我是Android的新手，所以这个问题可能很简单，但无论如何它仍然存在：
我正在创建一个Android应用程序，它将使用AsyncTask将用户的位置发送到远程数据库。现在，当您单击按钮时会发生这种情况，但我希望它能够以设定的间隔自动发生。
我试图制作一个处理程序和一个“scheduleAtFixedRate”，但它对我不起作用;可能只是因为我做错了。这是我的代码：
package com.paul.locations;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
import java.util.Timer;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.SystemClock;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
public class OptionsPage extends Activity implements OnClickListener {
private String lat="", lon="", current = "";
private Button bUpdate, bGoogleMap, Confirm;
private EditText TimerInterval;
private TextView Latit, Longit;
final Handler handler = new Handler();
private static final String TAG_SUCCESS = "success";
private static final String TAG_MESSAGE = "message";
private static final String UPDATE_INFO_URL = "http://192.168.1.16/locations/update_info.php";
// Progress Dialog
private ProgressDialog pDialog;
// JSON parser class`enter code here`
JSONParser jsonParser = new JSONParser();
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.options);
TimerInterval = (EditText) findViewById(R.id.etTimer);
Longit = (TextView) findViewById(R.id.tvLon);
Latit = (TextView) findViewById(R.id.tvLat);
bUpdate = (Button)findViewById(R.id.bUpdate);
bUpdate.setOnClickListener(this);
bGoogleMap = (Button)findViewById(R.id.bGoogleMap);
bGoogleMap.setOnClickListener(this);
Confirm = (Button)findViewById(R.id.bConfirm);
Confirm.setOnClickListener(this);
//This is the new line for timer task
TimerTask task = new TimerTask(){
@Override
public void run(){
new AttemptUpdate().execute();
}
};
new Timer().scheduleAtFixedRate(task,0,5000);
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.bGoogleMap:
Intent i = new Intent(OptionsPage.this, Location.class);
finish();
startActivity(i);
break;
case R.id.bUpdate:
LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
android.location.Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
lon = Double.toString(location.getLongitude());
lat = Double.toString(location.getLatitude());
System.out.println(lon + ", " + lat);
Calendar c = Calendar.getInstance();
SimpleDateFormat df = new SimpleDateFormat("HH:mm:ss");
current = df.format(c.getTime());
System.out.println(current);
new AttemptUpdate().execute();
break;
case R.id.bConfirm:
String Interval = TimerInterval.getText().toString();
int I = Integer.parseInt(Interval);
System.out.println(I);
break;
}
}
class AttemptUpdate extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(OptionsPage.this);
pDialog.setMessage("Attempting to store your location...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(final String... args) {
// TODO Auto-generated method stub
String success;
SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(OptionsPage.this);
String post_username = sp.getString("username", "anon");
try {
// Building Parameters
List<NameValuePair> params1 = new ArrayList<NameValuePair>();
params1.add(new BasicNameValuePair("username", post_username));
params1.add(new BasicNameValuePair("lat", lat));
params1.add(new BasicNameValuePair("lon", lon));
params1.add(new BasicNameValuePair("time", current));
Log.d("request!", "starting");
//Posting user data to script
JSONObject json = jsonParser.makeHttpRequest(
UPDATE_INFO_URL, "POST", params1);
// full json response
Log.d("Store location attempt", json.toString());
// json success element
success = json.getString(TAG_SUCCESS);
if(success.equals("SUCCESS")) {
Log.d("Location Stored!", json.toString());
finish();
return json.getString(TAG_MESSAGE);
}else{
Log.d("Storing Location Failure!", json.getString(TAG_MESSAGE));
return json.getString(TAG_MESSAGE);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_url) {
// dismiss the dialog once product deleted
pDialog.dismiss();
if (file_url != null){
Toast.makeText(OptionsPage.this, file_url, Toast.LENGTH_LONG).show();
}
Latit.setText("Latitude currently is: " + lat);
Longit.setText("Longitude currently is: " + lon);
}
}
}
在OnCreate方法中，您可以看到我尝试让计时器每5秒运行一次AttemptUpdate，但输入时会出现错误。任何帮助都将不胜感激！
添加计时器任务和计时器后，我运行了代码。应用程序崩溃了，我收到了以下logcat错误：
08-02 13:50:02.844: W/dalvikvm(29346): threadid=13: thread exiting with uncaught exception (group=0x41b11438)
08-02 13:50:02.854: E/AndroidRuntime(29346): FATAL EXCEPTION: Timer-0
08-02 13:50:02.854: E/AndroidRuntime(29346): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
08-02 13:50:02.854: E/AndroidRuntime(29346): at android.os.Handler.<init>(Handler.java:121)
08-02 13:50:02.854: E/AndroidRuntime(29346): at android.app.Dialog.<init>(Dialog.java:107)
08-02 13:50:02.854: E/AndroidRuntime(29346): at android.app.AlertDialog.<init>(AlertDialog.java:114)
08-02 13:50:02.854: E/AndroidRuntime(29346): at android.app.AlertDialog.<init>(AlertDialog.java:98)
08-02 13:50:02.854: E/AndroidRuntime(29346): at android.app.ProgressDialog.<init>(ProgressDialog.java:77)
08-02 13:50:02.854: E/AndroidRuntime(29346): at com.paul.locations.OptionsPage$AttemptUpdate.onPreExecute(OptionsPage.java:108)
08-02 13:50:02.854: E/AndroidRuntime(29346): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
08-02 13:50:02.854: E/AndroidRuntime(29346): at android.os.AsyncTask.execute(AsyncTask.java:534)
08-02 13:50:02.854: E/AndroidRuntime(29346): at com.paul.locations.OptionsPage$1.run(OptionsPage.java:69)
08-02 13:50:02.854: E/AndroidRuntime(29346): at java.util.Timer$TimerImpl.run(Timer.java:284)
答案 0 :(得分：4)
你把asynctask放在计时器任务应该去的地方。看一下这个例子TimerTask not executing?
TimerTask task = new TimerTask(){
@Override
public void run(){
new AttemptUpdate().execute();
}
}
new Timer().scheduleAtFixedRate(task,0,5000);
答案 1 :(得分：4)
使用以下代码替换错误行：
new Timer().scheduleAtFixedRate(new TimerTask() {
@Override
public void run() {
runOnUiThread(new Runnable() {
@Override
public void run() {
new AttemptUpdate().execute();
}
});
}
}, 0, 5000);