如何用Firebase数据填充Spinner? [英] How can I populate a Spinner with Firebase data?
问题描述
我在SO上的线程上浏览了在线文章，试图弄清楚我如何做到这一点，但是还没有进一步.
I've trawled through online articles on threads on SO to try and figure out how I can do this, but haven't come any closer.
此线程(如何从Firebase获取字符串列表以填充Spinner )似乎很有益，但是我不确定如何针对自己的情况实现它.
This thread (How to get a String List from Firebase to fill a Spinner) seems like it could be beneficial, however I'm unsure how to implement it for my own scenario.
我希望属性地址出现在微调器中.
I want the property addresses to be present in the spinner.
很抱歉，这个问题含糊不清，很难解释.
Apologies if the question seems vague, quite hard to explain.
维护活动
public class MaintenanceActivity extends AppCompatActivity {
EditText editTextTitle;
EditText editTextDesc;
Spinner spinnerPrimary;
Spinner spinnerSecondary;
Spinner spinnerProperty;
Button buttonSubmit;
DatabaseReference databaseMaintenance;
ListView listViewIssues;
List<Maintenance> maintenanceList;
fDatabaseRoot.child("propertyAddress").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// Is better to use a List, because you don't know the size
// of the iterator returned by dataSnapshot.getChildren() to
// initialize the array
final List<String> propertyAddress = new ArrayList<String>();
for (DataSnapshot addressSnapshot: dataSnapshot.getChildren()) {
String propertyAddress = addressSnapshot.child("propertyAddress").getValue(String.class);
propertyAddress.add(propertyAddress);
}
Spinner spinnerProperty = (Spinner) findViewById(R.id.spinnerProperty);
ArrayAdapter<String> addressAdapter = new ArrayAdapter<String>(MaintenanceActivity.this, android.R.layout.simple_spinner_item, areas);
addressAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerProperty.setAdapter(addressAdapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
activity_maintenance
<Spinner
android:id="@+id/spinnerProperty"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:entries="@array/fuel" />
Firebase数据库
错误
此答案出现多个错误.我以前有这些错误，不确定如何解决.
Getting several errors with this answer. I have had these errors previously, not sure how to solve them.
LogCat错误
03-01 17:19:53.402 28517-28517/com.example.***.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.***.myapplication, PID: 28517
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:445)
at android.widget.ArrayAdapter.getDropDownView(ArrayAdapter.java:493)
at android.widget.Spinner$DropDownAdapter.getDropDownView(Spinner.java:994)
at android.widget.Spinner$DropDownAdapter.getView(Spinner.java:990)
at android.widget.Spinner.measureContentWidth(Spinner.java:856)
at android.widget.Spinner$DropdownPopup.computeContentWidth(Spinner.java:1225)
at android.widget.Spinner$DropdownPopup.show(Spinner.java:1251)
at android.widget.Spinner.performClick(Spinner.java:780)
at android.support.v7.widget.AppCompatSpinner.performClick(AppCompatSpinner.java:442)
at android.view.View$PerformClick.run(View.java:24770)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
03-01 17:19:53.403 28517-28517/com.example.***.myapplication E/UncaughtException: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:445)
at android.widget.ArrayAdapter.getDropDownView(ArrayAdapter.java:493)
at android.widget.Spinner$DropDownAdapter.getDropDownView(Spinner.java:994)
at android.widget.Spinner$DropDownAdapter.getView(Spinner.java:990)
at android.widget.Spinner.measureContentWidth(Spinner.java:856)
at android.widget.Spinner$DropdownPopup.computeContentWidth(Spinner.java:1225)
at android.widget.Spinner$DropdownPopup.show(Spinner.java:1251)
at android.widget.Spinner.performClick(Spinner.java:780)
at android.support.v7.widget.AppCompatSpinner.performClick(AppCompatSpinner.java:442)
at android.view.View$PerformClick.run(View.java:24770)
at android.os.Handler.handleCallback(Handler.java:790)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
推荐答案
我可以为您提供很多帮助，但是您需要配置数据库和firebase，请参见
There so much I can help you with, but you'll need to configure the database and firebase, see docs.
之后，您的活动:
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference fDatabaseRoot = database.getReference();
fDatabaseRoot.child("properties").addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
// Is better to use a List, because you don't know the size
// of the iterator returned by dataSnapshot.getChildren() to
// initialize the array
final List<String> propertyAddressList = new ArrayList<String>();
for (DataSnapshot addressSnapshot: dataSnapshot.getChildren()) {
String propertyAddress = addressSnapshot.child("propertyAddress").getValue(String.class);
if (propertyAddress!=null){
propertyAddressList.add(propertyAddress);
}
}
Spinner spinnerProperty = (Spinner) findViewById(R.id.maintenanceProperty);
ArrayAdapter<String> addressAdapter = new ArrayAdapter<String>(MaintenanceActivity.this, android.R.layout.simple_spinner_item, propertyAddressList);
addressAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerProperty.setAdapter(addressAdapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
您已经为propertyAddress添加了一个侦听器，但是当datasnapshot返回时，您将再次探查propertyAddress，这是行不通的，因为侦听器已经返回了属性地址.我在上面编写的方式将返回数据库中的所有键，在每个键中都有一个可以检索的propertyAddress.试试看.
You had added a listener for the propertyAddress, but when the datasnapshot returned you were probing for propertyAddress again, which wouldn't work because the listener would return the property address already. The way I wrote above it will return all keys in your database, in each key you have a propertyAddress that can be retrieved. Give it a try.
这篇关于如何用Firebase数据填充Spinner?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
