如何使用Firebase列表适配器 [英] How to use Firebase List adapter

问题描述

我试图按照这个教程：

https://www.youtube.com/watch?v=2J6spwAVP0M

但在我的复杂应用程序上实现它只是没有我创建了这个简单的MainActivity：

 <$ c 
 $ c> public class MainActivity extends AppCompatActivity {
 
 Firebase mRef; 
 com.firebase.ui.FirebaseListAdapter< String> myAdapter; 
 
 @Override 
 protected void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.activity_main）; 
 mRef =新的Firebase（https：//< myURL> ..）; 
 $ b $ myAdapter = new FirebaseListAdapter< String>（this，String.class，android.R.layout.simple_list_item_1，mRef）{
 @Override 
 protected void populateView（View view， String s，int i）{
 TextView text =（TextView）view.findViewById（android.R.id.text1）; 
 text.setText（s）; 
 
} 
}; 
 Button addBtn =（Button）findViewById（R.id.add_button）; 
 addBtn.setOnClickListener（new View.OnClickListener（）{
 @Override 
 public void onClick（View v）{
 mRef.push（）。setValue（test123）; 
} 
}）; 
 
 
 $ / code $ / pre 
 
现在我有几个问题：
 
 <1>什么触发populateView？我只是不能让它运行 
 
 <2>什么应该是什么 android.R.layout.simple_list_item_1 是换成？我尝试创建我自己的列表视图，并用我的 R.id.listView 替换上面的，但没有任何反应..我无法弄清楚这个魔法是如何工作的。
 
 
 3）即使这个简单的应用程序没有工作..按钮确实添加test123在服务器上的正确位置，但我什么都看不到我的应用程序..什么是错的解决方案

我找到了什么错误，我错过了一个列表视图。
正确的代码： / p>

  public class MainActivity extends AppCompatActivity {
 
 Firebase mRef; 
 com.firebase.ui.FirebaseListAdapter< String> myAdapter; 
 
 @Override 
 protected void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 setContentView（R.layout.activity_main）; 
 mRef =新的Firebase（https：//< myURL> ..）; 
 $ b $ myAdapter = new FirebaseListAdapter< String>（this，String.class，android.R.layout.simple_list_item_1，mRef）{
 @Override 
 protected void populateView（View view， String s，int i）{
 TextView text =（TextView）view.findViewById（android.R.id.text1）; 
 text.setText（s）; 
} 
}; 
 final ListView lv =（ListView）findViewById（R.id.listView）; 
 lv.setAdapter（myAdapter）; 
 
 Button addBtn =（Button）findViewById（R.id.add_button）; 
 addBtn.setOnClickListener（new View.OnClickListener（）{
 @Override 
 public void onClick（View v）{
 mRef.push（）。setValue（test123）; 
} 
}）; 
 
 
 
 
 
 $ b $ <$ code> lv.setAdapter 是将适配器关联到我的列表，并触发populateView .. 
这基本上是我所有的3个问题的答案.. 
 
 
 
以下是xml： 
 
 
 <？xml version = 1.0encoding =utf-8？> 
< RelativeLayout xmlns：android =http://schemas.android.com/apk/res/android
 xmlns：tools =http://schemas.android.com/tools
 android：layout_width =match_parent
 android：layout_height =match_parent
 android：paddingBottom =@ dimen / activity_vertical_margin
 android：paddingLeft =@ dimen / activity_horizo​​ntal_margin
 android：paddingRight =@ dimen / activity_horizo​​ntal_margin
 android：paddingTop =@ dimen / activity_vertical_margin
 tools：context =com.twodwarfs.firebaselistadapter.MainActivity> 
 
 $ b< Button 
 android：layout_width =wrap_content
 android：layout_height =wrap_content
 android：text =add
 android：id =@ + id / add_button
 android：layout_alignParentBottom =true
 android：layout_alignParentEnd =true/> 
 $ b $ ListView 
 android：layout_width =wrap_content
 android：layout_height =wrap_content
 android：id =@ + id / listView
 android：layout_toStartOf =@ + id / add_button
 android：layout_below =@ + id / textView/> 
< / RelativeLayout> 
  
 
I'm trying to follow with this tutorial:


https://www.youtube.com/watch?v=2J6spwAVP0M

but implementing it on my complex app just didn't work so I tried from scratch..

I created this simple MainActivity:
public class MainActivity extends AppCompatActivity{

    Firebase mRef;
    com.firebase.ui.FirebaseListAdapter<String> myAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mRef = new Firebase("https://<myURL>..");

        myAdapter = new FirebaseListAdapter<String>(this,String.class,android.R.layout.simple_list_item_1,mRef) {
            @Override
            protected void populateView(View view, String s, int i) {
                TextView text = (TextView)view.findViewById(android.R.id.text1);
                text.setText(s);

            }
        };
        Button addBtn = (Button) findViewById(R.id.add_button);
        addBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mRef.push().setValue("test123");
            }
        });
    }
}
Now I have few questions:

1) what triggers the populateView? I just couldn't make it run

2) what exactly should the android.R.layout.simple_list_item_1 be replaced with? I tried creating my own listview and replace the above with my R.id.listView but nothing happens.. I can't figure out how this magic works..

3) even this simple app didn't work.. the button does add the "test123" to the right place on the server but I see nothing on my app.. whats wrong?
解决方案
I found out what was wrong, I was missing a Listview..
Heres the corrected code:
public class MainActivity extends AppCompatActivity {

    Firebase mRef;
    com.firebase.ui.FirebaseListAdapter<String> myAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mRef = new Firebase("https://<myURL>..");

        myAdapter = new FirebaseListAdapter<String>(this,String.class,android.R.layout.simple_list_item_1,mRef) {
            @Override
            protected void populateView(View view, String s, int i) {
                TextView text = (TextView) view.findViewById(android.R.id.text1);
                text.setText(s);
            }
        };
        final ListView lv = (ListView) findViewById(R.id.listView);
        lv.setAdapter(myAdapter);

        Button addBtn = (Button) findViewById(R.id.add_button);
        addBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mRef.push().setValue("test123");
            }
        });
    }


}
the lv.setAdapter is what associating the adapter to my list and also triggers the populateView..
That's basically the answer to all of my 3 questions at once..

here is the xml as well:
<?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: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.twodwarfs.firebaselistadapter.MainActivity">


    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="add"
        android:id="@+id/add_button"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true" />

    <ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/listView"
        android:layout_toStartOf="@+id/add_button"
        android:layout_below="@+id/textView" />
</RelativeLayout>


                        
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