Fragment를 이용한 TabActivity

MainActivity.java

package com.example.hellotabfragment;

import java.util.HashMap;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.util.Log;
import android.view.View;
import android.widget.TabHost;

import com.example.hellotabfragment.fragment.Fragment1;
import com.example.hellotabfragment.fragment.Fragment2;
import com.example.hellotabfragment.fragment.Fragment3;

/**
 * This demonstrates how you can implement switching between the tabs of a
 * TabHost through fragments.  It uses a trick (see the code below) to allow
 * the tabs to switch between fragments instead of simple views.
 */
public class MainActivity extends FragmentActivity {
    TabHost mTabHost;
    TabManager mTabManager;

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

        setContentView(R.layout.activity_main);
        mTabHost = (TabHost)findViewById(android.R.id.tabhost);//Container for a tabbed window view.
        mTabHost.setup();

        mTabManager = new TabManager(this, mTabHost, R.id.realtabcontent);// tab host와 탭을 눌렀을때 바뀌어야하는 부분의 id
        mTabManager.addTab(mTabHost.newTabSpec("simple").setIndicator("Simple"), Fragment1.class, null);	//새로운 탭을 만든다.
        //tabspec -> A tab has a tab indicator, content, and a tag that is used to keep track of it
        mTabManager.addTab(mTabHost.newTabSpec("contacts").setIndicator("Contacts"), Fragment2.class, null);
        mTabManager.addTab(mTabHost.newTabSpec("custom").setIndicator("Custom"), Fragment3.class, null);


        if (savedInstanceState != null) {
            mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));	// 방향 전환 전에 선택된 탭이 있다면 가져와서 설정
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString("tab", mTabHost.getCurrentTabTag());	// 방향 전환될때 넣어준다.
        Log.e("tab", mTabHost.getCurrentTabTag());
    }

    /**
     * This is a helper class that implements a generic mechanism for
     * associating fragments with the tabs in a tab host.  It relies on a
     * trick.  Normally a tab host has a simple API for supplying a View or
     * Intent that each tab will show.  This is not sufficient for switching
     * between fragments.  So instead we make the content part of the tab host
     * 0dp high (it is not shown) and the TabManager supplies its own dummy
     * view to show as the tab content.  It listens to changes in tabs, and takes
     * care of switch to the correct fragment shown in a separate content area
     * whenever the selected tab changes.
     */
    public static class TabManager implements TabHost.OnTabChangeListener {
        private final FragmentActivity mActivity;	//context
        private final TabHost mTabHost;
        private final int mContainerId;	
        private final HashMap mTabs = new HashMap();	// tag기준으로 tab에대한 정보가 들어있다.
        TabInfo mLastTab;

        static final class TabInfo {
            private final String tag;
            private final Class clss;
            private final Bundle args;
            private Fragment fragment;

            TabInfo(String _tag, Class _class, Bundle _args) {
                tag = _tag;
                clss = _class;
                args = _args;
            }
        }

        static class DummyTabFactory implements TabHost.TabContentFactory{ // Makes the content of a tab when it is selected. 
        	// 굳이 필요 없어 보이는 듯
            private final Context mContext;

            public DummyTabFactory(Context context) {
                mContext = context;
            }

            @Override
            public View createTabContent(String tag) {
                View v = new View(mContext);
                v.setMinimumWidth(0);
                v.setMinimumHeight(0);
                return v;
            }
        }

        public TabManager(FragmentActivity activity, TabHost tabHost, int containerId) {
            mActivity = activity;
            mTabHost = tabHost;
            mContainerId = containerId;
            mTabHost.setOnTabChangedListener(this);
        }

        public void addTab(TabHost.TabSpec tabSpec, Class clss, Bundle args) {	// tab추가하기
            tabSpec.setContent(new DummyTabFactory(mActivity));
            String tag = tabSpec.getTag();

            TabInfo info = new TabInfo(tag, clss, args);	// 그닥 필요없어 보이긴함

            // Check to see if we already have a fragment for this tab, probably
            // from a previously saved state.  If so, deactivate it, because our
            // initial state is that a tab isn't shown.
            info.fragment = mActivity.getSupportFragmentManager().findFragmentByTag(tag);	//tag로 프래그먼트 찾아서 넣어준다.
            if (info.fragment != null && !info.fragment.isDetached()) {	//frament가 null이아니고 떨어져있지 않으면 떼준다.
            	
                FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
                ft.detach(info.fragment);
                ft.commit();
            }

            mTabs.put(tag, info);	//자료형에 넣어준다. 이것도 불필요함
            mTabHost.addTab(tabSpec);	// 탭호스트에 실제로 탭을 넣어준다.
        }

        @Override
        public void onTabChanged(String tabId) {
            TabInfo newTab = mTabs.get(tabId);	// 넣어놨던 tabinfo찾아온다.
            if (mLastTab != newTab) {//라스트탭이 뉴탭과 같지 않다면
                FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
                if (mLastTab != null) {	//라스트탭이 널이 아니면
                    if (mLastTab.fragment != null) {	//라스트탭의 프래그먼트가 널이 아니면
                        ft.detach(mLastTab.fragment);	//떼어낸다
                    }
                }
                if (newTab != null) {	// 뉴탭이 널이 아니면
                    if (newTab.fragment == null) {	//프래그먼트가 널이면
                        newTab.fragment = Fragment.instantiate(mActivity,
                                newTab.clss.getName(), newTab.args);//새로 만들어준다
                        ft.add(mContainerId, newTab.fragment, newTab.tag);	//추가해준다
                    } else {
                        ft.attach(newTab.fragment);	//널이 아니면 그대로 붙여준다.
                    }
                }

                mLastTab = newTab;	//새로운탭이 라스트탭이 된다.
                ft.commit();
                mActivity.getSupportFragmentManager().executePendingTransactions();
            }
        }
    }
}

activity_main.xml