我在编写代码以删除数据库时遇到问题。 我想删除它:
在这种情况下,我不知道如何使用.child()
。我现在的代码是:
private void deleteKryterium(String kryteriumId) {
DatabaseReference drKryteria = FirebaseDatabase.getInstance().getReference().child(kryteriumId);
drKryteria.child(kryteriumId).removeValue();
Toast.makeText(this,"Kryterium zostało usunięte", Toast.LENGTH_LONG).show();
}
但这是错误的。你能帮助我吗?我从教程中编写的大部分代码都是绿色的。
在另一端,用于更新此child
的代码可以正常工作:
private boolean updateKryterium(String id, String name, int rating){
Kryterium kryterium = new Kryterium(id, name, rating);
databaseKryteria.child(id).setValue(kryterium);
Toast.makeText(this, "Nazwa kryterium zaktualizowana", Toast.LENGTH_LONG).show();
return true;
答案 0 :(得分:0)
您未指向要删除的正确参考。
该孩子的路径应始于:
DatabaseReference drKryteria = FirebaseDatabase.getInstance().getReference().child("piwo_kryteria");
然后在那一点上,您应将键-LI785bPiLU9Z2qEe35o移至子级,然后最后移至要删除的子级(ID为kryteriumId)。 您应该像对kyteriumId一样知道中间键的值。
请注意,您还可以使用1个单个child()函数向其传递完整路径,在该路径中,每个节点都用正斜杠分隔,例如:
.child("piwo_kryteria/" + intermediate_key + "/" + kryteriumId)
在该引用上,您将调用removeValue()或setValue(null)。
答案 1 :(得分:0)
这是目前的代码,当然,在删除项目时无法正常工作:
public class Piwo_AddKryterium extends AppCompatActivity {
TextView textViewAlkoholName, textViewRating;
SeekBar seekBarRating;
Spinner spinnerKryteria;
Button buttonAddKryterium;
ListView listViewKryteria;
DatabaseReference databaseKryteria;
List<Kryterium> kryteria;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.piwo_activity_add_kryterium);
textViewAlkoholName = (TextView) findViewById(R.id.textViewAlkoholName);
seekBarRating = (SeekBar) findViewById(R.id.seekBarRating);
textViewRating = (TextView) findViewById(R.id.textViewRating);
buttonAddKryterium = (Button) findViewById(R.id.buttonAddKryterium);
listViewKryteria = (ListView) findViewById(R.id.listViewKryteria);
spinnerKryteria = (Spinner) findViewById(R.id.spinnerKryteria);
Intent intent = getIntent();
kryteria = new ArrayList<>();
String id = intent.getStringExtra(Piwo_Program.ALKOHOL_ID);
String name = intent.getStringExtra(Piwo_Program.ALKOHOL_NAME);
textViewAlkoholName.setText(name);
databaseKryteria = FirebaseDatabase.getInstance().getReference("piwo_kryteria").child(id);
buttonAddKryterium.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
saveKryterium();
}
});
seekBarRating.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
@Override
public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
textViewRating.setText(String.valueOf(i));
}
@Override
public void onStartTrackingTouch(SeekBar seekBar) {
}
@Override
public void onStopTrackingTouch(SeekBar seekBar) {
}
});
listViewKryteria.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
}
});
listViewKryteria.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
Kryterium kryterium = kryteria.get(i);
showUpdateDialog(kryterium.getKryteriumId(), kryterium.getKryteriumName());
return true;
}
});
}
@Override
protected void onStart() {
super.onStart();
databaseKryteria.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
kryteria.clear();
for(DataSnapshot kryteriumSnapshot : dataSnapshot.getChildren()){
Kryterium kryterium = kryteriumSnapshot.getValue(Kryterium.class);
kryteria.add(kryterium);
}
KryteriumList kryteriumListAdapter = new KryteriumList(Piwo_AddKryterium.this, kryteria);
listViewKryteria.setAdapter(kryteriumListAdapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private void saveKryterium(){
String kryteriumName = spinnerKryteria.getSelectedItem().toString();
int rating = seekBarRating.getProgress();
if(!TextUtils.isEmpty(kryteriumName)){
String id = databaseKryteria.push().getKey();
Kryterium kryterium = new Kryterium(id, kryteriumName, rating);
databaseKryteria.child(id).setValue(kryterium);
Toast.makeText(this, "Kryterium zapisane poprawnie", Toast.LENGTH_LONG).show();
}else{
Toast.makeText(this, "Nazwa kryterium nie może pozostać pusta", Toast.LENGTH_SHORT).show();
}
}
private void showUpdateDialog(final String kryteriumId, String kryteriumName){
AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
LayoutInflater inflater = getLayoutInflater();
final View dialogView = inflater.inflate(R.layout.piwo_update_dialog_kryterium, null);
dialogBuilder.setView(dialogView);
final Spinner spinnerKryteria = (Spinner) dialogView.findViewById(R.id.spinnerKryteria);
final Button buttonUpdate = (Button) dialogView.findViewById(R.id.buttonUpdate);
final SeekBar seekBarRating = (SeekBar) dialogView.findViewById(R.id.seekBarRating);
final Button buttonDelete = (Button) dialogView.findViewById(R.id.buttonDelete);
dialogBuilder.setTitle("Aktualizacja Kryterium: " + kryteriumName);
final AlertDialog alertDialog = dialogBuilder.create();
alertDialog.show();
buttonUpdate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String kryteriumName = spinnerKryteria.getSelectedItem().toString();
int rating = seekBarRating.getProgress();
updateKryterium(kryteriumId, kryteriumName, rating);
alertDialog.dismiss();
}
});
buttonDelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
deleteKryterium(kryteriumId);
alertDialog.dismiss();
}
});
}
private void deleteKryterium(String kryteriumId) {
DatabaseReference drKryteria = FirebaseDatabase.getInstance().getReference().child(kryteriumId);
drKryteria.child(kryteriumId).removeValue();
Toast.makeText(this,"Kryterium zostało usunięte", Toast.LENGTH_LONG).show();
}
private boolean updateKryterium(String id, String name, int rating){
Kryterium kryterium = new Kryterium(id, name, rating);
databaseKryteria.child(id).setValue(kryterium);
Toast.makeText(this, "Nazwa kryterium zaktualizowana", Toast.LENGTH_LONG).show();
return true;
}
}