基本上我的Android应用程序出现了一个奇怪的问题，它应该抓取一个JSON数组并打印出一些值，该类看起来像这样：
ShowComedianActivity.class
package com.example.connecttest;
public class ShowComedianActivity extends Activity{
TextView name;
TextView add;
TextView email;
TextView tel;
String id;
// Progress Dialog
private ProgressDialog pDialog;
//JSON Parser class
JSONParser jsonParser = new JSONParser();
// Single Comedian url
private static final String url_comedian_details = "http://86.9.71.17/connect/get_comedian_details.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_COMEDIAN = "comedian";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_ADDRESS = "address";
private static final String TAG_EMAIL = "email";
private static final String TAG_TEL = "tel";
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.show_comedian);
// Getting Comedian Details from intent
Intent i = getIntent();
// Getting id from intent
id = i.getStringExtra(TAG_ID);
new GetComedianDetails().execute();
}
class GetComedianDetails extends AsyncTask<String, String, String>{
protected void onPreExecute(){
super.onPreExecute();
pDialog = new ProgressDialog(ShowComedianActivity.this);
pDialog.setMessage("Fetching Comedian details. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... params) {
runOnUiThread(new Runnable(){
public void run(){
int success;
try{
//Building parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("id",id));
// Getting comedian details via HTTP request
// Uses a GET request
JSONObject json = jsonParser.makeHttpRequest(url_comedian_details, "GET", params);
// Check Log for json response
Log.d("Single Comedian details", json.toString());
//JSON Success tag
success = json.getInt(TAG_SUCCESS);
if(success == 1){
// Succesfully received product details
JSONArray comedianObj = json.getJSONArray(TAG_COMEDIAN); //JSON Array
// get first comedian object from JSON Array
JSONObject comedian = comedianObj.getJSONObject(0);
// comedian with id found
name = (TextView) findViewById(R.id.name);
add = (TextView) findViewById(R.id.add);
email = (TextView) findViewById(R.id.email);
tel = (TextView) findViewById(R.id.tel);
// Set text to details
name.setText(comedian.getString(TAG_NAME));
add.setText(comedian.getString(TAG_ADDRESS));
email.setText(comedian.getString(TAG_EMAIL));
tel.setText(comedian.getString(TAG_TEL));
}
} catch (JSONException e){
e.printStackTrace();
}
}
});
return null;
}
}
}
我的JSON Parser类看起来像：
package com.example.connecttest;
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
// function get json from url
// by making HTTP POST or GET method
public JSONObject makeHttpRequest(String url, String method,
List<NameValuePair> params) {
// Making HTTP request
try {
// check for request method
if(method == "POST"){
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}else if(method == "GET"){
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
现在，当我运行调试时，它在URL的末尾用？id = 1查询正确的地址，当我导航到该URL时，我得到以下JSON数组：
{"success":1,"comedian":[{"id":"1","name":"Michael Coombes","address":"5 Trevethenick Road","email":"mc6415@gmail.com","tel":"xxxxxxxxxxxx"}]}
但是我的应用程序崩溃了，log-cat报告看起来像这样：
03-22 02:05:02.140: E/Trace(3776): error opening trace file: No such file or directory (2)
03-22 02:05:04.590: E/AndroidRuntime(3776): FATAL EXCEPTION: main
03-22 02:05:04.590: E/AndroidRuntime(3776): android.os.NetworkOnMainThreadException
03-22 02:05:04.590: E/AndroidRuntime(3776): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
03-22 02:05:04.590: E/AndroidRuntime(3776): at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
03-22 02:05:04.590: E/AndroidRuntime(3776): at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
03-22 02:05:04.590: E/AndroidRuntime(3776): at libcore.io.IoBridge.connect(IoBridge.java:112)
03-22 02:05:04.590: E/AndroidRuntime(3776): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
03-22 02:05:04.590: E/AndroidRuntime(3776): at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
03-22 02:05:04.590: E/AndroidRuntime(3776): at java.net.Socket.connect(Socket.java:842)
03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
03-22 02:05:04.590: E/AndroidRuntime(3776): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
03-22 02:05:04.590: E/AndroidRuntime(3776): at com.example.connecttest.JSONParser.makeHttpRequest(JSONParser.java:62)
03-22 02:05:04.590: E/AndroidRuntime(3776): at com.example.connecttest.ShowComedianActivity$GetComedianDetails$1.run(ShowComedianActivity.java:89)
03-22 02:05:04.590: E/AndroidRuntime(3776): at android.os.Handler.handleCallback(Handler.java:615)
03-22 02:05:04.590: E/AndroidRuntime(3776): at android.os.Handler.dispatchMessage(Handler.java:92)
03-22 02:05:04.590: E/AndroidRuntime(3776): at android.os.Looper.loop(Looper.java:137)
03-22 02:05:04.590: E/AndroidRuntime(3776): at android.app.ActivityThread.main(ActivityThread.java:4745)
03-22 02:05:04.590: E/AndroidRuntime(3776): at java.lang.reflect.Method.invokeNative(Native Method)
03-22 02:05:04.590: E/AndroidRuntime(3776): at java.lang.reflect.Method.invoke(Method.java:511)
03-22 02:05:04.590: E/AndroidRuntime(3776): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
03-22 02:05:04.590: E/AndroidRuntime(3776): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-22 02:05:04.590: E/AndroidRuntime(3776): at dalvik.system.NativeStart.main(Native Method)
从此我猜测错误发生在jsonParser.makeHttpRequest中但是我不能为我的生活弄清楚出了什么问题并且希望有人能比我更能照亮我。
答案 0 :(得分：2)
您将获得android.os.NetworkOnMainThreadException，因为您正在尝试在其主线程上执行网络操作。＆＃34; AsyncTask是一个Thread，所以删除：
runOnUiThread(new Runnable(){
public void run(){
和右括号。
答案 1 :(得分：1)
首先，记得实际读取堆栈跟踪，答案在第一行。在严格模式下运行您的应用程序时（我认为默认情况下Android版本较新），如果您尝试在UI线程上进行任何网络调用，Android将抛出NetworkOnMainThreadException，因为您不要想要阻止UI线程。
E/AndroidRuntime(3776): android.os.NetworkOnMainThreadException
E/AndroidRuntime(3776): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
在这里查看跟踪是导致问题的代码：
E/AndroidRuntime(3776): at com.example.connecttest.JSONParser.makeHttpRequest(JSONParser.java:62)
E/AndroidRuntime(3776): at com.example.connecttest.ShowComedianActivity$GetComedianDetails$1.run(ShowComedianActivity.java:89)
以下是实际行：
JSONObject json = jsonParser.makeHttpRequest(url_comedian_details, "GET", params);
经过检查，您实际上是在doInBackground运行网络呼叫，该网络呼叫在主线程上运行，这是您要进行网络呼叫的地方（因为您可以阻止该线程所需）。但是，您正在runOnUiThread内部运行网络呼叫，因此您在UI线程上转回并运行网络呼叫，然后Android抛出NetworkOnMainThreadException。
我建议您删除runOnUiThread部分，因为这是一种不好的做法，并将您的请求参数传递给AsyncTask。
有关错误的更多信息 - How to fix android.os.NetworkOnMainThreadException?。