通过使用NestedScrollingChild接口,我们可以在webview中实现NestedScrollView的属性。并在onTouchEvent()方法下定制滚动功能。
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;
if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) {
totalScrollOffset += mScrollOffset[1];
deltaY -= mScrollConsumed[1];
event.offsetLocation(0, -mScrollOffset[1]);
mNestedOffsetY += mScrollOffset[1];
}
returnValue = super.onTouchEvent(event);
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;
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
returnValue = super.onTouchEvent(event);
stopNestedScroll();
break;
}
return returnValue;
}
@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);
}
}
声明NestedWebView而不是在NestedScrollView内部声明webview。例如:
<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" />
你可以在Activity中将NestedWebView初始化,而不是声明Webview。
private NestedWebView mShopWebView;
mShopWebView = (NestedWebView) findViewById(R.id.url_load_webview);
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); } }
并且在活动的onCreate方法中像这样调用它:WebView webView = (WebView) findViewById(R.id.read_full_content_wv); webView.setWebViewClient(new MyBrowser()); webView.loadData(extra.get(1).toString(), "text/html", "utf-8");
- j.elmer