Question

As I am sure you all know. Setting up a WebView is a matter of creating a webview browser client, setting properties and loading a resource into the browser client. I have created several android apps that do exactly that.

What i would like to try now is horizontal swiping of different web resources. Imagine a main home page at one url, a categories page at another url and a search page at another url. I would like to create a UI construct that allows swiping from the main home page url view to a view displaying the categories url and then another swipe that shows the view with the search resource (think the new android market UI – swipe left shows categories).

I have read up on ViewFlipper and several posts here, but I am not able to find a comprehensive example of how to integrate the browser instantiation with view flipping/swiping.

Question: Can someone provide an example that can perform some variation of the above and/or provide a link to an example that shows browser instantiation with web view flipping/ swiping.

Feel free to correct my suggested implementation… there may be a better way to do this that I haven’t considered yet…

Answer 1

Well, I’ve worked on this for some time and I have a solution that works. I am not sure it is the most effective solution, but I just kept researching and writing code until I figured out something that made sense. With the following code I need to give a big shout out to Android & Amir at http://android-journey.blogspot.com/2010/01/android-webview.html for helping me figure this out. He’s got some great stuff and you all should check it out.

The first step is to create a class in your Activity package called SimpleGestureFilter and use the code found here. This comes directly from Amir and dramatically simplifies the gesture interactions for swipe.

The next step is to use ViewFlipper for your layout. I was using buttons and several other things so there is more in this layout file than necessary, but you should get the picture.

<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:paddingTop="5dp">
    <Button
        android:id="@+id/cat_btn"
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="Categories" />
    <Button
        android:id="@+id/home_btn"
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="Home" />
    <Button
        android:id="@+id/search_btn"
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="Search" />
</LinearLayout>
    <ViewFlipper
        android:id="@+id/flipview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
    <WebView
        android:id="@+id/mainview"
        android:layout_height="fill_parent"
        android:layout_width="fill_parent" />
    <WebView  xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/catview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"/>
    <WebView  xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/searchview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"/>
    </ViewFlipper>
</LinearLayout>

As you can see, the xml describes a linear layout that contains a ViewFlipper. In the view flipper there are three WebViews.

The final step is the Activity…

package example.swipetest;

// import Amir's SimpleGestureFilter
import example.swipetest.SimpleGestureFilter;
import example.swipetest.SimpleGestureFilter.SimpleGestureListener;

// import other required packages
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.ViewFlipper;

// class implements Amir's Swipe Listener
public class SwipeTest extends Activity implements SimpleGestureListener {

    // handler for JS interface
    private Handler handler = new Handler();

    // all the webviews to be loaded
    private WebView mainView;
    private WebView catView;
    private WebView searchView;

    // the viewflipper
    private ViewFlipper flipview;

    // buttons
    private Button cat_btn;
    private Button home_btn;
    private Button search_btn;

    // progress dialog
    private ProgressDialog progressDialog;

    // animations
    private Animation slideLeftIn;
    private Animation slideLeftOut;
    private Animation slideRightIn;
    private Animation slideRightOut;

    // the activity
    final Activity activity = this;

    // gesture filter
    private SimpleGestureFilter filter;

    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // set the main webview to the layout item
        mainView = (WebView) findViewById(R.id.mainview);

        // buttons
        cat_btn = (Button) findViewById(R.id.cat_btn);
        home_btn = (Button) findViewById(R.id.home_btn);
        search_btn = (Button) findViewById(R.id.search_btn);

        // set the client settings
        mainView = _clientSettings(mainView);

        // set the flipper
        flipview = (ViewFlipper) findViewById(R.id.flipview);

        // set onclick listeners for the buttons
        cat_btn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                _flipView(cat_btn);
            }
        });
        home_btn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                _flipView(home_btn);
            }
        });
        search_btn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                _flipView(search_btn);
            }
        });

        // these animations came from the sdk. they are xml files loaded
        // into the res folder into a folder called anim
        slideLeftIn = AnimationUtils.loadAnimation(this, R.anim.slide_in_left);
        slideLeftOut = AnimationUtils.loadAnimation(this, R.anim.slide_out_left);
        slideRightIn = AnimationUtils.loadAnimation(this, R.anim.slide_in_right);
        slideRightOut = AnimationUtils.loadAnimation(this, R.anim.slide_out_right);

        // listen for gestures
        this.filter = new SimpleGestureFilter(this, this);
        this.filter.setMode(SimpleGestureFilter.MODE_TRANSPARENT);

        // load the html resource into the main view
        mainView.loadUrl("file:///android_asset/test1.html");
        // set the client
        mainView.setWebViewClient(new BasicWebViewCient());
        // run async to load the other web resources into the views
        new ManageViews().execute();
    }

    // use a method to manage button clicks
private Boolean _flipView(Button button) {
    // Handle item selection
    switch (button.getId()) {
    case R.id.cat_btn:
        _setCategories();
        return true;
    case R.id.home_btn:
        _setHome();
        return true;
    case R.id.search_btn:
        _setSearch();
        return true;
    default:
        return false;
    }
}

    // adding client settings to the webviews
    // I did this way so that I could set the same settings
    // to all of the webviews
private WebView _clientSettings(WebView view) {
    view.getSettings().setJavaScriptEnabled(true);
    view.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);
    view.addJavascriptInterface(new PanelJSI(), "interface");
    return view;
}

// Web view client
private class BasicWebViewCient extends WebViewClient {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        view.loadUrl(url);
        return true;
    }

    @Override
    public void onLoadResource(WebView view, String url) {
        if (progressDialog == null) {
            progressDialog = new ProgressDialog(activity);
            progressDialog.setMessage("Locating");
            progressDialog.show();
        }
    }

    @Override
    public void onPageFinished(WebView view, String url) {
        if (progressDialog.isShowing()) {
            progressDialog.dismiss();
        }
    }
}

// Async to load the rest of the web resources into the webviews
private class ManageViews extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... args) {
                    // cat view will load a categories webview
        catView = (WebView) findViewById(R.id.catview);
        catView = _clientSettings(catView);
        catView.loadUrl("file:///android_asset/test2.html");
        catView.setWebViewClient(new BasicWebViewCient());

                    // load a search resource
        searchView = (WebView) findViewById(R.id.searchview);
        searchView = _clientSettings(searchView);
        searchView.loadUrl("file:///android_asset/test3.html");
        searchView.setWebViewClient(new BasicWebViewCient());

        return null;
    }
}

    // a method to manage the animation of the categories view  
private void _setCategories() {
    if (flipview.getDisplayedChild() != 1) {
        flipview.setInAnimation(slideLeftIn);
        flipview.setOutAnimation(slideRightOut);
        flipview.setDisplayedChild(1);
    }
}

    // a method to manage the "center" view called home
private void _setHome() {
    if (flipview.getDisplayedChild() != 0) {
        if (flipview.getDisplayedChild() == 1) {
            flipview.setInAnimation(slideRightIn);
            flipview.setOutAnimation(slideLeftOut);
        } else if (flipview.getDisplayedChild() == 2) {
            flipview.setInAnimation(slideLeftIn);
            flipview.setOutAnimation(slideRightOut);
        }
        flipview.setDisplayedChild(0);
    }
}

    // a method to handle the "right side" called search    
private void _setSearch() {
    if (flipview.getDisplayedChild() != 2) {
        flipview.setInAnimation(slideRightIn);
        flipview.setOutAnimation(slideLeftOut);
        flipview.setDisplayedChild(2);
    }
}

    // javascript interface
final class PanelJSI {

    public void setView(final String shift) {
        handler.post(new Runnable() {
            public void run() {
                if (shift.equals("categories")) {
                    _setCategories();
                } else if (shift.equals("home")) {
                    _setHome();
                } else {
                    _setSearch();
                }
            }
        });
    }
}

    // override the dispatch
@Override
public boolean dispatchTouchEvent(MotionEvent me) {
    this.filter.onTouchEvent(me);
    return super.dispatchTouchEvent(me);
}

    // manage swipe animations
@Override
public void onSwipe(int direction) {

    switch (direction) {

    case SimpleGestureFilter.SWIPE_RIGHT:
        if (flipview.getDisplayedChild() == 0) {
            _setCategories();
        } else if (flipview.getDisplayedChild() == 2) {
            _setHome();
        }
        break;
    case SimpleGestureFilter.SWIPE_LEFT:
        if (flipview.getDisplayedChild() == 1) {
            _setHome();
        } else if (flipview.getDisplayedChild() == 0) {
            _setSearch();
        }
        break;
    case SimpleGestureFilter.SWIPE_DOWN:
    case SimpleGestureFilter.SWIPE_UP:

    }
}

    // manage double tap
@Override
public void onDoubleTap() {}
}

So… The basic pattern I came up with is to use a single web client and browser settings. I use the onCreate method to load the views, set the first view and then an Async method to load the other views after the main view is loaded. So two of the views load in the background. I them use the patterns Amir passed on to manage swipe. I use buttons and JS interfaces to invoke the same animations on clicks.

The final result is swipe and click animations for ViewFlipping webviews similar to the UI you’ll see in the new android market UI. Feel free to recommend any additional implementation that might make this pattern stronger.