尝试调用虚拟方法'；android.content.Context.getSharedReferences（java.lang.String，int）和#x27；关于空对象引用
大家好，我是新来的，我正在开发出租车应用程序，需要跟踪司机，即使应用程序在后台，所以我启动了一项服务，我尝试了这段代码，但当我启动服务时，出现了一个错误，应用程序崩溃 我无法理解为什么在启动服务时出现此错误：尝试调用虚拟方法'；android.content.Context.getSharedReferences（java.lang.String，int）和#x27；关于空对象引用,java,android,service,nullpointerexception,sharedpreferences,Java,Android,Service,Nullpointerexception,Sharedpreferences,大家好，我是新来的，我正在开发出租车应用程序，需要跟踪司机，即使应用程序在后台，所以我启动了一项服务，我尝试了这段代码，但当我启动服务时，出现了一个错误，应用程序崩溃 我无法理解为什么在启动服务时出现此错误： Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedP
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
at com.raismedia.taxiclient.model.M.getUserCategorie(M.java:164)
at com.raismedia.taxiclient.TrackingService.onCreate(TrackingService.java:120)
public static String getUserCategorie(Context mContext) {
164 ----> mSharedPreferences = mContext.getSharedPreferences(pref_name, 0);
return mSharedPreferences.getString("user_cat", null);
}
public class TrackingService extends Service implements TaskLoadedCallback, GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener, LocationListener {
private static final int LOCATION_REQUEST_CODE = 101;
public static TextView user_name, user_phone,statut_conducteur, balance;
private SwitchCompat switch_statut;
private GoogleApiClient mGoogleAPIClient;
private LocationRequest mLocationRequest;
private FusedLocationProviderApi mLocationProvider;
private Location currentLocation;
private Context mContext;
private Location Location;
@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onCreate() {
super.onCreate();
mGoogleAPIClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();
mLocationProvider = LocationServices.FusedLocationApi;
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(5000);
mLocationRequest.setFastestInterval(1000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
if(!M.getUserCategorie(mContext).equals("user_app")) {
if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
}
if(!isLocationEnabled(mContext))
showMessageEnabledGPS();
}
}
public void showMessageEnabledGPS(){
final AlertDialog.Builder builder = new AlertDialog.Builder(mContext);
builder.setMessage("Activez le service GPS pour partager votre position avec les clients. Activez le GPS maintenant ?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
startActivity(new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS));
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
dialogInterface.cancel();
}
});
final AlertDialog alert = builder.create();
alert.show();
}
private boolean isLocationEnabled(Context context){
// String locationProviders;
boolean enabled = false;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT){
int mode = Settings.Secure.getInt(context.getContentResolver(), Settings.Secure.LOCATION_MODE,
Settings.Secure.LOCATION_MODE_OFF);
enabled = (mode != Settings.Secure.LOCATION_MODE_OFF);
}else{
LocationManager service = (LocationManager) context.getSystemService(LOCATION_SERVICE);
enabled = service.isProviderEnabled(LocationManager.GPS_PROVIDER)||service.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}
return enabled;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
mGoogleAPIClient.connect();
return START_STICKY;
}
@Override
public void onConnected(@Nullable Bundle bundle) {
RequestLocationUpdates();
}
private void RequestLocationUpdates() {
if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
}
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleAPIClient, mLocationRequest, this); //getting error here..for casting..!
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
private Boolean verif = false;
public static GoogleMap mMap;
public static Marker currentMarker = null, destinationMarker = null;
@Override
public void onLocationChanged(Location location) {
this.currentLocation = location;
// Toast.makeText(context, "Ok", Toast.LENGTH_SHORT).show();
if (currentLocation != null) {
if(!M.getUserCategorie(mContext).equals("user_app"))
new MainActivity.setCurrentLocation().execute(String.valueOf(location.getLatitude()),String.valueOf(location.getLongitude()));
}
}
/**driver position Update **/
public static class setCurrentLocation extends AsyncTask<String, Void, String> {
private Context context;
@Override
protected String doInBackground(String... params) {
String url = AppConst.Server_url+"set_position.php";
final String latitude = params[0];
final String longitude = params[1];
StringRequest jsonObjReq = new StringRequest(Request.Method.POST,
url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
}) {
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("id_user", M.getID(context));
params.put("user_cat", M.getUserCategorie(context));
params.put("latitude", latitude);
params.put("longitude", longitude);
return params;
}
};
AppController.getInstance().addToRequestQueue(jsonObjReq);
jsonObjReq.setRetryPolicy(new DefaultRetryPolicy(
10000,
DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
return null;
}
@Override
protected void onPostExecute(String result) {
//to add spacing between cards
if (this != null) {
}
}
@Override
protected void onPreExecute() {
}
}
private class changerStatut extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
String url = AppConst.Server_url+"change_statut.php";
final String online = params[0];
StringRequest jsonObjReq = new StringRequest(Request.Method.POST,
url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
M.hideLoadingDialog();
JSONObject json = new JSONObject(response);
JSONObject msg = json.getJSONObject("msg");
String etat = msg.getString("etat");
String online = msg.getString("online");
if(etat.equals("1")){
if(online.equals("yes")) {
switch_statut.setChecked(true);
statut_conducteur.setText("enabled");
M.setStatutConducteur(online,mContext);
}else {
switch_statut.setChecked(false);
statut_conducteur.setText("disabled");
M.setStatutConducteur(online,mContext);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
M.hideLoadingDialog();
if(switch_statut.isChecked())
switch_statut.setChecked(false);
else
switch_statut.setChecked(true);
}
}) {
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("id_driver", M.getID(mContext));
params.put("online", online);
return params;
}
};
AppController.getInstance().addToRequestQueue(jsonObjReq);
jsonObjReq.setRetryPolicy(new DefaultRetryPolicy(
10000,
DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
return null;
}
@Override
protected void onPostExecute(String result) {
//to add spacing between cards
if (this != null) {
}
}
@Override
protected void onPreExecute() {
}
}
@Override
public void onConnected() {
RequestLocationUpdates();
}
@Override
public void onTaskDone(Object... values) {
}
}
公共类TrackingService扩展服务实现TaskLoadedCallback、GoogleAppClient.ConnectionCallbacks、，
GoogleAppClient.OnConnectionFailedListener，LocationListener{
私有静态最终整数位置\请求\代码=101；
公共静态文本查看用户名、用户电话、状态导体、余额；
专用交换机兼容交换机状态；
私人GoogleapClient MGoogleapClient；
私人位置请求mLocationRequest；
私有FusedLocationProviderApi mLocationProvider；
私人位置；
私有上下文；
私人位置；
@可空
@凌驾
公共IBinder onBind（意向）{
返回null；
}
@凌驾
public void onCreate（）{
super.onCreate（）；
mgoogleapclient=新的Googleapclient.Builder（此）
.addApi（LocationServices.API）
.addConnectionCallbacks（此）
.addOnConnectionFailedListener（此）
.build（）；
mLocationProvider=LocationServices.FusedLocationApi；
mlLocationRequest=新位置请求（）；
mLocationRequest.setInterval（5000）；
mlLocationRequest.setFastTestInterval（1000）；
mLocationRequest.setPriority（位置请求、优先级、平衡、功率、精度）；
如果（！M.getUserCategorie（mContext）.equals（“用户应用程序”））{
if（ActivityCompat.checkSelfPermission（这个，android.Manifest.permission.ACCESS\u FINE\u位置）
！=PackageManager.PERMISSION\u已授予和&ActivityCompat.checkSelfPermission（此，android.Manifest.PERMISSION.ACCESS\u位置）
！=PackageManager.权限（已授予）{
}
如果（！isLocationEnabled（mContext））
showMessageEnabledGPS（）；
}
}
public void showMessageEnabledGPS（）{
final AlertDialog.Builder=新建AlertDialog.Builder（mContext）；
builder.setMessage（“Activez le服务GPS浇注零件votre位置avec les客户端。Activez le GPS主租户？”）
.setCancelable（错误）
.setPositiveButton（“是”，新的DialogInterface.OnClickListener（）{
@凌驾
公共void onClick（DialogInterface，inti）{
startActivity（新意图（设置、动作、位置、来源、设置））；
}
})
.setNegativeButton（“否”，新的DialogInterface.OnClickListener（）{
@凌驾
公共void onClick（DialogInterface，inti）{
dialogInterface.cancel（）；
}
});
final AlertDialog alert=builder.create（）；
alert.show（）；
}
私有布尔isLocationEnabled（上下文）{
//字符串位置提供者；
布尔启用=假；
if（Build.VERSION.SDK\u INT>=Build.VERSION\u code.KITKAT）{
int mode=Settings.Secure.getInt（context.getContentResolver（），Settings.Secure.LOCATION\u mode，
设置。安全。位置（模式（关闭）；
已启用=（模式！=设置。安全。位置\u模式\u关闭）；
}否则{
LocationManager服务=（LocationManager）context.getSystemService（LOCATION\u服务）；
enabled=服务.isProviderEnabled（LocationManager.GPS|u提供程序）|服务.isProviderEnabled（LocationManager.NETWORK|u提供程序）；
}
返回启用；
}
@凌驾
公共int onStartCommand（Intent Intent、int标志、int startId）{
mGoogleAPIClient.connect（）；
返回开始时间；
}
@凌驾
未连接的公共无效（@Nullable Bundle）{
RequestLocationUpdates（）；
}
私有void RequestLocationUpdates（）{
if（ActivityCompat.checkSelfPermission（这个，android.Manifest.permission.ACCESS\u FINE\u位置）
！=PackageManager.PERMISSION\u已授予和&ActivityCompat.checkSelfPermission（此，android.Manifest.PERMISSION.ACCESS\u位置）
！=PackageManager.权限（已授予）{
}
LocationServices.FusedLocationApi.requestLocationUpdates（mgoogleapClient，mlLocationRequest，this）；//此处获取错误..用于强制转换。。！
}
@凌驾
公共空间连接暂停（int i）{
}
@凌驾
public void onconnection失败（@NonNull ConnectionResult ConnectionResult）{
}
私有布尔verif=false；
公共静态谷歌地图；
公共静态标记currentMarker=null，destinationMarker=null；
@凌驾
已更改位置上的公共无效（位置）{
this.currentLocation=位置；
//Toast.makeText（上下文“Ok”，Toast.LENGTH_SHORT）.show（）；
if（currentLocation！=null）{
如果（！M.getUserCategorie（mContext）.equals（“用户应用程序”））
新建MainActivity.setCurrentLocation（）.execute（String.valueOf（location.getLatitude（）），String.valueOf（location.getLatitude（））；
}
}
/**驾驶员位置更新**/
公共静态类setCurrentLocation扩展了异步任务{
私人语境；
@凌驾
受保护的字符串doInBackground（字符串…参数）{
字符串url=AppConst.Server\uURL+“set\u position.php”；
最终字符串纬度=参数[0]；
最终字符串经度=参数[1]；
StringRequest JSONOBJEQ=新的StringRequest（Request.Method.POST，
网址，
public class TrackingService extends Service implements TaskLoadedCallback, GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener, LocationListener {
private static final int LOCATION_REQUEST_CODE = 101;
public static TextView user_name, user_phone,statut_conducteur, balance;
private SwitchCompat switch_statut;
private GoogleApiClient mGoogleAPIClient;
private LocationRequest mLocationRequest;
private FusedLocationProviderApi mLocationProvider;
private Location currentLocation;
private Context mContext;
private Location Location;
@Nullable
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onCreate() {
super.onCreate();
mGoogleAPIClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.build();
mLocationProvider = LocationServices.FusedLocationApi;
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(5000);
mLocationRequest.setFastestInterval(1000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
if(!M.getUserCategorie(mContext).equals("user_app")) {
if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
}
if(!isLocationEnabled(mContext))
showMessageEnabledGPS();
}
}
public void showMessageEnabledGPS(){
final AlertDialog.Builder builder = new AlertDialog.Builder(mContext);
builder.setMessage("Activez le service GPS pour partager votre position avec les clients. Activez le GPS maintenant ?")
.setCancelable(false)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
startActivity(new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS));
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
dialogInterface.cancel();
}
});
final AlertDialog alert = builder.create();
alert.show();
}
private boolean isLocationEnabled(Context context){
// String locationProviders;
boolean enabled = false;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT){
int mode = Settings.Secure.getInt(context.getContentResolver(), Settings.Secure.LOCATION_MODE,
Settings.Secure.LOCATION_MODE_OFF);
enabled = (mode != Settings.Secure.LOCATION_MODE_OFF);
}else{
LocationManager service = (LocationManager) context.getSystemService(LOCATION_SERVICE);
enabled = service.isProviderEnabled(LocationManager.GPS_PROVIDER)||service.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}
return enabled;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
mGoogleAPIClient.connect();
return START_STICKY;
}
@Override
public void onConnected(@Nullable Bundle bundle) {
RequestLocationUpdates();
}
private void RequestLocationUpdates() {
if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
}
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleAPIClient, mLocationRequest, this); //getting error here..for casting..!
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
private Boolean verif = false;
public static GoogleMap mMap;
public static Marker currentMarker = null, destinationMarker = null;
@Override
public void onLocationChanged(Location location) {
this.currentLocation = location;
// Toast.makeText(context, "Ok", Toast.LENGTH_SHORT).show();
if (currentLocation != null) {
if(!M.getUserCategorie(mContext).equals("user_app"))
new MainActivity.setCurrentLocation().execute(String.valueOf(location.getLatitude()),String.valueOf(location.getLongitude()));
}
}
/**driver position Update **/
public static class setCurrentLocation extends AsyncTask<String, Void, String> {
private Context context;
@Override
protected String doInBackground(String... params) {
String url = AppConst.Server_url+"set_position.php";
final String latitude = params[0];
final String longitude = params[1];
StringRequest jsonObjReq = new StringRequest(Request.Method.POST,
url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
}) {
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("id_user", M.getID(context));
params.put("user_cat", M.getUserCategorie(context));
params.put("latitude", latitude);
params.put("longitude", longitude);
return params;
}
};
AppController.getInstance().addToRequestQueue(jsonObjReq);
jsonObjReq.setRetryPolicy(new DefaultRetryPolicy(
10000,
DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
return null;
}
@Override
protected void onPostExecute(String result) {
//to add spacing between cards
if (this != null) {
}
}
@Override
protected void onPreExecute() {
}
}
private class changerStatut extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
String url = AppConst.Server_url+"change_statut.php";
final String online = params[0];
StringRequest jsonObjReq = new StringRequest(Request.Method.POST,
url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
M.hideLoadingDialog();
JSONObject json = new JSONObject(response);
JSONObject msg = json.getJSONObject("msg");
String etat = msg.getString("etat");
String online = msg.getString("online");
if(etat.equals("1")){
if(online.equals("yes")) {
switch_statut.setChecked(true);
statut_conducteur.setText("enabled");
M.setStatutConducteur(online,mContext);
}else {
switch_statut.setChecked(false);
statut_conducteur.setText("disabled");
M.setStatutConducteur(online,mContext);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
M.hideLoadingDialog();
if(switch_statut.isChecked())
switch_statut.setChecked(false);
else
switch_statut.setChecked(true);
}
}) {
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("id_driver", M.getID(mContext));
params.put("online", online);
return params;
}
};
AppController.getInstance().addToRequestQueue(jsonObjReq);
jsonObjReq.setRetryPolicy(new DefaultRetryPolicy(
10000,
DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
return null;
}
@Override
protected void onPostExecute(String result) {
//to add spacing between cards
if (this != null) {
}
}
@Override
protected void onPreExecute() {
}
}
@Override
public void onConnected() {
RequestLocationUpdates();
}
@Override
public void onTaskDone(Object... values) {
}
}
@Override
public void onCreate() {
super.onCreate();
mContext = this;
//rest of your code
}