仿qq底部Tab导航

本篇博客主要实现以下效果：

使用FragmentTabHost实现qq底部Tab切换
使用RadioGroup和RadioButton实现仿qq底部切换
使用RadioGroup和ViewPager 实现可以滑动切换的仿qq底部Tab切换
解决Fragment多次实例化的几种方案
Fragemnt的懒加载（网上很多人称之为Fragemnt的最优加载）

效果图

老规矩，废话不多说，先看效果图

FragmentTabHost实现qq底部Tab实践的效果图

RadioGroup和ViewPager 实现可以滑动切换的仿qq底部Tab效果图

使用FragmentTabHost实现qq底部Tab切换

第一步先看布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><!--用来填充Fragemnt的FrayLayout--><FrameLayoutandroid:id="@+id/main_layout_content"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"></FrameLayout><!--FragmentTabHost--><android.support.v4.app.FragmentTabHostandroid:id="@android:id/tabhost"android:layout_width="match_parent"android:layout_height="wrap_content"android:background="#F6F6F6"android:paddingBottom="5dp"android:paddingTop="5dp"><FrameLayoutandroid:id="@android:id/tabcontent"android:layout_width="0dp"android:layout_height="0dp"/></android.support.v4.app.FragmentTabHost></LinearLayout>

其实很简单，没什么好说的，就是一个vertical的LinearLayout中放置着一个FrameLayout和FragmentTabHost

接下来我们来看一下代码

public class FirstStyleActivity extends AppCompatActivity {FragmentTabHost mTabHost;private TabWidget mTabWidget;private List<FragmentInfo> mFragmentEntities;private static final String TAG = "xujun";private static final String tag = "tag";public static final String[] mTiltles = new String[]{"首页", "课程", "直播", "个人"};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_first_style);mTabHost = (FragmentTabHost) findViewById(android.R.id.tabhost);mTabHost.setup(this, getSupportFragmentManager(), R.id.main_layout_content);mTabWidget = mTabHost.getTabWidget();//  去掉分割线mTabWidget.setDividerDrawable(null);mFragmentEntities = MainFragmentFactory.getInstance().getList();initListener();initData();}private void initData() {int size = mFragmentEntities.size();for (int i = 0; i < size; i++) {Log.i(TAG, "size:=" + size);FragmentInfo fragmentInfo = mFragmentEntities.get(i);String title = fragmentInfo.getTitle();TabHost.TabSpec tabSpec = mTabHost.newTabSpec(title).setIndicator(getTabView(i));Bundle bundle = new Bundle();bundle.putString(tag, mTiltles[i]);mTabHost.addTab(tabSpec, fragmentInfo.getClz(), bundle);}updateTab(0);}private void initListener() {mTabHost.setOnTabChangedListener(new TabHost.OnTabChangeListener() {@Overridepublic void onTabChanged(String tabId) {int currentTab = mTabHost.getCurrentTab();Log.i(TAG, "onTabChanged：currentTab:=" + currentTab);updateTab(currentTab);}});}private View getTabView(int i) {View view = View.inflate(this, R.layout.tab_layout, null);int currentTab = mTabHost.getCurrentTab();Log.i(TAG, "currentTab:=" + currentTab);setSingleView(view, currentTab, i);return view;}private void setSingleView(View view, int currentTab, int index) {FragmentInfo fragmentInfo = mFragmentEntities.get(index);int[] imagIds = fragmentInfo.getImagIds();int[] colors = fragmentInfo.getColors();TextView tv = (TextView) view.findViewById(R.id.tab_tv);ImageView iv = (ImageView) view.findViewById(R.id.tab_icon);tv.setText(fragmentInfo.getTitle());Resources resources = getResources();if (index == currentTab) {tv.setTextColor(resources.getColor(colors[1]));iv.setImageDrawable(resources.getDrawable(imagIds[1]));} else {tv.setTextColor(getResources().getColor(colors[0]));iv.setImageDrawable(resources.getDrawable(imagIds[0]));}}private void updateTab(int currentTab) {int childCount = mTabWidget.getChildCount();for (int i = 0; i < childCount; i++) {View view = mTabWidget.getChildTabViewAt(i);setSingleView(view, currentTab, i);}}
}

其实说起来也很简单，主要分为以下步骤

第一步，实例化FragmentTabHost并设置相关样式

mTabHost = (FragmentTabHost) findViewById(android.R.id.tabhost);mTabHost.setup(this, getSupportFragmentManager(), R.id.main_layout_content);
mTabWidget = mTabHost.getTabWidget();
//  去掉分割线
mTabWidget.setDividerDrawable(null);

第二步,添加每一个TabHost

 for (int i = 0; i < size; i++) {Log.i(TAG, "size:=" + size);FragmentInfo fragmentInfo = mFragmentEntities.get(i);String title = fragmentInfo.getTitle();TabHost.TabSpec tabSpec = mTabHost.newTabSpec(title).setIndicator(getTabView(i));Bundle bundle = new Bundle();bundle.putString(tag, mTiltles[i]);mTabHost.addTab(tabSpec, fragmentInfo.getClz(), bundle);
}

第三步，通过设置监听器来实现底部tab颜色和图案样式的转换

 mTabHost.setOnTabChangedListener(new TabHost.OnTabChangeListener() {@Overridepublic void onTabChanged(String tabId) {int currentTab = mTabHost.getCurrentTab();Log.i(TAG, "onTabChanged：currentTab:=" + currentTab);updateTab(currentTab);}
});

运行上述代码及可以看到如下效果图

使用RadioGroup和RadioButton实现仿qq底部切换

第一步，先看布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayoutandroid:id="@+id/activity_second_style"xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"
><!--用来填充Fragemnt的FrayLayout--><FrameLayoutandroid:id="@+id/fl"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"></FrameLayout><!--使用RadioGroup来实现tab的切换--><RadioGroupandroid:id="@+id/rg"android:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"><RadioButtonandroid:id="@+id/rb_home"style="@style/bottom_tab"android:drawableTop="@drawable/sel_home"android:text="首页"/><RadioButtonandroid:id="@+id/rb_course"style="@style/bottom_tab"android:drawableTop="@drawable/sel_course"android:text="课程"/><RadioButtonandroid:id="@+id/rb_direct_seeding"style="@style/bottom_tab"android:drawableTop="@drawable/sel_direct_seeding"android:text="直播"/><RadioButtonandroid:id="@+id/rb_me"style="@style/bottom_tab"android:drawableTop="@drawable/sel_me"android:text="我的"/></RadioGroup></LinearLayout>

其实每一个tab的选中时利用RadioGroup中RadioButton的互相排斥的特性，即每一次只能选中一个 RadioButton

至于bottom_tab的style，只不过是将相同的arr提取出来，减少布局的代码量和方便统一修改而已，平时我们在写布局代码的时候也可以这样

<style name="bottom_tab"><item name="android:layout_width" >0dp</item><item name="android:layout_height" >wrap_content</item><item name="android:layout_weight" >1</item><item name="android:text" >0dp</item><item name="android:gravity" >center</item><item name="android:textColor" >@drawable/sel_bottom_tab_text</item><item name="android:padding" >8dp</item><item name="android:button" >@null</item>
</style>

第二步，我们来看一下Activity的代码

public class ThreeActivity extends AppCompatActivity {FrameLayout mFl;RadioGroup mRg;private FragmentManager mFragmentManager;private int position = 0;public static final String[] mTiltles = new String[]{"首页", "课程", "直播", "个人"};private List<Fragment> mFragments;private Fragment mCurFragment;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_three);mFl = (FrameLayout) findViewById(R.id.fl);mRg = (RadioGroup) findViewById(R.id.rg);mFragments = new ArrayList<>();for (int i = 0; i < mTiltles.length; i++) {ItemFragement itemFragement = ItemFragement.newInstance(mTiltles[i]);mFragments.add(itemFragement);}mCurFragment = mFragments.get(position);replaceFragment(mCurFragment);((RadioButton)mRg.getChildAt(position)).setChecked(true);initListener();}private void initListener() {mRg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {@Overridepublic void onCheckedChanged(RadioGroup group, int checkedId) {RadioButton radioButton = (RadioButton) group.findViewById(checkedId);if (false == radioButton.isChecked()) {return;}switch (checkedId) {case R.id.rb_home:position = 0;break;case R.id.rb_course:position = 1;break;case R.id.rb_direct_seeding:position = 2;break;case R.id.rb_me:position = 3;break;default:position = 0;break;}LUtils.i("position==" + position);Fragment to = mFragments.get(position);showFragment(mCurFragment, to);mCurFragment = to;}});}private void showFragment(Fragment from, Fragment to) {FragmentManager supportFragmentManager = getSupportFragmentManager();FragmentTransaction transaction = supportFragmentManager.beginTransaction();if (!to.isAdded()) {    // 先判断是否被add过transaction.hide(from).add(R.id.fl, to).commit(); // 隐藏当前的fragment，add下一个到Activity中} else {transaction.hide(from).show(to).commit(); // 隐藏当前的fragment，显示下一个}}/*** 这个方法用老替换fragment* xujun* 2016/5/3 17:28.*/private void replaceFragment(Fragment fragmeny) {FragmentManager supportFragmentManager = getSupportFragmentManager();FragmentTransaction fragmentTransaction = supportFragmentManager.beginTransaction();fragmentTransaction.replace(R.id.fl, fragmeny).commit();}}

思路解析

实例化各个控件，这里代码就不贴出来了
初始化 Fragemnt 和选中各个tab

 mFragments = new ArrayList<>();
for (int i = 0; i < mTiltles.length; i++) {ItemFragement itemFragement = ItemFragement.newInstance(mTiltles[i]);mFragments.add(itemFragement);
}
mCurFragment = mFragments.get(position);
replaceFragment(mCurFragment);((RadioButton)mRg.getChildAt(position)).setChecked(true);private void replaceFragment(Fragment fragmeny) {FragmentManager supportFragmentManager = getSupportFragmentManager();FragmentTransaction fragmentTransaction = supportFragmentManager.beginTransaction();fragmentTransaction.replace(R.id.fl, fragmeny).commit();
}

第三步，通过监听RadioGroup的 OnCheckedChangeListener事件，来实现tab和Fragemnt的切换

 mRg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {@Overridepublic void onCheckedChanged(RadioGroup group, int checkedId) {RadioButton radioButton = (RadioButton) group.findViewById(checkedId);if (false == radioButton.isChecked()) {return;}switch (checkedId) {case R.id.rb_home:position = 0;break;case R.id.rb_course:position = 1;break;case R.id.rb_direct_seeding:position = 2;break;case R.id.rb_me:position = 3;break;default:position = 0;break;}LUtils.i("position==" + position);Fragment to = mFragments.get(position);showFragment(mCurFragment, to);mCurFragment = to;}});

使用RadioGroup和ViewPager 实现可以滑动切换的仿qq底部Tab切换

第一步，我们同样先看布局代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayoutandroid:id="@+id/activity_second_style"xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"
><!--用来填充Fragemnt的ViewPager--><android.support.v4.view.ViewPagerandroid:id="@+id/viewPager"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"></android.support.v4.view.ViewPager><!--使用RadioGroup来实现tab的切换--><RadioGroupandroid:id="@+id/rg"android:layout_width="match_parent"android:layout_height="wrap_content"android:orientation="horizontal"><RadioButtonandroid:id="@+id/rb_home"style="@style/bottom_tab"android:drawableTop="@drawable/sel_home"android:text="首页"/><RadioButtonandroid:id="@+id/rb_course"style="@style/bottom_tab"android:drawableTop="@drawable/sel_course"android:text="课程"/><RadioButtonandroid:id="@+id/rb_direct_seeding"style="@style/bottom_tab"android:drawableTop="@drawable/sel_direct_seeding"android:text="直播"/><RadioButtonandroid:id="@+id/rb_me"style="@style/bottom_tab"android:drawableTop="@drawable/sel_me"android:text="我的"/></RadioGroup></LinearLayout>

第二步，我们一起来看一下Activity代码

public class SecondStyleActivity extends AppCompatActivity {public static final String[] mTiltles = new String[]{"首页", "课程", "直播", "个人"};private List<Fragment> mFragments;ViewPager mViewPager;RadioGroup mRg;private int position = 0;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_second_style);mViewPager = (ViewPager) findViewById(R.id.viewPager);mRg = (RadioGroup) findViewById(R.id.rg);initListener();initData();}private void initData() {mFragments = new ArrayList<>();for (int i = 0; i < mTiltles.length; i++) {ItemFragement itemFragement = ItemFragement.newInstance(mTiltles[i]);mFragments.add(itemFragement);}BaseFragmentAdapter fragmentAdapter = new BaseFragmentAdapter(getSupportFragmentManager(), mFragments, mTiltles);mViewPager.setAdapter(fragmentAdapter);mViewPager.setCurrentItem(position);((RadioButton) mRg.getChildAt(position)).setChecked(true);}private void initListener() {mViewPager.addOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {@Overridepublic void onPageSelected(int position) {RadioButton radioButton = (RadioButton) mRg.getChildAt(position);radioButton.setChecked(true);}});mRg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {@Overridepublic void onCheckedChanged(RadioGroup group, int checkedId) {RadioButton rb = (RadioButton) group.findViewById(checkedId);if (!rb.isChecked()) {return;}switch (checkedId) {case R.id.rb_home:position = 0;break;case R.id.rb_course:position = 1;break;case R.id.rb_direct_seeding:position = 2;break;case R.id.rb_me:position = 3;break;default:position = 0;break;}mViewPager.setCurrentItem(position);}});}
}

思路解析如下

实例化ViewPager和RadioGroup

 mViewPager = (ViewPager) findViewById(R.id.viewPager);mRg = (RadioGroup) findViewById(R.id.rg);

第二步，初始化ViewPager的适配器和选中那个tab

 mFragments = new ArrayList<>();
for (int i = 0; i < mTiltles.length; i++) {ItemFragement itemFragement = ItemFragement.newInstance(mTiltles[i]);mFragments.add(itemFragement);
}
BaseFragmentAdapter fragmentAdapter = new BaseFragmentAdapter(getSupportFragmentManager(), mFragments, mTiltles);
mViewPager.setAdapter(fragmentAdapter);
mViewPager.setCurrentItem(position);
((RadioButton) mRg.getChildAt(position)).setChecked(true);

第三步，监听ViewPager 的滑动事件和RadioGroup的OnCheckedChangeListener事件，分别切换到相应的 Fragemnt 和同步ViewPager中 position 与RadioGroup之间的联系

 mViewPager.addOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {@Overridepublic void onPageSelected(int position) {RadioButton radioButton = (RadioButton) mRg.getChildAt(position);radioButton.setChecked(true);}
});mRg.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {@Overridepublic void onCheckedChanged(RadioGroup group, int checkedId) {RadioButton rb = (RadioButton) group.findViewById(checkedId);if (!rb.isChecked()) {return;}switch (checkedId) {case R.id.rb_home:position = 0;break;case R.id.rb_course:position = 1;break;case R.id.rb_direct_seeding:position = 2;break;case R.id.rb_me:position = 3;break;default:position = 0;break;}mViewPager.setCurrentItem(position);}
});

注意事项

我们可以通过以下方法设置ViewPager左右页面能缓存的fragment 数量

//  设置左右页面 能缓存的fragment 数量
mViewPager.setOffscreenPageLimit(fragmentAdapter.getCount() - 1);

到此仿qq底部tab切换的集中方法已经讲解完毕，之所以讲解了三种方法，是想让大家了解多种实现方式，因为每一个人的习惯都不一样，有些人习惯使用与第一种方式，有人习惯使用第二种方式。。。。。。了解多种实现方式以后，我们要读懂别人的代码也容易得多了，其实我们还可以使用自定义控件来实现，方法也比较简单，这里就不讲解了，有兴趣的话，可以自行搜索

下面我将为大家讲解Fragment的一些优化

解决Fragment多次实例化的几种方案

目前本人了解到的解决方案，无非是利用一下两种思想

第一种解决方法

在onCreateView中避免多次实例化View，可通过判断View是否为空，来实现相应的逻辑操作,核心代码如下

   public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @NullableBundle savedInstanceState) {LUtils.i(getClass().getSimpleName()+">>>>>>>>>>>　　onCreateView");if(mView==null){mContext = getContext();mView=View.inflate(mContext,getLayoutId(),null);initView(mView);LUtils.i(getClass().getSimpleName()+">>>>>>>>>>>　　initView");}else{// 缓存的rootView需要判断是否已经被加过parent，如果有parent需要从parent删除，// 要不然会发生这个rootview已经有parent的错误。ViewGroup parent =(ViewGroup) mView.getParent();if(parent!=null){parent.removeView(mView);}LUtils.i(getClass().getSimpleName()+">>>>>>>>>>>　　removeView");}return mView;}

第二种解决方案

在项目中需要进行Fragment的切换，用hide（）和show（）方法结合起来来替代replace()方法来实现Fragment的切换：

private void showFragment(Fragment from, Fragment to) {FragmentManager supportFragmentManager = getSupportFragmentManager();FragmentTransaction transaction = supportFragmentManager.beginTransaction();if (!to.isAdded()) {    // 先判断是否被add过transaction.hide(from).add(R.id.fl, to).commit(); // 隐藏当前的fragment，add下一个到Activity中} else {transaction.hide(from).show(to).commit(); // 隐藏当前的fragment，显示下一个}}/*** 这个方法用老替换fragment* xujun* 2016/5/3 17:28.*/private void replaceFragment(Fragment fragmeny) {FragmentManager supportFragmentManager = getSupportFragmentManager();FragmentTransaction fragmentTransaction = supportFragmentManager.beginTransaction();fragmentTransaction.replace(R.id.fl, fragmeny).commit();
}

关于避免Fragment的多次实例化的分析与优化到此为止，下面我们一起来看一下则那样实现Fragemnt 的懒加载

Fragemnt的懒加载（网上很多人称之为Fragemnt的最优加载）

关于懒加载的这部分，代码是参考这篇博客的 ViewPager+Fragment LazyLoad最优解

我们知道 ViewPager通常会有预加载机制，默认情况下会先加载左右一页的数据，有时候我们想等待页面可见的时候在去加载网络数据，解决方案如下

下面先贴出代码

public abstract class BasePageFragment extends Fragment {protected View mView;/*** 表示View是否被初始化*/protected boolean isViewInitiated;/*** 表示对用户是否可见*/protected boolean isVisibleToUser;/*** 表示数据是否初始化*/protected boolean isDataInitiated;private Context mContext;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);LUtils.i(getClass().getSimpleName() + ">>>>>>>>>>>　　onCreate");}@Nullable@Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @NullableBundle savedInstanceState) {LUtils.i(getClass().getSimpleName() + ">>>>>>>>>>>　　onCreateView");if (mView == null) {mContext = getContext();mView = View.inflate(mContext, getLayoutId(), null);initView(mView);LUtils.i(getClass().getSimpleName() + ">>>>>>>>>>>　　initView");} else {// 缓存的rootView需要判断是否已经被加过parent，如果有parent需要从parent删除，// 要不然会发生这个rootview已经有parent的错误。ViewGroup parent = (ViewGroup) mView.getParent();if (parent != null) {parent.removeView(mView);}LUtils.i(getClass().getSimpleName() + ">>>>>>>>>>>　　removeView");}return mView;}protected abstract void initView(View view);protected abstract int getLayoutId();@Overridepublic void onActivityCreated(Bundle savedInstanceState) {super.onActivityCreated(savedInstanceState);LUtils.i(getClass().getSimpleName() + ">>>>>>>>>>>　　onActivityCreated");isViewInitiated = true;initData();prepareFetchData();}@Overridepublic void setUserVisibleHint(boolean isVisibleToUser) {super.setUserVisibleHint(isVisibleToUser);this.isVisibleToUser = isVisibleToUser;prepareFetchData();}public abstract void fetchData();public boolean prepareFetchData() {return prepareFetchData(false);}/**** * @param forceUpdate 表示是否在界面可见的时候是否强制刷新数据* @return*/public boolean prepareFetchData(boolean forceUpdate) {if (isVisibleToUser && isViewInitiated && (!isDataInitiated || forceUpdate)) {//  界面可见的时候再去加载数据fetchData();isDataInitiated = true;return true;}return false;}@Overridepublic void onDestroyView() {super.onDestroyView();LUtils.i(getClass().getSimpleName() + ">>>>>>>>>>>　　onDestroyView");}protected void initData() {}}

思路解析：
其实核心思想主要在setUserVisibleHint(boolean isVisibleToUser)方法中，这个方法在Fragemnt界面切换到可见或者不可见的时候调用，isVisibleToUser表示当前界面可见或者不可见

setUserVisibleHint(boolean isVisibleToUser)

Set a hint to the system about whether this fragment’s UI is currently visible to the user.

于是我们在prepareFetchData进行判断只有当界面可见的情况下才会尝试判断是否调用fetchData() 方法，于是我们就可以实现等到界面可见的时候才加载网络数据，将我们加载网络数据的逻辑的实现放在fetchData()
里面即可


/***** @param forceUpdate 表示是否在界面可见的时候是否强制刷新数据* @return*/
public boolean prepareFetchData(boolean forceUpdate) {if (isVisibleToUser && isViewInitiated && (!isDataInitiated || forceUpdate)) {//  界面可见的时候再去加载数据fetchData();isDataInitiated = true;return true;}return false;
}

题外话

转眼间校招季已经过去了一个多月了，虽然没能进入到bat，网易之类的公司，不过也找到了相对比较喜欢的公司，接下来的日子就专心做毕业设计了，计划在十一月的时候出省旅游一次，明年春节回来的时候再去公司实习，悄悄地告诉你一件事哦，本人还没有出过广东省，哈哈，是不是很low呢？

转载请注明博客地址：http://blog.csdn.net/gdutxiaoxu/article/details/52826810

源码下载地址：https://github.com/gdutxiaoxu/QQBottomTab.git