Java tutorial
/* * Copyright (c) 2013, Will Szumski * Copyright (c) 2013, Doug Szumski * * This file is part of Cyclismo. * * Cyclismo is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * Cyclismo 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 Cyclismo. If not, see <http://www.gnu.org/licenses/>. */ /* * Copyright 2012 Google Inc. * * 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 org.cowboycoders.cyclismo; import android.content.Context; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentActivity; import android.support.v4.app.FragmentTransaction; import android.view.View; import android.widget.TabHost; import android.widget.TabHost.TabContentFactory; import android.widget.TabHost.TabSpec; import java.util.HashMap; /** * This is a helper class that implements a generic mechanism for associating * fragments with the tabs in a tab host. It relies on a trick. Normally a tab * host has a simple API for supplying a View or Intent that each tab will show. * This is not sufficient for switching between fragments. So instead we make * the content part of the tab host 0dp high (it is not shown) and the * TabManager supplies its own dummy view to show as the tab content. It listens * to changes in tabs, and takes care of switch to the correct fragment shown in * a separate content area whenever the selected tab changes. * <p> * Copied from the Fragment Tabs example in the API 4+ Support Demos. * * @author Jimmy Shih */ public class TabManager implements TabHost.OnTabChangeListener { private final FragmentActivity fragmentActivity; private final TabHost tabHost; private final int containerId; private final HashMap<String, TabInfo> tabs = new HashMap<String, TabInfo>(); private TabInfo lastTabInfo; /** * An object to hold a tab's info. * * @author Jimmy Shih */ private static final class TabInfo { private final String tag; private final Class<?> clss; private final Bundle bundle; private Fragment fragment; public TabInfo(String tag, Class<?> clss, Bundle bundle) { this.tag = tag; this.clss = clss; this.bundle = bundle; } } /** * A dummy {@link TabContentFactory} that creates an empty view to satisfy the * {@link TabHost} API. * * @author Jimmy Shih */ private static class DummyTabContentFactory implements TabContentFactory { private final Context context; public DummyTabContentFactory(Context context) { this.context = context; } @Override public View createTabContent(String tag) { View view = new View(context); view.setMinimumWidth(0); view.setMinimumHeight(0); return view; } } public TabManager(FragmentActivity fragmentActivity, TabHost tabHost, int containerId) { this.fragmentActivity = fragmentActivity; this.tabHost = tabHost; this.containerId = containerId; tabHost.setOnTabChangedListener(this); } public void addTab(TabSpec tabSpec, Class<?> clss, Bundle bundle) { tabSpec.setContent(new DummyTabContentFactory(fragmentActivity)); String tag = tabSpec.getTag(); TabInfo tabInfo = new TabInfo(tag, clss, bundle); /* * Check to see if we already have a fragment for this tab, probably from a * previously saved state. If so, deactivate it, because our initial state * is that a tab isn't shown. */ tabInfo.fragment = fragmentActivity.getSupportFragmentManager().findFragmentByTag(tag); if (tabInfo.fragment != null && !tabInfo.fragment.isDetached()) { FragmentTransaction fragmentTransaction = fragmentActivity.getSupportFragmentManager() .beginTransaction(); fragmentTransaction.detach(tabInfo.fragment); fragmentTransaction.commit(); } tabs.put(tag, tabInfo); tabHost.addTab(tabSpec); } @Override public void onTabChanged(String tabId) { TabInfo newTabInfo = tabs.get(tabId); if (lastTabInfo != newTabInfo) { FragmentTransaction fragmentTransaction = fragmentActivity.getSupportFragmentManager() .beginTransaction(); if (lastTabInfo != null) { if (lastTabInfo.fragment != null) { fragmentTransaction.detach(lastTabInfo.fragment); } } if (newTabInfo != null) { if (newTabInfo.fragment == null) { newTabInfo.fragment = Fragment.instantiate(fragmentActivity, newTabInfo.clss.getName(), newTabInfo.bundle); fragmentTransaction.add(containerId, newTabInfo.fragment, newTabInfo.tag); } else { fragmentTransaction.attach(newTabInfo.fragment); } } lastTabInfo = newTabInfo; fragmentTransaction.commitAllowingStateLoss(); fragmentActivity.getSupportFragmentManager().executePendingTransactions(); } } }