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 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 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); }