Java Firebase removeValue()
我在编写删除数据库的代码时遇到问题。 我想删除以下内容: 我不知道在这种情况下如何使用Java Firebase removeValue(),java,android,firebase,firebase-realtime-database,Java,Android,Firebase,Firebase Realtime Database,我在编写删除数据库的代码时遇到问题。 我想删除以下内容: 我不知道在这种情况下如何使用.child()。我现在的代码是: private void deleteKryterium(String kryteriumId) { DatabaseReference drKryteria = FirebaseDatabase.getInstance().getReference().child(kryteriumId); drKryteria.child(kryteriumI
.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?我写的大部分代码都是从教程中获得的,所以它是非常绿色的。
另一方面,指定用于更新此子项的代码工作正常:
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;
您没有指向要删除的正确引用
指向该子级的路径应从以下位置开始:
DatabaseReference drKryteria = FirebaseDatabase.getInstance().getReference().child("piwo_kryteria");
然后,此时,您应该使用键-li785bpillu9z2qee35o移动到子级,最后移动到要删除的子级(id为kryteriumId)。
您应该知道中间键的值,就像您对kyteriumId所做的一样
请注意,您还可以使用1个单子()函数向其传递整个路径,其中每个节点由正斜杠分隔,如:
.child("piwo_kryteria/" + intermediate_key + "/" + kryteriumId)
在该引用上,您将调用removeValue()甚至setValue(null)。这是目前的代码,当然它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;
}
公共类Piwo\u AddKryterium扩展应用程序活动{
TextView textViewAlkoholName、textViewRating;
SeekBar seekbarranting;
纺纱机;
纽扣,纽扣,纽扣;
ListView listViewKryteria;
数据库参考数据库;
罗列kryteria;
@凌驾
创建时受保护的void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.piwo\u activity\u add\u kryterium);
textViewAlkoholName=(TextView)findViewById(R.id.textViewAlkoholName);
seekBarRating=(SeekBar)findViewById(R.id.seekBarRating);
textViewRating=(TextView)findViewById(R.id.textViewRating);
buttonadkryterium=(Button)findViewById(R.id.buttonadkryterium);
listViewKryteria=(ListView)findViewById(R.id.listViewKryteria);
喷丝头Kryteria=(喷丝头)findViewById(R.id.喷丝头Kryteria);
Intent=getIntent();
kryteria=newarraylist();
字符串id=intent.getStringExtra(Piwo_程序.ALKOHOL_id);
字符串名称=intent.getStringExtra(Piwo_程序.ALKOHOL_名称);
textViewAlkoholName.setText(名称);
databaseKryteria=FirebaseDatabase.getInstance().getReference(“piwo_kryteria”).child(id);
ButtonAddCryterium.setOnClickListener(新视图.OnClickListener(){
@凌驾
公共void onClick(视图){
saveKryterium();
}
});
seekbarranting.setOnSeekbarchaneListener(新的SeekBar.onSeekbarchaneListener(){
@凌驾
public void onProgressChanged(SeekBar SeekBar、int i、boolean b){
textViewRating.setText(String.valueOf(i));
}
@凌驾
开始跟踪触摸时的公共无效(SeekBar SeekBar){
}
@凌驾
TopTrackingTouch(SeekBar SeekBar)上的公共无效{
}
});
listViewKryteria.setOnItemClickListener(新的AdapterView.OnItemClickListener(){
@凌驾
公共无效onItemClick(AdapterView AdapterView、View视图、int i、long l){
}
});
listViewKryteria.setOnItemLongClickListener(新的AdapterView.OnItemLongClickListener(){
@凌驾
公共布尔值长单击(AdapterView AdapterView,视图视图,int i,long l){
Kryterium Kryterium=kryteria.get(i);
showUpdateDialog(kryterium.getKryteriumId(),kryterium.getKryteriumName());
返回true;
}
});
}
@凌驾
受保护的void onStart(){
super.onStart();
databaseKryteria.addValueEventListener(新的ValueEventListener(){
@凌驾
公共void onDataChange(DataSnapshot DataSnapshot){
kryteria.clear();
对于(DataSnapshot kryteriumSnapshot:DataSnapshot.getChildren()){
Kryterium Kryterium=kryteriumSnapshot.getValue(Kryterium.class);
添加(kryterium);
}
KryteriumList kryteriumlistatadapter=新的KryteriumList(Piwo_AddKryterium.this,kryteria);
setAdapter(kryteriumlistatadapter);
}
@凌驾
已取消的公共void(DatabaseError DatabaseError){
}
});
}
私有void saveKryterium(){
字符串kryteriumName=喷丝头kryteria.getSelectedItem().toString();
int rating=seekBarRating.getProgress();
如果(!TextUtils.isEmpty(kryteriumName)){
String id=databaseKryteria.push().getKey();
Kryterium Kryterium=新Kryterium(id、kryteriumName、评级);
databaseKryteria.child(id).setValue(kryterium);
Toast.makeText(这是“Kryterium zapisane poprawnie”,Toast.LENGTH_LONG.show();
}否则{
Toast.makeText(这是“Nazwa kryterium nie może pozostaćpusta”,Toast.LENGTH_SHORT).show();
}
}
私有void showUpdateDialog(最终字符串kryteriumId,字符串kryteriumName){
AlertDialog.Builder dialogBuilder=新建AlertDialog.Builder(此);
LayoutInflater充气机=getLayoutInflater();
最终视图对话框视图=充气机。充气(R.layout.piwo\u update\u dialog\u kryterium,null);
dialogBuilder.setView(dialogView);
最终喷丝器喷丝器Kryteria=(喷丝器)dialogView.findViewById(R.id.spinnerKryteria);
最终按钮buttonUpdate=(按钮)dialogView.findViewById(R.id.buttonUpdate);
final SeekBar seekBarRating=(SeekBar)dialogView.findviewbyd(R.id.seekBarRating);
最终按钮buttonDelete=(按钮)dialogView.findViewById(R.id.buttonDelete);
dialogBuilder.setTitle(“Aktualizacja Kryterium:+kryteriumName”);
final AlertDialog AlertDialog=dialogBuilder.create();
alertDialog.show();
buttonUpdate.setOnClickListener(新视图.OnClickListener(){
@凌驾
公共void onClick(视图){
字符串kryteriumName=喷丝头kryteria.getSelectedItem().toString();
int rating=seekBarRating.getProgress();
更新Cryterium(kryteriumId、kryteriumName、评级);
alertDialog.disclose();
}
});
按钮删除