我的应用程序允许用户在按下按钮时找到他们当前的位置。每当应用程序第一次启动时，它会询问用户权限，但是在授予权限时崩溃会导致以下logcat错误：< / p>
FATAL EXCEPTION: mainProcess: com.shubhamsharma.idonate, PID: 17404
java.lang.RuntimeException: Failure delivering result ResultInfo{who=@android:requestPermissions:, request=1, result=-1, data=Intent { act=android.content.pm.action.REQUEST_PERMISSIONS (has extras) }} to activity {com.shubhamsharma.idonate/com.shubhamsharma.idonate.iDonate}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.SupportMapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference
at android.app.ActivityThread.deliverResults(ActivityThread.java:4123)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4166)
at android.app.ActivityThread.-wrap20(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1562)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:163)
at android.app.ActivityThread.main(ActivityThread.java:6237)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:877)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.SupportMapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference
at com.shubhamsharma.idonate.iDonate.onRequestPermissionsResult(iDonate.java:165)
at android.app.Activity.dispatchRequestPermissionsResult(Activity.java:7263)
at android.app.Activity.dispatchActivityResult(Activity.java:7115)
at android.app.ActivityThread.deliverResults(ActivityThread.java:4119)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:4166)
at android.app.ActivityThread.-wrap20(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1562)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:163)
at android.app.ActivityThread.main(ActivityThread.java:6237)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:877)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
流程是这样的 主要活动（获取登录ID和密码并从firebase检查）---＆gt;然后是idonate Activity请求许可然后崩溃
我的主要活动代码
公共类MainActivity扩展了AppCompatActivity {
Button login, register;
EditText email,password;
FirebaseAuth mAuth;
FirebaseAuth.AuthStateListener firebaseAuthListener;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
email = (EditText) findViewById(R.id.email);
password = (EditText) findViewById(R.id.password);
login = (Button) findViewById(R.id.button2);
register=(Button)findViewById(R.id.button1);
mAuth = FirebaseAuth.getInstance();
firebaseAuthListener = new FirebaseAuth.AuthStateListener() {
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
if (user != null) {
Intent intent = new Intent(MainActivity.this, iDonate.class);
startActivity(intent);
return;
}
}
};
register.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
final String log= email.getText().toString();
final String pas= password.getText().toString();
if(log.length()!=0 && pas.length()!=0) {
mAuth.createUserWithEmailAndPassword(log, pas).addOnCompleteListener(MainActivity.this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (!task.isSuccessful()) {
Toast.makeText(getApplicationContext(), "Something Went Wrong", Toast.LENGTH_LONG).show();
} else {
String userid = mAuth.getCurrentUser().getUid();
DatabaseReference current_user_db = FirebaseDatabase.getInstance().getReference().child("Users").child("Drivers").child(userid);
current_user_db.setValue(true);
}
}
});
}
else{
Toast.makeText(getApplicationContext(), "Login Id or Password cannot be Empty", Toast.LENGTH_SHORT).show();
email.setText("");
password.setText("");
}
}
});
login.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
final String log = email.getText().toString();
final String pas = password.getText().toString();
if(log.length()!=0 && pas.length()!=0) {
mAuth.signInWithEmailAndPassword(log, pas).addOnCompleteListener(MainActivity.this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
if (!task.isSuccessful())
Toast.makeText(getApplicationContext(), "Signup Error", Toast.LENGTH_SHORT).show();
else {
Intent intent = new Intent(MainActivity.this, iDonate.class);
startActivity(intent);
finish();
return;
}
}
});
}
else{
Toast.makeText(getApplicationContext(), "Login Id or Password cannot be Empty", Toast.LENGTH_SHORT).show();
email.setText("");
password.setText("");
}
}
});
}
@Override
protected void onStart() {
super.onStart();
mAuth.addAuthStateListener(firebaseAuthListener);
}
@Override
protected void onStop() {
super.onStop();
mAuth.removeAuthStateListener(firebaseAuthListener);
}
}
下面的idonate代码
public class iDonate extends FragmentActivity implements OnMapReadyCallback, GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener, com.google.android.gms.location.LocationListener {
private GoogleMap mMap;
GoogleApiClient mGoogleApiClient;
Location mLastLocation;
LocationRequest mLocationRequest;
SupportMapFragment mapFragment;
private Button mlogout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_i_donate);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
mlogout=(Button)findViewById(R.id.logout);
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(iDonate.this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, LOCATION_REQUEST_CODE);
// return;
} else {
mapFragment.getMapAsync(this);
}
mlogout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
FirebaseAuth.getInstance().signOut();
Intent intent=new Intent(getApplicationContext(),MainActivity.class);
startActivity(intent);
finish();
return;
}
});
}
@Override
public void onMapReady(GoogleMap googleMap) {
mMap = googleMap;
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(iDonate.this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, LOCATION_REQUEST_CODE);
// return;
}
buildGoogleApiClient();
mMap.setMyLocationEnabled(true);
}
protected synchronized void buildGoogleApiClient(){
mGoogleApiClient= new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
mGoogleApiClient.connect();
}
@Override
public void onConnected(@Nullable Bundle bundle) {
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(1000);
mLocationRequest.setFastestInterval(1000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(iDonate.this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, LOCATION_REQUEST_CODE);
return;
}
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, (com.google.android.gms.location.LocationListener) this);
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
@Override
public void onLocationChanged(Location location) {
mLastLocation=location;
LatLng latLng=new LatLng(location.getLatitude(),location.getLongitude());
mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
mMap.animateCamera(CameraUpdateFactory.zoomTo(14));
String userId = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("DriversAvailable");
GeoFire geoFire = new GeoFire(ref);
geoFire.setLocation(userId,new GeoLocation(location.getLatitude(),location.getLongitude()));
}
final int LOCATION_REQUEST_CODE = 1;
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults ) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
// Toast.makeText(getApplicationContext(), String.valueOf(grantResults[0]), Toast.LENGTH_LONG).show();
switch (requestCode) {
case LOCATION_REQUEST_CODE: {
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
mapFragment.getMapAsync(this);
// break;
}
else {
Toast.makeText(getApplicationContext(), "Please allow your GPS Permission", Toast.LENGTH_LONG).show();
}
// return;
break;
}
}
}
public boolean hasAllPermissionsGranted(@NonNull int[] grantResults) {
for (int grantResult : grantResults) {
if (grantResult == PackageManager.PERMISSION_DENIED) {
return false;
}
}
return true;
}
@Override
protected void onStop() {
super.onStop();
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
FirebaseUser userId = FirebaseAuth.getInstance().getCurrentUser();/////////////////////////////
DatabaseReference ref = FirebaseDatabase.getInstance().getReference("DriversAvailable");
// Toast.makeText(getApplicationContext(),userId.getUid(),Toast.LENGTH_LONG).show();
GeoFire geoFire = new GeoFire(ref);
geoFire.removeLocation(userId.getUid());
// return;
}
}
答案 0 :(得分：0)
mapFragment.getMapAsync（this）返回null，因此检查该类