oschina源码首页解刨

不得不说，看大神写的代码是一种享受。学习开源中国的首页架构，解耦手法叹为观止，真是让小白受用。之前在guthub上学习了一套首页构造的开源项目，用起来确实很方便，可是，在实际开发中，我希望当我第一次点击底部tab按钮时，才创建对应的fragment。这是一个很正常的需求，而我之前写的一篇文章利用开源框架实现首页的视图框架搭建，这个框架是每次点击进入app，所有底部按钮对应的frament，全都被new出来了，这个很头疼。所以，我又学习了开源中国代码，经过分析，发现他这可以满足这个需求，而且纯手工，并且解耦得非常棒。故此分享。

效果图：

开源中国首页

新建一个MainActivity.java

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;

import com.dingfang.org.navbardemo.fragment.NavFragment;
import com.dingfang.org.navbardemo.view.NavigationButton;

public class MainActivity extends AppCompatActivity implements NavFragment.OnNavigationReselectListener{

    private NavFragment mNavBar;

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

        FragmentManager manager = getSupportFragmentManager();
        mNavBar = ((NavFragment) manager.findFragmentById(R.id.nav_bar));
        mNavBar.setup(this, manager, R.id.main_container, this);
    }


    @Override
    public void onReselect(NavigationButton navigationButton) {
        Fragment fragment = navigationButton.getFragment();
        if (fragment != null) {
            //do your business
        }
    }
}

以及activity_main.xml

第一眼看不明白的代码，没关系，先放在一边，后面就会一一列出来了。
很明显，其底部的tab是承载在fragment里面的，这里，我们新建NavFragment.java

import android.content.Context;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.dingfang.org.navbardemo.R;
import com.dingfang.org.navbardemo.view.NavigationButton;

import java.util.List;

public class NavFragment extends Fragment implements View.OnClickListener {


    NavigationButton mNavNews;
    NavigationButton mNavTweet;
    NavigationButton mNavExplore;
    NavigationButton mNavMe;

    View root;

    private Context mContext;
    private int mContainerId;
    private FragmentManager mFragmentManager;
    private NavigationButton mCurrentNavButton;

    private OnNavigationReselectListener mOnNavigationReselectListener;

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


    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        initData();
    }

    /**
     * 初始化视图数据
     */
    private void initData() {
        mNavNews.init(R.drawable.tab_icon_new, "综合", Frament01.class);
        mNavNews.setOnClickListener(this);

        mNavTweet.init(R.drawable.tab_icon_tweet, "动态", Frament02.class);
        mNavTweet.setOnClickListener(this);

        mNavExplore.init(R.drawable.tab_icon_explore, "发现", Frament03.class);
        mNavExplore.setOnClickListener(this);

        mNavMe.init(R.drawable.tab_icon_me, "我的", Frament04.class);
        mNavMe.setOnClickListener(this);
    }

    /**
     * 全局初始化
     */
    private void initView() {
        mNavNews = (NavigationButton) root.findViewById(R.id.nav_item_news);
        mNavTweet = (NavigationButton) root.findViewById(R.id.nav_item_tweet);
        mNavExplore = (NavigationButton) root.findViewById(R.id.nav_item_explore);
        mNavMe = (NavigationButton) root.findViewById(R.id.nav_item_me);
    }

    /**
     * 初始化
     * @param context
     * @param fragmentManager
     * @param contentId
     * @param listener
     */
    public void setup(Context context, FragmentManager fragmentManager, int contentId, OnNavigationReselectListener listener) {
        mContext = context;
        mFragmentManager = fragmentManager;
        mContainerId = contentId;
        mOnNavigationReselectListener = listener;

        // do clear
        clearOldFragment();
        // do select first
        doSelect(mNavNews);
    }

    /**
     * 以防万一，清除一遍fragment
     */
    @SuppressWarnings("RestrictedApi")
    private void clearOldFragment() {
        FragmentTransaction transaction = mFragmentManager.beginTransaction();
        List fragments = mFragmentManager.getFragments();
        if (transaction == null || fragments == null || fragments.size() == 0)
            return;
        boolean doCommit = false;
        for (Fragment fragment : fragments) {
            if (fragment != this && fragment != null) {
                transaction.remove(fragment);
                doCommit = true;
            }
        }
        if (doCommit)
            transaction.commitNow();
    }

    /**
     * tab 切换
     * @param newNavButton
     */
    private void doSelect(NavigationButton newNavButton) {
        // If the new navigation is me info fragment, we intercept it
        /*
        if (newNavButton == mNavMe) {
            if (interceptMessageSkip())
                return;
        }
        */

        NavigationButton oldNavButton = null;
        if (mCurrentNavButton != null) {
            oldNavButton = mCurrentNavButton;
            if (oldNavButton == newNavButton) {
                onReselect(oldNavButton);
                return;
            }
            oldNavButton.setSelected(false);
        }
        newNavButton.setSelected(true);
        doTabChanged(oldNavButton, newNavButton);
        mCurrentNavButton = newNavButton;
    }

    /**
     * fragment切换
     * 该方法，保证了，使用只有一个fragment与activity绑定
     * 在fragment不存在的时候，就创建，存在的时候，就绑定
     * @param oldNavButton
     * @param newNavButton
     */
    private void doTabChanged(NavigationButton oldNavButton, NavigationButton newNavButton) {
        FragmentTransaction ft = mFragmentManager.beginTransaction();
        if (oldNavButton != null) {
            if (oldNavButton.getFragment() != null) {
                ft.detach(oldNavButton.getFragment());//Fragment实例还在，只是解除了与activity的绑定
            }
        }
        if (newNavButton != null) {
            if (newNavButton.getFragment() == null) {
                //切换的时候，如果fragment存在，就切换，不存在，就创建
                Fragment fragment = Fragment.instantiate(mContext,
                        newNavButton.getClx().getName(), null);
                ft.add(mContainerId, fragment, newNavButton.getTag());
                newNavButton.setFragment(fragment);
            } else {
                ft.attach(newNavButton.getFragment());
            }
        }
        ft.commit();
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.nav_item_explore:
                Toast.makeText(mContext, "nav_item_explore", Toast.LENGTH_SHORT).show();
                break;
            case R.id.nav_item_news:
                Toast.makeText(mContext, "nav_item_news", Toast.LENGTH_SHORT).show();
                break;
            case R.id.nav_item_me:
                Toast.makeText(mContext, "nav_item_me", Toast.LENGTH_SHORT).show();
                break;
            case R.id.nav_item_tweet:
                Toast.makeText(mContext, "nav_item_tweet", Toast.LENGTH_SHORT).show();
                break;
        }
        if (view instanceof NavigationButton) {
            NavigationButton nav = (NavigationButton) view;
            doSelect(nav);
        }
    }

    public interface OnNavigationReselectListener {
        void onReselect(NavigationButton navigationButton);
    }

    private void onReselect(NavigationButton navigationButton) {
        if (mOnNavigationReselectListener != null) {
            mOnNavigationReselectListener.onReselect(navigationButton);
        }
    }
}

这个类，是本篇的精华，大多数关键地方都做了注释，可以看到，这个NavFragment碎片的onCreateView方法中返回了一个视图onCreateView.xml，其结构如下：

布局效果如下图：

onCreateView.xml布局效果图

由布局文件可以看到，这里的tab支持消息tag，就是那个红色部分，显示消息数量。在xml文件中可以看出有个NavigationButton自定义类，其代码如下：

package com.dingfang.org.navbardemo.view;

import android.content.Context;
import android.os.Build;
import android.support.annotation.DrawableRes;
import android.support.annotation.RequiresApi;
import android.support.annotation.StringRes;
import android.support.v4.app.Fragment;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.widget.FrameLayout;
import android.widget.ImageView;
import android.widget.TextView;

import com.dingfang.org.navbardemo.R;

/**
 * 底部切换按钮
 */

public class NavigationButton extends FrameLayout {
    private Fragment mFragment = null;
    private Class mClx;
    private ImageView mIconView;
    private TextView mTitleView;
    private TextView mDot;
    private String mTag;

    public NavigationButton(Context context) {
        super(context);
        init();
    }

    public NavigationButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public NavigationButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public NavigationButton(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        init();
    }

    private void init() {
        LayoutInflater inflater = LayoutInflater.from(getContext());
        inflater.inflate(R.layout.layout_nav_item, this, true);

        mIconView = (ImageView) findViewById(R.id.nav_iv_icon);
        mTitleView = (TextView) findViewById(R.id.nav_tv_title);
        mDot = (TextView) findViewById(R.id.nav_tv_dot);
    }

    public void setSelected(boolean selected) {
        super.setSelected(selected);
        mIconView.setSelected(selected);
        mTitleView.setSelected(selected);
    }

    public void showRedDot(int count) {
        mDot.setVisibility(count > 0 ? VISIBLE : GONE);
        mDot.setText(String.valueOf(count));
    }

    public void init(@DrawableRes int resId, @StringRes int strId, Class clx) {
        mIconView.setImageResource(resId);
        mTitleView.setText(strId);
        mClx = clx;
        mTag = mClx.getName();
    }

    public void init(@DrawableRes int resId, String strId, Class clx) {
        mIconView.setImageResource(resId);
        mTitleView.setText(strId);
        mClx = clx;
        mTag = mClx.getName();
    }

    public Class getClx() {
        return mClx;
    }

    public Fragment getFragment() {
        return mFragment;
    }

    public void setFragment(Fragment fragment) {
        this.mFragment = fragment;
    }

    public String getTag() {
        return mTag;
    }
}

其中在初始化时

   private void init() {
        LayoutInflater inflater = LayoutInflater.from(getContext());
        inflater.inflate(R.layout.layout_nav_item, this, true);

        mIconView = (ImageView) findViewById(R.id.nav_iv_icon);
        mTitleView = (TextView) findViewById(R.id.nav_tv_title);
        mDot = (TextView) findViewById(R.id.nav_tv_dot);
    }

layout_nav_item.xml文件如下：

看布局文件，有几个样式相关的xml文件，这里列举部分如tab_icon_new.xml

primarybar_txt.xml

代码实现的大致就是这样，需要源码的同学点击这里