Activity组件安全（下）

此前我们用HorizontalScrollView也实现了类似网易选项卡动态滑动效果，详见 Android选项卡动态滑动效果这篇文章

这里我们用TabLayout来实现这一效果。TabLayout是Android Design Support Library库中的控件。
Google在2015的IO大会上，给我们带来了更加详细的Material Design设计规范，同时，也给我们带来了全新的Android Design Support Library，在这个support库里面，Google给我们提供了更加规范的MD设计风格的控件。最重要的是，Android Design Support Library的兼容性更广，直接可以向下兼容到Android 2.2。

首先我们先来看看效果：

接下来开始实现

1. 配置build.gradle

在build.gradle加入如下代码

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.2.0'
    compile 'com.android.support:design:22.2.0'
    compile 'com.android.support:recyclerview-v7:22.2.0'
    compile 'com.android.support:cardview-v7:22.2.0'
}

com.android.support:design:22.2.0就是我们需要引入的Android Design Support Library，其次我们还引入了Recyclerview和Cardview,还不了解这两个控件的同学可以看下面这两篇文章：

Android5.x RecyclerView 应用解析和Android5.x CardView 应用解析

2.AppBarLayout、Toolbar与TabLayout

先看看主界面的布局 （activity_tab_layout.xml）

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".TabLayoutActivity"
    android:orientation="vertical">
    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">
        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:tabIndicatorColor="#ADBE107E"
            app:tabMode="scrollable"/>

        </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"/>

</LinearLayout>

这里用到了AppBarLayout和Toolbar，AppBarLayout是Android Design Support Library新加的控件继承自LinearLayout，它用来将Toolbar和TabLayout组合起来作为一个整体。Toolbar我们在这里不讲了，如果不熟悉可以看Android5.x Toolbar和Palette应用解析这篇文章
这布局文件最关键的一点就是android.support.design.widget.TabLayout 标签中的app:tabMode=”scrollable”，他设置tab的模式为“可滑动的”,现在我们把这句话去掉，来看看效果：

上面的tab由于太多（13个）却不能滑动就重叠了。

接下来在java中引用 （TabLayoutActivity.java）

package com.example.liuwangshu.mytablayout;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import java.util.ArrayList;
import java.util.List;

public class TabLayoutActivity extends AppCompatActivity {
    private DrawerLayout mDrawerLayout;
    private ViewPager mViewPager;
    private TabLayout mTabLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tab_layout);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        mViewPager = (ViewPager) findViewById(R.id.viewpager);
        initViewPager();
    }

initViewPager方法 （TabLayoutActivity.java）

private void initViewPager() {
    mTabLayout = (TabLayout) findViewById(R.id.tabs);
    List<String> titles = new ArrayList<>();
    titles.add("精选");
    titles.add("体育");
    titles.add("巴萨");
    titles.add("购物");
    titles.add("明星");
    titles.add("视频");
    titles.add("健康");
    titles.add("励志");
    titles.add("图文");
    titles.add("本地");
    titles.add("动漫");
    titles.add("搞笑");
    titles.add("精选");

    for(int i=;i<titles.size();i++){
        mTabLayout.addTab(mTabLayout.newTab().setText(titles.get(i)));
    }
    List<Fragment> fragments = new ArrayList<>();
    for(int i=;i<titles.size();i++){
        fragments.add(new ListFragment());
    }
    FragmentAdapter mFragmentAdapteradapter =
            new FragmentAdapter(getSupportFragmentManager(), fragments, titles);
    //给ViewPager设置适配器
    mViewPager.setAdapter(mFragmentAdapteradapter);
    //将TabLayout和ViewPager关联起来。
    mTabLayout.setupWithViewPager(mViewPager);
    //给TabLayout设置适配器
    mTabLayout.setTabsFromPagerAdapter(mFragmentAdapteradapter);
}

在这里我们设定了13个标题内容并创建了相应的TabLayout和Fragment，设置了ViewPager适配器和TabLayout适配器并将将TabLayout和ViewPager关联起来。
ListFragment的代码（ListFragment.java)

package com.example.liuwangshu.mytablayout;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class ListFragment extends Fragment {
    private RecyclerView mRecyclerView;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        mRecyclerView =
                (RecyclerView) inflater.inflate(R.layout.list_fragment, container, false);
        return mRecyclerView;
    }
    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(mRecyclerView.getContext()));
        mRecyclerView.setAdapter(new RecyclerViewAdapter(getActivity()));
    }
}

这里用RecyclerView来代替ListView来看看RecyclerViewAdapter（RecyclerViewAdapter.java)

package com.example.liuwangshu.mytablayout;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ObjectAnimator;
import android.annotation.TargetApi;
import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.ViewHolder> {
    private Context mContext;

    public RecyclerViewAdapter(Context mContext) {
        this.mContext = mContext;
    }
    @Override
    public RecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view =
                LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item_card_main, parent, false);
        return new ViewHolder(view);
    }
    @Override
    public void onBindViewHolder(final RecyclerViewAdapter.ViewHolder holder, int position) {
        final View view = holder.mView;
        view.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
    }

    @Override
    public int getItemCount() {
        return ;
    }
    public static class ViewHolder extends RecyclerView.ViewHolder {
        public final View mView;

        public ViewHolder(View view) {
            super(view);
            mView = view;
        }
    }
}

最后FragmentAdapter（FragmentAdapter.java)

package com.example.liuwangshu.mytablayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import java.util.List;

public class FragmentAdapter extends FragmentStatePagerAdapter {
    private List<Fragment> mFragments;
    private List<String> mTitles;
    public FragmentAdapter(FragmentManager fm, List<Fragment> fragments, List<String> titles) {
        super(fm);
        mFragments = fragments;
        mTitles = titles;
    }
    @Override
    public Fragment getItem(int position) {
        return mFragments.get(position);
    }
    @Override
    public int getCount() {
        return mFragments.size();
    }
    @Override
    public CharSequence getPageTitle(int position) {
        return mTitles.get(position);
    }
}

基本所有的代码都讲到了，当然这种稍微复杂的效果TabLayout能够实现，那么简单的3，4个Tab滑动TabLayout实现起来更是不再话下，修改TabLayoutActivity的initViewPager方法（TabLayoutActivity.java)

private void initViewPager() {
      mTabLayout = (TabLayout) findViewById(R.id.tabs);
      List<String> titles = new ArrayList<>();
      titles.add("精选");
      titles.add("体育");
      titles.add("巴萨");
      titles.add("购物");
      for(int i=;i<titles.size();i++){
          mTabLayout.addTab(mTabLayout.newTab().setText(titles.get(i)));
      }
      List<Fragment> fragments = new ArrayList<>();
      for(int i=;i<titles.size();i++){
          fragments.add(new ListFragment());
      }
      FragmentAdapter mFragmentAdapteradapter =
              new FragmentAdapter(getSupportFragmentManager(), fragments, titles);
      //给ViewPager设置适配器
      mViewPager.setAdapter(mFragmentAdapteradapter);
      //将TabLayout和ViewPager关联起来。
      mTabLayout.setupWithViewPager(mViewPager);
      //给TabLayout设置适配器
      mTabLayout.setTabsFromPagerAdapter(mFragmentAdapteradapter);
  }

我们只保留了4个Tab,然后去掉activity_tab_layout.xml android.support.design.widget.TabLayout 标签中的app:tabMode=”scrollable”
运行代码来看看效果

源码下载