Dialog: some fixes for CTS

Most Dialog test still fail, because we don't handle KeyEvents

src/api-impl-jni/app/android_app_Dialog.c

@@ -50,3 +50,9 @@ JNIEXPORT void JNICALL Java_android_app_Dialog_nativeClose(JNIEnv *env, jobject
 	GtkWindow *dialog = GTK_WINDOW(_PTR(ptr));
 	gtk_window_close(dialog);
 }
+
+JNIEXPORT jboolean JNICALL Java_android_app_Dialog_nativeIsShowing(JNIEnv *env, jobject this, jlong ptr)
+{
+	GtkWindow *dialog = GTK_WINDOW(_PTR(ptr));
+	return gtk_widget_is_visible(GTK_WIDGET(dialog));
+}

src/api-impl-jni/generated_headers/android_app_Dialog.h

@@ -47,6 +47,14 @@ JNIEXPORT void JNICALL Java_android_app_Dialog_nativeShow
 JNIEXPORT void JNICALL Java_android_app_Dialog_nativeClose
   (JNIEnv *, jobject, jlong);
 
+/*
+ * Class:     android_app_Dialog
+ * Method:    nativeIsShowing
+ * Signature: (J)Z
+ */
+JNIEXPORT jboolean JNICALL Java_android_app_Dialog_nativeIsShowing
+  (JNIEnv *, jobject, jlong);
+
 #ifdef __cplusplus
 }
 #endif

src/api-impl/android/app/DatePickerDialog.java

@@ -1,6 +1,12 @@
 package android.app;
 
-public class DatePickerDialog {
+import android.content.Context;
+
+public class DatePickerDialog extends Dialog {
+
+	public DatePickerDialog(Context context) {
+		super(context);
+	}
 
 	public interface OnDateSetListener {}
 }

src/api-impl/android/app/Dialog.java

@@ -20,6 +20,7 @@ public class Dialog implements Window.Callback, DialogInterface {
 	private native void nativeSetContentView(long ptr, long widget);
 	private native void nativeShow(long ptr);
 	private native void nativeClose(long ptr);
+	private native boolean nativeIsShowing(long ptr);
 
 	private Context context;
 	private Window window;
@@ -90,7 +91,7 @@ public class Dialog implements Window.Callback, DialogInterface {
 	}
 
 	public boolean isShowing() {
-		return false;
+		return nativeIsShowing(nativePtr);
 	}
 
 	public void dismiss() {