原文鏈接：http://blog.csdn.net/mad1989/article/details/25964495 ??
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看名字就應該知道，是網絡請求在MainThread中產生的異常
先來看一下官網的解釋：
Class Overview
The exception that is thrown when an application attempts to perform a networking operation on its main thread.
This is only thrown for applications targeting the Honeycomb SDK or higher. Applications targeting earlier SDK versions are allowed to do networking on their main event loop threads, but it's heavily discouraged. See the document?Designing for Responsiveness.
Also see?StrictMode.
http://developer.android.com/intl/zh-cn/reference/android/os/NetworkOnMainThreadException.html
解釋一下，從Honeycomb SDK（3.0）開始，google不再允許網絡請求（HTTP、Socket）等相關操作直接在Main Thread類中，其實本來就不應該這樣做，直接在UI線程進行網絡操作，會阻塞UI、用戶體驗相當bad！即便google不禁止，一般情況下我們也不會這么做吧~
所以，也就是說，在Honeycomb SDK（3.0）以下的版本，你還可以繼續在Main Thread里這樣做，在3.0以上，就不行了，建議
1，和network有關比較耗時的操作放到一個子線程里,然后用Handler消息機制與主線程通信。
- public?void?onCreate(Bundle?savedInstanceState)?{??
- ????super.onCreate(savedInstanceState);??
- ????this.setContentView(R.layout.test);??
- ??????
- ????new?Thread(networkTask).start();??
- }??
- ??
- Handler?handler?=?new?Handler()?{??
- ????@Override??
- ????public?void?handleMessage(Message?msg)?{??
- ????????super.handleMessage(msg);??
- ????????Bundle?data?=?msg.getData();??
- ????????String?val?=?data.getString("value");??
- ????????Log.i("mylog",?"請求結果為-->"?+?val);??
- ??????????
- ??????????
- ????}??
- };??
- ??
- ?
- ?
- ??
- Runnable?networkTask?=?new?Runnable()?{??
- ??
- ????@Override??
- ????public?void?run()?{??
- ??????????
- ??????????
- ????????Message?msg?=?new?Message();??
- ????????Bundle?data?=?new?Bundle();??
- ????????data.putString("value",?"請求結果");??
- ????????msg.setData(data);??
- ????????handler.sendMessage(msg);??
- ????}??
- };??
2，使用異步機制如：asynctask，這個舉個簡單的加載網絡圖片的例子
- class?DownImage?extends?AsyncTask?{??
- ??
- ????private?ImageView?imageView;??
- ??
- ????public?DownImage(ImageView?imageView)?{??
- ????????this.imageView?=?imageView;??
- ????}??
- ??
- ????@Override??
- ????protected?Bitmap?doInBackground(String...?params)?{??
- ????????String?url?=?params[0];??
- ????????Bitmap?bitmap?=?null;??
- ????????try?{??
- ??????????????
- ????????????InputStream?is?=?new?URL(url).openStream();??
- ????????????bitmap?=?BitmapFactory.decodeStream(is);??
- ????????}?catch?(Exception?e)?{??
- ????????????e.printStackTrace();??
- ????????}??
- ????????return?bitmap;??
- ????}??
- ??
- ????@Override??
- ????protected?void?onPostExecute(Bitmap?result)?{??
- ????????imageView.setImageBitmap(result);??
- ????}??
- }??
3，直接在main Thread 進行網絡操作的方法，網上給出的，我沒有具體測試：
在發起Http請求的Activity里面的onCreate函數里面添加如下代碼：
- StrictMode.setThreadPolicy(new?StrictMode.ThreadPolicy.Builder()??
- ????????.detectDiskReads().detectDiskWrites().detectNetwork()??
- ????????.penaltyLog().build());??
- StrictMode.setVmPolicy(new?StrictMode.VmPolicy.Builder()??
- ????????.detectLeakedSqlLiteObjects().detectLeakedClosableObjects()??
- ????????.penaltyLog().penaltyDeath().build());??
請記住，如果在Main Thread里聲明了一個handler，這個handler所Post 的 Runnable（Thread）、以及處理的message都是在當前的mian線程里，非子線程。
詳解)
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