enable cancelling editing nickname with simple UI

app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationActivity.java

@@ -274,6 +274,7 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
   private   ImageView                   muteIndicatorImageView;
   private   TextView                    subtitleTextView;
   private   View                        homeButtonContainer;
+  private   View                        cancelButtonContainer;
 
   private   AttachmentTypeSelector attachmentTypeSelector;
   private   AttachmentManager      attachmentManager;
@@ -398,10 +399,12 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
             textView.setText(getRecipient().getName());
           }
           imm.hideSoftInputFromWindow(v.getWindowToken(),0);
+          cancelButtonContainer.setVisibility(View.GONE);
         } else {
           String nickname = DatabaseFactory.getStorage(this).getDisplayName(getRecipient().getAddress().serialize());
           titleTextView.setText(nickname);
           imm.showSoftInput(v, 0);
+          cancelButtonContainer.setVisibility(View.VISIBLE);
         }
       });
     }
@@ -1293,6 +1296,7 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
     muteIndicatorImageView                 = ViewUtil.findById(this, R.id.muteIndicatorImageView);
     subtitleTextView                       = ViewUtil.findById(this, R.id.subtitleTextView);
     homeButtonContainer                    = ViewUtil.findById(this, R.id.homeButtonContainer);
+    cancelButtonContainer                  = ViewUtil.findById(this, R.id.cancelButtonContainer);
 
     ImageButton quickCameraToggle      = ViewUtil.findById(this, R.id.quick_camera_toggle);
     ImageButton inlineAttachmentButton = ViewUtil.findById(this, R.id.inline_attachment_button);
@@ -1338,6 +1342,10 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
     inlineAttachmentButton.setOnClickListener(v -> handleAddAttachment());
 
     homeButtonContainer.setOnClickListener(v -> onSupportNavigateUp());
+
+    cancelButtonContainer.setOnClickListener(v -> {
+      titleTextView.clearFocus();
+    });
   }
 
   protected void initializeActionBar() {

app/src/main/res/layout/conversation_activity.xml

@@ -99,6 +99,26 @@
                 android:layout_height="match_parent"
                 android:layout_weight="1" />
 
+            <LinearLayout
+                android:id="@+id/cancelButtonContainer"
+                android:layout_width="wrap_content"
+                android:layout_height="match_parent"
+                android:gravity="center_vertical"
+                android:clickable="true"
+                android:focusable="true"
+                android:visibility="gone">
+
+                <ImageView
+                    android:layout_width="18dp"
+                    android:layout_height="18dp"
+                    android:src="@drawable/ic_baseline_clear_24"
+                    android:layout_marginRight="8dp"
+                    android:layout_marginLeft="8dp" />
+
+            </LinearLayout>
+
+
+
         </LinearLayout>
 
     </androidx.appcompat.widget.Toolbar>