Java 从google firebase检索数据并在android studio应用程序的列表视图中显示
我和我的团队正在进行一个android studio项目。我们可以向firebase添加数据。我们试图从数据库中检索数据,但我们认为无法引用正确的ID来检索列表视图中的数据。我们试图在Feedings类下检索数量、类型和开始。 这是我的密码:Java 从google firebase检索数据并在android studio应用程序的列表视图中显示,java,android,firebase,firebase-realtime-database,Java,Android,Firebase,Firebase Realtime Database,我和我的团队正在进行一个android studio项目。我们可以向firebase添加数据。我们试图从数据库中检索数据,但我们认为无法引用正确的ID来检索列表视图中的数据。我们试图在Feedings类下检索数量、类型和开始。 这是我的密码: @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.lay
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_feeding_list);
mListView = (ListView) findViewById(R.id.listView);
mAuth = FirebaseAuth.getInstance();
database = FirebaseDatabase.getInstance();
//myRef = database.getReference();
FirebaseUser user = mAuth.getCurrentUser();
userID = user.getUid();
myRef = database.getReference("/Users/" + userID + "/Feedings");
mAuthListener = new FirebaseAuth.AuthStateListener() {
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
FirebaseUser user = firebaseAuth.getCurrentUser();
if(user != null){
Log.d(TAG, "Signed in" + user.getUid());
toastMessage("Successfully signed in: ");
}else{
Log.d(TAG, "Currently signed out");
}
}
};
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
showData(dataSnapshot);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private void showData(DataSnapshot dataSnapshot) {
for(DataSnapshot ds: dataSnapshot.getChildren()){
Feeding feeding = new Feeding();
feeding.setAmount(ds.child(userID).getValue(Feeding.class).getAmount());
Log.d(TAG, "showData: name: " + feeding.getAmount());
ArrayList<String> arrayList = new ArrayList<>();
arrayList.add(feeding.getAmount());
ArrayAdapter adapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1, arrayList);
mListView.setAdapter(adapter);
}
}
@Override
public void onStart(){
super.onStart();
mAuth.addAuthStateListener(mAuthListener);
}
@Override
public void onStop(){
super.onStop();
if(mAuthListener != null){
mAuth.removeAuthStateListener(mAuthListener);
}
}
private void toastMessage(String message){
Toast.makeText(this, message, Toast.LENGTH_LONG).show();
}
@覆盖
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity\u feed\u列表);
mListView=(ListView)findViewById(R.id.ListView);
mAuth=FirebaseAuth.getInstance();
database=FirebaseDatabase.getInstance();
//myRef=database.getReference();
FirebaseUser=mAuth.getCurrentUser();
userID=user.getUid();
myRef=database.getReference(“/Users/”+userID+“/Feedings”);
mAuthListener=new FirebaseAuth.AuthStateListener(){
@凌驾
AuthStateChanged上的公共void(@NonNull FirebaseAuth FirebaseAuth){
FirebaseUser=firebaseAuth.getCurrentUser();
如果(用户!=null){
Log.d(标记“登录”+user.getUid());
toastMessage(“成功登录:”;
}否则{
Log.d(标签“当前已注销”);
}
}
};
myRef.addValueEventListener(新的ValueEventListener(){
@凌驾
公共void onDataChange(DataSnapshot DataSnapshot){
showData(dataSnapshot);
}
@凌驾
已取消的公共void(DatabaseError DatabaseError){
}
});
}
私有void showData(DataSnapshot DataSnapshot){
对于(DataSnapshot ds:DataSnapshot.getChildren()){
喂食=新喂食();
feeding.setAmount(ds.child(userID).getValue(feeding.class.getAmount());
d(标记“showData:name:”+feed.getAmount());
ArrayList ArrayList=新的ArrayList();
add(feed.getAmount());
ArrayAdapter=新的ArrayAdapter(这是android.R.layout.simple\u list\u item\u 1,arrayList);
mListView.setAdapter(适配器);
}
}
@凌驾
public void onStart(){
super.onStart();
mAuth.addAuthStateListener(mAuthListener);
}
@凌驾
公共void onStop(){
super.onStop();
if(mAuthListener!=null){
removeAuthStateListener(mAuthListener);
}
}
专用无效toastMessage(字符串消息){
Toast.makeText(这个,消息,Toast.LENGTH_LONG).show();
}
}试着像这样使用参考资料,它是在官方文件中提供的。 请注意您的ShowData方法,它不正确
myRef = database.getReference();
myRef.child("Users").child(userID).child("Feedings")
.getReference().addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
showData(dataSnapshot);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
private void showData(DataSnapshot dataSnapshot) {
ArrayList<String> arrayList = new ArrayList<>();
for(DataSnapshot ds: dataSnapshot.getChildren()){
Feeding feeding = ds.getValue(Feeding.class);
Log.d(TAG, "showData: name: " + feeding.getAmount());
arrayList.add(feeding.getAmount());
}
ArrayAdapter adapter = new
ArrayAdapter(this,android.R.layout.simple_list_item_1, arrayList);
mListView.setAdapter(adapter);
}
myRef=database.getReference();
myRef.child(“用户”).child(用户ID).child(“喂养”)
.getReference().addValueEventListener(新的ValueEventListener()){
@凌驾
公共void onDataChange(DataSnapshot DataSnapshot){
showData(dataSnapshot);
}
@凌驾
已取消的公共void(DatabaseError DatabaseError){
}
});
私有void showData(DataSnapshot DataSnapshot){
ArrayList ArrayList=新的ArrayList();
对于(DataSnapshot ds:DataSnapshot.getChildren()){
feed feed=ds.getValue(feed.class);
d(标记“showData:name:”+feed.getAmount());
add(feed.getAmount());
}
ArrayAdapter适配器=新
ArrayAdapter(这是android.R.layout.simple\u list\u item\u 1,arrayList);
mListView.setAdapter(适配器);
}
没有输出,应用程序崩溃。我运行了调试器,发现问题在于引用数据库。