我的代码有问题,我希望获得一些帮助。我首先使用的是此代码:
new DefaultHttpClient().execute(new HttpGet(linkk)).getEntity().writeTo(
new FileOutputStream(f));
[它在android 2.3上工作正常,但在4.0上却没有。经过一些研究,我听说使用AndroidHttpClient更好,并且这种方式可以在4.0和3.1上运行。问题是我不知道我是否正确修改了代码,并且互联网上没有太多有关AndroidhttpClient的示例。
这里是我的代码已调整:
AndroidHttpClient client = AndroidHttpClient.newInstance("Android");
HttpGet request = new HttpGet(linkk);
HttpResponse response = client.execute(request); //here is where the exception is thrown
response.getEntity().writeTo(new FileOutputStream(f));
这是logcat显示的内容:
01-03 01:32:11.950: W/dalvikvm(17991): threadid=1: thread exiting with uncaught exception (group=0x40a2e1f8)
01-03 01:32:11.986: E/AndroidRuntime(17991): FATAL EXCEPTION: main
01-03 01:32:11.986: E/AndroidRuntime(17991): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.lacra.fbirthdays/com.lacra.fbirthdays.ListV}: android.os.NetworkOnMainThreadException
01-03 01:32:11.986: E/AndroidRuntime(17991): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
01-03 01:32:11.986: E/AndroidRuntime(17991): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
01-03 01:32:11.986: E/AndroidRuntime(17991): at android.app.ActivityThread.access$600(ActivityThread.java:123)
01-03 01:32:11.986: E/AndroidRuntime(17991): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
01-03 01:32:11.986: E/AndroidRuntime(17991): at android.os.Handler.dispatchMessage(Handler.java:99)
01-03 01:32:11.986: E/AndroidRuntime(17991): at android.os.Looper.loop(Looper.java:137)
01-03 01:32:11.986: E/AndroidRuntime(17991): at android.app.ActivityThread.main(ActivityThread.java:4424)
01-03 01:32:11.986: E/AndroidRuntime(17991): at java.lang.reflect.Method.invokeNative(Native Method)
01-03 01:32:11.986: E/AndroidRuntime(17991): at java.lang.reflect.Method.invoke(Method.java:511)
01-03 01:32:11.986: E/AndroidRuntime(17991): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-03 01:32:11.986: E/AndroidRuntime(17991): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-03 01:32:11.986: E/AndroidRuntime(17991): at dalvik.system.NativeStart.main(Native Method)
01-03 01:32:11.986: E/AndroidRuntime(17991): Caused by: android.os.NetworkOnMainThreadException
01-03 01:32:11.986: E/AndroidRuntime(17991): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099)
01-03 01:32:11.986: E/AndroidRuntime(17991): at java.net.InetAddress.lookupHostByName(InetAddress.java:391)
01-03 01:32:11.986: E/AndroidRuntime(17991): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)
01-03 01:32:11.986: E/AndroidRuntime(17991): at java.net.InetAddress.getAllByName(InetAddress.java:220)
01-03 01:32:11.986: E/AndroidRuntime(17991): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
01-03 01:32:11.986: E/AndroidRuntime(17991): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
01-03 01:32:11.986: E/AndroidRuntime(17991): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
01-03 01:32:11.986: E/AndroidRuntime(17991): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
01-03 01:32:11.986: E/AndroidRuntime(17991): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
StrictMode.ThreadPolicy自API级别9开始引入,并且默认线程策略自API级别11开始已更改,这简而言之,不允许在UI线程上执行网络操作(包括HttpClient和HttpUrlConnection)。如果执行此操作,则会得到NetworkOnMainThreadException。
可以使用以下方式更改此限制:
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
将上面的代码添加到主活动的onCreate()方法中。
此外,总是建议将网络操作移出UI线程,例如,使用AsyncTask。
希望获得帮助。
使用AsyncTask,以便网络请求不会阻塞UI线程。 NetworkOnMainThreadException是从API版本11开始引入的,这就是为什么它仅显示3.0或更高版本的原因。
private class NetworkTask extends AsyncTask<String, Void, HttpResponse> {
@Override
protected HttpResponse doInBackground(String... params) {
String link = params[0];
HttpGet request = new HttpGet(link);
AndroidHttpClient client = AndroidHttpClient.newInstance("Android");
try {
return client.execute(request);
} catch (IOException e) {
e.printStackTrace();
return null;
} finally {
client.close();
}
}
@Override
protected void onPostExecute(HttpResponse result) {
//Do something with result
if (result != null)
result.getEntity().writeTo(new FileOutputStream(f));
}
}
要简单地将此线程称为此操作。
new NetworkTask().execute(linkk);
[看一下Android开发者网站上写的this article。它更详细地说明了如何编写应用程序以处理线程。