在 Firebase 数据库中读取和写入数据
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【中文标题】在 Firebase 数据库中读取和写入数据【英文标题】：Reading and writing data in Firebase Database 【发布时间】：2017-10-12 06:34:12 【问题描述】：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器。
我正在开发一个 android Map 应用程序，用户可以在其中找到他们朋友的当前位置并存储我使用 FireBase 实时数据库的当前位置。因此，当用户点击查找按钮时，他们朋友的当前位置将在地图上显示他们的用户名。
但是当我尝试从 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映。数据反映在日志中的 2 行不同的行中：
第 1 行：- 纬度和经度为 0.0，但电子邮件显示在中 第 2 行：- 纬度和经度反映正确，但电子邮件为空我不知道如何将两者合二为一。我在谷歌上搜索了很多但失败了。请帮助我了解如何以正确的方式完成。
以下是我的代码和 android studio 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);
Login.class
@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 Android Studio 日志截图
【问题讨论】：
【参考方案1】：您的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，而您的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。
使用您的UserInformation 对象来标准化您的数据库并使用DatabaseReference#setValue(Object) 将是有益的
和DataSnapshot#getValue(Class<CT>) 存储和检索数据。因此，当您想要存储用户的位置时，您可以这样做：
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，为了稍后检索这些详细信息，您可以使用现有的 ValueEventListener 并进行一些调整：
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)
);
希望我正确理解了您的要求，如果我遗漏了什么，请告诉我。
【讨论】：
感谢您的回复，它帮助我在一个父级“电子邮件”下组织数据，但现在我在 Firebase 中没有收到用户的登录电子邮件。 如下图所示：- ffinder-b4617 电子邮件：“email” 纬度：31.5037501 经度：74.3502436 您可以在当前用户登录后使用FirebaseAuth.getInstance().getCurrentUser().getEmail()获取当前用户的电子邮件地址，因此您可以在saveToFirebase()方法中使用它。这行得通吗？
我已将此代码“FirebaseAuth.getInstance().getCurrentUser().getEmail()”放在 saveToFirebase() 中，但什么也没发生。
public void saveToFirebase() DatabaseReference ref = FirebaseDatabase.getInstance().getReference(); UserInformation userInformation = new UserInformation("email", mLastLocation.getLatitude(), mLastLocation.getLongitude()); FirebaseAuth.getInstance().getCurrentUser().getEmail(); ref.setValue(userInformation); 以上是关于在 Firebase 数据库中读取和写入数据的主要内容，如果未能解决你的问题，请参考以下文章
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