/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.fsck.k9.view;
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.webkit.WebView;
import android.widget.ScrollView;
import java.util.ArrayList;
import java.util.List;
/**
* A {@link ScrollView} that will never lock scrolling in a particular direction.
*
* Usually ScrollView will capture all touch events once a drag has begun. In some cases,
* we want to delegate those touches to children as normal, even in the middle of a drag. This is
* useful when there are childviews like a WebView that handles scrolling in the horizontal direction
* even while the ScrollView drags vertically.
*
* This is only tested to work for ScrollViews where the content scrolls in one direction.
*/
public class NonLockingScrollView extends ScrollView {
public NonLockingScrollView(Context context) {
super(context);
}
public NonLockingScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public NonLockingScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
/**
* Whether or not the contents of this view is being dragged by one of the children in
* {@link #mChildrenNeedingAllTouches}.
*/
private boolean mInCustomDrag = false;
/**
* The list of children who should always receive touch events, and not have them intercepted.
*/
private final List<View> mChildrenNeedingAllTouches = new ArrayList<View>();
private boolean mSkipWebViewScroll = true;
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
final int action = getActionMasked(ev);
final boolean isUp = action == MotionEvent.ACTION_UP;
if (isUp && mInCustomDrag) {
// An up event after a drag should be intercepted so that child views don't handle
// click events falsely after a drag.
mInCustomDrag = false;
onTouchEvent(ev);
return true;
}
if (!mInCustomDrag && !isEventOverChild(ev, mChildrenNeedingAllTouches)) {
return super.onInterceptTouchEvent(ev);
}
// Note the normal scrollview implementation is to intercept all touch events after it has
// detected a drag starting. We will handle this ourselves.
mInCustomDrag = super.onInterceptTouchEvent(ev);
if (mInCustomDrag) {
onTouchEvent(ev);
}
// Don't intercept events - pass them on to children as normal.
return false;
}
private int getActionMasked(MotionEvent ev) {
// Equivalent to MotionEvent.getActionMasked() which is in API 8+
return ev.getAction() & MotionEvent.ACTION_MASK;
}
@Override
protected void onFinishInflate() {
super.onFinishInflate();
setupDelegationOfTouchAndHierarchyChangeEvents();
}
private void setupDelegationOfTouchAndHierarchyChangeEvents() {
OnHierarchyChangeListener listener = new HierarchyTreeChangeListener();
setOnHierarchyChangeListener(listener);
for (int i = 0, childCount = getChildCount(); i < childCount; i++) {
listener.onChildViewAdded(this, getChildAt(i));
}
}
private final Rect sHitFrame = new Rect();
private boolean isEventOverChild(MotionEvent ev, List<View> children) {
final int actionIndex = ev.getActionIndex();
final float x = ev.getX(actionIndex) + getScrollX();
final float y = ev.getY(actionIndex) + getScrollY();
for (View child : children) {
if (!canViewReceivePointerEvents(child)) {
continue;
}
child.getHitRect(sHitFrame);
// child can receive the motion event.
if (sHitFrame.contains((int) x, (int) y)) {
return true;
}
}
return false;
}
private static boolean canViewReceivePointerEvents(View child) {
return child.getVisibility() == VISIBLE || (child.getAnimation() != null);
}
@Override
public void requestChildFocus(View child, View focused) {
/*
* Normally a ScrollView will scroll the child into view.
* Prevent this when a MessageWebView is first touched,
* assuming it already is at least partially in view.
*
*/
if (mSkipWebViewScroll &&
focused instanceof MessageWebView &&
focused.getGlobalVisibleRect(new Rect())) {
mSkipWebViewScroll = false;
super.requestChildFocus(child, child);
ViewParent parent = getParent();
if (parent != null) {
parent.requestChildFocus(this, focused);
}
} else {
super.requestChildFocus(child, focused);
}
}
class HierarchyTreeChangeListener implements OnHierarchyChangeListener {
@Override
public void onChildViewAdded(View parent, View child) {
if (child instanceof WebView) {
mChildrenNeedingAllTouches.add(child);
} else if (child instanceof ViewGroup) {
ViewGroup childGroup = (ViewGroup) child;
childGroup.setOnHierarchyChangeListener(this);
for (int i = 0, childCount = childGroup.getChildCount(); i < childCount; i++) {
onChildViewAdded(childGroup, childGroup.getChildAt(i));
}
}
}
@Override
public void onChildViewRemoved(View parent, View child) {
if (child instanceof WebView) {
mChildrenNeedingAllTouches.remove(child);
} else if (child instanceof ViewGroup) {
ViewGroup childGroup = (ViewGroup) child;
for (int i = 0, childCount = childGroup.getChildCount(); i < childCount; i++) {
onChildViewRemoved(childGroup, childGroup.getChildAt(i));
}
childGroup.setOnHierarchyChangeListener(null);
}
}
}
}