ViewPager,RadioGroup,FragmentManager 详解 <二> 主菜单 RadioGroup 和ViewPager 实现联动

0：首先创建3个Fragment ，这写Fragment 必须是v4包里面的

1：然后布局里面添加ViewPager和RadioGroup，RadioGroup的orientation 一定要是horization

ViewPage 一定要写全路径

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <android.support.v4.view.ViewPager
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:id="@+id/viewPager">
    </android.support.v4.view.ViewPager>
    <RadioGroup
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:id="@+id/radiogroup">
        <RadioButton
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="a"
            android:textSize="35dp"
            android:textAlignment="center"
            android:id="@+id/radiobutton_a"/>
        <RadioButton
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="b"
            android:textSize="35dp"
            android:textAlignment="center"
            android:id="@+id/radiobutton_b"/>
        <RadioButton
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="a"
            android:textSize="35dp"
            android:textAlignment="center"
            android:id="@+id/radiobutton_c"/>

    </RadioGroup>

</LinearLayout>

2：创建Adapter，和Fragment 相关的ViewPager的adapte 是FragmentPagerAdapter或者是FragmentStatePagerAdapter，如果是后者的话默认的就是加载3个Fragment，前后和当前的，其他的Fragmet 都是销毁的。我们这里使用FragmentPagerAdapter

package tech.androidstudio.fragmentviewpagerradiogroup.adapter;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;

import java.util.List;

/**
 * Created by Kodulf on 2016/3/14.
 */
public class RadioGroupFragmentPagerAdapter extends FragmentPagerAdapter {
    List<Fragment> list;

    //创建的构造方法一定要包含List<Fragment>的参数，
    //FragmentManager 一定要是v4包里面的
    public RadioGroupFragmentPagerAdapter(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();
    }
}

2：在MainActivty 里面实现联动。

package tech.androidstudio.fragmentviewpagerradiogroup;

import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.RadioGroup;

import java.util.ArrayList;
import java.util.List;

import tech.androidstudio.fragmentviewpagerradiogroup.adapter.RadioGroupFragmentPagerAdapter;

public class MainActivity extends AppCompatActivity implements ViewPager.OnPageChangeListener, RadioGroup.OnCheckedChangeListener {

    private ViewPager mViewPager;
    private RadioGroup mRadioGroup;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //Fragment 的列表，将会显示在ViewPager里面。
        List<Fragment> mList = new ArrayList<Fragment>();
        mList.add(new BlankFragment());
        mList.add(new SecondFragment());
        mList.add(new ThirdFragment());

        //Adapter设置，这里面的 FragmentManager 一定要是支持包里面的SupportFragmentManager
        RadioGroupFragmentPagerAdapter adapter = new RadioGroupFragmentPagerAdapter(getSupportFragmentManager(),mList);

        mViewPager = (ViewPager) findViewById(R.id.viewPager);
        mViewPager.setAdapter(adapter);
        mRadioGroup = (RadioGroup)findViewById(R.id.radiogroup);

        //设置联动，设置ViewPager的PageChange的监听器，RadioGroup的CheckedChange监听器
        mViewPager.setOnPageChangeListener(this);
        mRadioGroup.setOnCheckedChangeListener(this);
        //默认的是 让第一个 RadioButton 是选中的状态
        mRadioGroup.check(R.id.radiobutton_a);
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

    }

    //ViewPager 翻页以后，RadioGroup 也进行 相应的操作。
    @Override
    public void onPageSelected(int position) {
        switch (position){
            case 0:
                mRadioGroup.check(R.id.radiobutton_a);
                break;
            case 1:
                mRadioGroup.check(R.id.radiobutton_b);
                break;
            case 2:
                mRadioGroup.check(R.id.radiobutton_c);
                break;
        }
    }

    @Override
    public void onPageScrollStateChanged(int state) {

    }

    //RadioGroup 点击之后切换viewPager
    @Override
    public void onCheckedChanged(RadioGroup group, int checkedId) {
        switch (checkedId){
            case R.id.radiobutton_a:
                mViewPager.setCurrentItem(0);
                break;
            case R.id.radiobutton_b:
                mViewPager.setCurrentItem(1);
                break;
            case R.id.radiobutton_c:
                mViewPager.setCurrentItem(2);
                break;
        }
    }
}