Java tutorial
/* * Copyright 2014 Dario B darizotas at gmail dot com * * This software is licensed under a new BSD License. * Unported License. http://opensource.org/licenses/BSD-3-Clause * */ package com.darizotas.metadatastrip; import java.io.File; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import android.app.Activity; import android.os.Bundle; import android.support.v4.app.ListFragment; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuInflater; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.widget.ListView; import android.widget.SimpleAdapter; import android.widget.TextView; import com.darizotas.metadatastrip.file.FileManager; /** * A list fragment representing a list of Files. 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 FileDetailFragment}. * <p> * Activities containing this fragment MUST implement the {@link Callbacks} * interface. */ public class FileListFragment extends ListFragment { /** * 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 serialization (saved instance state) Bundle key representing the * current path. */ private static final String STATE_CURRENT_PATH = "current_path"; /** * 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; /** * List of contents of the current directory. */ private List<HashMap<String, String>> mDirContents = new ArrayList<HashMap<String, String>>(); /** * Current path. */ private String mPath; /** * 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(String path); } /** * 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(String path) { } }; /** * Mandatory empty constructor for the fragment manager to instantiate the * fragment (e.g. upon screen orientation changes). */ public FileListFragment() { } @Override public void onAttach(Activity activity) { //http://developer.android.com/guide/components/fragments.html 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 onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setHasOptionsMenu(true); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { //http://developer.android.com/reference/android/app/ListFragment.html // Let's instantiate my customized view. return inflater.inflate(R.layout.fragment_file_list, container, false); } @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 void onActivityCreated(Bundle savedInstanceState) { //http://developer.android.com/reference/android/app/Fragment.html //http://stackoverflow.com/questions/8041206/android-fragment-oncreateview-vs-onactivitycreated super.onActivityCreated(savedInstanceState); // Retrieves the current path. mPath = (savedInstanceState != null && savedInstanceState.containsKey(STATE_CURRENT_PATH)) ? savedInstanceState.getString(STATE_CURRENT_PATH) : "/"; updateListAdapter(mPath); } @Override public void onDetach() { super.onDetach(); // Reset the active callbacks interface to the dummy implementation. mCallbacks = sDummyCallbacks; } @Override public void onListItemClick(ListView listView, View view, int position, long id) { super.onListItemClick(listView, view, position, id); // Retrieves the content of the current folder HashMap<String, String> selected = mDirContents.get(position); mCallbacks.onItemSelected(selected.get(FileManager.KEY_PATH)); } @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); } // Serialize and persist the current path outState.putString(STATE_CURRENT_PATH, mPath); } /** * Turns on activate-on-click mode. When this mode is on, list items will be * given the 'activated' state when touched. */ public void setActivateOnItemClick(boolean activateOnItemClick) { // When setting CHOICE_MODE_SINGLE, ListView will automatically // give items the 'activated' state when touched. getListView().setChoiceMode(activateOnItemClick ? ListView.CHOICE_MODE_SINGLE : ListView.CHOICE_MODE_NONE); } private void setActivatedPosition(int position) { if (position == ListView.INVALID_POSITION) { getListView().setItemChecked(mActivatedPosition, false); } else { getListView().setItemChecked(position, true); } mActivatedPosition = position; } @Override public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) { inflater.inflate(R.menu.list_menu, menu); } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle item selection switch (item.getItemId()) { case R.id.folder_back: File f = new File(mPath); if (f.getParent() != null) mCallbacks.onItemSelected(f.getParent()); return true; default: return super.onOptionsItemSelected(item); } } /** * Updates the current Fragment with the contents of the given path. * @param path Current path. */ public void updateListAdapter(String path) { // Updates the current folder mPath = path; TextView currentPath = (TextView) getView().findViewById(R.id.current_path); currentPath.setText(path); // Updates the list mDirContents = FileManager.getDirContents(path); String[] from = { FileManager.KEY_ICON, FileManager.KEY_FILENAME }; int[] to = { R.id.file_icon, R.id.file_name }; SimpleAdapter adapter = new SimpleAdapter(getActivity(), mDirContents, R.layout.fragment_file_row, from, to); setListAdapter(adapter); } }