目标
通过Firebase数据库中的数据树获取当前用户的数据,例如姓名,地址,邻居等
数据树的图片
宗旨
数据树中的“伦敦”和“华盛顿”子级是通过管理员帐户添加的,这意味着它们不是固定的,并且可以添加其他子级,例如“纽约”。
这意味着新编辑的数据树将位于“用户”下,其中将有“伦敦”,“华盛顿”和“纽约”
其他孩子,例如下面显示的孩子是固定的。
守卫
名称
邻里
警察
地址
名称
邻里
居民
地址
图片
名称
邻里
位置
状态
问题
尝试提示登录的当前用户的数据后,我收到“ java.lang.NullPointerException”。
错误显示在代码String stgUserHomeName = dataSnapshot.child("Users").getValue().toString();
处。
我以前可以获取所需的数据,例如“名称”,“地址”等,但是当我添加“伦敦”和“华盛顿”之类的非固定父母时遇到了问题。
设置活动类别
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
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.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;
import com.google.firebase.storage.UploadTask;
import com.squareup.picasso.Callback;
import com.squareup.picasso.NetworkPolicy;
import com.squareup.picasso.Picasso;
import java.io.File;
public class SettingsActivity extends AppCompatActivity {
private DatabaseReference jSettingsDatabase;
private FirebaseUser jFirebaseCurrentUser;
private Toolbar jSettingsToolbar;
private ImageView jSettingsImageView;
private TextView jSettingsDisplayName;
private TextView jSettingsStatus;
private TextView jSettingsAddress;
private TextView jSettingsHomeName;
private Button jSettingsDetailsBtn;
private Button jSettingsImageBtn;
private static final int jSettingsGallerySelect = 1;
private StorageReference jSettingsStorageReference;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings);
jSettingsStorageReference = FirebaseStorage.getInstance().getReference();
jFirebaseCurrentUser = FirebaseAuth.getInstance().getCurrentUser();
String settingsUserID = jFirebaseCurrentUser.getUid();
jSettingsDatabase = FirebaseDatabase.getInstance().getReference().child("Resident").child(settingsUserID);
jSettingsDatabase.keepSynced(true);
jSettingsImageView = (ImageView) findViewById(R.id.settingUserImg);
jSettingsToolbar = (Toolbar) findViewById(R.id.settingsToolBar);
setSupportActionBar(jSettingsToolbar);
getSupportActionBar().setTitle("Settings");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
jSettingsDisplayName = (TextView) findViewById(R.id.settingUserNameTxt);
jSettingsStatus = (TextView) findViewById(R.id.settingUserStatusTxt);
jSettingsAddress = (TextView) findViewById(R.id.settingUserAddressTxt);
jSettingsHomeName = (TextView) findViewById(R.id.settingsUserHomeTxt);
jSettingsDetailsBtn = (Button) findViewById(R.id.settingChangeDetailsBtn);
jSettingsImageBtn = (Button) findViewById(R.id.settingChangeImageBtn);
jSettingsDatabase.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String stgUserHomeName = dataSnapshot.child("Users").getValue().toString();
String stgUserName = dataSnapshot.child("Users").child(stgUserHomeName).child("name").getValue().toString();
String stgUserStatus = dataSnapshot.child("Users").child(stgUserHomeName).child("status").getValue().toString();
String stgUserHomeAddress = dataSnapshot.child("Users").child(stgUserHomeName).child("address").getValue().toString();
final String stgUserImage = dataSnapshot.child("Users").child(stgUserHomeName).child("image").getValue().toString();
jSettingsDisplayName.setText(stgUserName);
jSettingsStatus.setText(stgUserStatus);
jSettingsAddress.setText(stgUserHomeAddress);
if(!stgUserImage.equals("default")){
Picasso.with(SettingsActivity.this).load(stgUserImage).networkPolicy(NetworkPolicy.OFFLINE)
.placeholder(R.drawable.avataricon).into(jSettingsImageView, new Callback() {
@Override
public void onSuccess() {
}
@Override
public void onError() {
Picasso.with(SettingsActivity.this).load(stgUserImage).placeholder(R.drawable.avataricon).into(jSettingsImageView);
}
});
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
jSettingsDetailsBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String stgUserStatusValue = jSettingsStatus.getText().toString();
String stgUserAddressValue = jSettingsAddress.getText().toString();
String stgUserNameValue = jSettingsDisplayName.getText().toString();
Intent intentDetails = new Intent(SettingsActivity.this, DetailsActivity.class);
intentDetails.putExtra("stgUserNameValue" , stgUserNameValue);
intentDetails.putExtra("stgUserStatusValue", stgUserStatusValue);
intentDetails.putExtra("stgUserAddressValue", stgUserAddressValue);
startActivity(intentDetails);
}
});
jSettingsImageBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intentGallery = new Intent();
intentGallery.setType("image/*");
intentGallery.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(intentGallery, "SELECT IMAGE"), jSettingsGallerySelect);
}
});
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(requestCode == jSettingsGallerySelect && resultCode == RESULT_OK){
Uri imageUri = data.getData();
String currentUserID = jFirebaseCurrentUser.getUid();
StorageReference imageFilePath = jSettingsStorageReference.child("profileImages").child(currentUserID+".jpg");
imageFilePath.putFile(imageUri).addOnCompleteListener(new OnCompleteListener<UploadTask.TaskSnapshot>(){
@Override
public void onComplete(@NonNull Task<UploadTask.TaskSnapshot> task) {
@SuppressWarnings("VisibleForTests")
String downloadImageUrl = task.getResult().getDownloadUrl().toString();
jSettingsDatabase.child("image").setValue(downloadImageUrl).addOnCompleteListener(new OnCompleteListener<Void>() {
@Override
public void onComplete(@NonNull Task<Void> task) {
if(task.isSuccessful()){
Toast.makeText(SettingsActivity.this, "Upload Successful", Toast.LENGTH_SHORT).show();
}else{
Toast.makeText(SettingsActivity.this, "Upload Failed", Toast.LENGTH_SHORT).show();
}
}
});
}
});
}
}
}
代码说明
jSettingsHomeName
和stgUserHomeName
分别是“伦敦”,“华盛顿”等。解决几乎类似的问题
在链接:How to get child of child value from firebase in android?中,它显示了程序员如何获取孩子的孩子,但之所以无法遵循的原因是因为我的“伦敦”和“华盛顿”孩子层未固定
更新:Ewald B提供的尝试解决方案。
jSettingsDatabase.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot node : dataSnapshot.getChildren()) {
String stgUserHomeName = node.getKey();
String stgUserName = node.child("Resident").child(settingsUserID).child("name").getValue().toString();
String stgUserStatus = node.child("Resident").child(settingsUserID).child("status").getValue().toString();
String stgUserHomeAddress = node.child("Resident").child(settingsUserID).child("address").getValue().toString();
final String stgUserImage = node.child("Resident").child(settingsUserID).child("image").getValue().toString();
jSettingsHomeName.setText(stgUserHomeName);
jSettingsDisplayName.setText(stgUserName);
jSettingsStatus.setText(stgUserStatus);
jSettingsAddress.setText(stgUserHomeAddress);
if(!stgUserImage.equals("default")){
Picasso.with(SettingsActivity.this).load(stgUserImage).networkPolicy(NetworkPolicy.OFFLINE)
.placeholder(R.drawable.avataricon).into(jSettingsImageView, new Callback() {
@Override
public void onSuccess() {
}
@Override
public void onError() {
Picasso.with(SettingsActivity.this).load(stgUserImage).placeholder(R.drawable.avataricon).into(jSettingsImageView);
}
});
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
错误
com.example.task.app.SettingsActivity $ 1.onDataChange(SettingsActivity.java:91)上的java.lang.NullPointerException
第91行指向
String stgUserName = node.child("Resident").child(settingsUserID).child("name").getValue().toString();
最佳答案
根据数据模型并查看此语句
jSettingsDatabase = FirebaseDatabase.getInstance().getReference().child("Resident").child(settingsUserID);
User
下没有节点/Resident/userId
。查询需要从数据库的根目录开始,我假设该根目录为User
。为了获得
London, Washington, etc.
,您需要将代码修改为:jSettingsDatabase = FirebaseDatabase.getInstance().getReference().child("Users");
...
jSettingsDatabase.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot node : dataSnapshot.getChildren()) {
// you will get all cities
String stgUserHomeName = node.getKey();
if(!"Washington".equals(stgUserHomeName)) // or whatever city you need
continue;
// add some more conditional logic to cope with the distinct subtrees that don't have the same properties
// London's Resident has more properties than Washington --> exception is thrown then
// to get the resident's data
node.child("Resident").child(userId).child("address")...
node.child("Resident").child(userId).child("image")...
// or
node.child("Resident").child(userId).getValue(Resident.class);
...
}
....
}
});
您的树中没有此查询所需的用户ID。但是根据数据库的访问规则,可能有必要。显然,其他查询也需要进行调整。城市名称也不是值,而是键(必须唯一),因此调用
DataSnapshot.getKey()
方法很重要。在您的情况下,将从用户向下的整个数据库中获取数据,并在客户端上丢弃所有不需要的城市。那是浪费资源。