Fragment模拟Tab以及简单优化

一、前言
在郭霖大大的博客（http://blog.csdn.net/guolin_blog/article/details/13171191）的基础上试着进行代码优化。
二、分析
有4个tab页：message，contacts，news，setting。每个tab页的点击事件流程基本一致。相应的ui组件命名规则一致（都以tab名为前缀）。
原文用switch语句写了4遍点击事件（作为给新手看的教程无可厚非），作为一个程序猿，试着来优化一下。
三、优化前准备
1 使用数组存放tab名，用到tab名的地方从数组取。

String tabs[] = {"message", "contacts", "news", "setting"};

2 ui组件也和tab名相关，怎么根据数组tabs获取ui呢？使用getResources().getIdentifier（相比直接用findViewById耗费些许性能）

//name为ui的id名，type传入"id"
 private View findView(String name, String type) {
        int resId = getResources().getIdentifier(name, type, "com.shadow.zyw.sdu.fragmenttabs");
        Log.d("test", "find view:" + name + resId);
        View view = (View) findViewById(resId);
        return view;
    }

3 对于xml布局文件和图片资源等，需要用java发射机制

    //mipmap下图片资源id
    private Integer findImage(String name) {
        Integer value = null;
        Class<R.mipmap> cls = R.mipmap.class;
        try {
            value = cls.getDeclaredField(name).getInt(null);
        } catch (Exception e) {
            Log.d("test", "findimage error" + name);
        }
        return value;

    }

    //返回布局文件id
     private Integer findLayout(String name) {
        Integer value = null;
        Class<R.layout> cls = R.layout.class;
        try {
            value = cls.getDeclaredField(name).getInt(null);
        } catch (Exception e) {
            Log.d("test", "findlayout error" + name);
        }
        return value;

    }

四、优化开始
1 对于tabs绑定监听器可以使用for循环

        for (int i = 0; i < tabs.length; i++) {
            View view = findView(tabs[i] + "_layout", "id");            
            view.setOnClickListener(this);
            //将id和tas名保存，可以知道哪个控件被点击
            map.put(String.valueOf(view.getId()), tabs[i]);
        }

2 fragment对象的生成：有2种方式
（1）使用java发射机制，动态根据类名生成对象

    private static Object newInstance(String className) throws Exception {
        //类名首字母大写
        StringBuilder sb = new StringBuilder(className);
        sb.setCharAt(0, Character.toUpperCase(sb.charAt(0)));
        className = sb.toString();
        Log.d("test", "classname:" + className);
        Class clazz = Class.forName("com.shadow.zyw.sdu.fragmenttabs." + className);
        return clazz.newInstance();

    }

 fragment = (Fragment) newInstance(name + "Frag");

（2）在fragment的onCreateView中根据tabs名，引入不同的布局文件。（感觉这样灵活性很差，这里只是练手，扩展思路）

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(findLayout(xml), container, false);
        Log.d("test", "frag create" + xml);
        return view;
    }

        fragObject = new FragObject();
        fragObject.setXml(name + "_layout");

3 onclick事件

  @Override
    public void onClick(View v) {
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        Log.d("test", String.valueOf(v.getId()));
        String name = map.get(String.valueOf(v.getId()));
        Log.d("test", "name" + name);

        fragObject = new FragObject();
        fragObject.setXml(name + "_layout");
        try {
            fragment = (Fragment) newInstance(name + "Frag");    

        } catch (Exception e) {
            e.printStackTrace();
            Log.d("test", "cannot create class:" + name);
            return;
        }
        ImageView imageView = (ImageView) findView(name + "_image", "id");
        imageView.setImageResource(findImage(name + "_selected"));
        TextView textView = (TextView) findView(name + "_text", "id");
        textView.setTextColor(Color.WHITE);

        fragmentTransaction.add(R.id.content, fragment);
        // fragmentTransaction.add(R.id.content, fragObject);
        fragmentTransaction.commit();

    }

4 判断是否已经产生过fragment，清空fragment等，使用Map保存fragment对象

        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        if (fragmentMap.get(name) == null) {
            try {
                fragment = (Fragment) newInstance(name + "Frag");
                fragInterface = (FragInterface) newInstance(name + "Frag");

            } catch (Exception e) {
                e.printStackTrace();
                Log.d("test", "cannot create class:" + name);
                return;
            }
            fragmentMap.put(name, fragment);
            fragmentTransaction.add(R.id.content, fragment);
        } else {
            fragment = fragmentMap.get(name);
            fragmentTransaction.show(fragment);
        }
        fragmentTransaction.commit();

5 清空点击状态

    private void clearSelected() {
        for (int i = 0; i < tabs.length; i++) {
            ImageView imageView = (ImageView) findView(tabs[i] + "_image", "id");
            imageView.setImageResource(findImage(tabs[i] + "_unselected"));
            TextView textView = (TextView) findView(tabs[i] + "_text", "id");
            textView.setTextColor(Color.parseColor("#82858b"));
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            if (fragmentMap.get(tabs[i]) != null) {
                fragmentTransaction.hide(fragmentMap.get(tabs[i]));
            }

            fragmentTransaction.commit();

        }
    }

6 优化后

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fragmentManager = getFragmentManager();
        for (int i = 0; i < tabs.length; i++) {
            View view = findView(tabs[i] + "_layout", "id");
            map.put(String.valueOf(view.getId()), tabs[i]);
            view.setOnClickListener(this);
        }
        setSelected(tabs[0]);
    }

    @Override
    public void onClick(View v) {
        Log.d("test", String.valueOf(v.getId()));
        String name = map.get(String.valueOf(v.getId()));
        Log.d("test", "name" + name);

        clearSelected();
        setSelected(name);

    }

    private void clearSelected() {
        for (int i = 0; i < tabs.length; i++) {
            ImageView imageView = (ImageView) findView(tabs[i] + "_image", "id");
            imageView.setImageResource(findImage(tabs[i] + "_unselected"));
            TextView textView = (TextView) findView(tabs[i] + "_text", "id");
            textView.setTextColor(Color.parseColor("#82858b"));
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            if (fragmentMap.get(tabs[i]) != null) {
                fragmentTransaction.hide(fragmentMap.get(tabs[i]));
            }

            fragmentTransaction.commit();

        }
    }

    private void setSelected(String name) {
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        if (fragmentMap.get(name) == null) {
            try {
                fragment = (Fragment) newInstance(name + "Frag");
                fragInterface = (FragInterface) newInstance(name + "Frag");

            } catch (Exception e) {
                e.printStackTrace();
                Log.d("test", "cannot create class:" + name);
                return;
            }
            fragmentMap.put(name, fragment);
            fragmentTransaction.add(R.id.content, fragment);
        } else {
            fragment = fragmentMap.get(name);
            fragmentTransaction.show(fragment);
        }
        fragmentTransaction.commit();
        ImageView imageView = (ImageView) findView(name + "_image", "id");
        imageView.setImageResource(findImage(name + "_selected"));
        TextView textView = (TextView) findView(name + "_text", "id");
        textView.setTextColor(Color.WHITE);
    }