我有一个应用程序，每当用户启动应用程序时，它都会在数据库中创建一个新条目。此外，应该有一个函数在用户退出时删除用户的注册表。对于这两个函数，我有2个asynctasks。第一个工作正常，它在数据库中创建用户。但是，虽然没有错误，但是当调用onDestroy（）时，应删除用户的asynctask不执行任何操作。我已经使用onPause（）进行了测试，应用删除了用户，但我不知道为什么不能使用onDestroy（）。 这是我使用的相关代码：
public class Titulacion extends Activity {
@Override
public void onDestroy(){
super.onDestroy();
new Borrar().execute();
// UIHelper.killApp(true);
}
public static int titulacion;
Button bAceptar;
RadioGroup radGrp;
RadioButton radBot1;
RadioButton radBot2;
RadioButton radBot3;
RadioButton radBot4;
ImageButton bAdmin;
static int nTest = 0;
private ProgressDialog pDialog;
private static final String TAG_SUCCESS = "success";
JSONParser jsonParser = new JSONParser();
private static final int DIALOG_CONFIRMAR_USUARIO = 0;
int level = -1;
String levelstring;
int pid;
static String pids;
BroadcastReceiver batteryReceiver;
String url = "10.0.0.13";
private static String url_crear = "http://10.0.0.13/subida/create_candidato.php";
private static final String url_delete = "http://10.0.0.13/subida/delete_candidato.php";
@SuppressLint("NewApi")
static String device_id = Build.SERIAL;
static String PDA = device_id.substring(device_id.length() - 6);
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.titulacion);
batteryReceiver = new BroadcastReceiver() {
int scale = -1;
int voltage = -1;
int temp = -1;
@Override
public void onReceive(Context context, Intent intent) {
level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
levelstring = String.valueOf(level)+"%";
scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
temp = intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE, -1);
voltage = intent.getIntExtra(BatteryManager.EXTRA_VOLTAGE, -1);
}
};
IntentFilter filter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
registerReceiver(batteryReceiver, filter);
radGrp = (RadioGroup) findViewById(R.id.titGroup);
radBot1 = (RadioButton) findViewById(R.id.bot_superior);
radBot2 = (RadioButton) findViewById(R.id.bot_medio);
radBot3 = (RadioButton) findViewById(R.id.bot_tecnico);
radBot4 = (RadioButton) findViewById(R.id.bot_administrativo);
bAdmin = (ImageButton) findViewById(R.id.administradorinit);
bAceptar = (Button) findViewById(R.id.BtnAceptar);
StrictMode.ThreadPolicy policy = new StrictMode. ThreadPolicy.Builder().permitAll().build(); StrictMode.setThreadPolicy(policy);
boolean isReachable = false;
try{
isReachable = InetAddress.getByName("10.0.0.13").isReachable(1000);
} catch (Exception e){
Log.e("InetAddress", e.getMessage());
}finally {
if (isReachable) {
new CreateCandidato().execute();
}else{
Toast.makeText(getApplicationContext(), R.string.errorserver, Toast.LENGTH_LONG).show();
}
}
bAceptar.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (radBot1.isChecked()) {
titulacion = 1;
Intent i = new Intent(Titulacion.this, Ident.class);
startActivity(i);
unregisterReceiver(batteryReceiver);
} else if (radBot2.isChecked()) {
titulacion = 2;
Intent i = new Intent(Titulacion.this, Ident.class);
startActivity(i);
unregisterReceiver(batteryReceiver);
}
else if (radBot3.isChecked()) {
titulacion = 3;
Intent i = new Intent(Titulacion.this, MenuInterna.class);
startActivity(i);
unregisterReceiver(batteryReceiver);
}
else if (radBot4.isChecked()) {
titulacion = 4;
Intent i = new Intent(Titulacion.this, MenuSup.class);
startActivity(i);
unregisterReceiver(batteryReceiver);
}
}
});
bAdmin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(Titulacion.this, Admin.class);
startActivity(i);
unregisterReceiver(batteryReceiver);
}
});
}
class CreateCandidato extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(Titulacion.this);
pDialog.setMessage("Actualizando ..");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
protected String doInBackground(String... args) {
try {
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("nserie", PDA));
params.add(new BasicNameValuePair("bateria", levelstring));
JSONObject json = jsonParser.makeHttpRequest(url_crear,
"POST", params);
Log.d("Create Response", json.toString());
pid = json.getInt("id");
pids = String.valueOf(pid);
int success = json.getInt(TAG_SUCCESS);
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_url) {
// dismiss the dialog once done
pDialog.dismiss();
}
}
class Borrar extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
Log.d("LLEGA1", "LLEGA1");
}
protected String doInBackground(String... args) {
// Check for success tag
int success;
try {
} catch (Exception e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("id", Titulacion.getPID()));
JSONObject json = jsonParser.makeHttpRequest(
url_delete, "POST", params);
Log.d("Delete Product", json.toString());
success = json.getInt("success");
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_url) {
Log.d("llega", "LLEGA");
}
}
感谢您的帮助
答案 0 :(得分：1)
您的活动被破坏，但AsyncTask正在完成其工作（在后台工作）。不会有任何ANR，因为您没有在UI上执行任何后台操作。如果您在AsyncTask完成后更新UI上的任何视图，那么会有NULLPOINTER Exception。但是，在onDestroy()中运行AsyncTask不是一个好主意。
在onDestroy()中使用asyntask而不是你可以有一个扩展IntentService的活动，并从onDestroy中调用该活动