androidでタブとフラグメントを使用して画面を切り替え

今回はこれが精一杯

なんか既存のテーマではエラーになりまくりだけど
どうすればいいのかわからないのでテーマなしでやった

実装

MainActivity

package jp.mshige1979.app.sampleapptab3;

import android.app.ActionBar;
import android.app.Activity;

import android.app.Fragment;
import android.app.FragmentTransaction;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // ActionBar を取得
        ActionBar actionBar = getActionBar();

        // ActionBar をタブモードにセット
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // tab1
        ActionBar.Tab tab1 = actionBar.newTab();
        tab1.setText("tab1");
        tab1.setTabListener(new MyTabListener<PlaceholderFragment>(this,
                "tab2", PlaceholderFragment.class));
        actionBar.addTab(tab1);

        // tab2
        ActionBar.Tab tab2 = actionBar.newTab();
        tab2.setText("タブ２");
        tab2.setTabListener(new MyTabListener<PlaceholderFragment2>(this,
                "tab2", PlaceholderFragment2.class));
        actionBar.addTab(tab2);

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public class MyTabListener<T extends Fragment> implements
            ActionBar.TabListener {

        private Fragment mFragment;
        private final Context mContext;
        private final String mTag;
        private final Class<T> mClass;

        public MyTabListener(Activity activity, String tag, Class<T> clz) {
            mContext = activity;
            mTag = tag;
            mClass = clz;
        }

        @Override
        public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
            // このタブに関連するフラグメントがすでに生成されているかどうか調べる
            if (mFragment == null) {
                // まだ生成されていない場合は、アクティビティとクラス名から生成
                mFragment = Fragment.instantiate(mContext, mClass.getName());
            }
            // Fragment を android.R.id.content に表示するよう Activity に追加
            ft.add(android.R.id.content, mFragment, mTag);
        }

        @Override
        public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
            // Fragment を Activity から削除
            ft.remove(mFragment);
        }

        @Override
        public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
        }
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            return rootView;
        }
    }

    public static class PlaceholderFragment2 extends Fragment {

        public PlaceholderFragment2() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main2, container, false);
            return rootView;
        }
    }

}

fragment_main.xml

<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$PlaceholderFragment"
    android:clickable="true">

    <TextView android:text="@string/hello_world" android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</RelativeLayout>

fragment_main2.xml

<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$PlaceholderFragment">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Large Text"
        android:id="@+id/textView"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="207dp" />
</RelativeLayout>