Android Fortschrittsbalken in Swipe-Layout unsichtbar

Question

In einer Layoutdatei möchte ich eine Fortschrittsanzeige und eine swipeable Webview zeigen. Wenn ich das Wischlayout implementiere, verschwindet die Fortschrittsleiste automatisch und kann nicht angezeigt werden.

Was ist das Problem?

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    xmlns:mlns="http://schemas.android.com/apk/res-auto" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context="com.xy.MainActivity"> 

    <ProgressBar 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:id="@+id/progressBarCenter" 
    android:layout_centerVertical="true" 
    android:layout_centerHorizontal="true" 
    android:visibility="visible" 
    android:background="#ff0303" /> 

<android.support.v4.widget.SwipeRefreshLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    xmlns:mlns="http://schemas.android.com/apk/res-auto" 
    android:id="@+id/swiper" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context="com.xy.MainActivity"> 

    <WebView 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" 
     android:id="@+id/webView" 
     android:layout_alignParentTop="true" 
     android:layout_alignParentLeft="true" 
     android:layout_alignParentStart="true" /> 
</android.support.v4.widget.SwipeRefreshLayout> 
</RelativeLayout> 

Answer 1

Es ist, weil SwipeRefreshLayout ist ProgressBar abdeckt. In RelativeLayout bedeutet der, der im Xml unten liegt, höher in der Z-Achse.

Umgekehrt sollte die Reihenfolge funktionieren.

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    xmlns:mlns="http://schemas.android.com/apk/res-auto" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    tools:context="com.xy.MainActivity"> 

    <android.support.v4.widget.SwipeRefreshLayout 
     xmlns:android="http://schemas.android.com/apk/res/android" 
     xmlns:tools="http://schemas.android.com/tools" 
     xmlns:mlns="http://schemas.android.com/apk/res-auto" 
     android:id="@+id/swiper" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     tools:context="com.xy.MainActivity"> 

     <WebView 
      android:layout_width="fill_parent" 
      android:layout_height="fill_parent" 
      android:id="@+id/webView" 
      android:layout_alignParentTop="true" 
      android:layout_alignParentLeft="true" 
      android:layout_alignParentStart="true" /> 
    </android.support.v4.widget.SwipeRefreshLayout> 

    <ProgressBar 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/progressBarCenter" 
     android:layout_centerVertical="true" 
     android:layout_centerHorizontal="true" 
     android:visibility="visible" 
     android:background="#ff0303" /> 
</RelativeLayout>