akhil.alltrans.NestedScrollingMarkDownView.java Source code

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Here is the source code for akhil.alltrans.NestedScrollingMarkDownView.java

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/*
 * Copyright 2017 Akhil Kedia
 * This file is part of AllTrans.
 *
 * AllTrans is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * AllTrans is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with AllTrans. If not, see <http://www.gnu.org/licenses/>.
 *
 */

package akhil.alltrans;

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;

// Taken from https://github.com/rhlff/NestedScrollWebView/blob/master/lib/src/main/java/com/tobiasrohloff/view/NestedScrollWebView.java

public class NestedScrollingMarkDownView extends WebView implements NestedScrollingChild {

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

    private NestedScrollingChildHelper mChildHelper;

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

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

            result = super.onTouchEvent(trackedEvent);
            trackedEvent.recycle();
            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 boolean isNestedScrollingEnabled() {
        return mChildHelper.isNestedScrollingEnabled();
    }

    @Override
    public void setNestedScrollingEnabled(boolean enabled) {
        mChildHelper.setNestedScrollingEnabled(enabled);
    }

    @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);
    }

}