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Android之NetworkOnMainThreadException异常
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原文鏈接：http://blog.csdn.net/mad1989/article/details/25964495 ??
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看名字就應(yīng)該知道，是網(wǎng)絡(luò)請(qǐng)求在MainThread中產(chǎn)生的異常
先來看一下官網(wǎng)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
1，和network有關(guān)比較耗時(shí)的操作放到一個(gè)子線程里,然后用Handler消息機(jī)制與主線程通信。
[java] ?view plaincopy
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(qǐng)求結(jié)果為-->" ?+?val);?? ?????????? ?????????? ????}?? };?? ?? ? ? ?? Runnable?networkTask?=?new ?Runnable()?{?? ?? ????@Override ?? ????public ? void ?run()?{?? ?????????? ?????????? ????????Message?msg?=?new ?Message();?? ????????Bundle?data?=?new ?Bundle();?? ????????data.putString("value" ,? "請(qǐng)求結(jié)果" );?? ????????msg.setData(data);?? ????????handler.sendMessage(msg);?? ????}?? };??
2，使用異步機(jī)制如：asynctask，這個(gè)舉個(gè)簡單的加載網(wǎng)絡(luò)圖片的例子
[java] ?view plaincopy
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(jìn)行網(wǎng)絡(luò)操作的方法，網(wǎng)上給出的，我沒有具體測(cè)試：
在發(fā)起Http請(qǐng)求的Activity里面的onCreate函數(shù)里面添加如下代碼：
[java] ?view plaincopy
StrictMode.setThreadPolicy( new ?StrictMode.ThreadPolicy.Builder()?? ????????.detectDiskReads().detectDiskWrites().detectNetwork()?? ????????.penaltyLog().build());?? StrictMode.setVmPolicy(new ?StrictMode.VmPolicy.Builder()?? ????????.detectLeakedSqlLiteObjects().detectLeakedClosableObjects()?? ????????.penaltyLog().penaltyDeath().build());??
請(qǐng)記住，如果在Main Thread里聲明了一個(gè)handler，這個(gè)handler所Post 的 Runnable（Thread）、以及處理的message都是在當(dāng)前的mian線程里，非子線程。
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