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WebApp – An Android experiment

by Connorhd on February 3rd, 2010

After thinking about a JavaScript API to allow alerts on an Android phone in this post, I came up with a method of adding this using the current Java Android app API. The solution involves starting a Webkit instance in a custom app, and intercepting links with a certain prefix. In this example android://alert/description creates an alert with title “alert” and description “description”.

To demonstrate here are some screenshots of a sample page using a sample application (if you have an Android phone you can use that link to download it and try it yourself):

The application when you load it:

When clicking go an alert is created:

Viewing the created alert:

The example page is very simple javascript:

function go() {
	window.location = 'android://'+document.getElementById('title').value
		+'/'+document.getElementById('text').value;
}

The source for the app follows and is also fairly simple, most of the code is the rather complex way alerts are generated on Android:

package uk.co.connorhd.android.webapp;
 
import java.net.URLDecoder;
 
import uk.co.connorhd.android.webapp.R;
import uk.co.connorhd.android.webapp.WebApp;
import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast;
 
public class WebApp extends Activity {
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    WebView webview = new WebView(this);
 
    // We're testing, clear the cache.
    webview.clearCache(true);
 
    setContentView(webview);
 
    webview.getSettings().setJavaScriptEnabled(true);
 
    final Activity activity = this;
    webview.setWebViewClient(new WebViewClient() {
      int alert = 1;
 
      public void onReceivedError(WebView view, int errorCode,
          String description, String failingUrl) {
        Toast.makeText(activity, "Oh no! " + description,
            Toast.LENGTH_SHORT).show();
      }
 
      public boolean shouldOverrideUrlLoading(WebView view, String url) {
        // Is it a hack?
        if (url.startsWith("android")) {
          String ns = Context.NOTIFICATION_SERVICE;
          NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns);
          int icon = R.drawable.icon;
          CharSequence tickerText = "WebApp Alert!";
          long when = System.currentTimeMillis();
 
          Notification notification = new Notification(icon,
              tickerText, when);
          notification.flags = Notification.FLAG_AUTO_CANCEL;
          Context context = getApplicationContext();
 
          String[] split = url.split("/");
 
          CharSequence contentTitle = URLDecoder.decode(split[2]);
          CharSequence contentText = URLDecoder.decode(split[3]);
 
          Intent notificationIntent = new Intent(activity,
              WebApp.class);
          PendingIntent contentIntent = PendingIntent.getActivity(
              activity, 0, notificationIntent, 0);
 
          notification.setLatestEventInfo(context, contentTitle,
              contentText, contentIntent);
 
          mNotificationManager.notify(alert++, notification);
        } else {
          view.loadUrl(url);
        }
        return true;
      }
    });
 
    webview.loadUrl("http://connorhd.co.uk/files/WebApp.htm");
  }
}

This could easily be extended (and I may try to do this myself for Ircster) to provide all the standard browser functionality (for example the back button doesn’t currently work) and a more complete API to interface with Android.

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