Android: 擴充WebView 和ViewPager實作viewpager中的水準滑動，類似Gmail的效果Extending the WebViewExtending the ViewPager

The following is a real working solution which will scroll the

WebView

on a horizontal swipe as long as it can scroll. If the

WebView

cannot further scroll, the next horizontal swipe will be consumed by the

ViewPager

to switch the page.

Extending the

WebView

With API-Level 14 (ICS) the

View

method

canScrollHorizontally()

has been introduced, which we need to solve the problem. If you develop only for ICS or above you can directly use this method and skip to the next section. Otherwise we need to implement this method on our own, to make the solution work also on pre-ICS.

To do so simply derive your own class from

WebView

:

public class ExtendedWebView extends WebView {
    public ExtendedWebView(Context context) {
        super(context);
    }

    public ExtendedWebView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public boolean canScrollHor(int direction) {
        final int offset = computeHorizontalScrollOffset();
        final int range = computeHorizontalScrollRange() - computeHorizontalScrollExtent();
        if (range == 0) return false;
        if (direction < 0) {
            return offset > 0;
        } else {
            return offset < range - 1;
        }
    }
}

           

Important: Remember to reference your

ExtendedWebView

inside your layout file instead of the standard

WebView

.

Extending the

ViewPager

Now you need to extend the

ViewPager

to handle handle horizontal swipes correctly. This needs to be done in any case -- no matter whether you are using ICS or not:

public class WebViewPager extends ViewPager {
    public WebViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
        if (v instanceof ExtendedWebView) {
            return ((ExtendedWebView) v).canScrollHor(-dx);
        } else {
            return super.canScroll(v, checkV, dx, x, y);
        }
    }
}

           

Important: Remember to reference your

WebViewPager

inside your layout file instead of the standard

ViewPager

.

That's it!

Update 2012/07/08: I've recently noticed that the stuff shown above seems to be no longer required when using the "current" implementation of the

ViewPager

. The "current" implementation seems to check the sub views correctly before capturing the scroll event on it's own (see

canScroll

method of

ViewPager

here). Don't know exactly, when the implementation has been changed to handle this correctly -- I still need the code above on Android Gingerbread (2.3.x) and before.

share | edit | flag

edited Jul 8 at 11:13

answered Mar 29 at 13:07 sven 1,272 8 21