ViewPager,RadioGroup,FragmentManager 详解 <一> 主菜单 RadioGroup 控制显示Fragment ，FragmentManager

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

1：然后在MainActivity的布局里面添加一个FrameLayout和一个RadioGroup的布局，注意这个RadioGroup的布局一定要设置orientation 为horization

<?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">

<FrameLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:id="@+id/framelayout"></FrameLayout>
<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="35sp"
android:id="@+id/radiobutton_a"/>
<RadioButton
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="b"
android:textSize="35sp"
android:id="@+id/radiobutton_b"/>
<RadioButton
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="c"
android:textSize="35sp"
android:id="@+id/radiobutton_c"/>
</RadioGroup>
</LinearLayout>

2：在MainActivity 里面执行

package tech.androidstudio.viewpagerdemo;

import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.RadioGroup;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements RadioGroup.OnCheckedChangeListener {

private BlankFragment mBlankFragment;
private SecondFragmentT mSecnodFragment;
private ThridFragmentT mThirdFragment;
private RadioGroup mRadioGroup;

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

//创建Fragment
mBlankFragment = new BlankFragment();
mSecnodFragment = new SecondFragmentT();
mThirdFragment = new ThridFragmentT();

//获取支持包里面的FragmentManager，然后获取事务transaction
FragmentManager supportFragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = supportFragmentManager.beginTransaction();

//将三个 Fragment 都添加到事务里面来，同时将后两个隐藏
fragmentTransaction.add(R.id.framelayout, mBlankFragment);
fragmentTransaction.add(R.id.framelayout,mSecnodFragment);
fragmentTransaction.add(R.id.framelayout,mThirdFragment);
fragmentTransaction.hide(mSecnodFragment);
fragmentTransaction.hide(mThirdFragment);
//提交事务
fragmentTransaction.commit();

//实现 RadioGroup 来控制FragmentManager的显示 ，设置监听器
mRadioGroup = (RadioGroup) findViewById(R.id.radioGroup);
mRadioGroup.check(0);
mRadioGroup.setOnCheckedChangeListener(this);
}

@Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
//注意在回调方法里面 也要 获取FragmentManger 和事务transaction，
FragmentManager supportFragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = supportFragmentManager.beginTransaction();
//判断checkedId 是要通过RadioButton 来判断的，如果是自己在代码里面创建的 RadioButton的话 可以设置id，
//例如设置0，1，2. 而这里是通过布局来创建的 ，所以 这里的 id 就使用布局里面的id就好了
switch (checkedId){
case R.id.radiobutton_a:
Toast.makeText(this,"0",Toast.LENGTH_LONG).show();
fragmentTransaction.show(mBlankFragment);
fragmentTransaction.hide(mSecnodFragment);
fragmentTransaction.hide(mThirdFragment);
break;
case R.id.radiobutton_b:
Toast.makeText(this,"1",Toast.LENGTH_LONG).show();
fragmentTransaction.hide(mBlankFragment);
fragmentTransaction.show(mSecnodFragment);
fragmentTransaction.hide(mThirdFragment);
break;
case R.id.radiobutton_c:
Toast.makeText(this,"2",Toast.LENGTH_LONG).show();
fragmentTransaction.hide(mBlankFragment);
fragmentTransaction.hide(mSecnodFragment);
fragmentTransaction.show(mThirdFragment);
break;
}
//别忘了提交事务
fragmentTransaction.commit();
}
}