如何在后台访问位置Android 12

Question

我正在制作一个应用程序，当用户单击电源键两次时，它会获取最后一个已知位置。我使用前台服务注册广播接收器，对于位置，我使用fusedlocationproviderclient。用户可以在应用程序处于后台时获取位置。我的问题是我只能获取一次位置。第二时间位置为空。我该如何解决？

注：它在android 7版本中运行良好。

服务：

public class ScreenOnOffBackgroundService extends Service {
private ScreenOnOffReceiver screenOnOffReceiver = null;
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
createNotificationChannel();
Intent mainIntent = new Intent(this, DashboardActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(this,0,mainIntent, 0);
Notification notification = new NotificationCompat.Builder(this,"safetyId")
.setContentTitle("Safety Service")
.setContentText("Press power key to send alert")
.setSmallIcon(R.drawable.android)
.setContentIntent(pendingIntent)
.build();
startForeground(1,notification);
return START_STICKY;
}
@Override
public void onCreate() {
super.onCreate();
// Create an IntentFilter instance.
IntentFilter intentFilter = new IntentFilter();
// Add network connectivity change action.
intentFilter.addAction("android.intent.action.SCREEN_ON");
// Set broadcast receiver priority.
intentFilter.setPriority(100);
screenOnOffReceiver = new ScreenOnOffReceiver();
HandlerThread broadcastHandlerThread = new HandlerThread("SafetyThread");
broadcastHandlerThread.start();
Looper looper = broadcastHandlerThread.getLooper();
Handler broadcastHandler = new Handler(looper);
registerReceiver(screenOnOffReceiver,intentFilter,null,broadcastHandler);
}
private void createNotificationChannel() {
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O ){
NotificationChannel channel = new NotificationChannel(
"safetyId",
"Safety Service",
NotificationManager.IMPORTANCE_DEFAULT
);
NotificationManager manager = getSystemService(NotificationManager.class);
manager.createNotificationChannel(channel);
}
}

@Override
public void onDestroy() {
stopForeground(true);
stopSelf();
// Unregister screenOnOffReceiver when destroy.
if(screenOnOffReceiver!=null)
{
unregisterReceiver(screenOnOffReceiver);
}
}
}

广播接收机：

public class ScreenOnOffReceiver extends BroadcastReceiver {
private int count = 0;
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (Intent.ACTION_SCREEN_ON.equals(action) || Intent.ACTION_SCREEN_OFF.equals(action)) {
count++;
if (count == 2) {
count = 0;
DashboardActivity.getInstance().getLastLocation();
}
}
}
}

仪表板活动：

public class DashboardActivity extends AppCompatActivity {
public Button btnAlert;
private static DashboardActivity instance;
private final static int REQUEST_CODE = 123;
private FusedLocationProviderClient locationProviderClient;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dashboard);
instance = this;
registerService();
btnAlert = findViewById(R.id.btnAlert);
locationProviderClient = LocationServices.getFusedLocationProviderClient(this);
btnAlert.setOnClickListener(view -> getLastLocation());
}
public static DashboardActivity getInstance(){
return instance;
}
public void registerService(){
if(!foregroundServiceRunning()){
Intent backgroundService = new Intent(this, ScreenOnOffBackgroundService.class);
ContextCompat.startForegroundService(this,backgroundService);
}
}
public boolean foregroundServiceRunning(){
ActivityManager manager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
for(ActivityManager.RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)){
if(ScreenOnOffBackgroundService.class.getName().equals(service.service.getClassName())){
return true;
}
}
return false;
}
@SuppressLint("MissingPermission")
public void getLastLocation() {
// check if permissions are given
if (checkPermissions()) {
// check if location is enabled
if (isLocationEnabled()) {
locationProviderClient.getLastLocation().addOnCompleteListener(task -> {
Location location = task.getResult();
if (location == null) {
requestNewLocationData();
} else {
Toast.makeText(this, "Latitude: "+location.getLatitude(), Toast.LENGTH_LONG).show();
}
});
} else {
Toast.makeText(this, "Please turn on your location", Toast.LENGTH_LONG).show();
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(intent);
}
} else {
requestPermissions();
}
}

private boolean checkPermissions() {
return ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED;
}
private void requestPermissions() {
String[] permissionArray = new String[]{
android.Manifest.permission.ACCESS_COARSE_LOCATION,
android.Manifest.permission.ACCESS_FINE_LOCATION,};
ActivityCompat.requestPermissions(this, permissionArray, REQUEST_CODE);
}
@SuppressLint("MissingPermission")
private void requestNewLocationData() {
LocationRequest mLocationRequest = LocationRequest.create()
.setInterval(100)
.setFastestInterval(3000)
.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY)
.setMaxWaitTime(100).setNumUpdates(1);
locationProviderClient = LocationServices.getFusedLocationProviderClient(this);
locationProviderClient.requestLocationUpdates(mLocationRequest, mLocationCallback, Looper.myLooper());
}
private final LocationCallback mLocationCallback = new LocationCallback() {
@Override
public void onLocationResult(LocationResult locationResult) {
Location mLastLocation = locationResult.getLastLocation();
}
};
private boolean isLocationEnabled() {
LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
return locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER) || locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
}
@Override
public void
onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (requestCode == REQUEST_CODE) {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
getLastLocation();
}
}
if (requestCode == 0) {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
notifyPolice();
}
}
}

}

Answer 1

首先-DashboardActivity.getInstance((-永远不要这样做。您假设一个活动始终只有一个实例。这是错误的。可以有0。可以有2个。不能将活动设为单例。此外，这总是会造成内存泄漏。永远不要将"活动"存储在静态变量中，这总是内存泄漏。它也是(由于第一个事实(错误的，因为它可能指向错误的"活动"实例。

其次，您正在使用getLastLocation。不要那样做。该函数用于优化，通常会返回null(我知道文档的说法正好相反。那里的文档总是错误的。(如果你需要位置，请请求它。getLastLocation只能用于在请求位置更新之前乐观地获得快速结果。

第三，对requestNewLocation的调用传递了一个什么都不做的位置处理程序。它甚至没有更新mLastLocation，因为这是一个方法级变量，而不是类变量。

第四，你读过ANdroid12中后台定位处理的新规则吗？https://proandroiddev.com/android-12-privacy-changes-for-location-55ffd8c016fd

这些只是重大错误，而不是让我放弃的小事；嗯&"；。出于善意，这段代码需要进行重大重构。感觉就像是一个不太懂安卓的人从十几个他不懂的例子中拼凑出来的。如果我是你，我会从简化概念开始——做一件事，理解它，然后做另一件事。你现在一次做这一切超出了你的能力，你最好一次学一件事。