[WEEX-581][android] fix 'onFocus invoked twice (#1460)

* fix @Focus invoked twice

when set @foucus & @blur method to <input> ，@Focus will be called twice when <input> is focused

android/sdk/src/main/java/com/taobao/weex/ui/component/WXComponent.java

@@ -176,6 +176,7 @@ public abstract class WXComponent<T extends View> extends WXBasicComponent imple
   public boolean mIsAddElementToTree = false;
   //for fix element case
   public int interactionAbsoluteX=0,interactionAbsoluteY=0;
+  private boolean mHasAddFocusListener = false;
 
   public WXTracing.TraceInfo mTraceInfo = new WXTracing.TraceInfo();
 
@@ -347,14 +348,17 @@ public void addEvent(final String type) {
       }
       addClickListener(mClickEventListener);
     } else if ((type.equals(Constants.Event.FOCUS) || type.equals(Constants.Event.BLUR))) {
-      addFocusChangeListener(new OnFocusChangeListener() {
+      if (!mHasAddFocusListener){
+        mHasAddFocusListener = true;
+        addFocusChangeListener(new OnFocusChangeListener() {
         @Override
         public void onFocusChange(boolean hasFocus) {
           Map<String, Object> params = new HashMap<>();
           params.put("timeStamp", System.currentTimeMillis());
           fireEvent(hasFocus ? Constants.Event.FOCUS : Constants.Event.BLUR, params);
         }
       });
+      }
     } else if (needGestureDetector(type)) {
       if (null == view) {
         // wait next time to add.