简单快速实现导航条（Viewpager+Fragment+Radiogroup）

每个应用几乎都逃不开导航条，导航条的制作方法有很多
1、TabActivity+TabHost（已经过期）
2、Fragment + RadioGroup 【必要时首选】
3、Fragment + ViewPager + RadioGroup自定义固定导航条 【推荐使用】
4、Fragment + ViewPager 带滑动导航条 【推荐使用】
5、Fragment + ViewPager + HorizontalScrollView自定义滑动导航条 【推荐使用】
一般来说都需要用户能进行滑动，所以我们采取第三种方式进行导航条的制作。
先上图 看是不是你想要的效果

先看MainActivity的布局 采用的是RadioGroup+viewpager
xml文件奉上

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout android:id="@+id/activity_main"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="c.navigationbar.MainActivity">
    <RadioGroup
        android:id="@+id/rb_layout"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:layout_alignParentBottom="true"
        android:orientation="horizontal">

        <RadioButton
            android:id="@+id/healthy_life"
            style="@style/radio_button_style"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:button="@null"
            android:checked="true"
            android:gravity="center"
            android:text="健康生活" />

        <RadioButton
            android:id="@+id/home"
            style="@style/radio_button_style"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:button="@null"
            android:gravity="center"
            android:text="我的" />
    </RadioGroup>

    <android.support.v4.view.ViewPager
        android:id="@+id/vp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@id/rb_layout"></android.support.v4.view.ViewPager>
</RelativeLayout>

style

<style name="radio_button_style">
        <item name="android:gravity">center</item>
        <item name="android:layout_weight">1</item>
        <item name="android:layout_width">wrap_content</item>
        <item name="android:layout_height">wrap_content</item>
        <item name="android:button">@null</item>
        <item name="android:textSize">20sp</item>
        <item name="android:textColor">@drawable/text_color_selector</item>
    </style>

drawable中的xml文件 text_color_selector.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:color="#f00" android:state_checked="true"></item>
    <item android:color="#000"></item>
</selector>

然后处理逻辑

public class MainActivity extends AppCompatActivity{
    private RadioGroup radioGroup;
    private ViewPager viewPager;

    @Override
    protected void onCreate (Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        List<Fragment> list = new ArrayList<>();
        list.add(new OneFragment());
        list.add(new TwoFragment());
        ViewpagerAdapter adapter = new ViewpagerAdapter(getSupportFragmentManager(), list);
        viewPager = (ViewPager) findViewById(R.id.vp);
        viewPager.setAdapter(adapter);
        radioGroup = (RadioGroup) findViewById(R.id.rb_layout);
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener(){
            @Override
            public void onPageScrolled (int position, float positionOffset, int positionOffsetPixels){
            }

            @Override
            public void onPageSelected (int position){
                ((RadioButton) radioGroup.getChildAt(position)).setChecked(true);
            }

            @Override
            public void onPageScrollStateChanged (int state){
            }
        });
        radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener(){
            @Override
            public void onCheckedChanged (RadioGroup group, int checkedId){
                switch(checkedId){
                    case R.id.healthy_life:
                        viewPager.setCurrentItem(0);
                        break;
                    case R.id.home:
                        viewPager.setCurrentItem(1);
                        break;
                }
            }
        });
    }
}

其中也要一个ViewpagerAdapter

public class ViewpagerAdapter extends FragmentPagerAdapter{

    private List<Fragment> list;

    public ViewpagerAdapter (FragmentManager fm, List<Fragment> list) {
        super(fm);
        this.list = list;
    }

    @Override
    public Fragment getItem(int position) {
        return list.get(position);
    }

    @Override
    public int getCount() {
        return list.size();
    }
}

结束！！！