com.jecelyin.common.adapter.ViewPagerAdapter.java Source code

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Here is the source code for com.jecelyin.common.adapter.ViewPagerAdapter.java

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/*
 * Copyright (C) 2016 Jecelyin Peng <jecelyin@gmail.com>
 *
 * This file is part of 920 Text Editor.
 *
 * 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.jecelyin.common.adapter;

import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;

import com.jecelyin.common.utils.L;

/**
 * @author Jecelyin Peng <jecelyin@gmail.com>
 */
public abstract class ViewPagerAdapter extends PagerAdapter {
    private View mCurrentPrimaryItem;

    /**
     * Get a View that displays the data at the specified position in the data set.
     *
     * @param position The position of the item within the adapter's data set of the item whose view we want.
     * @param pager    The ViewPager that this view will eventually be attached to.
     *
     * @return A View corresponding to the data at the specified position.
     */
    public abstract View getView(int position, ViewGroup pager);

    /**
     * Determines whether a page View is associated with a specific key object as
     * returned by instantiateItem(ViewGroup, int).
     *
     * @param view   Page View to check for association with object
     * @param object Object to check for association with view
     *
     * @return true if view is associated with the key object object.
     */
    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    /**
     * Create the page for the given position.
     *
     * @param container The containing View in which the page will be shown.
     * @param position  The page position to be instantiated.
     *
     * @return Returns an Object representing the new page. This does not need
     *         to be a View, but can be some other container of the page.
     */
    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        View view = getView(position, container);

        if (view != mCurrentPrimaryItem) {
            view.setVisibility(View.INVISIBLE);
        }

        container.addView(view);

        return view;
    }

    @Override
    public void setPrimaryItem(ViewGroup container, int position, Object object) {
        super.setPrimaryItem(container, position, object);

        View view = (View) object;
        if (view != mCurrentPrimaryItem) {
            if (mCurrentPrimaryItem != null) {
                mCurrentPrimaryItem.setVisibility(View.INVISIBLE);
            }
            if (view != null) {
                view.setVisibility(View.VISIBLE);
            }
            mCurrentPrimaryItem = view;
        }
    }

    /**
     * Remove a page for the given position.
     *
     * @param container The containing View from which the page will be removed.
     * @param position  The page position to be removed.
     * @param view      The same object that was returned by instantiateItem(View, int).
     */
    @Override
    public void destroyItem(ViewGroup container, int position, Object view) {
        L.d("remove page %d", position);
        if (mCurrentPrimaryItem == view)
            mCurrentPrimaryItem = null;
        container.removeView((View) view);
    }
}