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POAvoid page switching in a ViewPager until the content on the next page is ready
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  1. POAvoid page switching in a ViewPager until the content on the next page is ready
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    copied!<p>I am using a ViewPager so the user can browse through an infinite collection of images that need to be fetched from the Internet.</p> <p>I would not like to change to the next/previous page, unless its image has already been loaded. So if the user swiped right/left, the current image would still be on display with a progressbar spinning on top, and the change to the next/previous page would not be performed until the image was ready. At that very instant pages would swap and the progressbar would disappear.</p> <p>At the moment I was trying to implement this using the following layout for the children views of the ViewPager and a FragmentStatePageAdapter.</p> <pre><code>&lt;FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" &gt; &lt;ImageView android:id="@+id/imageview" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:contentDescription="@string/label_painting" android:visibility="gone" /&gt; &lt;ProgressBar android:id="@+id/progressbar" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:visibility="gone" /&gt; &lt;/FrameLayout&gt; </code></pre> <p>In the Fragment I follow the steps listed below: </p> <ul> <li>In its onCreateView I make the progressbar visible.</li> <li>In that same method I start a thread that fetches the image and decodes the byte stream into a bitmap. </li> <li>Once the bitmap is available, the thread sends a message to a handler that sets the bitmap in the ImageView, makes it visible and hides the progressbar.</li> </ul> <p>The problem with this approach I am following is that in case the image has not been fetched yet when the user swipes, the previous image disappears and he sees a spinning progressbar until the new image is available. It would be much nicer to keep seeing an image.</p> <p>Has anyone been able to implement this with a ViewPager or knows what could I change in my code?</p> <p>Thanks in advance.</p>
 

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