很簡單的目錄結構，其中fragment2還是做為靜態UI使用，動態載入的是fragment1跟fragment3，這裡對fragment2的程式碼不再展示

先看看fragment1.java跟fragment3.java檔案，這裡沒什麼特別的。

package com.example.root.fragmentproject;

import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.app.Fragment;
import android.view.LayoutInflater;
import 
 
android.view.View;
import android.view.ViewGroup;

public class Fragment1 extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
 
return inflater.inflate(R.layout.fragment_fragment1, container, false);
    }
}

<FrameLayout 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="com.example.root.fragmentproject.Fragment1"
android:background="#a5a5a5">

    <!-- TODO: Update blank fragment layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="我是對應Button1的Fragment，預設載入的也是我" />

</FrameLayout>

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
        <LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:orientation="horizontal">
            <fragment
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/id_fragment2"
android:name="com.example.root.fragmentproject.Fragment2">
            </fragment>
        </LinearLayout>
        <LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:id="@+id/linear1">

        </LinearLayout>
    </LinearLayout>

</RelativeLayout>

package com.example.root.fragmentproject;

import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends FragmentActivity implements OnClickListener {
    private FragmentManager fragmentManager;
    private FragmentTransaction fragmentTransaction;
    private Fragment1 fragment1;
    private Fragment3 fragment3;
    private Button button1;
    private Button button2;
    @Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        button1 = (Button) findViewById(R.id.button1);
        button2 = (Button) findViewById(R.id.button2);
        button1.setOnClickListener(this);
        button2.setOnClickListener(this);

        fragmentManager = getFragmentManager();
        mrFragment();

    }

    //預設載入的fragment
public void mrFragment(){
        fragmentTransaction = fragmentManager.beginTransaction();
        if(fragment1 == null){
            fragment1 = new Fragment1();
        }
        fragmentTransaction.replace(R.id.linear1, fragment1);
        fragmentTransaction.commit();
    }

    @Override
public void onClick(View view) {
        Log.v("debug","進入點選方法。。。。。。。。。。。。。。。。。。。。。");
//        每次都必須重新獲得一個fragmentTransaction，即重新執行下面這行程式碼。
fragmentTransaction = fragmentManager.beginTransaction();
        switch (view.getId()){
            case R.id.button1:
                if(fragment1 == null){
                    fragment1 = new Fragment1();
                }
                fragmentTransaction.replace(R.id.linear1, fragment1);
                break;
            case R.id.button2:
                if(fragment3 == null){
                    fragment3 = new Fragment3();
                }
                fragmentTransaction.replace(R.id.linear1, fragment3);
                break;
        }
        fragmentTransaction.commit();
    }
}

最後看看效果吧，首先是當剛進入APP時，以及點選“按鈕1”時：

當點選“按鈕2”時：

該文章主要是為了記錄一點小例項，所以沒有許多更深入的理解或是講解之類的。