尝试使用 Intent 获取字符串时未设置 .child()
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【中文标题】尝试使用 Intent 获取字符串时未设置 .child()【英文标题】：.child() is not getting set when trying to use intent to Get String 【发布时间】：2019-12-25 18:41:24 【问题描述】：我正在尝试从 firebase 检索数据，为此我试图在代码中设置地址。我必须为数据库位置提供一个字符串值，然后将其传递给下一个活动并将该字符串用作地址。但是，地址未在代码中设置，因此将地图上的位置设置为 0,0 （字符串在 MAINACTIVITY.JAVA 中设置并通过意图发送）
我曾尝试直接在代码中设置 firebase 地址，并且成功了。只有当我试图传递它时，它才会停止设置 Firebase 地址
MainActivity.java
这里设置的是字符串值
package com.manavchordia.aplparent;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
public class MainActivity extends AppCompatActivity implements View.OnClickListener
private
RadioGroup route;
public static final String ARG_FROM_MAIN = "arg";
private FirebaseAuth mAuth;
private FirebaseDatabase mDatabase = FirebaseDatabase.getInstance();
private DatabaseReference mDatabaseReference = mDatabase.getReference().child("Locations");
public String someVariable;
TextView numberbs;
Button getLocationBtn;
private Button btnSignOut;
Button busb1;
Button busb2;
Button busb3;
Button busb4;
Button busb5;
Button busb6;
Button busb7;
Button busb8;
Button busb9;
Button busb10;
Button busb11;
Button busb12;
Button busb13;
Button busb14;
Button busb15;
Button busb16;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
numberbs = findViewById(R.id.busnotext);
btnSignOut = findViewById(R.id.signoutbtn);
getLocationBtn = findViewById(R.id.getLocationBtn);
numberbs = findViewById(R.id.busnotext);
busb1 = findViewById(R.id.busbtn1);
busb2 = findViewById(R.id.busbtn2);
busb3 = findViewById(R.id.busbtn3);
busb4 = findViewById(R.id.busbtn4);
busb5 = findViewById(R.id.busbtn5);
busb6 = findViewById(R.id.busbtn6);
busb7 = findViewById(R.id.busbtn7);
busb8 = findViewById(R.id.bustbtn8);
busb9 = findViewById(R.id.busbtn9);
busb10 = findViewById(R.id.busbtn10);
busb11 = findViewById(R.id.busbtn11);
busb12 = findViewById(R.id.busbtn12);
busb13 = findViewById(R.id.busbtn13);
busb14 = findViewById(R.id.busbtn14);
busb15 = findViewById(R.id.bustbtn15);
busb16 = findViewById(R.id.busbtn16);
busb1.setOnClickListener(this);
busb2.setOnClickListener(this);
busb3.setOnClickListener(this);
busb4.setOnClickListener(this);
busb5.setOnClickListener(this);
busb6.setOnClickListener(this);
busb7.setOnClickListener(this);
busb8.setOnClickListener(this);
busb9.setOnClickListener(this);
busb10.setOnClickListener(this);
busb11.setOnClickListener(this);
busb12.setOnClickListener(this);
busb13.setOnClickListener(this);
busb14.setOnClickListener(this);
busb15.setOnClickListener(this);
busb16.setOnClickListener(this);
getLocationBtn.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
//startService(new Intent(this, MyService.class));
Intent intent = new Intent(MainActivity.this, MapsActivity.class);
Bundle bundle = new Bundle();
bundle.putString("message", someVariable);
intent.putExtras(bundle);
startActivity(intent);
);
/**
Intent intent = new Intent(MainActivity.this, MapsActivity.class);
intent.putExtra("Ref", someVariable);
startActivity(intent);
*/
@Override
public void onClick(View v)
switch (v.getId())
case R.id.busbtn1:
someVariable ="BUS1";
numberbs.setText("Selected: BUS 1");
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS1");
break;
case R.id.busbtn2:
numberbs.setText("Selected: BUS 2");
someVariable ="BUS2";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS2");
break;
case R.id.busbtn3:
numberbs.setText("Selected: BUS 3");
someVariable ="BUS3";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS3");
break;
case R.id.busbtn4:
numberbs.setText("Selected: BUS 4");
someVariable ="BUS4";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS4");
break;
case R.id.busbtn5:
numberbs.setText("Selected: BUS 5");
someVariable ="BUS5";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS5");
break;
case R.id.busbtn6:
numberbs.setText("Selected: BUS 6");
someVariable ="BUS6";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS6");
break;
case R.id.busbtn7:
numberbs.setText("Selected: BUS 7");
someVariable ="BUS7";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS7");
break;
case R.id.bustbtn8:
numberbs.setText("Selected: BUS 8");
someVariable ="BUS8";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS8");
break;
case R.id.busbtn9:
numberbs.setText("Selected: BUS 9");
someVariable ="BUS9";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS9");
break;
case R.id.busbtn10:
numberbs.setText("Selected: BUS 10");
someVariable ="BUS10";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS10");
break;
case R.id.busbtn11:
numberbs.setText("Selected: BUS 11");
someVariable ="BUS11";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS11");
break;
case R.id.busbtn12:
numberbs.setText("Selected: BUS 12");
someVariable ="BUS12";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS12");
break;
case R.id.busbtn13:
numberbs.setText("Selected: BUS 13");
someVariable ="BUS13";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS13");
break;
case R.id.busbtn14:
someVariable ="BUS14";
numberbs.setText("Selected: BUS 14");
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS14");
break;
case R.id.bustbtn15:
numberbs.setText("Selected: BUS 15");
someVariable ="BUS15";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS15");
break;
case R.id.busbtn16:
numberbs.setText("Selected: BUS 16");
someVariable ="BUS16";
mDatabaseReference = mDatabase.getReference().child("Locations").child("BUS16");
break;
MapsActivity.java
在此处检索字符串并设置为数据库的地址
package com.manavchordia.aplparent;
import androidx.fragment.app.FragmentActivity;
import android.content.Intent;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.google.firebase.database.annotations.NotNull;
public class MapsActivity extends FragmentActivity implements OnMapReadyCallback, View.OnClickListener
private GoogleMap mMap;
private FirebaseAuth mAuth;
//String value_latitude = "0";
// String value_longitue = "0";
Double longi = 0.0;
Double lati = 0.0;
// String message = "BUS1";
Button Refreshh;
Double latitude = 0.0;
Double longitude = 0.0;
String vali;
Button Backp;
TextView BusNO;
private CountDownTimer timer;
private FirebaseDatabase mDatabase = FirebaseDatabase.getInstance();
private DatabaseReference myRef = mDatabase.getReference().child("Locations").child(vali);
// private DatabaseReference mDatabaseReference = mDatabase.getReference();
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
Backp = findViewById(R.id.backbuttonmap);
BusNO = findViewById(R.id.busnotext);
Intent intent = getIntent();
Bundle bundle = intent.getExtras();
String str = bundle.getString("message");
vali = str;
// 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);
BusNO.setText(vali);
timer = new CountDownTimer(5000, 500)
@Override
public void onTick(long millisUntilFinished)
@Override
public void onFinish()
try
timer.start();
Toast.makeText(MapsActivity.this, "Refreshing", Toast.LENGTH_LONG).show();
getBussGeo();
catch (Exception e)
Log.e("Error", "Error: " + e.toString());
.start();
Backp.setOnClickListener(this);
Backp.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
Intent intent = new Intent(MapsActivity.this, MainActivity.class);
timer.cancel();
startActivity(intent);
);
/**
* Manipulates the map once available.
* This callback is triggered when the map is ready to be used.
* This is where we can add markers or lines, add listeners or move the camera. In this case,
* we just add a marker near Sydney, Australia.
* If Google Play services is not installed on the device, the user will be prompted to install
* it inside the SupportMapFragment. This method will only be triggered once the user has
* installed Google Play services and returned to the app.
*/
@Override
public void onMapReady(GoogleMap googleMap)
mMap = googleMap;
/*
if (mMap != null)
LatLng sydney = new LatLng(lati, longi);
mMap.addMarker(new MarkerOptions().position(sydney).title(vali));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
*/
public void getBussGeo()
myRef.addValueEventListener(new ValueEventListener()
@Override
public void onDataChange(@NotNull DataSnapshot dataSnapshot)
for (DataSnapshot ds : dataSnapshot.getChildren())
double latitude = dataSnapshot.child("latitude").getValue(Double.class);
double longitude = dataSnapshot.child("longitude").getValue(Double.class);
Log.e("Long", "onDataChange: " + longitude);
Log.d("lato","onDataChange" + latitude);
lati = latitude;
longi = longitude;
if (mMap != null)
LatLng sydney = new LatLng(lati, longi);
mMap.addMarker(new MarkerOptions().position(sydney).title(vali));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
@Override
public void onCancelled(@NotNull DatabaseError error)
// Failed to read value
Toast.makeText(getApplicationContext(), "Error!!", Toast.LENGTH_SHORT).show();
);
@Override
public void onClick(View view)
当BUS11被点击时，地图应该会显示一个位置（因为已经设置了坐标）。
但地图将位置设置为 0,0
【问题讨论】：
值是否添加到数据库中？ 是的，值在那里，它们在 "vail = "BUS11"" 时起作用，但当我将它作为字符串从 MainActivity.java 传递时它们不起作用 你收到错误了吗？ 不，它只是在地图上将位置设置为 0,0。我知道它与意图、vali、Str 与 firebase 地址有关 从 Intent 中获取 String str 的值后尝试记录它 【参考方案1】：您没有使用新的 vali 值将侦听器更新为引用，请在 getBussGeo() 中执行此操作：
myRef = mDatabase.getReference().child("Locations").child(vali);
因为引用会保存vali的初始值，从intent获取后需要更新。
另外，尝试使用 Bundle 在活动之间传递数据。
在 MainActivity 中：
Intent intent = new Intent(this, MapsActivity.class);
Bundle bundle = new Bundle();
bundle.putString("message", someVariable);
intent.putExtras(bundle);
startActivity(intent);
在 MapsActivity 中：
Bundle bundle = intent.getExtras();
str = bundle.getString("message");
【讨论】：
不。当 Firebase 中有坐标存储时，仍然会在 0,0 处添加一个标记 能不能把str的值记录下来分享一下 TextView 正确设置字符串 好的。我一会儿再联系你。 我更新了我的代码，但它现在在尝试检索数据时崩溃。旧代码也是这样以上是关于尝试使用 Intent 获取字符串时未设置 .child()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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