Load contents on demand in ViewPager

When i open a page in ViewPager, it instantiates the n开发者_运维问答eighboring pages. What I would like to achieve is

1.load the contents the page only when the page is on focus.

2.show a loading screen, while i populate the page layout which is on focus and replace the loading screen with page layout after that.

Can someone point me in the right direction to achieve these 2 features?

I'm not sure of a good way to solve your first question (I don't believe you can control which pages get loaded, and in which order), but I have something that can help for your second:

Here is an example of a view I created that is loaded in every view of my ViewPager:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:gravity="center">
    <LinearLayout 
        android:id="@+id/loading_message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <ProgressBar 
            style="@style/GenericProgressIndicator"/>
        <TextView
            android:id="@+id/loading_message_text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/loading_message_text"/>
    </LinearLayout>
    <WebView
        android:id="@+id/webview"
        android:layout_height="fill_parent"
        android:layout_width="fill_parent"
        android:fadingEdge="vertical"
        android:visibility="gone"
        />
</RelativeLayout>

There are two elements nested in the RelativeLayout: a LinearLayout that represents my loading message (including a ProgressBar and a TextView) and a WebView that will hold my content once it is loaded. The WebView initially has its visibility set to GONE to completely hide it. In code, I inflate the view and start an AsyncTask to load my data. Once the data is loaded, I set the LinearLayout's visibility to GONE and the WebView's visibility to VISIBLE.

onPostExecute in my AsyncTask - after the data is loaded, hide the loading message and show the data

protected void onPostExecute(Void v)
{
    LinearLayout loadingMessage = (LinearLayout)articleLayout.findViewById(R.loading_message);
    WebView articleContent = (WebView)articleLayout.findViewById(R.id.webview);

    [...]
    loadingMessage.setVisibility(View.GONE);
    articleContent.setVisibility(View.VISIBLE);

}