Java 通过构造函数| ListView传递数组适配器
我正在尝试将适配器从我的Java 通过构造函数| ListView传递数组适配器,java,android,android-studio,listview,android-fragments,Java,Android,Android Studio,Listview,Android Fragments,我正在尝试将适配器从我的位置fragment.class添加到我的设备admin.class中,以向我的列表视图添加两个字符串,即mylatitude和MyLongitute。 我正在学习构造函数方法。 但每当我调用adapter.add(mylatitude+“”+mylongitude)时,它似乎都返回null在我的设备管理员类中 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.
位置fragment.class
添加到我的设备admin.class
中,以向我的列表视图
添加两个字符串,即mylatitude
和MyLongitute
。
我正在学习构造函数方法。
但每当我调用adapter.add(mylatitude+“”+mylongitude)时,它似乎都返回null代码>在我的设备管理员类中
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ArrayAdapter.add(java.lang.Object)' on a null object reference
at com.ayush.trixter.ui.captures.DeviceAdmin$1.onLocationChanged(DeviceAdmin.java:103)
第103行是:adapter.add(“纬度:+mylat+”经度:+mylon”)代码>
设备管理员类
import android.Manifest;
import android.annotation.SuppressLint;
import android.app.admin.DeviceAdminReceiver;
import android.app.admin.DevicePolicyManager;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.graphics.Paint;
import android.graphics.SurfaceTexture;
import android.hardware.Camera;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraManager;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Build;
import android.os.Looper;
import android.os.UserHandle;
import android.util.Log;
import android.util.SparseIntArray;
import android.view.ContextThemeWrapper;
import android.view.Surface;
import android.view.View;
import android.widget.Adapter;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.core.content.PermissionChecker;
import com.ayush.trixter.R;
import com.ayush.trixter.ui.locations.LocationFragment;
import com.google.android.gms.location.LocationCallback;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;
import com.google.android.material.snackbar.Snackbar;
import com.google.firebase.database.FirebaseDatabase;
import java.util.ArrayList;
public class DeviceAdmin extends DeviceAdminReceiver
{
private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
public CameraManager cam;
LocationManager locationManager;
final String TAG = "[Trixter]";
DevicePolicyManager mgr;
FirebaseDatabase db;
public boolean mTracking = false;
public ArrayList<String> listItems=new ArrayList<>();
LocationFragment lf = new LocationFragment();
ArrayAdapter<String> adapter = lf.adapter;
@Override
public void onPasswordFailed(@NonNull Context ctx, @NonNull Intent intent, @NonNull UserHandle user) {
super.onPasswordFailed(ctx, intent, user);
cam = (CameraManager) ctx.getSystemService(Context.CAMERA_SERVICE);
mgr = (DevicePolicyManager) ctx.getSystemService(Context.DEVICE_POLICY_SERVICE);
Log.d(TAG,"PasswordFailed");
int pwdfailcount = mgr.getCurrentFailedPasswordAttempts();
if(pwdfailcount==3)
{
takeSnapShots();
getloc(ctx);
}
}
public void getloc(Context ctx)
{
locationManager = (LocationManager) ctx.getSystemService(Context.LOCATION_SERVICE);
Criteria criteria = new Criteria();
String provider = locationManager.getBestProvider(criteria,true);
boolean gps_enabled = false;
boolean network_enabled = false;
try
{ gps_enabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER); }
catch (Exception e) {}
try { network_enabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);} catch (Exception e) {}
if(PermissionChecker.checkSelfPermission(ctx, Manifest.permission.ACCESS_COARSE_LOCATION) == PermissionChecker.PERMISSION_GRANTED && PermissionChecker.checkSelfPermission(ctx,Manifest.permission.ACCESS_FINE_LOCATION) == PermissionChecker.PERMISSION_GRANTED) {
if(gps_enabled == true && network_enabled ==true) {
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, new LocationListener() {
@Override
public void onLocationChanged(@NonNull Location loc) {
double mylat = loc.getLatitude();
double mylon = loc.getLongitude();
double myacc = loc.getAccuracy();
double time = loc.getTime();
double myalt = loc.getAltitude();
Log.d("[TrixterLocation]", "The Latitude:- " + mylat + "\nThe Longitude:- " + mylon + "\nThe Altitude:- " + myalt + "\n The Accuracy" + myacc + "\nThe Time:- " + time);
adapter.add("Latitude: " + mylat + "Longitude: " + mylon);
}
});
}
else
{
Toast.makeText(ctx, "Location is not enabled", Toast.LENGTH_SHORT).show();
Log.d("[Trixter] ","Error: Location or Internet Not Enabled");
}
}
}
private void takeSnapShots()
{
}
}
导入android.Manifest;
导入android.annotation.SuppressLint;
导入android.app.admin.DeviceAdminReceiver;
导入android.app.admin.DevicePolicyManager;
导入android.content.Context;
导入android.content.Intent;
导入android.content.pm.PackageManager;
导入android.graphics.Paint;
导入android.graphics.SurfaceTexture;
导入android.hardware.Camera;
导入android.hardware.camera2.CameraAccessException;
导入android.hardware.camera2.CameraCaptureSession;
导入android.hardware.camera2.CameraCharacteristics;
导入android.hardware.camera2.CameraManager;
导入android.location.Criteria;
导入android.location.location;
导入android.location.LocationListener;
导入android.location.LocationManager;
导入android.os.Build;
导入android.os.Looper;
导入android.os.UserHandle;
导入android.util.Log;
导入android.util.SparseIntArray;
导入android.view.contexthemewrapper;
导入android.view.Surface;
导入android.view.view;
导入android.widget.Adapter;
导入android.widget.ArrayAdapter;
导入android.widget.ListView;
导入android.widget.Toast;
导入androidx.annotation.NonNull;
导入androidx.core.content.PermissionChecker;
导入com.ayush.trixter.R;
导入com.ayush.trixter.ui.locations.LocationFragment;
导入com.google.android.gms.location.LocationCallback;
导入com.google.android.gms.location.LocationRequest;
导入com.google.android.gms.location.LocationServices;
导入com.google.android.material.snackbar.snackbar;
导入com.google.firebase.database.FirebaseDatabase;
导入java.util.ArrayList;
公共类DeviceAdmin扩展DeviceAdminReceiver
{
专用静态最终SparseIntArray方向=新SparseIntArray();
公共摄像机管理器;
地点经理地点经理;
最后一个字符串标记=“[Trixter]”;
设备运营经理;
FirebaseDB数据库;
公共布尔mTracking=false;
public ArrayList listItems=新建ArrayList();
LocationFragment lf=新的LocationFragment();
ArrayAdapter适配器=左前适配器;
@凌驾
public void onPasswordFailed(@NonNull Context ctx、@NonNull Intent Intent Intent、@NonNull UserHandle user){
super.onPasswordFailed(ctx、intent、user);
cam=(CameraManager)ctx.getSystemService(Context.CAMERA_服务);
mgr=(DevicePolicyManager)ctx.getSystemService(Context.DEVICE\u POLICY\u SERVICE);
Log.d(标记“PasswordFailed”);
int pwdfailcount=mgr.getCurrentFailedPasswordAttempts();
如果(pwdfailcount==3)
{
takeSnapShots();
getloc(ctx);
}
}
公共无效getloc(上下文ctx)
{
locationManager=(locationManager)ctx.getSystemService(Context.LOCATION\u服务);
标准=新标准();
字符串提供程序=locationManager.getBestProvider(条件为true);
布尔值gps_enabled=false;
布尔网络_enabled=false;
尝试
{gps_enabled=locationManager.isProviderEnabled(locationManager.gps_PROVIDER);}
捕获(例外e){}
请尝试{network_enabled=locationManager.isProviderEnabled(locationManager.network_PROVIDER);}捕获(异常e){}
if(PermissionChecker.checkSelfPermission(ctx,Manifest.permission.ACCESS\u rough\u LOCATION)=授予PermissionChecker.permission\u和PermissionChecker.checkSelfPermission(ctx,Manifest.permission.ACCESS\u FINE\u LOCATION)=授予PermissionChecker.permission\u){
如果(gps_启用==true&&network_启用==true){
locationManager.RequestLocationUpdate(locationManager.GPS_提供程序,0,0,新LocationListener(){
@凌驾
public void onLocationChanged(@NonNull Location){
双mylat=loc.getLatitude();
double mylon=loc.getLongitude();
double myacc=loc.getAccurance();
double time=loc.getTime();
double myalt=loc.getAltitude();
Log.d(“[TrixterLocation]”,纬度:-“+mylat+”\n经度:-“+mylon+”\n海拔:-“+myalt+”\n精度“+myacc+”\n时间:-“+Time”);
添加(“纬度:+mylat+”经度:+mylon);
}
});
}
其他的
{
Toast.makeText(ctx,“位置未启用”,Toast.LENGTH_SHORT.show();
Log.d(“[Trixter]”,“错误:位置或互联网未启用”);
}
}
}
私有快照()
{
}
}
LocationsFragment.class
package com.ayush.trixter.ui.locations;
import android.content.Context;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.ListFragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;
import com.ayush.trixter.R;
import com.ayush.trixter.ui.captures.DeviceAdmin;
import java.util.ArrayList;
public class LocationFragment extends ListFragment {
ListView loclst;
LocationManager locationManager;
public ArrayList<String> listItems=new ArrayList<>();
public ArrayAdapter<String> adapter = (ArrayAdapter<String>) getListAdapter();
public LocationFragment()
{
}
public View onCreateView(@NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.fragment_locations, container, false);
loclst = root.findViewById(android.R.id.list);
Context context = getActivity();
locationManager = (LocationManager) getActivity().getSystemService(Context.LOCATION_SERVICE);
adapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_2 , listItems);
loclst.setAdapter(adapter);
return root;
}
}
package com.ayush.trixter.ui.locations;
导入android.content.Context;
导入android.location.LocationManager;
导入android.os.Bundle;
导入android.view.LayoutInflater;
导入android.view.view;
导入android.view.ViewGroup;
导入android.widget.AdapterView;
导入android.widget.ArrayAdapter;
导入android.widget.ListView;
导入android.widget.TextView;
导入android.widget.Toast;
导入androidx.annotation.NonNull;
导入androidx.annotation.Nullable;
导入androidx.fragment.app.fragment;
导入androidx.fragment.app.ListFragment;
导入androidx.lifecycle.Observer;
导入androidx.lifecycle.ViewModelProviders;
导入com.ayush.trixter.R;
导入com.ayush.trixter.ui.captures.DeviceAdmin;
导入java.util.ArrayList;
公共级Locat