Reduce memory consumption

In order to achieve smoother viewing experience, PDFViewCtrl keeps certain amount of invisible content. However, keeping invisible content increases memory usage. Android sets an upper bound on the VM heap size allowed for an app. By default, PDFViewCtrl is set to use a quarter of maximum VM heap size for keeping visible and invisible content. Based on the memory footprint of your app, you may want to customize it.

To customize the memory usage:

var allowedMax = Runtime.GetRuntime().MaxMemory() / (1024 * 1024);
//should NOT use close to allowed_max
pdfViewCtrl.SetRenderedContentCacheSize(allowedMax * 0.25);

where pdfViewCtrl is an instance of PDFViewCtrl.

Question:

We are experiencing a lot of out of memory errors when rotating the device multiple times. Since the Activity is destroyed while rotating, we get a new (quite heavy) PDFViewCtrl every time we rotate the device.

Answer:

PDFViewCtrl can handle rotation properly, it is recommended that you configure your activity to handle configuration changes. This way the view will not be recreated and it will be resized accordingly.

1. In your app AndroidManifest.xml file, add android:configChanges to your activity tag.

   <activity
       android:configChanges="keyboardHidden|orientation|screenSize|screenLayout|smallestScreenSize"
       >
     </activity>

2. Override onConfigurationChanged() in your activity:

   public override void OnConfigurationChanged(Android.Content.Res.Configuration newConfig)
   {
       base.OnConfigurationChanged(newConfig);
       mPdfViewCtrl?.OnConfigurationChanged(newConfig);
   }

   where mPdfViewCtrl is an instance of PDFViewCtrl.

On Android 3.0 and above, you can also increase the allowed heap size of an app.

In your app AndroidManifest.xml file, add the android:largeHeap="true" attribute to the <application> tag:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  >
  <application
    android:largeHeap="true"
    >
  </application>

</manifest>