我是android的新手，我正在尝试从服务器读取数据。我使用一个util并像这样调用那个
private void ParseSource(String Url){
String source = new Cls_SourceGrabber().grabSource(Url);
}
但我得到android.os.networkonmainthreadexception。我怎样才能减少呢？
My SourceGrabber util：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.conn.ConnectTimeoutException;
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;
public class Cls_SourceGrabber {
private HttpGet mRequest;
private HttpClient mClient;
private BufferedReader mReader;
private StringBuffer mBuffer;
private String mNewLine;
public Cls_SourceGrabber() {
mRequest = new HttpGet();
InitializeClient();
mReader = null;
mBuffer = new StringBuffer(10000);
mNewLine = System.getProperty("line.separator");
}
private void InitializeClient() {
if (mClient == null || mClient.getConnectionManager() == null) {
HttpParams httpParameters = new BasicHttpParams();
HttpConnectionParams.setConnectionTimeout(httpParameters, 4500);
HttpConnectionParams.setSoTimeout(httpParameters, 10000);
// HttpConnectionParams.setTcpNoDelay(httpParameters, true);
mClient = new DefaultHttpClient(httpParameters);
}
}
/*
*Grab the full source
*/
public String grabSource(String url) {
mBuffer.setLength(0);
InitializeClient();
String source = "";
try {
mRequest.setURI(new URI(url));
HttpResponse response = mClient.execute(mRequest);
mReader = new BufferedReader(new InputStreamReader(response
.getEntity().getContent()));
String line = "";
while ((line = mReader.readLine()) != null) {
mBuffer.append(line);
mBuffer.append(mNewLine);
source = mBuffer.toString();
if (Thread.interrupted()) {
break;
}
}
} catch (ConnectTimeoutException e) {
source = "Connection Timed Out.";
} catch (java.net.UnknownHostException e) {
source = "No Internet Connection available!";
} catch (java.lang.ArrayIndexOutOfBoundsException e) {
source = "Site Parsing Exception.";
} catch (ClientProtocolException e) {
source = "Protocol Exception.";
} catch (IOException e) {
source = "Server not responding.";
} catch (URISyntaxException e) {
source = "Wrong URL!";
} catch (Exception e) {
source = "Exception - " + e.toString() + " - "
+ e.getMessage();
e.printStackTrace();
} finally {
closeReader();
}
return source;
}
}
答案 0 :(得分：0)
首先，我不建议再使用HTTPClient，因为sdk版本23不再支持它。
因此，最好将网络操作迁移到URL连接。
现在，android永远不允许在主线程上进行网络操作，因为它会在相当长的时间内阻塞UI线程，因此可能导致崩溃或糟糕的用户体验。
您可以查看以下文档：Doc 1
更好的网络操作方法是创建AsyncTask。
请注意不要访问doInBackground方法中的任何UI线程元素。您可以在onPreExecute或onPostExecute方法上修改UI线程元素。
我创建了一个NetworkOps Util。您可以查看一下，无论它对您有用：
import android.content.Context;
import android.net.Uri;
import android.util.Log;
import com.csehelper.variables.Constants;
import com.csehelper.variables.Keys;
import com.csehelper.variables.Url;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.ProtocolException;
import java.net.SocketTimeoutException;
import java.net.URL;
import java.util.ArrayList;
public class NetworkOps {
public final String EXCEPTION = "~Exception~";
/****************************
* Method to Grab Source
****************************/
public static String GrabSource(String URL) {
return PostData(URL, null);
}
/**
* *****************************************
* Method to Grab Source code from URL
* Posting Data
* *****************************************
*/
private static String PostData(String url, Uri.Builder uribuilder) {
String Source;
HttpURLConnection.setFollowRedirects(false);
HttpURLConnection urlConnection = null;
try {
urlConnection = (HttpURLConnection) new URL(url).openConnection();
urlConnection.setDoOutput(true);
urlConnection.setConnectTimeout(10000);
if(uribuilder != null) {
String query = uribuilder.build().getEncodedQuery();
OutputStream os = urlConnection.getOutputStream();
BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(os, "UTF-8"));
writer.write(query);
writer.flush();
writer.close();
os.close();
}
urlConnection.connect();
if (urlConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
String line;
StringBuilder builder = new StringBuilder();
InputStreamReader isr = new InputStreamReader(
urlConnection.getInputStream());
BufferedReader reader = new BufferedReader(isr);
while ((line = reader.readLine()) != null) {
builder.append(line);
}
Source = builder.toString();
} else {
Source = EXCEPTION + "Server unreachable. Check network connection.";
}
} catch (SocketTimeoutException e) {
Source = EXCEPTION + "Connection timed out.";
} catch (java.net.UnknownHostException e) {
Source = EXCEPTION + Constants.EXCEPTION_NO_NET;
} catch (ArrayIndexOutOfBoundsException e) {
Source = EXCEPTION + "Server error";
} catch (ProtocolException e) {
Source = EXCEPTION + "Protocol error";
} catch (IOException e) {
Source = EXCEPTION + "Server unreachable. Check network connection.";
} catch (Exception e) {
Source = EXCEPTION + "Error:" + e.toString() + " - "
+ e.getMessage();
e.printStackTrace();
} finally {
if (urlConnection != null) urlConnection.disconnect();
}
return Source;
}
}
从AsyncTask调用这些静态函数：
/*********************************
* AsyncTask to GrabSource
********************************/
class AsyncTask_GrabSource extends AsyncTask<Void, Void, Void> {
String Source = null;
String url = "https://enigmatic-woodland-35608.herokuapp.com/pager.json";
@Override
protected void onPreExecute() {
//Runs on Main Thread. You can access your UI elements here.
}
@Override
protected Void doInBackground(Void... params) {
// Don't access any UI elements from this function
Source = NetworkOps.GrabSource(this.url);
return null;
}
@Override
protected void onPostExecute(Void result) {
if (Source != null) {
if (!Source.contains("~Exception~")) {
//Show Error Message or do whatever you want
} else {
//Do Whatever with your Grabbed Sourcecode.
// This function runs on UI Thread, so you can update UI elements here
}
}
}
您还可以使用PostData函数发布数据。在方法doInBackground中，添加：
Uri.Builder builder = new Uri.Builder()
.appendQueryParameter("key", "value")
.appendQueryParameter("key2", "value2");
Source = NetworkOps.PostData(getApplicationContext(), url, builder);