位置 returns 空 google API 客户端
location returns null by google API client
我试图创建一个简单的应用程序来标记当前位置并添加到列表中。
我正在按照 android 教程使用 google 播放服务 API 获取位置。但是，当我尝试启动位置服务以获取位置更新时，位置 returns 为空并给出空指针异常。
下面是 MainActivity 代码：
public class MainActivity extends AppCompatActivity implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, LocationListener {
private GoogleApiClient mGoogleApiClient;
private Location mLastLocation, mCurrentLocation;
private double currentLatitude, currentLongitude;
private String lastUpdateTime, addressMessage = null;
private AddressResultReceiver resultReceiver;
private MainList listFragment = new MainList();
private MaterialDialog dialog;
boolean mHasLastLocation = false, mAddressRequested = false;
private FragmentManager mFragmentManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addOnConnectionFailedListener(this)
.addConnectionCallbacks(this)
.build();
mFragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
fragmentTransaction.add(R.id.fragment,listFragment);
fragmentTransaction.commit();
dialog = new MaterialDialog(this)
.setTitle("Select an address")
.setMessage(addressMessage)
.setPositiveButton("SELECT", new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.dismiss();
listFragment.list.add(addressMessage);
listFragment.mAdapter.notifyDataSetChanged();
}
})
.setNegativeButton("CANCEL", new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.dismiss();
}
});
Toolbar toolbar = (Toolbar) findViewById(R.id.tool_bar);
setSupportActionBar(toolbar);
FloatingActionButton floatingActionButton = (FloatingActionButton) findViewById(R.id.fab_button);
LayoutInflater inflater = LayoutInflater.from(getApplicationContext());
floatingActionButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startAddressLookUp();
mAddressRequested = true;
dialog.setMessage(addressMessage);
dialog.show();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onPause() {
super.onPause();
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
}
@Override
public void onResume() {
super.onResume();
if(mGoogleApiClient.isConnected()) {
LocationRequest locationRequest = createLocationRequest();
startLocationUpdates(locationRequest);
}
}
@Override
public void onConnected(Bundle bundle) {
mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
if (mLastLocation != null) {
mHasLastLocation = true;
String toastText = "lastLocation exists!";
Toast.makeText(getApplicationContext(), toastText, Toast.LENGTH_LONG).show();
}
LocationRequest locationRequest = createLocationRequest();
if (locationRequest != null) {
startLocationUpdates(locationRequest);
}
if (mAddressRequested) {
startAddressLookUp();
}
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onLocationChanged(Location location) {
mCurrentLocation = location;
currentLatitude = mCurrentLocation.getLatitude();
currentLongitude = mCurrentLocation.getLongitude();
lastUpdateTime = DateFormat.getDateTimeInstance().format(new Date());
}
protected LocationRequest createLocationRequest() {
LocationRequest mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(8000);
mLocationRequest.setFastestInterval(5000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
return mLocationRequest;
}
protected void startLocationUpdates(LocationRequest request) {
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, request, this);
}
protected void startAddressLookUp() {
Intent intent = new Intent(this,AddressLookUpService.class);
intent.putExtra(AddressLookUpService.Constants.RECEIVER, resultReceiver);
intent.putExtra(AddressLookUpService.Constants.LOCATION_DATA_EXTRA, mCurrentLocation);
startService(intent);
}
class AddressResultReceiver extends ResultReceiver {
public AddressResultReceiver(Handler handler) {
super(handler);
}
@Override
protected void onReceiveResult(int resultCode, Bundle result) {
if (resultCode == AddressLookUpService.Constants.SUCCESS) {
addressMessage = result.getString(AddressLookUpService.Constants.RESULT_DATA_KEY);
}
}
}
}
按照教程的建议，我还创建了一个地址查询服务来获取地理编码地址，如下所示：
public class AddressLookUpService extends IntentService {
private Location location;
private ResultReceiver receiver;
private Geocoder geocoder;
public static final String TAG = "AddressLookUpService";
public AddressLookUpService() {
super("AddressLookUpService");
}
@Override
protected void onHandleIntent (Intent intent) {
geocoder = new Geocoder(this, Locale.getDefault());
String errorMsg = "";
location = intent.getParcelableExtra(Constants.LOCATION_DATA_EXTRA);
List<Address> addressList = null;
try{
addressList = geocoder.getFromLocation(location.getLatitude(), location.getLongitude(), 1);
}
catch (IOException ioException) {
errorMsg = getString(R.string.service_not_available);
Log.e(TAG, errorMsg, ioException);
}
catch (IllegalArgumentException illegalArgumentException) {
errorMsg = getString(R.string.invalid_lat_long);
Log.e(TAG, errorMsg + ". " +
"Latitude = " + location.getLatitude() +
", Longitude = " +
location.getLongitude(), illegalArgumentException);
}
if (addressList == null || addressList.size() == 0) {
if (errorMsg.isEmpty()) {
errorMsg = getString(R.string.no_address_found);
Log.e(TAG, errorMsg);
}
if (location == null) {
if (errorMsg.isEmpty()) {
errorMsg = "Location is null";
Log.e(TAG, errorMsg);
}
}
deliverResultToReceiver(Constants.FAIL, errorMsg);
}
else {
ArrayList<String> addressFragments = new ArrayList<String>();
/*for (Address address : addressList) {
for (int i=0; i<address.getMaxAddressLineIndex(); i++) {
addressFragments.add(address.getAddressLine(i));
}
}*/
Address address = addressList.get(0);
for (int i=0; i<address.getMaxAddressLineIndex(); i++) {
addressFragments.add(address.getAddressLine(i));
}
Log.i(TAG, getString(R.string.address_found));
deliverResultToReceiver(Constants.SUCCESS, TextUtils.join(System.getProperty("line.separator"), addressFragments));
}
}
public final class Constants {
public static final int SUCCESS = 0;
public static final int FAIL = 1;
public static final String PACKAGE_NAME = "com.pyason.heremark";
public static final String RECEIVER = PACKAGE_NAME + ".RECEIVER";
public static final String RESULT_DATA_KEY = PACKAGE_NAME + ".RESULT_DATA_KEY";
public static final String LOCATION_DATA_EXTRA = PACKAGE_NAME + ".LOCATION_DATA_EXTRA";
}
private void deliverResultToReceiver(int resultCode, String message) {
Bundle bundle = new Bundle();
bundle.putString(Constants.RESULT_DATA_KEY, message);
receiver.send(resultCode, bundle);
}
}
所以当我尝试获取新地址时，应用程序抛出以下异常：
07-31 00:35:13.538 28055-28519/? E/AndroidRuntime﹕ FATAL EXCEPTION: IntentService[AddressLookUpService]
Process: com.pyason.heremark, PID: 28055
java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at com.pyason.heremark.AddressLookUpService.onHandleIntent(AddressLookUpService.java:45)
at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
它只是说 AddressLookupService 中的位置 returns null，我想我已经开始位置更新了。
有人可以帮忙吗？感谢您的帮助:)
谢谢，
保罗
你设置了吗<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> ?
Returns 一个位置，表示从给定提供者处获得的最后一个已知位置定位的数据。
这可以在不启动提供程序的情况下完成。请注意，此位置可能已过时，例如，如果设备已关闭并移至其他位置。
如果提供程序当前被禁用，则返回 null。
更改您的代码
@Override
public void onLocationChanged(Location location) {
mCurrentLocation = location;
if(mCurrentLocation !=null){
currentLatitude = mCurrentLocation.getLatitude();
currentLongitude = mCurrentLocation.getLongitude();
lastUpdateTime = DateFormat.getDateTimeInstance().format(new Date());
}
}
看起来主要问题是你没有调用 mGoogleApiClient.connect()，所以 onConnected() 没有被调用，而 mGoogleApiClient.isConnected() 总是 return false，所以结果，startLocationUpdates() 永远不会被调用。
构建 GoogleApiClient 后调用 connect()：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addOnConnectionFailedListener(this)
.addConnectionCallbacks(this)
.build();
//add this here:
mGoogleApiClient.connect();
此外，您似乎应该禁用 floatingActionButton，直到您获得第一个非空位置，否则当用户单击该按钮时，AddressLookUpService 将获得一个空位置。
此外，为了安全起见，请在 AddressLookUpService 中进行空检查，以防它传递空位置：
@Override
protected void onHandleIntent (Intent intent) {
geocoder = new Geocoder(this, Locale.getDefault());
String errorMsg = "";
location = intent.getParcelableExtra(Constants.LOCATION_DATA_EXTRA);
//Just exit if location is null:
if (location == null) return;
//..................
我试图创建一个简单的应用程序来标记当前位置并添加到列表中。
我正在按照 android 教程使用 google 播放服务 API 获取位置。但是，当我尝试启动位置服务以获取位置更新时，位置 returns 为空并给出空指针异常。
下面是 MainActivity 代码：
public class MainActivity extends AppCompatActivity implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, LocationListener {
private GoogleApiClient mGoogleApiClient;
private Location mLastLocation, mCurrentLocation;
private double currentLatitude, currentLongitude;
private String lastUpdateTime, addressMessage = null;
private AddressResultReceiver resultReceiver;
private MainList listFragment = new MainList();
private MaterialDialog dialog;
boolean mHasLastLocation = false, mAddressRequested = false;
private FragmentManager mFragmentManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addOnConnectionFailedListener(this)
.addConnectionCallbacks(this)
.build();
mFragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
fragmentTransaction.add(R.id.fragment,listFragment);
fragmentTransaction.commit();
dialog = new MaterialDialog(this)
.setTitle("Select an address")
.setMessage(addressMessage)
.setPositiveButton("SELECT", new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.dismiss();
listFragment.list.add(addressMessage);
listFragment.mAdapter.notifyDataSetChanged();
}
})
.setNegativeButton("CANCEL", new View.OnClickListener() {
@Override
public void onClick(View v) {
dialog.dismiss();
}
});
Toolbar toolbar = (Toolbar) findViewById(R.id.tool_bar);
setSupportActionBar(toolbar);
FloatingActionButton floatingActionButton = (FloatingActionButton) findViewById(R.id.fab_button);
LayoutInflater inflater = LayoutInflater.from(getApplicationContext());
floatingActionButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startAddressLookUp();
mAddressRequested = true;
dialog.setMessage(addressMessage);
dialog.show();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onPause() {
super.onPause();
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
}
@Override
public void onResume() {
super.onResume();
if(mGoogleApiClient.isConnected()) {
LocationRequest locationRequest = createLocationRequest();
startLocationUpdates(locationRequest);
}
}
@Override
public void onConnected(Bundle bundle) {
mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
if (mLastLocation != null) {
mHasLastLocation = true;
String toastText = "lastLocation exists!";
Toast.makeText(getApplicationContext(), toastText, Toast.LENGTH_LONG).show();
}
LocationRequest locationRequest = createLocationRequest();
if (locationRequest != null) {
startLocationUpdates(locationRequest);
}
if (mAddressRequested) {
startAddressLookUp();
}
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onLocationChanged(Location location) {
mCurrentLocation = location;
currentLatitude = mCurrentLocation.getLatitude();
currentLongitude = mCurrentLocation.getLongitude();
lastUpdateTime = DateFormat.getDateTimeInstance().format(new Date());
}
protected LocationRequest createLocationRequest() {
LocationRequest mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(8000);
mLocationRequest.setFastestInterval(5000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
return mLocationRequest;
}
protected void startLocationUpdates(LocationRequest request) {
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, request, this);
}
protected void startAddressLookUp() {
Intent intent = new Intent(this,AddressLookUpService.class);
intent.putExtra(AddressLookUpService.Constants.RECEIVER, resultReceiver);
intent.putExtra(AddressLookUpService.Constants.LOCATION_DATA_EXTRA, mCurrentLocation);
startService(intent);
}
class AddressResultReceiver extends ResultReceiver {
public AddressResultReceiver(Handler handler) {
super(handler);
}
@Override
protected void onReceiveResult(int resultCode, Bundle result) {
if (resultCode == AddressLookUpService.Constants.SUCCESS) {
addressMessage = result.getString(AddressLookUpService.Constants.RESULT_DATA_KEY);
}
}
}
}
按照教程的建议，我还创建了一个地址查询服务来获取地理编码地址，如下所示：
public class AddressLookUpService extends IntentService {
private Location location;
private ResultReceiver receiver;
private Geocoder geocoder;
public static final String TAG = "AddressLookUpService";
public AddressLookUpService() {
super("AddressLookUpService");
}
@Override
protected void onHandleIntent (Intent intent) {
geocoder = new Geocoder(this, Locale.getDefault());
String errorMsg = "";
location = intent.getParcelableExtra(Constants.LOCATION_DATA_EXTRA);
List<Address> addressList = null;
try{
addressList = geocoder.getFromLocation(location.getLatitude(), location.getLongitude(), 1);
}
catch (IOException ioException) {
errorMsg = getString(R.string.service_not_available);
Log.e(TAG, errorMsg, ioException);
}
catch (IllegalArgumentException illegalArgumentException) {
errorMsg = getString(R.string.invalid_lat_long);
Log.e(TAG, errorMsg + ". " +
"Latitude = " + location.getLatitude() +
", Longitude = " +
location.getLongitude(), illegalArgumentException);
}
if (addressList == null || addressList.size() == 0) {
if (errorMsg.isEmpty()) {
errorMsg = getString(R.string.no_address_found);
Log.e(TAG, errorMsg);
}
if (location == null) {
if (errorMsg.isEmpty()) {
errorMsg = "Location is null";
Log.e(TAG, errorMsg);
}
}
deliverResultToReceiver(Constants.FAIL, errorMsg);
}
else {
ArrayList<String> addressFragments = new ArrayList<String>();
/*for (Address address : addressList) {
for (int i=0; i<address.getMaxAddressLineIndex(); i++) {
addressFragments.add(address.getAddressLine(i));
}
}*/
Address address = addressList.get(0);
for (int i=0; i<address.getMaxAddressLineIndex(); i++) {
addressFragments.add(address.getAddressLine(i));
}
Log.i(TAG, getString(R.string.address_found));
deliverResultToReceiver(Constants.SUCCESS, TextUtils.join(System.getProperty("line.separator"), addressFragments));
}
}
public final class Constants {
public static final int SUCCESS = 0;
public static final int FAIL = 1;
public static final String PACKAGE_NAME = "com.pyason.heremark";
public static final String RECEIVER = PACKAGE_NAME + ".RECEIVER";
public static final String RESULT_DATA_KEY = PACKAGE_NAME + ".RESULT_DATA_KEY";
public static final String LOCATION_DATA_EXTRA = PACKAGE_NAME + ".LOCATION_DATA_EXTRA";
}
private void deliverResultToReceiver(int resultCode, String message) {
Bundle bundle = new Bundle();
bundle.putString(Constants.RESULT_DATA_KEY, message);
receiver.send(resultCode, bundle);
}
}
所以当我尝试获取新地址时，应用程序抛出以下异常：
07-31 00:35:13.538 28055-28519/? E/AndroidRuntime﹕ FATAL EXCEPTION: IntentService[AddressLookUpService]
Process: com.pyason.heremark, PID: 28055
java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at com.pyason.heremark.AddressLookUpService.onHandleIntent(AddressLookUpService.java:45)
at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
它只是说 AddressLookupService 中的位置 returns null，我想我已经开始位置更新了。
有人可以帮忙吗？感谢您的帮助:)
谢谢， 保罗
你设置了吗<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> ?
Returns 一个位置，表示从给定提供者处获得的最后一个已知位置定位的数据。
这可以在不启动提供程序的情况下完成。请注意，此位置可能已过时，例如，如果设备已关闭并移至其他位置。
如果提供程序当前被禁用，则返回 null。
更改您的代码
@Override
public void onLocationChanged(Location location) {
mCurrentLocation = location;
if(mCurrentLocation !=null){
currentLatitude = mCurrentLocation.getLatitude();
currentLongitude = mCurrentLocation.getLongitude();
lastUpdateTime = DateFormat.getDateTimeInstance().format(new Date());
}
}
看起来主要问题是你没有调用 mGoogleApiClient.connect()，所以 onConnected() 没有被调用，而 mGoogleApiClient.isConnected() 总是 return false，所以结果，startLocationUpdates() 永远不会被调用。
构建 GoogleApiClient 后调用 connect()：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addOnConnectionFailedListener(this)
.addConnectionCallbacks(this)
.build();
//add this here:
mGoogleApiClient.connect();
此外，您似乎应该禁用 floatingActionButton，直到您获得第一个非空位置，否则当用户单击该按钮时，AddressLookUpService 将获得一个空位置。
此外，为了安全起见，请在 AddressLookUpService 中进行空检查，以防它传递空位置：
@Override
protected void onHandleIntent (Intent intent) {
geocoder = new Geocoder(this, Locale.getDefault());
String errorMsg = "";
location = intent.getParcelableExtra(Constants.LOCATION_DATA_EXTRA);
//Just exit if location is null:
if (location == null) return;
//..................