WebView inside NestedScrollView cannot be scrolled

Question

I've got an activity that use WebView to load the web content. The problem arise when I want to implement Flexible Space with image. I can expand and collapse the Toolbar, but when the Toolbar already collapsed, The scrollbar stuck there. I can't scroll the content inside the WebView.

This is the XML:

<android.support.v4.widget.NestedScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:clipToPadding="false"
    android:fillViewport="true"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">

    <WebView
        android:id="@+id/read_full_content_wv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>


</android.support.v4.widget.NestedScrollView>

Do you have any solution for this?

Regards, Elmer

---

EDIT After I look at the link that given by LinX64. I tried to add:

public class FullContentActivity extends AppCompatActivity {
   ...
   @Override
   protected void onCreate(Bundle savedInstance){
      ...
      WebView webView = (WebView) findViewById(R.id.read_full_content_wv);
      webView.setWebViewClient(new MyBrowser());
      webView.loadData(extra.get(1).toString(), "text/html", "utf-8");
      ...
   }
   ...
   private class MyBrowser extends WebViewClient {
      @Override
      public void onPageStarted(WebView view, String url, Bitmap favicon){
         NestedScrollView nsv = (NestedScrollView) findViewById(R.id.nsv_fc);
         nsv.scrollTo(0,0);
      }
   }
}

and still got stucked.

---

EDIT 2 FYI: I tried on ASUS Zenfone 6 - KitKat 4.4.2 Is it possible KitKat can't load it correctly?

---

EDIT 3: The best solution I've got for this question

After working around, I think I cannot get experience I want for Flexible Space using CollapsingToolbarLayout combined with WebView, so I changed WebView to TextView and use Html.fromHtml() to read the content. Unless Google gonna update or fix some features so we can combine CollapsingToolbarLayout and WebView together.

Answer 1

By the usage of NestedScrollingChild Interface, we can implements the NestedScrollView properties in the webview. And customize the scrolling functionality under the onTouchEvent() method.

public class NestedWebView extends WebView implements NestedScrollingChild {
    private int mLastY;
    private final int[] mScrollOffset = new int[2];
    private final int[] mScrollConsumed = new int[2];
    private int mNestedOffsetY;
    private NestedScrollingChildHelper mChildHelper;

    public NestedWebView(Context context) {
        this(context, null);
    }

    public NestedWebView(Context context, AttributeSet attrs) {
        this(context, attrs, android.R.attr.webViewStyle);
    }

    public NestedWebView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mChildHelper = new NestedScrollingChildHelper(this);
        setNestedScrollingEnabled(true);
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        boolean returnValue = false;

        MotionEvent event = MotionEvent.obtain(ev);
        final int action = MotionEventCompat.getActionMasked(event);
        if (action == MotionEvent.ACTION_DOWN) {
            mNestedOffsetY = 0;
        }
        int eventY = (int) event.getY();
        event.offsetLocation(0, mNestedOffsetY);
        switch (action) {
            case MotionEvent.ACTION_MOVE:
                int totalScrollOffset = 0;
                int deltaY = mLastY - eventY;
                // NestedPreScroll
                if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) {
                    totalScrollOffset += mScrollOffset[1];
                    deltaY -= mScrollConsumed[1];
                    event.offsetLocation(0, -mScrollOffset[1]);
                    mNestedOffsetY += mScrollOffset[1];
                }
                returnValue = super.onTouchEvent(event);

                // NestedScroll
                if (dispatchNestedScroll(0, mScrollOffset[1], 0, deltaY, mScrollOffset)) {
                    totalScrollOffset += mScrollOffset[1];
                    event.offsetLocation(0, mScrollOffset[1]);
                    mNestedOffsetY += mScrollOffset[1];
                    mLastY -= mScrollOffset[1];
                }
                mLastY = eventY - totalScrollOffset;
                break;
            case MotionEvent.ACTION_DOWN:
                returnValue = super.onTouchEvent(event);
                mLastY = eventY;
                // start NestedScroll
                startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                returnValue = super.onTouchEvent(event);
                // end NestedScroll
                stopNestedScroll();
                break;
        }
        return returnValue;
    }

    // Nested Scroll implements
    @Override
    public void setNestedScrollingEnabled(boolean enabled) {
        mChildHelper.setNestedScrollingEnabled(enabled);
    }

    @Override
    public boolean isNestedScrollingEnabled() {
        return mChildHelper.isNestedScrollingEnabled();
    }

    @Override
    public boolean startNestedScroll(int axes) {
        return mChildHelper.startNestedScroll(axes);
    }

    @Override
    public void stopNestedScroll() {
        mChildHelper.stopNestedScroll();
    }

    @Override
    public boolean hasNestedScrollingParent() {
        return mChildHelper.hasNestedScrollingParent();
    }

    @Override
    public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed,
                                        int[] offsetInWindow) {
        return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
    }

    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
        return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
    }

    @Override
    public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
        return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
    }

    @Override
    public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
        return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
    }

}

Declare NestedWebView instead of declaring webview inside the NestedScrollView.For example,

<com.nestedscrollwebviewexample.NestedWebView
        android:id="@+id/nested_webview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#000000"
        android:fillViewport="true"
        android:focusable="true"
        android:isScrollContainer="false"
        android:visibility="visible"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        app:layout_scrollFlags="scroll|exitUntilCollapsed" />

Instead of declaring Webview you can initialize as NestedWebView inside your Activity

 private NestedWebView mShopWebView;
        mShopWebView = (NestedWebView) findViewById(R.id.url_load_webview);