androidlocalstorage's Introduction

AndroidLocalStorage

LocalStorage is partially broken in Android webviews : Local storage is supposed to be a persistent storage available accros all tabs (or windows) of a browser. On Android, LocalStorage works well but only in the current webview. Multiple webviews of the same app can't share the same data with LocalStorage. That is sad !

JavaScriptInterface to the rescue !

This sample Android app shows you how you can fix the webview LocalStorage with a JavaScriptInterface.

What we do here is :

Create an Android database with a simple key/value table
Create a JavaScriptInterface which implements all LocalStorage's methods (getItem, setItem, removeItem, clear)
Add it to the webview
Replace the JavaScript LocalStorage with this "new one" so that you don't have to change the way you use your localStorage usually.

How to use it in your own project ?

Include the LocalStorage.java
Create the JavaScriptInterface and add it to the webview as shown in MainFragment.java
Bind the JavaScript LocalStorage to the new one as shown in assets/index.html

This last step is as simple as this :

<script type="text/javascript">
        try{
            //we replace default localStorage with our Android Database one
            window.localStorage=LocalStorage;    
        }catch(e){
            //LocalStorage class was not found. be sure to add it to the webview
		         	alert("LocalStorage ERROR : can't find android class LocalStorage. switching to raw localStorage")		        
		      }
    //then use your localStorage as usual
    localStorage.setItem('foo','it works')
    alert(localStorage.getItem('foo'))
    
</script>

Play with this example project to see how it works.

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