de.xikolo.views.NestedScrollWebView.java Source code

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Here is the source code for de.xikolo.views.NestedScrollWebView.java

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/*
 * Copyright (C) 2016 Tobias Rohloff
 *
 * 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 de.xikolo.views;

import android.content.Context;
import android.support.v4.view.MotionEventCompat;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.ViewCompat;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.webkit.WebView;

public class NestedScrollWebView extends WebView implements NestedScrollingChild {

    public static final String TAG = NestedScrollWebView.class.getSimpleName();

    private int mLastMotionY;

    private final int[] mScrollOffset = new int[2];
    private final int[] mScrollConsumed = new int[2];

    private int mNestedYOffset;

    private NestedScrollingChildHelper mChildHelper;

    public NestedScrollWebView(Context context) {
        super(context);
        init();
    }

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

    public NestedScrollWebView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        mChildHelper = new NestedScrollingChildHelper(this);
        setNestedScrollingEnabled(true);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        boolean result = false;

        MotionEvent trackedEvent = MotionEvent.obtain(event);

        final int action = MotionEventCompat.getActionMasked(event);

        if (action == MotionEvent.ACTION_DOWN) {
            mNestedYOffset = 0;
        }

        int y = (int) event.getY();

        event.offsetLocation(0, mNestedYOffset);

        switch (action) {
        case MotionEvent.ACTION_DOWN:
            mLastMotionY = y;
            startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
            result = super.onTouchEvent(event);
            break;
        case MotionEvent.ACTION_MOVE:
            int deltaY = mLastMotionY - y;

            if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) {
                deltaY -= mScrollConsumed[1];
                trackedEvent.offsetLocation(0, mScrollOffset[1]);
                mNestedYOffset += mScrollOffset[1];
            }

            int oldY = getScrollY();
            mLastMotionY = y - mScrollOffset[1];
            if (deltaY < 0) {
                int newScrollY = Math.max(0, oldY + deltaY);
                deltaY -= newScrollY - oldY;
                if (dispatchNestedScroll(0, newScrollY - deltaY, 0, deltaY, mScrollOffset)) {
                    mLastMotionY -= mScrollOffset[1];
                    trackedEvent.offsetLocation(0, mScrollOffset[1]);
                    mNestedYOffset += mScrollOffset[1];
                }
            }

            trackedEvent.recycle();
            result = super.onTouchEvent(trackedEvent);
            break;
        case MotionEvent.ACTION_POINTER_DOWN:
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            stopNestedScroll();
            result = super.onTouchEvent(event);
            break;
        }
        return result;
    }

    // NestedScrollingChild

    @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);
    }

}