问题
I am having a similar issue in which I have my files as follow in which I want to be able to view all child items and add new child items.
I understand that you will have to modify the code in the Java file, but I am having trouble understanding how to manipulate my own code and I tried to follow the confusing documentation provided by Firebase.
Below is the structure of my database followed by my code. Any help would be greatly appreciated.
The only problem I have now is how to properly populate the listview with the values of the following structure of my database.
It is as follows: Messages --> Message --> value of which has concatenated string
I hope this isn't confusing
Here is my MainActivity.java
package com.example.sean.messengerappsean;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import com.firebase.client.DataSnapshot;
import com.firebase.client.Firebase;
import com.firebase.client.FirebaseError;
import com.firebase.client.Query;
import com.firebase.client.ValueEventListener;
import com.firebase.client.collection.ArraySortedMap;
import com.firebase.client.realtime.util.StringListReader;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
//TextView mTextFieldCondition;
EditText editUsername, editValue;
ArrayAdapter arrayAdapter;
Button btnSend;
Firebase mRef;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
protected void onStart() {
super.onStart();
//mTextFieldCondition = (TextView) findViewById(R.id.textViewCondition);
editUsername = (EditText) findViewById(R.id.editUsername);
editValue = (EditText) findViewById(R.id.editValue);
btnSend = (Button) findViewById(R.id.btnSend);
mRef = new Firebase("https://androidmessagetest.firebaseio.com/"); //CAN USE THE CODE HERE TO PUBLISH TO SPECIFIC LOCATION OR DB
//TRYING TO SET LISTVIEW
final ListView listView = (ListView) findViewById(R.id.listview);
final ArrayList<String> msgsArray = new ArrayList<String>(); //USE THIS FOR POPULATING THE VIEW
final ValueEventListener valueEventListener = mRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
//----------CONDITION FOR LISTING DATA----------------
//MIGHT NEED TO PUT VALUES INTO ARRAY AND READ THEM OUT IN ORDER OF PUBLISH
//String text = dataSnapshot.child("Message").child("Enter Username3").getValue(String.class);
//mTextFieldCondition.setText(text);
//POPULATE LISTVIEW
for (DataSnapshot Datasnapshot : dataSnapshot.getChildren()) {
msgsArray.add(Datasnapshot.child("Messages").child("Message").getKey());
}
ArrayAdapter arrayAdapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_list_item_1, msgsArray);
listView.setAdapter(arrayAdapter);
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
});
btnSend.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//NEED TO DYNAMICALLY CHANGE VALUE TO USERNAME: MESSAGE
String textoutput = String.valueOf(editUsername.getText());
String MessageText = String.valueOf(editValue.getText());
//FIXED MESSAGE ADD CHILD AND HOW TO ADD VALUE TO MESSAGE
//TRY TO USE BELOW CODE FOR MESSAGES LATER ON
mRef.child("Messages").child("Message").push().setValue(textoutput + ": " + MessageText);
}
});
//ADD FUNCTION TO LOOK FOR DATA
}
}
Here is my XML file activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.sean.messengerappsean.MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<!--<TextView
android:id="@+id/textViewCondition"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/mTextFieldCondition"
android:layout_centerHorizontal="true"
android:layout_marginBottom="89dp"
android:text="Condition" />-->
//ENTER IN CODE BELOW FOR VIEWING OUTPUT OF DATA
<ListView
android:id="@+id/listview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
></ListView>
</LinearLayout>
<Button
android:id="@+id/btnSend"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:text="Send" />
<EditText
android:id="@+id/editValue"
android:layout_width="fill_parent"
android:layout_height="50dp"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignTop="@+id/btnSend"
android:layout_toLeftOf="@+id/btnSend"
android:layout_toStartOf="@+id/btnSend"
android:backgroundTint="@color/colorPrimaryDark"
android:inputType="textMultiLine"
android:text="Enter Message Here" />
<EditText
android:id="@+id/editUsername"
android:layout_width="fill_parent"
android:layout_height="50dp"
android:layout_above="@+id/btnSend"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_gravity="bottom"
android:background="@color/colorAccent"
android:inputType="textCapWords"
android:text="Enter Username" />
</RelativeLayout>
回答1:
These imports are for classes in the legacy SDK:
import com.firebase.client.DataSnapshot;
import com.firebase.client.Firebase;
import com.firebase.client.FirebaseError;
import com.firebase.client.Query;
import com.firebase.client.ValueEventListener;
These are for the new SDK:
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
You cannot mix the two SDKs. You should use the new SDK only. Remove this statement from your build.gradle dependencies:
compile 'com.firebase:firebase-client-android:2.x.x'
and make the approriate code changes to use the new SDK. Documentation and examples are here. There is also an Upgrade Guide.
来源：https://stackoverflow.com/questions/41266787/how-to-add-and-view-child-objects-in-firebase-android