====== Track and Manage Viewer Plugin State ======
Closing your host application usually means that the viewer component is destroyed and loses all state. The SDK offers a mechanism to a) be notified when you should save viewer state and b) restore the viewer using that state. These can be used to persist viewer state across host application sessions.
This "state" object is made available as a string.
===== Saving state =====
To listen for state changes, we listen to the ''onAppStateChanged'' signal of the viewer. Save state whenever it changes.
// Listen to the state-changed signal
viewer.onAppStateChanged.add(handleAppStateChanged);
===== Loading state on startup =====
When creating the viewer, you have the ability to pass [[glossary|startup options]]. The available options are defined by the ''Constants'' class. You can use the ''Constants.STARTUP_APP_STATE'' startup option to restore a previously saved state.
Startup options can be provided only once.
===== Example =====
Below is a Javascript-specific example using ''window.localStorage'' for storing state.\\
Try logging in to the viewer with "Remember me" checked, and refresh the page.
var viewer;
/**
* Called when something changes to the viewer state.
*/
function handleAppStateChanged(state) {
// Save state somewhere...
window.localStorage.setItem("m3dviewer_state",state);
}
/**
* Called when the viewer component is ready for interaction.
*/
function handleReady() {
// Listen to the state-changed signal
viewer.onAppStateChanged.add(handleAppStateChanged);
}
/**
* Called when the page is full loaded.
*/
function handleDOMReady() {
// Create viewer startup options
var options = new orbitgt.mapping3d.sdk.viewer.AMap();
options.set(orbitgt.mapping3d.sdk.viewer.Constants.STARTUP_APP_STATE,window.localStorage.getItem("m3dviewer_state"));
// Create viewer
var appElement = document.getElementById("m3dviewer");
viewer = new orbitgt.mapping3d.sdk.viewer.SDKViewer("example application",appElement,options);
viewer.setSize(600,400);
viewer.isReady.then(handleReady);
}
// Wait for page to load
document.addEventListener("DOMContentLoaded", handleDOMReady);