Question

也许有人可以告诉我为什么下面的代码适用于Api超过25，但是在Api 19上现在我正在测试我之后我尝试获得经度和纬度？我读过官方docs，但我使用的每种方法（目标Api 25）都与Api 19兼容

public class GPStracker implements LocationListener {

    Context context;

    public GPStracker(Context c) {
        context = c;
    }

    public Location getlocation() {
        if (ContextCompat.checkSelfPermission(context, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            Toast.makeText(context, "Uprawnienia nie przyznane", Toast.LENGTH_SHORT).show();
        }

        LocationManager lm = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
        boolean isGPSenabled;
        isGPSenabled = lm.isProviderEnabled(LocationManager.GPS_PROVIDER);

        if (isGPSenabled) {
            lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 1, this);
            Location location = lm.getLastKnownLocation(LocationManager.GPS_PROVIDER);
            return location;
        } else {
            Toast.makeText(context, "Proszę włączyć GPS", Toast.LENGTH_LONG).show();
        }
        return null;
    }

    @Override
    public void onLocationChanged(Location location) {

        //Toast.makeText(context, String.valueOf(dis), Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onStatusChanged(String s, int i, Bundle bundle) {

    }

    @Override
    public void onProviderEnabled(String s) {

    }

    @Override
    public void onProviderDisabled(String s) {

    }
}

和gpsTracker类：

DATEDIFF(month, OLH.DateStamp, GETDATE()) = 1

Answer 1

即使您拨打getLastKnownLocation，函数null也可能会返回requestLocationUpdates。此外，由于在getLocation函数中，您也可以返回null，我建议您按如下方式添加一个检查：

Location loc = gpStracker.getlocation();
if (loc != null) {
    latitude = loc.getLatitude();
    longitude = loc.getLongitude();
}

Answer 2

要使用位置管理器，请通过app build.gradle文件提供Google Play服务。

dependencies {
    compile 'com.google.android.gms:play-services:9.2.0'
    compile 'com.google.android.gms:play-services-location:9.2.0'
    }

还在清单中指定以下必需权限。

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>


public class LocationActivity extends Activity implements
        LocationListener,
        GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener {

    private static final String TAG = "LocationActivity";
    private static final long INTERVAL = 1000 * 10;
    private static final long FASTEST_INTERVAL = 1000 * 5;
    Button btnFusedLocation;
    TextView tvLocation;
    LocationRequest mLocationRequest;
    GoogleApiClient mGoogleApiClient;
    Location mCurrentLocation;
    String mLastUpdateTime;

    protected void createLocationRequest() {
        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(INTERVAL);
        mLocationRequest.setFastestInterval(FASTEST_INTERVAL);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG, "onCreate ...............................");
        //show error dialog if GoolglePlayServices not available
        if (!isGooglePlayServicesAvailable()) {
            finish();
        }
        createLocationRequest();
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addApi(LocationServices.API)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .build();

        setContentView(R.layout.activity_main);
        tvLocation = (TextView) findViewById(R.id.tvLocation);

        btnFusedLocation = (Button) findViewById(R.id.btnShowLocation);
        btnFusedLocation.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                updateUI();
            }
        });

    }

    @Override
    public void onStart() {
        super.onStart();
        Log.d(TAG, "onStart fired ..............");
        mGoogleApiClient.connect();
    }

    @Override
    public void onStop() {
        super.onStop();
        Log.d(TAG, "onStop fired ..............");
        mGoogleApiClient.disconnect();
        Log.d(TAG, "isConnected ...............: " + mGoogleApiClient.isConnected());
    }

    private boolean isGooglePlayServicesAvailable() {
        int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
        if (ConnectionResult.SUCCESS == status) {
            return true;
        } else {
            GooglePlayServicesUtil.getErrorDialog(status, this, 0).show();
            return false;
        }
    }

    @Override
    public void onConnected(Bundle bundle) {
        Log.d(TAG, "onConnected - isConnected ...............: " + mGoogleApiClient.isConnected());
        startLocationUpdates();
    }

    protected void startLocationUpdates() {
        PendingResult<Status> pendingResult = LocationServices.FusedLocationApi.requestLocationUpdates(
                mGoogleApiClient, mLocationRequest, this);
        Log.d(TAG, "Location update started ..............: ");
    }

    @Override
    public void onConnectionSuspended(int i) {

    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
        Log.d(TAG, "Connection failed: " + connectionResult.toString());
    }

    @Override
    public void onLocationChanged(Location location) {
        Log.d(TAG, "Firing onLocationChanged..............................................");
        mCurrentLocation = location;
        mLastUpdateTime = DateFormat.getTimeInstance().format(new Date());
        updateUI();
    }

    private void updateUI() {
        Log.d(TAG, "UI update initiated .............");
        if (null != mCurrentLocation) {
            String lat = String.valueOf(mCurrentLocation.getLatitude());
            String lng = String.valueOf(mCurrentLocation.getLongitude());
            tvLocation.setText("At Time: " + mLastUpdateTime + "\n" +
                    "Latitude: " + lat + "\n" +
                    "Longitude: " + lng + "\n" +
                    "Accuracy: " + mCurrentLocation.getAccuracy() + "\n" +
                    "Provider: " + mCurrentLocation.getProvider());
        } else {
            Log.d(TAG, "location is null ...............");
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        stopLocationUpdates();
    }

    protected void stopLocationUpdates() {
        LocationServices.FusedLocationApi.removeLocationUpdates(
                mGoogleApiClient, this);
        Log.d(TAG, "Location update stopped .......................");
    }

    @Override
    public void onResume() {
        super.onResume();
        if (mGoogleApiClient.isConnected()) {
            startLocationUpdates();
            Log.d(TAG, "Location update resumed .....................");
        }
    }
}


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="40dip"
        android:orientation="horizontal" >

        <TextView
            android:id="@+id/TextView01"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dip"
            android:layout_marginRight="5dip"
            android:text="Latitude: "
            android:textSize="20dip" >
        </TextView>

        <TextView
            android:id="@+id/TextView02"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="unknown"
            android:textSize="20dip" >
        </TextView>
    </LinearLayout>

    <LinearLayout
        android:id="@+id/linearLayout2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <TextView
            android:id="@+id/TextView03"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="10dip"
            android:layout_marginRight="5dip"
            android:text="Longitute: "
            android:textSize="20dip" >
        </TextView>

        <TextView
            android:id="@+id/TextView04"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="unknown"
            android:textSize="20dip" >
        </TextView>
    </LinearLayout>

</LinearLayout>

LoactionManager Api19 NullPointerException

2 个答案: