Is local storage for a Phonegap app on an Android

问题:

My question is essentially a follow up or clarification to this question.

I have an Android app built using Javascript and Adobe's Phonegap Build service, and I'm using "local storage" to store data on the device.

From that other question, I learned that data stored in local storage is essentially "permanent", in that it will stay on the device indefinitely, unless the user acts on it by manually clearing the cache for the app or deletes the app (and maybe other unusual circumstances that I'm willing to live with).

However, part of the accepted answer was confusing to me in that it started to blur the lines between talking about the phone's browser and talking about a Phonegap app.

What is unclear to me is if an app on Android using Phonegap uses the same cache as the phone's built in browser. Is Phonegap essentially an extension of the existing browser facility, or is it it's own separate stand-alone and self contained browser?

Critically, if a user clears the cache in their browser, will that impact an installed app based on Phonegap?

回答1:

Since Phonegap uses Webiview to render your app : WebView and Phonegap.

And For security reason each app that uses WebView has its own cache and history. "No User or OS wants such data to be accessed by 3rd party applications". So in a nutshell, your app will keep its own history and data in its cache folder and will be deleted in one of the following cases:

• User manually deleted them.
• User used app setting screen and deleted them.
• App uninstalled.

To read more about this. take look at WebView cache : Cookie and window management

回答2:

Nope, the cache created within the in-app browser can only be deleted with the methods:

window.localStorage.removeItem("key");

or

window.localStorage.clear();

or app uninstall

or manual action (delete data/cache) in the application manager.

But the best answer is to make an experiment yourself and see what happens.

回答3:

Yes it is separate but there are time where you need to pass a variable of some kind to the In App Browser. It makes coding so much more easier to pass a ls item from a current webview to another one like in iOS.

Here is what I did in PhoneGap

I use the InAppBrowser executeScript() to pass a copy of the current webviews localStorage to another.

//add the listener to detect when the page loads after inappbrowser is called into view
ref.addEventListener('loadstop', function(){
     ref.executeScript({code: 'SetInAppBrowserLocalStorage(\''+localStorage+'\');'});
});

---

//In your inAppBrowser page you create a function that  will get called on loadStop
//This will pass "all" the contents of the main webviws localStorage to the webview 
//created by InAppBrowser
function SetInAppBrowserLocalStorage(localStorageThatWasPassed){
    localStorage = localStorageThatWasPassed;
};

You could also clear the localStorage created by SetInAppBrowserLocalStorage() before the use leaves that view as well.

Tested and working 100% :)...let me know if you need more help

***UPDATE*****

This still works ...but not consistently anymore. After much testing I realize this is simply not the way to go. Sometimes the data simply is not passed fast enough when the inappbrowser instance is created. I talked to the cordova guys via there issue tracker and they told me it wasn't a secure way of doing things...I get that...but my response to them was what if I just want to pass ls variables between pages in my app..those are not even accessible from the internet... I honestly don't understand why the ls items can't be accessible globally in the app like it is in iOS and the rest of the web. If anyone has a better solution I would love to hear about it.

回答4:

By making this setting in your mainActivity (which is extending Droidgap.)

  super.appView.getSettings().setCacheMode(WebSettings.LOAD_NO_CACHE);

We are making our app to not to store cache.