modify opening SlidingPane when the navigation icon is tapped.

app/src/main/java/chat/rocket/android/activity/MainActivity.java

@@ -3,6 +3,7 @@ package chat.rocket.android.activity;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.v4.widget.SlidingPaneLayout;
+import android.support.v7.widget.Toolbar;
 import android.view.View;
 import chat.rocket.android.LaunchUtil;
 import chat.rocket.android.R;
@@ -48,6 +49,13 @@ public class MainActivity extends AbstractAuthedActivity {
           }
         }
       });
+
+      Toolbar toolbar = (Toolbar) findViewById(R.id.activity_main_toolbar);
+      toolbar.setNavigationOnClickListener(view -> {
+        if (pane.isSlideable() && !pane.isOpen()) {
+          pane.openPane();
+        }
+      });
     }
   }