com.facebook.react.views.scroll.ReactScrollViewHelper.java Source code

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Here is the source code for com.facebook.react.views.scroll.ReactScrollViewHelper.java

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/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

package com.facebook.react.views.scroll;

import android.view.View;
import android.view.ViewGroup;
import com.facebook.react.bridge.JSApplicationIllegalArgumentException;
import com.facebook.react.bridge.ReactContext;
import com.facebook.react.uimanager.UIManagerModule;

/** Helper class that deals with emitting Scroll Events. */
public class ReactScrollViewHelper {

    public static final long MOMENTUM_DELAY = 20;
    public static final String OVER_SCROLL_ALWAYS = "always";
    public static final String AUTO = "auto";
    public static final String OVER_SCROLL_NEVER = "never";

    /** Shared by {@link ReactScrollView} and {@link ReactHorizontalScrollView}. */
    public static void emitScrollEvent(ViewGroup scrollView, float xVelocity, float yVelocity) {
        emitScrollEvent(scrollView, ScrollEventType.SCROLL, xVelocity, yVelocity);
    }

    public static void emitScrollBeginDragEvent(ViewGroup scrollView) {
        emitScrollEvent(scrollView, ScrollEventType.BEGIN_DRAG);
    }

    public static void emitScrollEndDragEvent(ViewGroup scrollView, float xVelocity, float yVelocity) {
        emitScrollEvent(scrollView, ScrollEventType.END_DRAG, xVelocity, yVelocity);
    }

    public static void emitScrollMomentumBeginEvent(ViewGroup scrollView, int xVelocity, int yVelocity) {
        emitScrollEvent(scrollView, ScrollEventType.MOMENTUM_BEGIN, xVelocity, yVelocity);
    }

    public static void emitScrollMomentumEndEvent(ViewGroup scrollView) {
        emitScrollEvent(scrollView, ScrollEventType.MOMENTUM_END);
    }

    private static void emitScrollEvent(ViewGroup scrollView, ScrollEventType scrollEventType) {
        emitScrollEvent(scrollView, scrollEventType, 0, 0);
    }

    private static void emitScrollEvent(ViewGroup scrollView, ScrollEventType scrollEventType, float xVelocity,
            float yVelocity) {
        View contentView = scrollView.getChildAt(0);

        if (contentView == null) {
            return;
        }

        ReactContext reactContext = (ReactContext) scrollView.getContext();
        reactContext.getNativeModule(UIManagerModule.class).getEventDispatcher()
                .dispatchEvent(ScrollEvent.obtain(scrollView.getId(), scrollEventType, scrollView.getScrollX(),
                        scrollView.getScrollY(), xVelocity, yVelocity, contentView.getWidth(),
                        contentView.getHeight(), scrollView.getWidth(), scrollView.getHeight()));
    }

    public static int parseOverScrollMode(String jsOverScrollMode) {
        if (jsOverScrollMode == null || jsOverScrollMode.equals(AUTO)) {
            return View.OVER_SCROLL_IF_CONTENT_SCROLLS;
        } else if (jsOverScrollMode.equals(OVER_SCROLL_ALWAYS)) {
            return View.OVER_SCROLL_ALWAYS;
        } else if (jsOverScrollMode.equals(OVER_SCROLL_NEVER)) {
            return View.OVER_SCROLL_NEVER;
        } else {
            throw new JSApplicationIllegalArgumentException("wrong overScrollMode: " + jsOverScrollMode);
        }
    }
}