Syncing PDF Annotations in Flutter
By default, PSPDFKit Instant automatically synchronizes annotations with your Document Engine instance in real time. This is configurable, and you can instead choose for it to sync manually when your app requests it.
Using a network, especially a cellular network, is one of the most energy-intensive tasks on mobile devices. While we do our best to minimize the energy impact of Instant, it can be reduced further by disabling listening for changes from the server or by syncing less often after local changes are made.
Syncing after making local changes and listening for server changes can be configured separately. However, syncing always sends all local changes and fetches all changes from the server. It isn’t possible to fetch remote changes without pushing local changes or to push local changes without fetching remote changes.
By default, when you show a document managed by Instant in an
InstantPdfFragment on Android and an
InstantViewController on iOS , real-time syncing of annotations is fully automatic: Instant will push local changes to the server as they happen and listen for changes from the server.
Instant uses the network efficiently by coalescing changes with a one-second delay. You can reduce energy consumption at the cost of less immediate syncing by using
Pspdfkit.setDelayForSyncingLocalChanges to increase the delay.
Disabling Listening for Server Changes
If your app doesn’t require real-time syncing, it may be better to manually fetch changes from the server to reduce energy consumption — for example, when the view showing the document appears, or with a button the user can tap.
If you show the document in a native module , you can disable listening by using
Pspdfkit.setListenToServerChanges(false). Then, sync manually whenever you want to by calling
Disabling Syncing after Local Changes
In addition to disabling listening for changes from the server (see above), you can disable syncing after local changes are made by calling
Pspdfkit.setDelayForSyncingLocalChanges(). This means that Instant will never sync annotations with the server unless your app requests this by calling
It’s possible to configure Instant to not sync after local changes are made but to listen for changes. However, this combination makes little sense and isn’t recommended, as the local changes would be pushed at seemingly random times when changes are received from the server.