如何从Firebase数据库读取数据并使用ArrayAdapter在ListView中显示多个字段 [英] How to Read Data from Firebase Database and Display Multiple Fields in ListView with ArrayAdapter
问题描述
我花了大部分时间试图弄清楚如何从我的Firebase数据库中读取数据并通过ArrayAdapter在ListView中显示多个字段.终于让ListView在一个textview中显示一个数据后，我被困在尝试显示其他两个字段.
I have spent the better half of the day trying to figure out how to read data from my firebase database and display multiple fields in a ListView via an ArrayAdapter. After finally getting my ListView to display one piece of data in one textview, I am stuck trying to display two other fields.
在我的MainActivity类中，我在Adapter构造函数中使用了android.R.layout.simple_list_item_1，因为有人告诉我textViewResourceID参数只能包含一个TextView.因此，重申我的问题:我不知道如何使用数组适配器显示多个字段.该应用程序当前仅显示 make 字段.在此先多谢了，我大约一周前才开始android开发！这是我的代码如下:
In my MainActivity class I used the android.R.layout.simple_list_item_1 in the Adapter constructor because I was told that the textViewResourceID argument must only contain one TextView. So to reiterate my problem: I can not figure out how to display multiple fields with an array adapter. This app currently only displays the make field. Thanks so much in advance, I only started android development about a week ago! Here is my code below:
public class SearchModel {
public String make;
private String model;
private String stock;
public SearchModel() {}
public String getMake() {
return this.make;
}
public void setMake(String make) {
this.make = make;
}
public String getModel() {
return model;
}
public void setModel(String model) {
this.model = model;
}
public String getStock() {
return stock;
}
public void setStock(String stock) {
this.stock = stock;
}
}
MainActivity.java
(我省略了onCreate()之后的班级无关部分)
MainActivity.java
(I omitted the irrelevant bottom section of the class after onCreate())
public class MainActivity extends AppCompatActivity {
private DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference().child("users").child("user1");
private ListView mListView;
private TextView tv_make;
private TextView tv_model;
private TextView tv_stock;
private ArrayList<String> list = new ArrayList<>();
private ArrayAdapter<String> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
tv_make = (TextView) findViewById(R.id.tv_list_item_make);
tv_model = (TextView) findViewById(R.id.tv_list_item_model);
tv_stock = (TextView) findViewById(R.id.tv_list_item_stock);
databaseReference.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {
String value = snapshot.child("make").getValue(String.class);
list.add(value);
mListView = (ListView) findViewById(R.id.lv_searches);
adapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout.simple_list_item_1, list);
mListView.setAdapter(adapter);
}
@Override
public void onChildChanged(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {
}
@Override
public void onChildRemoved(@NonNull DataSnapshot snapshot) {
}
@Override
public void onChildMoved(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
FloatingActionButton fab = findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
这是content.main.xml中的ListView:
<ListView
android:id="@+id/lv_searches"
android:layout_width="match_parent"
android:layout_height="match_parent">
</ListView>
这是list_item.xml，它应该位于我的ListView中.在这里，我想在SearchModel.java的实例中显示三个String值(品牌，型号，库存).
And here is the list_item.xml which is supposed to sit inside my ListView. This is where I would like to display the three String values (make, model, stock) in an instance of SearchModel.java.
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="100dp"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:padding="10dp">
<TextView
android:id="@+id/tv_list_item_make"
android:layout_width="wrap_content"
android:layout_height="50dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tv_list_item_model"
android:layout_width="wrap_content"
android:layout_height="40dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintBottom_toBottomOf="parent" />
<TextView
android:id="@+id/tv_list_item_stock"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
这是我的firebase数据库布局:
This is my firebase database layout:
推荐答案
被困两天后，我得以回答自己的问题！希望这将有助于将来的初学者尝试在ArrayAdapter中显示自定义视图.基本上，我创建了一个自定义的ArrayAdapter类，其中可以包含三个TextViews.
after two days of being stuck I was able to answer my own question! Hopefully this will help future beginners stuck trying to display a custom view within an ArrayAdapter. Basically, I created a custom ArrayAdapter class which could hold three TextViews inside of it.
我绝不是专家，也无法像其他人一样对此进行解释，因此，我将粘贴指向我遵循并成功的两个视频教程的链接.
I am in no means an expert and will not be able to explain this as well as others, so instead, I will paste a link to the two video tutorials that I followed and had success with.
Android初学者教程#8-用于显示多列的自定义ListView适配器 https://www.youtube.com/watch?v=E6vE8fqQPTE&t= 392s
Android Beginner Tutorial #8 - Custom ListView Adapter For Displaying Multiple Columns https://www.youtube.com/watch?v=E6vE8fqQPTE&t=392s
Android初学者教程#9-自定义ListView适配器[带有加载动画] https://www.youtube.com/watch?v=SApBLHIpH8A
Android Beginner Tutorial #9 - Custom ListView Adapter [With Loading Animation] https://www.youtube.com/watch?v=SApBLHIpH8A
这是我下面更新的代码:
Here is my updated code below:
public class CustomAdapter extends BaseAdapter {
private static ArrayList<SearchModel> searchArrayList;
private LayoutInflater mInflater;
private Context mContext;
private int lastPosition;
/**
* Holds elements in a view
*/
static class ViewHolder {
TextView make;
TextView model;
TextView stock;
}
public CustomAdapter(Context context, ArrayList<SearchModel> results) {
searchArrayList = results;
mContext = context;
mInflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
return searchArrayList.size();
}
@Override
public Object getItem(int position) {
return searchArrayList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
String make = searchArrayList.get(position).getMake();
String model = searchArrayList.get(position).getModel();
String stock = searchArrayList.get(position).getStock();
final View result;
ViewHolder holder;
if (convertView == null) {
LayoutInflater inflater = LayoutInflater.from(mContext);
convertView = inflater.inflate(R.layout.list_item, parent, false);
holder = new ViewHolder();
holder.make = (TextView) convertView.findViewById(R.id.tv_list_item_make);
holder.model = (TextView) convertView.findViewById(R.id.tv_list_item_model);
holder.stock = (TextView) convertView.findViewById(R.id.tv_list_item_stock);
result = convertView;
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
result = convertView;
}
Animation animation = AnimationUtils.loadAnimation(mContext,
(position > lastPosition) ? R.anim.load_down_anim : R.anim.load_up_anim);
result.startAnimation(animation);
lastPosition = position;
holder.make.setText(make);
holder.model.setText(model);
holder.stock.setText(stock);
return convertView;
}
}
MainActivity.java(仅onCreate方法)
MainActivity.java (Only the onCreate method)
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
databaseReference.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {
String make = snapshot.child("make").getValue(String.class);
String model = snapshot.child("model").getValue(String.class);
String stock = snapshot.child("stock").getValue(Long.class).toString();
SearchModel searchModel = new SearchModel(make, model, stock);
searchList.add(searchModel);
CustomAdapter customAdapter = new CustomAdapter(getApplicationContext(), searchList);
mListView = (ListView) findViewById(R.id.lv_searches);
mListView.setAdapter(customAdapter);
}
@Override
public void onChildChanged(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {
}
@Override
public void onChildRemoved(@NonNull DataSnapshot snapshot) {
}
@Override
public void onChildMoved(@NonNull DataSnapshot snapshot, @Nullable String previousChildName) {
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
这篇关于如何从Firebase数据库读取数据并使用ArrayAdapter在ListView中显示多个字段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！
