Step 4: Open External Links With a Webview

In this step, you will learn:

  • How to show external web content inside your app in a secure and sandboxed way.

Estimated time to complete this step: 10 minutes.
To preview what you will complete in this step, jump down to the bottom of this page ↓.

Learn about the webview tag

Some applications need to present external web content directly to the user but keep them inside the application experience. For example, a news aggregator might want to embed the news from external sites with all the formatting, images, and behavior of the original site. For these and other usages, Chrome Apps have a custom HTML tag called webview.

The Todo app using a webview

Implement the webview tag

Update the Todo app to search for URLs in the todo item text and create a hyperlink. The link, when clicked, opens a new Chrome App window (not a browser tab) with a webview presenting the content.

Update permissions

In manifest.json, request the webview permission:

"permissions": [ "storage", "alarms", "notifications", "webview" ],

Create a webview embedder page

Create a new file in the root of your project folder and name it webview.html. This file is a basic webpage with one <webview> tag:

<!DOCTYPE html> <html> <head> <meta charset="utf-8"> </head> <body> <webview style="width: 100%; height: 100%;"></webview> </body> </html>

Parse for URLs in todo items

At the end of controller.js, add a new method called _parseForURLs():

 Controller.prototype._getCurrentPage = function () {  return document.location.hash.split('/')[1];  };  Controller.prototype._parseForURLs = function (text) {  var re = /(https?:\/\/[^\s"<>,]+)/g;  return text.replace(re, '<a href="$1" data-src="$1">$1</a>');  };  // Export to window  window.app.Controller = Controller; })(window);

Whenever a string starting with "http://" or "https://" is found, a HTML anchor tag is created to wrap around the URL.

Find showAll() in controller.js. Update showAll() to parse for links by using the _parseForURLs() method added previously:

/**  * An event to fire on load. Will get all items and display them in the  * todo-list  */ Controller.prototype.showAll = function () {  this.model.read(function (data) {  this.$todoList.innerHTML = this.view.show(data);  this.$todoList.innerHTML = this._parseForURLs(this.view.show(data));  }.bind(this)); };

Do the same for showActive() and showCompleted():

/**  * Renders all active tasks  */ Controller.prototype.showActive = function () {  this.model.read({ completed: 0 }, function (data) {  this.$todoList.innerHTML = this.view.show(data);  this.$todoList.innerHTML = this._parseForURLs(this.view.show(data));  }.bind(this)); }; /**  * Renders all completed tasks  */ Controller.prototype.showCompleted = function () {  this.model.read({ completed: 1 }, function (data) {  this.$todoList.innerHTML = this.view.show(data);  this.$todoList.innerHTML = this._parseForURLs(this.view.show(data));  }.bind(this)); };

And finally, add _parseForURLs() to editItem():

Controller.prototype.editItem = function (id, label) {  ...  var onSaveHandler = function () {  ...  // Instead of re-rendering the whole view just update  // this piece of it  label.innerHTML = value;  label.innerHTML = this._parseForURLs(value);  ...  }.bind(this);  ... }

Still in editItem(), fix the code so that it uses the innerText of the label instead of the label's innerHTML:

Controller.prototype.editItem = function (id, label) {  ...  // Get the innerHTML of the label instead of requesting the data from the  // Get the innerText of the label instead of requesting the data from the  // ORM. If this were a real DB this would save a lot of time and would avoid  // a spinner gif.  input.value = label.innerHTML;  input.value = label.innerText;  ... }

Open new window containing webview

Add a _doShowUrl() method to controller.js. This method opens a new Chrome App window via chrome.app.window.create() with webview.html as the window source:

 Controller.prototype._parseForURLs = function (text) {  var re = /(https?:\/\/[^\s"<>,]+)/g;  return text.replace(re, '<a href="$1" data-src="$1">$1</a>');  };  Controller.prototype._doShowUrl = function(e) {  // only applies to elements with data-src attributes  if (!e.target.hasAttribute('data-src')) {  return;  }  e.preventDefault();  var url = e.target.getAttribute('data-src');  chrome.app.window.create(  'webview.html',  {hidden: true}, // only show window when webview is configured  function(appWin) {  appWin.contentWindow.addEventListener('DOMContentLoaded',  function(e) {  // when window is loaded, set webview source  var webview = appWin.contentWindow.  document.querySelector('webview');  webview.src = url;  // now we can show it:  appWin.show();  }  );  });  };  // Export to window  window.app.Controller = Controller; })(window);

In the chrome.app.window.create() callback, note how the webview's URL is set via the src tag attribute.

Lastly, add a click event listener inside the Controller constructor to call doShowUrl() when a user clicks on a link:

function Controller(model, view) {  ...  this.router = new Router();  this.router.init();  this.$todoList.addEventListener('click', this._doShowUrl);  window.addEventListener('load', function () {  this._updateFilterState();  }.bind(this));  ... }

Launch your finished Todo app

You are done Step 4! If you reload your app and add a todo item with a full URL starting with http:// or https://, you should see something like this:

For more information

For more detailed information about some of the APIs introduced in this step, refer to:

Ready to continue onto the next step? Go to Step 5 - Add images from the web »