我收到错误发生异常：android.os.NetworkOnMainThreadException，即使我已经使用AsyncTask。该行的LongOperation.java出错
while ((line = reader.readLine()) != null) {
这是代码：
package com.example.myfirstapp;
import java.util.concurrent.ExecutionException;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
public class AsyncTaskActivity extends Activity implements OnClickListener {
Button btn;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btn = (Button) findViewById(R.id.button1);
btn.setOnClickListener(this);
}
public void onClick(View view) {
switch (view.getId()) {
case R.id.button1:
try {
TextView txt = (TextView) findViewById(R.id.output);
txt.setText(new LongOperation().execute("http://search.twitter.com/search.json?q=javacodegeeks").get());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
break;
}
}
}
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<ProgressBar
android:id="@+id/progressBar"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:indeterminate="false"
android:max="10"
android:padding="10dip" >
</ProgressBar>
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Start Progress" >
</Button>
<TextView
android:id="@+id/output"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Replace" />
</LinearLayout>
package com.example.myfirstapp;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpConnectionParams;
import org.apache.http.params.HttpParams;
import android.os.AsyncTask;
import android.util.Log;
public class LongOperation extends AsyncTask<String, Void, String> {
InputStream is = null;
@Override
protected String doInBackground(String... urls) {
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(urls[0]);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
HttpParams myParams = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(myParams, 10000);
HttpConnectionParams.setSoTimeout(myParams, 10000);
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
return is.toString();
}
@Override
protected void onPostExecute(String result) {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = "";
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
// System.out.println("Result = " + result);
} catch (Exception e) {
Log.e("log_tag", "Error converting result " + e.toString());
}
}
@Override
protected void onPreExecute() {
}
@Override
protected void onProgressUpdate(Void... values) {
}
}
有人可以帮忙吗？
答案 0 :(得分：2)
onPostExecute()和onPreExecute()在主UI线程上运行。将网络操作移至doInBackground()。
答案 1 :(得分：2)
new LongOperation().execute("http://search.twitter.com/search.json?q=javacodegeeks").get()
调用get()不会使其异步。阻止ui线程。
public final Result get ()
如果需要等待计算完成，然后检索其结果。
你需要
new LongOperation().execute("http://search.twitter.com/search.json?q=javacodegeeks")
我会使用一个接口作为回调来将结果传回给活动。
类似于以下链接中黑带的回答
How do I return a boolean from AsyncTask?
同时将所有与网络相关的操作移至doInbackground并在onPostExecute更新ui
示例：
public class MainActivity extends Activity implements LongOperation.callBack {
Button btn;
TextView txt;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
txt = (TextView) findViewById(R.id.textView1);
btn = (Button) findViewById(R.id.button1);
btn.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
new LongOperation(MainActivity.this).execute("http://search.twitter.com/search.json?q=javacodegeeks");
}
});
}
@Override
public void returnText(String value) {
// TODO Auto-generated method stub
txt.setText(value);
}
}
activity_main.xml中
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:text="Button" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="48dp"
android:text="TextView" />
</RelativeLayout>
LongOperation.java
public class LongOperation extends AsyncTask<String, Void, String> {
InputStream is = null;
String _response;
callBack cb;
ProgressDialog pd;
interface callBack
{
public void returnText(String value);
};
public LongOperation(Context context) {
// TODO Auto-generated constructor stub
cb = (callBack) context;
pd = new ProgressDialog(context);
pd.setMessage("LongOperation...");
}
@Override
protected String doInBackground(String... urls) {
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(urls[0]);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
HttpParams myParams = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(myParams, 10000);
HttpConnectionParams.setSoTimeout(myParams, 10000);
HttpEntity resEntity = response.getEntity();
_response=EntityUtils.toString(resEntity);
is = entity.getContent();
} catch (Exception e) {
Log.e("log_tag", "Error in http connection " + e.toString());
}
return _response;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
pd.dismiss();
if(cb!=null)
{
cb.returnText(result);
}
}
@Override
protected void onPreExecute() {
super.onPreExecute();
pd.show();
}
@Override
protected void onProgressUpdate(Void... values) {
}
}