java - 在 Firebase 数据库中读取和写入数据

标签 java android firebase firebase-realtime-database

注意:- 抱歉我的英语不好，因为英语不是我的母语，我为此使用了谷歌翻译。

我正在开发一个 Android map 应用程序，用户可以在其中找到他们 friend 的当前位置，并使用 FireBase 实时数据库存储当前位置。因此，当用户点击查找按钮时，他们 friend 的当前位置将与他们的用户名一起显示在 map 上。

但是当我试图从 firebase 获取用户数据时，我无法解决一个问题。它没有以正确的方式反射(reflect)。数据反射(reflect)在日志中的 2 行不同的行中:

  • 第 1 行:- 纬度和经度为 0.0，但电子邮件显示在
  • 第 2 行:- 纬度和经度反射(reflect)正确，但电子邮件为空

我不知道如何在一行中同时获取两者。我在谷歌上搜索了很多但都失败了。请帮助我了解如何以正确的方式完成它。

下面是我的代码和 android studio 的屏幕截图。

MainActivity.java 

    findfriend.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivity(new Intent(MainActivity.this, MapsActivity.class));
        }
    });

    final TextView tname;
    tname = (TextView) findViewById(R.id.textview);

    ref = FirebaseDatabase.getInstance().getReferenceFromUrl("https://ffinder-b4617.firebaseio.com/Email");
    mReferece2 = ref.child("email");
    mReferece2 = ref.child("location");

    proceed.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            ref.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for (DataSnapshot dataSnapshot1: dataSnapshot.getChildren()){
                        UserInformation details = dataSnapshot1.getValue(UserInformation.class);

                        String email = details.email;
                        Double lat = details.latitude;
                        Double lon = details.longitude;
                        tname.setText(lat+" "+'\n'+lon+'\n'+email);

                        System.out.println("-->"+ lat+" " + lon+" "+ email);
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

        }
    });
}

MapsActivity.java

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        Firebase.setAndroidContext(this);

        if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            checkLocationPermission();
        }

        //Check if Google Play Services Available or not
        if (!CheckGooglePlayServices()) {
            Log.d("onCreate", "Finishing test case since Google Play Services are not available");
            finish();
        } else {
            Log.d("onCreate", "Google Play Services available.");
        }

        auth = FirebaseAuth.getInstance();

        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);

 FirebaseDatabase.getInstance().getReference().child("Location");
    }

    @Override
    public void onLocationChanged(Location location) {
        Log.d("onLocationChanged", "entered");

        mLastLocation = location;

        DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
        dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
        Date date = new Date();
        mLastUpdateTime = ((dateFormat.format(date).toString()));

        saveToFirebase();

        if (mCurrLocationMarker != null) {
            mCurrLocationMarker.remove();
        }

        latitude = location.getLatitude();
        longitude = location.getLongitude();

        LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.position(latLng);
        markerOptions.draggable(true);
        markerOptions.title("Current Position");
        markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
        mCurrLocationMarker = mMap.addMarker(markerOptions);
        mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        mMap.animateCamera(CameraUpdateFactory.zoomTo(11));

        Toast.makeText(MapsActivity.this,"Your Current Location", Toast.LENGTH_LONG).show();

        //stop location updates
        if (mGoogleApiClient != null) {
            LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
            Log.d("onLocationChanged", "Removing Location Updates");
        }

    }

    public void saveToFirebase() {

        Firebase firebase = new Firebase("https://ffinder-b4617.firebaseio.com").child("Email").child("location");

        Map mLoactions = new HashMap();
        mLoactions.put("timestamp",mLastUpdateTime);
        mLoactions.put("latitude", mLastLocation.getLatitude());
        mLoactions.put("longitude", mLastLocation.getLongitude());

        firebase.setValue(mLoactions);
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {
}

    public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
    public boolean checkLocationPermission(){
        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {

            // Asking user if explanation is needed
            if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    Manifest.permission.ACCESS_FINE_LOCATION)) {

                ActivityCompat.requestPermissions(this,
                        new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);


            } else {
                // No explanation needed, we can request the permission.
                ActivityCompat.requestPermissions(this,
                        new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);
            }
            return false;
        } else {
            return true;
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode,
                                           String permissions[], int[] grantResults) {
        switch (requestCode) {
            case MY_PERMISSIONS_REQUEST_LOCATION: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                    if (ContextCompat.checkSelfPermission(this,
                            Manifest.permission.ACCESS_FINE_LOCATION)
                            == PackageManager.PERMISSION_GRANTED) {

                        if (mGoogleApiClient == null) {
                            buildGoogleApiClient();
                        }
                        mMap.setMyLocationEnabled(true);
                    }

                } else {

                    // Permission denied, Disable the functionality that depends on this permission.
                    Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
                }
                return;
            }
        }
    }

    @Override
    public boolean onMarkerClick(Marker marker) {
        marker.setDraggable(true);
        return false;
    }

    @Override
    public void onMarkerDragStart(Marker marker) {}

    @Override
    public void onMarkerDrag(Marker marker) {}

    @Override
    public void onMarkerDragEnd(Marker marker) {
        end_latitude = marker.getPosition().latitude;
        end_longitude =  marker.getPosition().longitude;

        Log.d("end_lat",""+end_latitude);
        Log.d("end_lng",""+end_longitude);
    }
}

登录类

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        Firebase.setAndroidContext(this);

        auth = FirebaseAuth.getInstance();

        if (auth.getCurrentUser() != null){
            startActivity(new Intent(LoginActivity.this, MainActivity.class));
            finish();
        }

        setContentView(R.layout.activity_login);

        inputEmail = (EditText) findViewById(R.id.email);
        inputPassword = (EditText) findViewById(R.id.password);
        progressBar = (ProgressBar) findViewById(R.id.progressBar);
        btnSignup = (Button) findViewById(R.id.btn_signup);
        btnLogin = (Button) findViewById(R.id.btn_login);
        btnReset = (Button) findViewById(R.id.btn_reset_password);

        auth = FirebaseAuth.getInstance();

        btnSignup.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(LoginActivity.this, SignupActivity.class));
            }
        });

        btnReset.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(LoginActivity.this, ResetPasswordActivity.class));
            }
        });

        btnLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String email = inputEmail.getText().toString();
                final String password = inputPassword.getText().toString();

                if (TextUtils.isEmpty(email)) {
                    Toast.makeText(getApplicationContext(), "Enter email address!", Toast.LENGTH_SHORT).show();
                    return;
                }

                if (TextUtils.isEmpty(password)) {
                    Toast.makeText(getApplicationContext(), "Enter password!", Toast.LENGTH_SHORT).show();
                    return;
                }
         progressBar.setVisibility(View.VISIBLE);

                //authenticate user
                auth.signInWithEmailAndPassword(email, password)
                        .addOnCompleteListener(LoginActivity.this, new OnCompleteListener<AuthResult>() {
                            @Override
                            public void onComplete(@NonNull Task<AuthResult> task) {

                                progressBar.setVisibility(View.GONE);
                                if (!task.isSuccessful()) {
                                    // there was an error
                                    if (password.length() < 6) {
                                        inputPassword.setError(getString(R.string.minimum_password));
                                    } else {
                                        Toast.makeText(LoginActivity.this, getString(R.string.auth_failed), Toast.LENGTH_LONG).show();
                                    }
                                } else {
                                    Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                                    startActivity(intent);
                                    finish();
       }
      }
    });
  }
 });
 }

    public void userLoginInfo(){

      String email = inputEmail.getText().toString();

        mDatabase = FirebaseDatabase.getInstance().getReference().child("Email").push();
        String userId = mDatabase.child("email").getKey();
        mDatabase.child(userId).setValue(email);
    }
}

UserInformation.class

public class UserInformation {

    public String email;
    public double latitude;
    public double longitude;

    public UserInformation() {
    }

    public UserInformation(String email, double latitude, double longitude) {
        this.email = email;
        this.latitude = latitude;
        this.longitude = longitude;
    }

    public String getEmail() {
        return email;
    }

    public double getLatitude() {
        return latitude;
    }

    public double getLongitude() {
        return longitude;
    }
}

Firebase 数据库截图 enter image description here Android Studio日志截图 enter image description here

最佳答案

你的 userLoginInfo()方法使用 push() 在数据库中创建一个唯一键来存储电子邮件地址，以及您的 saveToFirebase()方法以不同方式存储纬度/经度值，这意​​味着数据最终位于不同的位置。

利用您的 UserInformation 会很有帮助对象标准化您的数据库并使用 DatabaseReference#setValue(Object) 和 DataSnapshot#getValue(Class<CT>) 来存储和检索数据。因此，当您想要存储用户的位置时:

public void saveToFirebase() {
    DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("Email").push();

    String email = FirebaseAuth.getInstance().getCurrentUser().getEmail();

    UserInformation userInformation = new UserInformation(email, mLastLocation.getLatitude(), mLastLocation.getLongitude());

    ref.setValue(userInformation);
}

然后，稍后要检索这些详细信息，您可以使用现有的 ValueEventListener进行了一些调整:

DatabaseReference ref = FirebaseDatabase.getInstance().getReference().child("Email");

ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot child : dataSnapshot.getChildren()){
            UserInformation details = child.getValue(UserInformation.class);

            System.out.println("-->" + details.getLatitude() +" " + details.getLongitude() +" "+ details.getEmail());
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
});

希望我已经正确理解了您的要求，如果我遗漏了什么，请告诉我。

关于java - 在 Firebase 数据库中读取和写入数据，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/46702930/

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