Java tutorial
/* * Copyright (C) 2011 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 org.orange.querysystem.content; import org.orange.querysystem.R; import android.content.Context; import android.os.Build; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentActivity; import android.support.v4.app.FragmentPagerAdapter; import android.support.v4.view.ViewPager; import android.view.View; import android.view.View.OnFocusChangeListener; import android.view.ViewGroup; import android.widget.HorizontalScrollView; import android.widget.RelativeLayout; import android.widget.TabHost; import android.widget.TabWidget; import android.widget.TextView; import java.lang.ref.WeakReference; import java.util.ArrayList; import java.util.List; /** * This is a helper class that implements the management of tabs and all * details of connecting a ViewPager with associated TabHost. 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 pages. So instead we make the content part of the tab host * 0dp high (it is not shown) and the TabsAdapter 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 paged in the ViewPager whenever the selected * tab changes. */ public class TabsAdapter extends FragmentPagerAdapter implements TabHost.OnTabChangeListener, ViewPager.OnPageChangeListener { private final Context mContext; private final TabHost mTabHost; private final ViewPager mViewPager; private final List<WeakReference<Fragment>> mFragmentPagers = new ArrayList<>(); private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>(); static final class TabInfo { // private final String tag; private final Class<?> clss; private final Bundle args; TabInfo(Class<?> _class, Bundle _args) { // tag = _tag; clss = _class; args = _args; } } static class DummyTabFactory implements TabHost.TabContentFactory { private final Context mContext; public DummyTabFactory(Context context) { mContext = context; } @Override public View createTabContent(String tag) { View v = new View(mContext); v.setMinimumWidth(0); v.setMinimumHeight(0); return v; } } public TabsAdapter(FragmentActivity activity, TabHost tabHost, ViewPager pager) { super(activity.getSupportFragmentManager()); mContext = activity; mTabHost = tabHost; mTabHost.setOnFocusChangeListener(new OnFocusChangeListener() { @Override public void onFocusChange(View v, boolean hasFocus) { adjustSelectedTabToCenter(); } }); mViewPager = pager; mTabHost.setOnTabChangedListener(this); mViewPager.setAdapter(this); mViewPager.setOnPageChangeListener(this); } public void addTab(TabHost.TabSpec tabSpec, Class<?> clss, Bundle args) { tabSpec.setContent(new DummyTabFactory(mContext)); // String tag = tabSpec.getTag(); TabInfo info = new TabInfo(clss, args); mTabs.add(info); notifyDataSetChanged(); mTabHost.addTab(tabSpec); setTabForIfLowerThanHONEYCOMB(); } private void setTabForIfLowerThanHONEYCOMB() { if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) { View child = mTabHost.getTabWidget().getChildAt(getCount() - 1); child.setBackgroundColor(0xFFB5E61D); TextView tv = (TextView) child.findViewById(android.R.id.title); RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) tv.getLayoutParams(); params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, 0); //?? params.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE); //? params.setMargins(dp2px(10), dp2px(4), dp2px(10), dp2px(4)); child.getLayoutParams().height = RelativeLayout.LayoutParams.WRAP_CONTENT; } } private int dp2px(int dp) { return (int) (mTabHost.getContext().getResources().getDisplayMetrics().density * dp + 0.5f); } /** * Tabs */ public void clear() { mTabs.clear(); mFragmentPagers.clear(); mTabHost.setCurrentTab(0); mTabHost.clearAllTabs(); mViewPager.removeAllViews(); notifyDataSetChanged(); } public List<Fragment> getAddedFragmentPagers() { ArrayList<Fragment> result = new ArrayList<>(); for (WeakReference<Fragment> ref : mFragmentPagers) { Fragment f = ref.get(); if (f != null) { result.add(f); } } return result; } @Override public int getCount() { return mTabs.size(); } @Override public Fragment getItem(int position) { TabInfo info = mTabs.get(position); Fragment fragment = Fragment.instantiate(mContext, info.clss.getName(), info.args); mFragmentPagers.add(new WeakReference<>(fragment)); return fragment; } @Override public void onTabChanged(String tabId) { int position = mTabHost.getCurrentTab(); adjustSelectedTabToCenter(); mViewPager.setCurrentItem(position); } public void adjustSelectedTabToCenter() { View currentTab = mTabHost.getCurrentTabView(); if (currentTab == null) { return; } HorizontalScrollView hsv = (HorizontalScrollView) mTabHost.findViewById(R.id.tabs_scroll); hsv.smoothScrollTo(currentTab.getLeft() + (currentTab.getWidth() - hsv.getWidth()) / 2, 0); } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { } @Override public void onPageSelected(int position) { // Unfortunately when TabHost changes the current tab, it kindly // also takes care of putting focus on it when not in touch mode. // The jerk. // This hack tries to prevent this from pulling focus out of our // ViewPager. TabWidget widget = mTabHost.getTabWidget(); int oldFocusability = widget.getDescendantFocusability(); widget.setDescendantFocusability(ViewGroup.FOCUS_BLOCK_DESCENDANTS); mTabHost.setCurrentTab(position); widget.setDescendantFocusability(oldFocusability); } @Override public void onPageScrollStateChanged(int state) { } }