email/activity/MailboxListFragment.java

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * 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.android.email.activity;

import com.android.email.Email;
import com.android.email.RefreshManager;
import com.android.email.Utility;

import android.app.Activity;
import android.app.ListFragment;
import android.app.LoaderManager.LoaderCallbacks;
import android.content.Loader;
import android.database.Cursor;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;

import java.security.InvalidParameterException;

/**
 * This fragment presents a list of mailboxes for a given account.  The "API" includes the
 * following elements which must be provided by the host Activity.
 *
 *  - call bindActivityInfo() to provide the account ID and set callbacks
 *  - provide callbacks for onOpen and onRefresh
 *  - pass-through implementations of onCreateContextMenu() and onContextItemSelected() (temporary)
 *
 * TODO Restoring ListView state -- don't do this when changing accounts
 */
public class MailboxListFragment extends ListFragment implements OnItemClickListener {
    private static final String BUNDLE_KEY_SELECTED_MAILBOX_ID
            = "MailboxListFragment.state.selected_mailbox_id";
    private static final String BUNDLE_LIST_STATE = "MailboxListFragment.state.listState";
    private static final int LOADER_ID_MAILBOX_LIST = 1;

    private long mLastLoadedAccountId = -1;
    private long mAccountId = -1;
    private long mSelectedMailboxId = -1;

    // UI Support
    private Activity mActivity;
    private MailboxesAdapter mListAdapter;
    private Callback mCallback = EmptyCallback.INSTANCE;

    private ListView mListView;

    private boolean mOpenRequested;
    private boolean mResumed;

    private Utility.ListStateSaver mSavedListState;

    /**
     * Callback interface that owning activities must implement
     */
    public interface Callback {
        public void onMailboxSelected(long accountId, long mailboxId);
    }

    private static class EmptyCallback implements Callback {
        public static final Callback INSTANCE = new EmptyCallback();
        @Override
        public void onMailboxSelected(long accountId, long mailboxId) {
        }
    }

    /**
     * Called to do initial creation of a fragment.  This is called after
     * {@link #onAttach(Activity)} and before {@link #onActivityCreated(Bundle)}.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment onCreate");
        }
        super.onCreate(savedInstanceState);

        mActivity = getActivity();
        mListAdapter = new MailboxesAdapter(mActivity, MailboxesAdapter.MODE_NORMAL);
        if (savedInstanceState != null) {
            restoreInstanceState(savedInstanceState);
        }
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment onActivityCreated");
        }
        super.onActivityCreated(savedInstanceState);

        mListView = getListView();
        mListView.setOnItemClickListener(this);
        mListView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
        registerForContextMenu(mListView);
    }

    public void setCallback(Callback callback) {
        mCallback = (callback == null) ? EmptyCallback.INSTANCE : callback;
    }

    /**
     * @param accountId the account we're looking at
     */
    public void openMailboxes(long accountId) {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment openMailboxes");
        }
        if (accountId == -1) {
            throw new InvalidParameterException();
        }
        if (mAccountId == accountId) {
            return;
        }
        mOpenRequested = true;
        mAccountId = accountId;
        if (mResumed) {
            startLoading();
        }
    }

    public void setSelectedMailbox(long mailboxId) {
        mSelectedMailboxId = mailboxId;
        if (mResumed) {
            highlightSelectedMailbox(true);
        }
    }

    /**
     * Called when the Fragment is visible to the user.
     */
    @Override
    public void onStart() {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment onStart");
        }
        super.onStart();
    }

    /**
     * Called when the fragment is visible to the user and actively running.
     */
    @Override
    public void onResume() {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment onResume");
        }
        super.onResume();
        mResumed = true;

        // If we're recovering from the stopped state, we don't have to reload.
        // (when mOpenRequested = false)
        if (mAccountId != -1 && mOpenRequested) {
            startLoading();
        }
    }

    @Override
    public void onPause() {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment onPause");
        }
        mResumed = false;
        super.onPause();
        mSavedListState = new Utility.ListStateSaver(getListView());
    }

    /**
     * Called when the Fragment is no longer started.
     */
    @Override
    public void onStop() {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment onStop");
        }
        super.onStop();
    }

    /**
     * Called when the fragment is no longer in use.
     */
    @Override
    public void onDestroy() {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment onDestroy");
        }
        super.onDestroy();
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment onSaveInstanceState");
        }
        super.onSaveInstanceState(outState);
        outState.putLong(BUNDLE_KEY_SELECTED_MAILBOX_ID, mSelectedMailboxId);
        outState.putParcelable(BUNDLE_LIST_STATE, new Utility.ListStateSaver(getListView()));
    }

    private void restoreInstanceState(Bundle savedInstanceState) {
        mSelectedMailboxId = savedInstanceState.getLong(BUNDLE_KEY_SELECTED_MAILBOX_ID);
        mSavedListState = savedInstanceState.getParcelable(BUNDLE_LIST_STATE);
    }

    private void startLoading() {
        if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
            Log.d(Email.LOG_TAG, "MailboxListFragment startLoading");
        }
        mOpenRequested = false;
        // Clear the list.  (ListFragment will show the "Loading" animation)
        setListShown(false);

        // If we've already loaded for a different account, discard the previous result and
        // start loading again.
        // We don't want to use restartLoader(), because if the Loader is retained, we *do* want to
        // reuse the previous result.
        // Also, when changing accounts, we don't preserve scroll position.
        boolean accountChanging = false;
        if ((mLastLoadedAccountId != -1) && (mLastLoadedAccountId != mAccountId)) {
            accountChanging = true;
            getLoaderManager().stopLoader(LOADER_ID_MAILBOX_LIST);
        }
        getLoaderManager().initLoader(LOADER_ID_MAILBOX_LIST, null,
                new MailboxListLoaderCallbacks(accountChanging));
    }

    private class MailboxListLoaderCallbacks implements LoaderCallbacks<Cursor> {
        private boolean mAccountChanging;

        public MailboxListLoaderCallbacks(boolean accountChanging) {
            mAccountChanging = accountChanging;
        }

        @Override
        public Loader<Cursor> onCreateLoader(int id, Bundle args) {
            if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
                Log.d(Email.LOG_TAG, "MailboxListFragment onCreateLoader");
            }
            return MailboxesAdapter.createLoader(getActivity(), mAccountId,
                    MailboxesAdapter.MODE_NORMAL);
        }

        @Override
        public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
            if (Email.DEBUG_LIFECYCLE && Email.DEBUG) {
                Log.d(Email.LOG_TAG, "MailboxListFragment onLoadFinished");
            }
            mLastLoadedAccountId = mAccountId;

            // Save list view state (primarily scroll position)
            final ListView lv = getListView();
            final Utility.ListStateSaver lss;
            if (mAccountChanging) {
                lss = null; // Don't preserve list state
            } else if (mSavedListState != null) {
                lss = mSavedListState;
                mSavedListState = null;
            } else {
                lss = new Utility.ListStateSaver(lv);
            }

            if (cursor.getCount() == 0) {
                // If there's no row, don't set it to the ListView.
                // Instead use setListShown(false) to make ListFragment show progress icon.
                mListAdapter.changeCursor(null);
                setListShown(false);
            } else {
                // Set the adapter.
                mListAdapter.changeCursor(cursor);
                setListAdapter(mListAdapter);
                setListShown(true);

                // We want to make selection visible only when account is changing..
                // i.e. Refresh caused by content changed events shouldn't scroll the list.
                highlightSelectedMailbox(mAccountChanging);
            }

            // Restore the state
            if (lss != null) {
                lss.restore(lv);
            }

            // Clear this for next reload triggered by content changed events.
            mAccountChanging = false;
        }
    }

    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        mCallback.onMailboxSelected(mAccountId, id);
    }

    public void onRefresh() {
        if (mAccountId != -1) {
            RefreshManager.getInstance(getActivity()).refreshMailboxList(mAccountId);
        }
    }

    /**
     * Highlight the selected mailbox.
     */
    private void highlightSelectedMailbox(boolean ensureSelectionVisible) {
        if (mSelectedMailboxId == -1) {
            // No mailbox selected
            mListView.clearChoices();
            return;
        }
        final int count = mListView.getCount();
        for (int i = 0; i < count; i++) {
            if (mListView.getItemIdAtPosition(i) != mSelectedMailboxId) {
                continue;
            }
            mListView.setItemChecked(i, true);
            if (ensureSelectionVisible) {
                Log.w(Email.LOG_TAG, "MailboxListFragment -- ensure visible");
                Utility.listViewSmoothScrollToPosition(getActivity(), mListView, i);
            }
            break;
        }
    }
}