MultiSwipeRefreshLayout.java

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/*
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 * Copyright 2014 The Android Open Source Project
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 *
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 * Licensed under the Apache License, Version 2.0 (the "License");
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 * you may not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 *       http://www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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 */
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package com.example.android.swiperefreshmultipleviews;
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import android.content.Context;
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import android.support.v4.view.ViewCompat;
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import android.support.v4.widget.SwipeRefreshLayout;
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import android.util.AttributeSet;
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import android.view.View;
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import android.widget.AbsListView;
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/**
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 * A descendant of {@link android.support.v4.widget.SwipeRefreshLayout} which supports multiple
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 * child views triggering a refresh gesture. You set the views which can trigger the gesture via
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 * {@link #setSwipeableChildren(int...)}, providing it the child ids.
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 */
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public class MultiSwipeRefreshLayout extends SwipeRefreshLayout {
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    private View[] mSwipeableChildren;
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    public MultiSwipeRefreshLayout(Context context) {
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        super(context);
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    }
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    public MultiSwipeRefreshLayout(Context context, AttributeSet attrs) {
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        super(context, attrs);
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    }
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    /**
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     * Set the children which can trigger a refresh by swiping down when they are visible. These
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     * views need to be a descendant of this view.
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     */
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    public void setSwipeableChildren(final int... ids) {
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        assert ids != null;
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        // Iterate through the ids and find the Views
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        mSwipeableChildren = new View[ids.length];
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        for (int i = 0; i < ids.length; i++) {
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            mSwipeableChildren[i] = findViewById(ids[i]);
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        }
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    }
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    /**
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     * This method controls when the swipe-to-refresh gesture is triggered. By returning false here
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     * we are signifying that the view is in a state where a refresh gesture can start.
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     *
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     * <p>As {@link android.support.v4.widget.SwipeRefreshLayout} only supports one direct child by
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     * default, we need to manually iterate through our swipeable children to see if any are in a
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     * state to trigger the gesture. If so we return false to start the gesture.
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     */
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    @Override
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    public boolean canChildScrollUp() {
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        if (mSwipeableChildren != null && mSwipeableChildren.length > 0) {
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            // Iterate through the scrollable children and check if any of them can not scroll up
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            for (View view : mSwipeableChildren) {
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                if (view != null && view.isShown() && !canViewScrollUp(view)) {
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                    // If the view is shown, and can not scroll upwards, return false and start the
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                    // gesture.
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                    return false;
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                }
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            }
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        }
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        return true;
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    }
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    /**
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     * Utility method to check whether a {@link View} can scroll up from it's current position.
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     * Handles platform version differences, providing backwards compatible functionality where
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     * needed.
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     */
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    private static boolean canViewScrollUp(View view) {
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        if (android.os.Build.VERSION.SDK_INT >= 14) {
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            // For ICS and above we can call canScrollVertically() to determine this
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            return ViewCompat.canScrollVertically(view, -1);
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        } else {
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            if (view instanceof AbsListView) {
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                // Pre-ICS we need to manually check the first visible item and the child view's top
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                // value
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                final AbsListView listView = (AbsListView) view;
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                return listView.getChildCount() > 0 &&
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                        (listView.getFirstVisiblePosition() > 0
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                                || listView.getChildAt(0).getTop() < listView.getPaddingTop());
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            } else {
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                // For all other view types we just check the getScrollY() value
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                return view.getScrollY() > 0;
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            }
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        }
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    }
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}