源码：https://github.com/bkhacker/business

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2-1 首页框架—搭建铺垫

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add、replace（先remove、再add）、remove、hide、show、detach

注意包和类和布局文件的命名规则：

首先看到ImoocApplication，它是整个程序的入口，写完在清单文件声明。

接下来创建Fragment，他们都继承BaseFragment.

Fragment和activity都要做一个base，方便公共部分的修改。

这个activity，我们在开发之前直接把所有控件初始化，这样开发比较有效率。

public class HomeActivity extends BaseActivity implements View.OnClickListener {
    //Fragment
    private android.app.FragmentManager fm;
    private HomeFragment mHomeFragment;
    private Fragment mCommonFragmentOne;
    private MessageFragment mMessageFragment;
    private MineFragment mMineFragment;
    private Fragment mCurrent;
    //底部导航布局
    private RelativeLayout mHomeLayout;//首页
    private RelativeLayout mPondLayout;//鱼塘
    private RelativeLayout mMessageLayout;//消息
    private RelativeLayout mMineLayout;//我的
    //底部导航图片切换
    private TextView mHomeView;
    private TextView mPondView;
    private TextView mMessageView;
    private TextView mMineView;

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

        //初始化我们页面中的所有控件
        initView();

        //添加默认显示的fragment
        mHomeFragment = new HomeFragment();
        fm = getFragmentManager();//获得FM
        FragmentTransaction fragmentTransaction = fm.beginTransaction();
        //replace 先remove再add
        fragmentTransaction.replace(R.id.content_layout, mHomeFragment);
        fragmentTransaction.commit();

    }

    //初始化控件 设置监听事件
    private void initView() {
        //底部导航的初始化和事件监听
        mHomeLayout = (RelativeLayout) findViewById(R.id.home_layout_view);
        mHomeLayout.setOnClickListener(this);
        mPondLayout = (RelativeLayout) findViewById(R.id.pond_layout_view);
        mPondLayout.setOnClickListener(this);
        mMessageLayout = (RelativeLayout) findViewById(R.id.message_layout_view);
        mMessageLayout.setOnClickListener(this);
        mMineLayout = (RelativeLayout) findViewById(R.id.mine_layout_view);
        mMineLayout.setOnClickListener(this);

        //底部导航图片控件，用于点击切换选中图片
        mHomeView = (TextView) findViewById(R.id.home_image_view);
        mPondView = (TextView) findViewById(R.id.fish_image_view);
        mMessageView = (TextView) findViewById(R.id.message_image_view);
        mMineView = (TextView) findViewById(R.id.mine_image_view);
        mHomeView.setBackgroundResource(R.drawable.comui_tab_home_selected);
    }

    //用来隐藏具体的Fragment
    private void hideFragment(Fragment fragment, FragmentTransaction ft) {
        if (fragment != null) {
            ft.hide(fragment);
        }
    }

    @Override
    public void onClick(View v) {
        FragmentTransaction fragmentTransaction = fm.beginTransaction();
        switch (v.getId()) {
            //首页
            case R.id.home_layout_view:
                mHomeView.setBackgroundResource(R.drawable.comui_tab_home_selected);
                mPondView.setBackgroundResource(R.drawable.comui_tab_pond);
                mMessageView.setBackgroundResource(R.drawable.comui_tab_message);
                mMineView.setBackgroundResource(R.drawable.comui_tab_person);

                //隐藏其他两个Fragment
                hideFragment(mMessageFragment, fragmentTransaction);
                hideFragment(mMineFragment, fragmentTransaction);

                //将我们的HomeFragment显示出来
                if (mHomeFragment == null) {
                    mHomeFragment = new HomeFragment();
                    fragmentTransaction.add(R.id.content_layout, mHomeFragment);
                } else {
                    //已经创建过了
                    fragmentTransaction.show(mHomeFragment);
                }
                break;
            //消息
            case R.id.message_layout_view:
                mMessageView.setBackgroundResource(R.drawable.comui_tab_message_selected);
                mHomeView.setBackgroundResource(R.drawable.comui_tab_home);
                mPondView.setBackgroundResource(R.drawable.comui_tab_pond);
                mMineView.setBackgroundResource(R.drawable.comui_tab_person);

                //隐藏其他两个Fragment
                hideFragment(mHomeFragment, fragmentTransaction);
                hideFragment(mMineFragment, fragmentTransaction);

                //将我们的mMessageFragment显示出来
                if (mMessageFragment == null) {
                    mMessageFragment = new MessageFragment();
                    fragmentTransaction.add(R.id.content_layout, mMessageFragment);
                } else {
                    //已经创建过了
                    fragmentTransaction.show(mMessageFragment);
                }

                break;
            //我的
            case R.id.mine_layout_view:
                mMineView.setBackgroundResource(R.drawable.comui_tab_person_selected);
                mHomeView.setBackgroundResource(R.drawable.comui_tab_home);
                mPondView.setBackgroundResource(R.drawable.comui_tab_pond);
                mMessageView.setBackgroundResource(R.drawable.comui_tab_message);

                //隐藏其他两个Fragment
                hideFragment(mMessageFragment, fragmentTransaction);
                hideFragment(mHomeFragment, fragmentTransaction);

                //将我们的HomeFragment显示出来
                if (mMineFragment == null) {
                    mMineFragment = new MineFragment();
                    fragmentTransaction.add(R.id.content_layout, mMineFragment);
                } else {
                    //已经创建过了
                    fragmentTransaction.show(mMineFragment);
                }

                break;

        }
        fragmentTransaction.commit();

    }
}

完成一些点击的逻辑和fragment的切换 必知必会