基本上我的 Android 应用程序遇到了一个奇怪的问题，它应该获取一个 JSON 数组并打印出一些值，该类如下所示：
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，它会在 URL 末尾使用 ?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 报告如下所示：
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)
据此，我猜测错误出在 jsonParser.makeHttpRequest 中，但是我终其一生都无法弄清楚出了什么问题，并希望比我更聪明的人能照亮我。