net.illusor.swipeplayer.fragments.TrackPagerAdapter.java Source code

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Here is the source code for net.illusor.swipeplayer.fragments.TrackPagerAdapter.java

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/*Copyright 2014 Nikita Kobzev
    
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 net.illusor.swipeplayer.fragments;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import net.illusor.swipeplayer.domain.AudioFile;

import java.util.ArrayList;
import java.util.Dictionary;
import java.util.Hashtable;
import java.util.List;

/**
 * Controls set of fragments, representing playlist tracks of the {@link AudioControlFragment}
 */
public class TrackPagerAdapter extends PagerAdapter {
    private final List<AudioFile> audioFiles;
    private final Dictionary<Integer, TrackFragment> fragments = new Hashtable<>();
    private final FragmentManager fragmentManager;
    private FragmentTransaction currentTransaction;

    public TrackPagerAdapter(List<AudioFile> audioFiles, FragmentManager fragmentManager) {
        //adapter should support cyclic scrolling, so if we have enough items to cycle (at least 2)
        //we add 2 fake null items at the begining and at the end of the playlist
        if (audioFiles.size() > 1) {
            this.audioFiles = new ArrayList<>(audioFiles.size() + 2);
            this.audioFiles.add(null);
            this.audioFiles.addAll(1, audioFiles);
            this.audioFiles.add(null);
        } else {
            //if we have not enough items for cycling, we just use the provided playlist
            this.audioFiles = audioFiles;
        }
        this.fragmentManager = fragmentManager;
    }

    @Override
    public void finishUpdate(ViewGroup container) {
        super.finishUpdate(container);
        if (this.currentTransaction != null) {
            this.currentTransaction.commitAllowingStateLoss();
            this.currentTransaction = null;
            this.fragmentManager.executePendingTransactions();
        }
    }

    @Override
    public Object instantiateItem(ViewGroup container, int fragmentPosition) {
        //if we are going to cycle adapter content, we should adjust audioFile index
        int filePosition = this.coerceCyclicPosition(fragmentPosition);

        TrackFragment fragment = this.fragments.get(fragmentPosition);
        if (fragment != null)
            return fragment;

        if (this.currentTransaction == null)
            this.currentTransaction = this.fragmentManager.beginTransaction();

        AudioFile audioFile = this.audioFiles.get(filePosition);
        fragment = TrackFragment.newInstance(audioFile);
        this.fragments.put(fragmentPosition, fragment);

        this.currentTransaction.add(container.getId(), fragment);

        return fragment;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        this.fragments.remove(position);

        if (this.currentTransaction == null)
            this.currentTransaction = this.fragmentManager.beginTransaction();

        TrackFragment fragment = (TrackFragment) object;
        this.currentTransaction.remove(fragment);
    }

    @Override
    public int getCount() {
        return this.audioFiles.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return ((Fragment) object).getView() == view;
    }

    /**
     * Gets adapter contents
     * @return Adapter contents
     */
    public List<AudioFile> getData() {
        return this.audioFiles;
    }

    /**
     * Coerces the input index to provide cycle-scrolling effect
     * @param position Requested fragment position
     * @return Real fragment position
     */
    private int coerceCyclicPosition(int position) {
        if (this.audioFiles.size() > 1) {
            //if we ViewPager requests first or last elements of the playlist, which are "virtual",
            // we return an "opposite" item from another size of the playlist; see code of
            if (position == 0)
                return this.getCount() - 2;
            else if (position == this.getCount() - 1)
                return 1;
        }

        return position;
    }
}