Android: Using WebView outside an Activity context

Question

I am trying to achieve Web Scraping through a background IntentService that periodically scrape a website without a view displaying on the users phone.

• Since I have to do call some javascript on the loaded page I cannot use any HttpGet's etc.
• I therefore have to use a WebView instance which can only run on an UI thread.
• Any attempts to start an Activity that use a WebView results in a View coming into the phones foreground (as per Android's design of Activities)
• Any attempts to use a WebView outside of an Activity context resulted in error pointing to the fact that you cannot use WebView on a non-UI thread.
• For various complexity reasons I cannot consider using libraries such as Rhino for UI-less web scraping.

Is there any way of working around this problem?

Solution 1

Correct me if I am wrong but the correct answer to this question is that there is NO possible way to use a WebView in the background while the user is doing other things on the phone without interrupting the user by means of an Activity.

I have applied both Randy and Code_Yoga's suggestions: Using an activity with "Theme.NoDisplay" to launch a background service with a WebView to do some work. However even though no view is visible the switching to that activity for that second to start the services interrupts the user (ex. like pausing a running game that was being played).

Totally disastrous news for my app so I am still hoping someone will give me a way to use a WebView that does not need an Activity (or a substitute for a WebView that can accomplish the same)

Solution 2

You can display a webview from a service. Code below creates a window which your service has access to. The window isn't visible because the size is 0 by 0.

public class ServiceWithWebView extends Service {

    @Override
    public void onCreate() {
        super.onCreate();

        WindowManager windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
        params = new WindowManager.LayoutParams(WindowManager.LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY, WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE, PixelFormat.TRANSLUCENT);
        params.gravity = Gravity.TOP | Gravity.LEFT;
        params.x = 0;
        params.y = 0;
        params.width = 0;
        params.height = 0;

        LinearLayout view = new LinearLayout(this);
        view.setLayoutParams(new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT));

        WebView wv = new WebView(this);
        wv.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT));
        view.addView(wv);
        wv.loadUrl("http://google.com");

        windowManager.addView(view, params);
    }
}

Also this will require the android.permission.SYSTEM_ALERT_WINDOW permission.

Solution 3

You can use this to hide the Activity

         <activity android:name="MyActivity"
          android:label="@string/app_name"
          android:theme="@android:style/Theme.NoDisplay">

Doing this will prevent the app from showing any Activity. And then you can do your stuff in the Activity.

Solution 4

the solution was like this, but with Looper.getMainLooper() :

https://github.com/JonasCz/save-for-offline/blob/master/app/src/main/java/jonas/tool/saveForOffline/ScreenshotService.java

@Override
public void onCreate() {
    super.onCreate();
    //HandlerThread thread = new HandlerThread("ScreenshotService", Process.THREAD_PRIORITY_BACKGROUND);
    //thread.start();
    //mServiceHandler = new ServiceHandler(thread.getLooper()); // not working
    mServiceHandler = new ServiceHandler(Looper.getMainLooper()); // working
}

with help of @JonasCz : https://stackoverflow.com/a/28234761/466363

Solution 5

I used the following code to get round this problem:

Handler handler = new Handler(Looper.getMainLooper());
try
{
    handler.post(
        new Runnable()
        {
            @Override
            public void run()
            {
                ProcessRequest(); // Where this method runs the code you're needing
            }
        }
    );
} catch (Exception e)
{
    e.printStackTrace();
}

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