space-android/src/com/owncloud/android/ui/fragment/TaskRetainerFragment.java

/**
 *   ownCloud Android client application
 *
 *   Copyright (C) 2016 ownCloud Inc.
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License version 2,
 *   as published by the Free Software Foundation.
 *
 *   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
package com.owncloud.android.ui.fragment;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;

import com.owncloud.android.ui.activity.ReceiveExternalFilesActivity;
import com.owncloud.android.ui.asynctasks.CopyAndUploadContentUrisTask;

/**
 * Fragment retaining a background task across configuration changes.
 */
public class TaskRetainerFragment extends Fragment {

    public static final String FTAG_TASK_RETAINER_FRAGMENT = "TASK_RETAINER_FRAGMENT";

    private CopyAndUploadContentUrisTask mTask;

    /**
     * Updates the listener of the retained task whenever the parent
     * Activity is attached.
     *
     * Since its done in main thread, and provided the AsyncTask only accesses
     * the listener in the main thread (should so), no sync problem should occur.
     */
    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        if (mTask != null) {
            if (context instanceof ReceiveExternalFilesActivity) {
                mTask.setListener((CopyAndUploadContentUrisTask.OnCopyTmpFilesTaskListener) context);
            } else {
                mTask.setListener(null);
            }
        }
    }

    /**
     * Only called once, since the instance is retained across configuration changes
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);    // the key point
    }

    /**
     * Sets the task to retain across configuration changes
     *
     * @param task  Task to retain
     */
    public void setTask(CopyAndUploadContentUrisTask task) {
        if (mTask != null) {
            mTask.setListener(null);
        }
        mTask = task;
        Context context = getContext();
        if (mTask != null && context != null) {
            if (context instanceof ReceiveExternalFilesActivity) {
                task.setListener((CopyAndUploadContentUrisTask.OnCopyTmpFilesTaskListener) context);
            } else {
                task.setListener(null);
            }
        }
    }
}