To deliver a web application or some web pages as a part of an android client application,
you can do it using
The
How to get started with
To add a
Following is full example in onCreate function:
WebView
.The
WebView
class is an
extension of Android's View
class that allows you to display web pages as a
part of your activity layout. It does not include web
browser, navigation controls or an address bar,.. just web page content.WebView can be used to
display static document that's
hosted online.WebView can also be used to
build dynamic data for users.How to get started with
WebView
? How to do some
additional things, such as handle page navigation and bind JavaScript from your web page to
client-side code in your Android application.1-Adding a WebView to Your Application
To add a
WebView
to your Application, simply include the <WebView>
element in your activity layout. For example, here's a layout file in which the
WebView
fills the screen (in webview.xml, for example):<?xml version="1.0" encoding="utf-8"?> <WebView xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/webview" android:layout_width="fill_parent" android:layout_height="fill_parent" />To load a web page in the
WebView
, use loadUrl()
. For example, in MainActivity.java:WebView myWebView = (WebView) findViewById(R.id.webview); myWebView.loadUrl("http://countrytex.blogspot.com");Before this will work, however, your application must have access to the Internet. To get Internet access, request the
INTERNET
permission in your
manifest file. For example, in AndroidManifest.xml:<manifest ... > <uses-permission android:name="android.permission.INTERNET" /> ...</manifest>
That's all basic of
WebView
that can displays a web page.2-Using JavaScript in WebView
If the web page you plan to load in your
WebView
use JavaScript, you must enable JavaScript for your WebView
. Once JavaScript is enabled, you can also create interfaces between your application code and your JavaScript code.2.1 Enabling JavaScript
JavaScript is disabled in a
WebView
by default. You can enable it through the WebSettings
attached to your WebView
. You can retrieve WebSettings
with getSettings()
, then enable JavaScript with setJavaScriptEnabled()
.
For example:
WebView myWebView = (WebView) findViewById(R.id.webview); WebSettings webSettings = myWebView.getSettings(); webSettings.setJavaScriptEnabled(true);
WebSettings
provides access to a variety of other settings that you might find useful. For example, if you're developing a web application that's designed specifically for the WebView
in your Android application, then you can define a custom user agent string with setUserAgentString()
, then query the custom user agent in your web page to verify that the client requesting your web page is actually your Android application.Following is full example in onCreate function:
public void onCreate(Bundle savedInstanceState) {
final Context context = this;
String url = "file:///android_asset/index.html";
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
button = (Button) findViewById(R.id.buttonViewNextFile);
button.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
Intent intent = new Intent(context, WebViewActivity.class);
startActivity(intent);
}
});
myWebView = (WebView)findViewById(R.id.firstWebview);
WebSettings webSetting = myWebView.getSettings();
webSetting.setBuiltInZoomControls(true);
webSetting.setJavaScriptEnabled(true);
myWebView.setWebViewClient(new WebViewClient());
myWebView.loadUrl(url);
}
2.2 Binding JavaScript code to Android code
When developing a web application that's designed specifically for the
WebView
in your Android application, you can create interfaces between your JavaScript code and client-side Android code. For example, your JavaScript code can call a method in your Android code to display a Dialog
, instead of using JavaScript's alert()
function.
To bind a new interface between your JavaScript and Android code, call
addJavascriptInterface()
, passing it a class instance to bind to your JavaScript and an interface name that your JavaScript can call to access the class.
For example, you can include the following class in your Android application:
public class WebAppInterface { Context mContext; /** Instantiate the interface and set the context */ WebAppInterface(Context c) { mContext = c; } /** Show a toast from the web page */ @JavascriptInterface public void showToast(String toast) { Toast.makeText(mContext, toast, Toast.LENGTH_SHORT).show(); } }
Caution: If you've set your
targetSdkVersion
to 17 or higher, you must add the @JavascriptInterface
annotation to any method that you want available to your JavaScript (the method must also be public). If you do not provide the annotation, the method is not accessible by your web page when running on Android 4.2 or higher.
In this example, the
WebAppInterface
class allows the web page to create a Toast
message, using the showToast()
method.
You can bind this class to the JavaScript that runs in your
WebView
with addJavascriptInterface()
and name the interface Android
. For example:WebView webView = (WebView) findViewById(R.id.webview); webView.addJavascriptInterface(new WebAppInterface(this), "Android");
This creates an interface called
Android
for JavaScript running in the WebView
. At this point, your web application has access to the WebAppInterface
class. For example, here's some HTML and JavaScript that creates a toast message using the new interface when the user clicks a button:<input type="button" value="Say hello" onClick="showAndroidToast('Hello Android!')" /> <script type="text/javascript"> function showAndroidToast(toast) { Android.showToast(toast); } </script>
There's no need to initialize the
Android
interface from JavaScript. The WebView
automatically makes it available to your web page. So, at the click of the button, the showAndroidToast()
function uses the Android
interface to call the WebAppInterface.showToast()
method.3-Handling Page Navigation
When the user clicks a link from a web page in your
WebView
, the default behavior is for Android to launch an application that handles URLs. Usually, the default web browser opens and loads the destination URL. However, you can override this behavior for your WebView
, so links open within your WebView
. You can then allow the user to navigate backward and forward through their web page history that's maintained by your WebView
.
To open links clicked by the user, simply provide a
WebViewClient
for your WebView
, using setWebViewClient()
. For example:WebView myWebView = (WebView) findViewById(R.id.webview);
myWebView.setWebViewClient
(new WebViewClient());
That's it. Now all links the user clicks load in your
WebView
.
If you want more control over where a clicked link load, create your own
WebViewClient
that overrides the shouldOverrideUrlLoading()
method. For example:private class MyWebViewClient extends WebViewClient {
@Override
public boolean shouldOverrideUrlLoading
(WebView view, String url) {
if (Uri.parse(url).getHost().equals("www.example.com")) {
// This is my web site, so do not override; let my WebView
load the page
return false;
}
// Otherwise, the link is not for a page on my site, so launch another
Activity that handles URLs
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
startActivity(intent);
return true;
}
}
Then create an instance of this new
WebViewClient
for the WebView
:WebView myWebView = (WebView) findViewById(R.id.webview);
myWebView.setWebViewClient
(new MyWebViewClient());
Now when the user clicks a link, the system calls
shouldOverrideUrlLoading()
, which checks whether the URL host matches a specific domain (as defined above). If it does match, then the method returns false in order to not override the URL loading (it allows the WebView
to load the URL as usual). If the URL host does not match, then an Intent
is created to launch the default Activity for handling URLs (which resolves to the user's default web browser).Navigating web page history
When your
WebView
overrides URL loading, it automatically accumulates a history of visited web pages. You can navigate backward and forward through the history with goBack()
and goForward()
.
For example, here's how your
Activity
can use the device Back button to navigate backward:@Override public booleanonKeyDown
(int keyCode, KeyEvent event) { // Check if the key event was the Back button and if there's history if ((keyCode == KeyEvent.KEYCODE_BACK) && myWebView.canGoBack
()) { myWebView.goBack
(); return true; } // If it wasn't the Back key or there's no web page history, bubble up to the default // system behavior (probably exit the activity) return super.onKeyDown(keyCode, event); }
The
canGoBack()
method returns true if there is actually web page history for the user to visit. Likewise, you can use canGoForward()
to check whether there is a forward history. If you don't perform this check, then once the user reaches the end of the history, goBack()
or goForward()
does nothing.
Source: Building Web Apps in WebView
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