我已在我的应用中集成了货币转换器，但当我尝试从互联网上获取结果时，应用程序崩溃了。我收到一个错误：android.os.NetworkOnMainThreadException，有人说你必须添加asynctask以解决问题，因为它在主线程上运行。那么我怎样才能在当前的代码中做到这一点？
以下是代码：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpEntity;
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.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
public class Activity_Currency_Converter extends DashBoardActivity {
public int to;
public int from;
public String [] val;
public String s;
public Handler handler;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_currency_converter);
Spinner s1 = (Spinner) findViewById(R.id.spinner1);
Spinner s2 = (Spinner) findViewById(R.id.spinner2);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.name, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.select_dialog_singlechoice);
val = getResources().getStringArray(R.array.value);
s1.setAdapter(adapter);
s2.setAdapter(adapter);
s1.setOnItemSelectedListener(new spinOne(1));
s2.setOnItemSelectedListener(new spinOne(2));
Button b = (Button) findViewById(R.id.button1);
b.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
TextView t = (TextView) findViewById(R.id.textView4);
if(from == to)
{
Toast.makeText(getApplicationContext(), "Invalid", 4000).show();
}
else
{
try {
s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject jObj;
jObj = new JSONObject(s);
String exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
t.setText(exResult);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
}
public String getJson(String url)throws ClientProtocolException, IOException {
StringBuilder build = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = client.execute(httpGet);
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String con;
while ((con = reader.readLine()) != null) {
build.append(con);
}
return build.toString();
}
private class spinOne implements OnItemSelectedListener
{
int ide;
spinOne(int i)
{
ide =i;
}
public void onItemSelected(AdapterView<?> parent, View view,
int index, long id) {
if(ide == 1)
from = index;
else if(ide == 2)
to = index;
}
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
}
}
Logcat日志：
11-27 13:58:17.120: E/AndroidRuntime(1470): android.os.NetworkOnMainThreadException
11-27 13:58:17.120: E/AndroidRuntime(1470): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1133)
11-27 13:58:17.120: E/AndroidRuntime(1470): at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
11-27 13:58:17.120: E/AndroidRuntime(1470): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
11-27 13:58:17.120: E/AndroidRuntime(1470): at java.net.InetAddress.getAllByName(InetAddress.java:214)
11-27 13:58:17.120: E/AndroidRuntime(1470): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
11-27 13:58:17.120: E/AndroidRuntime(1470): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
11-27 13:58:17.120: E/AndroidRuntime(1470): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
11-27 13:58:17.120: E/AndroidRuntime(1470): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
11-27 13:58:17.120: E/AndroidRuntime(1470): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
11-27 13:58:17.120: E/AndroidRuntime(1470): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
11-27 13:58:17.120: E/AndroidRuntime(1470): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
答案 0 :(得分：1)
使用Asynctask执行网络相关操作.. 请查看此详细信息NetworkOnMainThread和Asynchtask
答案 1 :(得分：1)
试试这个，
public class Activity_Currency_Converter extends DashBoardActivity {
public int to;
public int from;
public String [] val;
public String s;
public Handler handler;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_currency_converter);
Spinner s1 = (Spinner) findViewById(R.id.spinner1);
Spinner s2 = (Spinner) findViewById(R.id.spinner2);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.name, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.select_dialog_singlechoice);
val = getResources().getStringArray(R.array.value);
s1.setAdapter(adapter);
s2.setAdapter(adapter);
s1.setOnItemSelectedListener(new spinOne(1));
s2.setOnItemSelectedListener(new spinOne(2));
Button b = (Button) findViewById(R.id.button1);
b.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
TextView t = (TextView) findViewById(R.id.textView4);
if(from == to)
{
Toast.makeText(getApplicationContext(), "Invalid", 4000).show();
}
else
{
new GetResponseData(t).execute();
}
}
});
}
public String getJson(String url)throws ClientProtocolException, IOException {
StringBuilder build = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = client.execute(httpGet);
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String con;
while ((con = reader.readLine()) != null) {
build.append(con);
}
return build.toString();
}
private class spinOne implements OnItemSelectedListener
{
int ide;
spinOne(int i)
{
ide =i;
}
public void onItemSelected(AdapterView<?> parent, View view,
int index, long id) {
if(ide == 1)
from = index;
else if(ide == 2)
to = index;
}
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
}
class GetResponseData extends AsyncTask<String, String, String> {
private ProgressDialog dialog;
private ArrayList<String> titleList;
private TextView textView;
public GetResponseData(TextView textView) {
this.textView=textView;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog = ProgressDialog.show(Activity_Currency_Converter.this, "", "Loading",
false);
}
@Override
protected String doInBackground(String... params) {
try {
String s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject jObj;
jObj = new JSONObject(s);
String exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
return exResult;
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
if (dialog != null)
dialog.dismiss();
if(result!=null)
{
textView.setText(result);
}
}
}
}
答案 2 :(得分：0)
制作StringBuilder班级，相应地创建ProgressDialog。
在getJSON方法中，创建一个像这样的异步任务
new AsyncTask<Void, Void, Void>() {
protected void onPreExecute() {
//Your code
}
@Override
protected Void doInBackground(Void... params) {
StringBuilder build = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = client.execute(httpGet);
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String con;
while ((con = reader.readLine()) != null) {
build.append(con);
}
return null;
}
protected void onPostExecute(Void result) {
//Update UI from here
}
}.execute();
答案 3 :(得分：0)
使用AsyncTask作为
class myAsyncTask extends AsyncTask<String[] ,String,String>
{
String s=null;
String output=null;
JSONObject main;
@Override
protected void onPreExecute()
{
}
@Override
protected String doInBackground(String[]... val) {
s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
JSONObject jObj;
jObj = new JSONObject(s);
String exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
return exResult;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
t.setText(result);
}
}
然后从'else'块
调用以下方法new myAsyncTask().execute(val);
答案 4 :(得分：0)
由于严格的模式政策导致应用崩溃，在您向服务发送请求或连接到网络之前插入以下给定的行：
ThreadPolicy tp = ThreadPolicy.LAX;
StrictMode.setThreadPolicy(tp);
希望它能帮助你：）