Java tutorial
/* * Copyright (c) 2014 Jono Vanhie-Van Gerwen * * 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.github.jvanhie.discogsscrobbler; import android.app.Activity; import android.os.Bundle; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.AbsListView; import android.widget.AdapterView; import android.widget.FrameLayout; import android.widget.ListView; import android.widget.TextView; import com.github.jvanhie.discogsscrobbler.adapters.ReleaseAdapter; import com.github.jvanhie.discogsscrobbler.models.Release; import com.github.jvanhie.discogsscrobbler.queries.DiscogsSearchRelease; import com.github.jvanhie.discogsscrobbler.util.Discogs; import java.util.ArrayList; import java.util.List; /** * A list fragment representing a list of Releases. This fragment * also supports tablet devices by allowing list items to be given an * 'activated' state upon selection. This helps indicate which item is * currently being viewed in a {@link ReleaseDetailFragment}. * <p> * Activities containing this fragment MUST implement the {@link Callbacks} * interface. */ public class ReleaseVersionsFragment extends Fragment { public static final String ARG_ITEM_ID = "item_id"; /** * The serialization (saved instance state) Bundle key representing the * activated item position. Only used on tablets. */ private static final String STATE_ACTIVATED_POSITION = "activated_position"; /** * The fragment's current callback object, which is notified of list item * clicks. */ private Callbacks mCallbacks = sDummyCallbacks; /** * The current activated item position. Only used on tablets. */ private int mActivatedPosition = ListView.INVALID_POSITION; private Release mRelease; private List<Release> mReleases; private AbsListView mList; private Discogs mDiscogs; private int mPage = 1; private int mLoadpage = 1; /** * A callback interface that all activities containing this fragment must * implement. This mechanism allows activities to be notified of item * selections. */ public interface Callbacks { /** * Callback for when an item has been selected. */ public void onItemSelected(long id); } /** * A dummy implementation of the {@link Callbacks} interface that does * nothing. Used only when this fragment is not attached to an activity. */ private static Callbacks sDummyCallbacks = new Callbacks() { @Override public void onItemSelected(long id) { } }; /** * Mandatory empty constructor for the fragment manager to instantiate the * fragment (e.g. upon screen orientation changes). */ public ReleaseVersionsFragment() { } @Override public void onViewCreated(View view, Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); // Restore the previously serialized activated item position. if (savedInstanceState != null && savedInstanceState.containsKey(STATE_ACTIVATED_POSITION)) { setActivatedPosition(savedInstanceState.getInt(STATE_ACTIVATED_POSITION)); } } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { //setup list view mList = new ListView(getActivity()); mList.setId(android.R.id.list); mList.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) { onListItemClick(view, i, l); } }); //create superframe for adding list and empty view FrameLayout superFrame = new FrameLayout(getActivity()); FrameLayout.LayoutParams layoutparams = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT); superFrame.setLayoutParams(layoutparams); View emptyView = inflater.inflate(R.layout.fragment_empty, container, false); ((TextView) emptyView.findViewById(R.id.empty_heading)).setText("No versions found"); ((TextView) emptyView.findViewById(R.id.empty_text)).setText( "No alternative versions of this release were found, this could also mean Discogs did not add a master id to this release"); /*initialize list with local discogs collection*/ if (mDiscogs == null) mDiscogs = Discogs.getInstance(getActivity()); if (mRelease == null) { mDiscogs.getRelease(getArguments().getLong(ARG_ITEM_ID, 0), new Discogs.DiscogsDataWaiter<Release>() { @Override public void onResult(boolean success, Release data) { if (success) { mRelease = data; loadList(); } } }); } else { loadList(); } superFrame.addView(emptyView); mList.setEmptyView(emptyView); superFrame.addView(mList); return superFrame; } public void loadList() { if (mReleases == null || mPage != mLoadpage) { mDiscogs.getMasterReleases(mRelease.master_id, mLoadpage, new Discogs.DiscogsDataWaiter<List<DiscogsSearchRelease>>() { @Override public void onResult(boolean success, List<DiscogsSearchRelease> data) { if (success && data != null) { mPage = mLoadpage; if (mReleases == null) { mReleases = new ArrayList<Release>(); } else { //it's an additional load, remove the previous loader mReleases.remove(mReleases.size() - 1); } for (DiscogsSearchRelease r : data) { //create release object that releaseadapter will understand (discogs does not provide artist name with it's master versions call, get it from the current release) Release release = new Release(r); release.artist = mRelease.artist; //don't add the current release if (release.releaseid != mRelease.releaseid) { mReleases.add(release); } } if (mReleases.size() != 0) { if (mList.getAdapter() == null) { mList.setAdapter(new ReleaseAdapter(getActivity(), mReleases)); } else { ((ReleaseAdapter) mList.getAdapter()).updateReleases(mReleases); } } } } }); } else { if (mReleases.size() != 0) { if (mList.getAdapter() == null) { mList.setAdapter(new ReleaseAdapter(getActivity(), mReleases)); } else { ((ReleaseAdapter) mList.getAdapter()).updateReleases(mReleases); } } } } @Override public void onAttach(Activity activity) { super.onAttach(activity); // Activities containing this fragment must implement its callbacks. if (!(activity instanceof Callbacks)) { throw new IllegalStateException("Activity must implement fragment's callbacks."); } mCallbacks = (Callbacks) activity; } @Override public void onDetach() { super.onDetach(); // Reset the active callbacks interface to the dummy implementation. mCallbacks = sDummyCallbacks; } public void onListItemClick(View view, int position, long id) { // Notify the active callbacks interface (the activity, if the // fragment is attached to one) that an item has been selected. if (id == 0) { //it's a loader, get the next page mLoadpage = mPage + 1; loadList(); } else { mCallbacks.onItemSelected(id); } } @Override public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); if (mActivatedPosition != ListView.INVALID_POSITION) { // Serialize and persist the activated item position. outState.putInt(STATE_ACTIVATED_POSITION, mActivatedPosition); } } private void setActivatedPosition(int position) { if (position == AbsListView.INVALID_POSITION) { mList.setItemChecked(mActivatedPosition, false); } else { mList.setItemChecked(position, true); } mActivatedPosition = position; } }