    /** Override this method to be informed when the back button is pressed on a device.
+
+        This is currently only implemented on Android devices.
+     */
+    virtual void backButtonPressed() { }
+
     //==============================================================================
     /** Signals that the main message loop should stop and the application should terminate.
 

modules/juce_gui_basics/native/juce_android_Windowing.cpp

@@ -437,6 +437,12 @@ public:
     {
     }
 
+    void handleBackButtonCallback()
+    {
+        if (JUCEApplicationBase* const app = JUCEApplicationBase::getInstance())
+            app->backButtonPressed();
+    }
+
     //==============================================================================
     bool isFocused() const override
     {
@@ -664,6 +670,7 @@ JUCE_VIEW_CALLBACK (void, viewSizeChanged,  (JNIEnv* env, jobject /*view*/, jlon
 JUCE_VIEW_CALLBACK (void, focusChanged,     (JNIEnv* env, jobject /*view*/, jlong host, jboolean hasFocus),                       handleFocusChangeCallback (hasFocus))
 JUCE_VIEW_CALLBACK (void, handleKeyDown,    (JNIEnv* env, jobject /*view*/, jlong host, jint k, jint kc),                         handleKeyDownCallback ((int) k, (int) kc))
 JUCE_VIEW_CALLBACK (void, handleKeyUp,      (JNIEnv* env, jobject /*view*/, jlong host, jint k, jint kc),                         handleKeyUpCallback ((int) k, (int) kc))
+JUCE_VIEW_CALLBACK (void, handleBackButton, (JNIEnv* env, jobject /*view*/, jlong host),                                          handleBackButtonCallback())
 
 //==============================================================================
 ComponentPeer* Component::createNewPeer (int styleFlags, void*)