示例代码中的 SlidingTabLayout 简单使用（一）

在程序中为侧向屏幕导航提供可选的选项卡。Google 已经淘汰了以前的许多选项卡，如 TabWiget，ActionBar，但是SlidingTabLayout 符合当前选项卡的设计模式。

SlidingTabLayout 旨在与 ViewPager 密切协作，因为选项卡设计模式的一部分是允许在每个视图之间轻扫。轻扫 ViewPager 时，当前选项卡自动滚动以同时显示出来。

效果如下 （AndroidStudio 1.5）：

复制  android-sdk-windows\samples\android-23_1\ui\SlidingTabsBasic\Application\src\main\java\com\example\android\common\view  目录（Android 的示例目录）下的 SlidingTabLayout.java 和 SlidingTabStrip.java 两个类到自己项目的 java 包目录下。

content_main.xml :

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.crazy.tabs.MainActivity"
    tools:showIn="@layout/activity_main">

    <com.crazy.tabs.SlidingTabLayout
        android:id="@+id/tabs"
        android:background="#0ff"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    </android.support.v4.view.ViewPager>

</LinearLayout>

MainActivity.java :

package com.crazy.tabs;

import android.content.Context;
import android.graphics.Color;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.view.ViewGroup;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        ViewPager viewPager = (ViewPager)findViewById(R.id.pager);
        SlidingTabLayout tabLayout = (SlidingTabLayout)findViewById(R.id.tabs);

        viewPager.setAdapter(new TabsPagerAdapter(this));

        /**
         *  SlidingTabLayout 与 ViewPager 关联，继承选项卡标题和滚动跟踪行为
         */
        tabLayout.setViewPager(viewPager);
        tabLayout.setCustomTabColorizer(new SlidingTabLayout.TabColorizer(){
            @Override
            public int getIndicatorColor(int position) {
                // 显示在每个选项卡位置下方的颜色
                return Color.MAGENTA;
            }

            @Override
            public int getDividerColor(int position) {
                // 透明以隐藏分隔线
                return 0;
            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    private static class TabsPagerAdapter extends PagerAdapter{

        private Context mContext;
        private static final int[] IMAGES = {
                R.drawable.bg_01, R.drawable.bg_02, R.drawable.bg_03,
                R.drawable.bg_04, R.drawable.bg_05, R.drawable.bg_06,
                R.drawable.bg_07
        };

        public TabsPagerAdapter(Context context){
            mContext = context;
        }

        /**
         *  SlidingTabLayout 要求此方法定义每个选项卡将显示的文本
         */
        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "Monday";
                case 1:
                    return "Tuesday";
                case 2:
                    return "Wednesday";
                case 3:
                    return "Thursday";
                case 4:
                    return "Friday";
                case 5:
                    return "Saturday";
                case 6:
                    return "Sunday";
                default:
                    return "";
            }
        }

        @Override
        public int getCount() {
            return 7;
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            ImageView pageView = new ImageView(mContext);
            pageView.setScaleType(ImageView.ScaleType.CENTER);

            pageView.setImageResource(IMAGES[position]);

            container.addView(pageView);
            return pageView;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View)object);
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return (view == object);
        }
    }
}