我是Android开发的新手，这是我的第一个应用程序。我的应用是使用其他应用程序跟踪一部手机。我现在设法做第一个发送gps坐标的应用程序。现在我正在做第二个应用程序，到目前为止应用程序可以从mysql服务器检索GPS坐标并在谷歌地图上显示它。问题是我的mysql数据库每秒都会更新，我在应用程序中刷新gps坐标时遇到问题。我尝试使用
new Handler().postDelayed(new Runnable() {
public void run() {
// call JSON methods here
new JsonReadTask ().execute();
}
}, 60000 );
调用我的异步任务，但应用程序崩溃并显示错误消息
E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #2
Process
我一直在寻找，因为我对android缺乏了解，我发现很难改变并实施解决方案来解决我的问题。谁能帮帮我吗。
我的活动代码
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.widget.Toast;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
public class MyActivity extends FragmentActivity {
private String jsonResult;
private String url = "http://address.com/recieve1.php";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.myactivity);
accessWebService();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
// Async Task to access the web
private class JsonReadTask extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(params[0]);
try {
HttpResponse response = httpclient.execute(httppost);
jsonResult = inputStreamToString(
response.getEntity().getContent()).toString();
}
catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
private StringBuilder inputStreamToString(InputStream is) {
String rLine = "";
StringBuilder answer = new StringBuilder();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
try {
while ((rLine = rd.readLine()) != null) {
answer.append(rLine);
}
}
catch (IOException e) {
// e.printStackTrace();
Toast.makeText(getApplicationContext(),
"Error..." + e.toString(), Toast.LENGTH_LONG).show();
}
return answer;
}
@Override
protected void onPostExecute(String result) {
jsonvalue();
}
}// end async task
public void accessWebService() {
JsonReadTask task = new JsonReadTask();
// passes values for the urls string array
task.execute(new String[] { url });
}
public void jsonvalue() {
List<Map<String, String>> employeeList = new ArrayList<Map<String, String>>();
try {
JSONObject jsonResponse = new JSONObject(jsonResult);
JSONArray jsonMainNode = jsonResponse.optJSONArray("my_coor");
for (int i = 0; i < jsonMainNode.length(); i++) {
JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
String latitude = jsonChildNode.optString("latitude");
String longitude = jsonChildNode.optString("longitude");
String coordinates[] = {latitude, longitude};
double lat = Double.parseDouble(coordinates[0]);
double lng = Double.parseDouble(coordinates[1]);
// Getting reference to SupportMapFragment
SupportMapFragment fragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
// Creating GoogleMap from SupportMapFragment
mapView = fragment.getMap();
LatLng location;
location = new LatLng(lat, lng);
mapView.addMarker(new MarkerOptions().position(location));
mapView.moveCamera(CameraUpdateFactory.newLatLng(location));
mapView.animateCamera(CameraUpdateFactory.zoomTo(15));
}
} catch (JSONException e) {
Toast.makeText(getApplicationContext(), "Error" + e.toString(),
Toast.LENGTH_SHORT).show();
}
}
完整的错误日志
04-22 20:50:25.236 11023-11023/com.unmcbus.unmcbustracker E/Zygote﹕ MountEmulatedStorage()
04-22 20:50:25.236 11023-11023/com.unmcbus.unmcbustracker E/Zygote﹕ v2
04-22 20:50:25.236 11023-11023/com.unmcbus.unmcbustracker E/SELinux﹕ [DEBUG] get_category: variable seinfo: default sensitivity: NULL, cateogry: NULL
04-22 20:51:34.331 11023-12546/com.unmcbus.unmcbustracker E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #2
Process: com.unmcbus.unmcbustracker, PID: 11023
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:300)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:818)
Caused by: java.lang.ArrayIndexOutOfBoundsException: length=0; index=0
at com.unmcbus.unmcbustracker.UNMCtoTTSActivity$JsonReadTask.doInBackground(UNMCtoT TSActivity.java:66)
at com.unmcbus.unmcbustracker.UNMCtoTTSActivity$JsonReadTask.doInBackground(UNMCtoTTSActivity.java:61)
at android.os.AsyncTask$2.call(AsyncTask.java:288)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
答案 0 :(得分：0)
请发布完整的错误日志，以便清楚了解错误。
但是我能在您的代码中找到问题
- ＆GT;您无法从后台线程（doInBackground()方法）
答案 1 :(得分：0)
我相信你在doInBackground中执行任务的方式是空的，因为你没有传递一个URL。
我可以看到，这应该通过URL：
new Handler().postDelayed(new Runnable() {
public void run() {
// call JSON methods here
accessWebService();
}
}, 60000 );