Add methods to be used by both button presses and gesture detection

HW4/src/com/example/hw4/ImageViewerActivity.java

@@ -32,17 +32,27 @@ public class ImageViewerActivity extends Activity {
 	}
 	
 	public void onClickPrev(View v) {
-		
+		displayPrev();
 	}
 		
 	public void onClickNext(View v) {
-		
+		displayNext();
 	}
 	
 	public void onClickBack(View v) {
 		finish();
 	}
 	
+	private void displayPrev() {
+		currentIndex -= 1;
+		displayImage(currentIndex);
+	}
+	
+	private void displayNext() {
+		currentIndex += 1;
+		displayImage(currentIndex);
+	}
+	
 	public void displayImage(int indexToDisplay) {