你如何从firebase数据库制作arraylist以填充到ArrayAdapter中？

Posted 2023-05-07

【中文标题】你如何从firebase数据库制作arraylist以填充到ArrayAdapter中？

【英文标题】：how do you make arraylist from firebase database to populate in ArrayAdapter?

【发布时间】：2018-12-06 13:32:09

【问题描述】：

来自数据库的人员类型：

 key = personTypes, value = RESIDENT_HOMEOWNER=Resident Homeowner, RESIDENT_VISITOR=Resident Visitor, RESIDENT_RELATIVE=Resident Relative, RESIDENT_TENANT=Resident Tenant, HELPER_OUT=Helper Stay-out, PERSONNEL_1=Personnel 1, MAINTENANCE=Maintenance, PERSONNEL_2=Personnel 2, DRIVER_IN=Driver Stay-in, HELPER_IN=Helper Stay-in, PERSONNEL_3=Personnel 3, CONSTRUCTION=Construction Worker, PERSONNEL_4=Personnel 4, SECURITY=Security, RESIDENT_CHILD=Resident Child, ADMIN=Admin, DRIVER_OUT=Driver Stay-out 

我需要从 spinneradapter 中显示的 personTypes（从数据库中获取）中选择对象；

来自 DetailPresenter.java

    private MutableLiveData<List<String>> mPersonTypes = new MutableLiveData<>();
    public MutableLiveData<List<String>> observerPersonTypes() 
    return mPersonTypes;


private void setupPersonType() 
    List<String> personTypes = new ArrayList<>();
    for(String personType : personAccessor.getPersonTypes()) 
        personTypes.add(personAccessor.getPersonCategoryDisplay(personType));
    
    mPersonTypes.postValue(personTypes);

我在 spinneradapter 中显示 mPersonTypeList 时遇到问题，这是原始代码：

DetailsActivity.java

private static final String PERSON_TYPE_PROMPT = "Select Person Type";
private DetailPresenter mPresenter;
private ArrayAdapter<String> mPersonTypeAdapter;
List<String> mPersonTypeList = new ArrayList<>();

mPresenter.observerPersonTypes().observe(this, personTypes -> 
        mPersonTypeAdapter = new ArrayAdapter<>(this, R.layout.spinner_item_textview);
        mPersonTypeAdapter.setDropDownViewResource(R.layout.spinner_dropdown_item);
        mPersonTypeList = personTypes;
        mPersonTypeAdapter.addAll(mPersonTypeList);
        mSpinnerPersonType.setAdapter(new NothingSelectedSpinnerAdapter(mPersonTypeAdapter,
                R.layout.spinner_row_nothing_selected, PERSON_TYPE_PROMPT, this));
        mSpinnerPersonType.setOnItemSelectedListener(mSpinnerPersonTypeOnItemSelectedListener);
    );

当我调试时显示 ArrayList size =17;以及 mPersonTypeList 但在 spinneradapter 中显示时出错。

然后我尝试制作 mPersonTypeList，如下所示：

mPersonTypeList = Arrays.asList("DRIVER_IN", "DRIVER_OUT", "HELPER_IN","HELPER_OUT","CONSTRUCTION","ADMIN"
    ,"MAINTENANCE","SECURITY","RESIDENT_CHILD","RESIDENT_HOMEOWNER","RESIDENT_RELATIVE","RESIDENT_TENANT","RESIDENT_VISITOR");

成功显示mPersonTypeList Arrays$ArrayList size=13，我认为将mPersonTypeList转为Arrays.asList是显示personTypes的解决方案，但是如何转换呢？

NothingSelectedSpinnerAdapter.java

public class NothingSelectedSpinnerAdapter implements SpinnerAdapter, ListAdapter 

protected static final int EXTRA = 1;
protected SpinnerAdapter adapter;
protected Context context;
protected int nothingSelectedLayout;
protected String nothingSelectedPrompt;
protected int nothingSelectedDropdownLayout;
protected LayoutInflater layoutInflater;

/**
 * Use this constructor to have NO 'Select One...' item, instead use
 * the standard prompt or nothing at all.
 * @param spinnerAdapter wrapped Adapter.
 * @param nothingSelectedLayout layout for nothing selected, perhaps
 * you want text grayed out like a prompt...
 * @param context
 */
public NothingSelectedSpinnerAdapter(
        SpinnerAdapter spinnerAdapter,
        int nothingSelectedLayout, String nothingSelectedPrompt, Context context) 

    this(spinnerAdapter, nothingSelectedLayout, nothingSelectedPrompt, -1, context);


/**
 * Use this constructor to Define your 'Select One...' layout as the first
 * row in the returned choices.
 * If you do this, you probably don't want a prompt on your spinner or it'll
 * have two 'Select' rows.
 * @param spinnerAdapter wrapped Adapter. Should probably return false for isEnabled(0)
 * @param nothingSelectedLayout layout for nothing selected, perhaps you want
 * text grayed out like a prompt...
 * @param nothingSelectedDropdownLayout layout for your 'Select an Item...' in
 * the dropdown.
 * @param context
 */
public NothingSelectedSpinnerAdapter(SpinnerAdapter spinnerAdapter,
                                     int nothingSelectedLayout, String nothingSelectedPrompt,
                                     int nothingSelectedDropdownLayout, Context context) 

    this.adapter = spinnerAdapter;
    this.context = context;
    this.nothingSelectedLayout = nothingSelectedLayout;
    this.nothingSelectedPrompt = nothingSelectedPrompt;
    this.nothingSelectedDropdownLayout = nothingSelectedDropdownLayout;
    layoutInflater = LayoutInflater.from(context);


@Override
public final View getView(int position, View convertView, ViewGroup parent) 
    // This provides the View for the Selected Item in the Spinner, not
    // the dropdown (unless dropdownView is not set).
    if (position == 0) 
        return getNothingSelectedView(parent);
    
    return adapter.getView(position - EXTRA, null, parent); // Could re-use
    // the convertView if possible.


/**
 * View to show in Spinner with Nothing Selected
 * Override this to do something dynamic... e.g. "37 Options Found"
 * @param parent
 * @return
 */
protected View getNothingSelectedView(ViewGroup parent) 
    TextView textView = (TextView)layoutInflater.inflate(nothingSelectedLayout, parent, false);
    if(nothingSelectedPrompt !=null && nothingSelectedPrompt.length()>0) 
        textView.setText(nothingSelectedPrompt);
    
    return textView;


@Override
public View getDropDownView(int position, View convertView, ViewGroup parent) 
    // android BUG! http://code.google.com/p/android/issues/detail?id=17128 -
    // Spinner does not support multiple view types
    if (position == 0) 
        return nothingSelectedDropdownLayout == -1 ?
                new View(context) :
                getNothingSelectedDropdownView(parent);
    

    // Could re-use the convertView if possible, use setTag...
    return adapter.getDropDownView(position - EXTRA, null, parent);


/**
 * Override this to do something dynamic... For example, "Pick your favorite
 * of these 37".
 * @param parent
 * @return
 */
protected View getNothingSelectedDropdownView(ViewGroup parent) 
    return layoutInflater.inflate(nothingSelectedDropdownLayout, parent, false);


@Override
public int getCount() 
    int count = adapter.getCount();
    return count == 0 ? 0 : count + EXTRA;


@Override
public Object getItem(int position) 
    return position == 0 ? null : adapter.getItem(position - EXTRA);


@Override
public int getItemViewType(int position) 
    return 0;


@Override
public int getViewTypeCount() 
    return 1;


@Override
public long getItemId(int position) 
    return position >= EXTRA ? adapter.getItemId(position - EXTRA) : position - EXTRA;


@Override
public boolean hasStableIds() 
    return adapter.hasStableIds();


@Override
public boolean isEmpty() 
    return adapter.isEmpty();


@Override
public void registerDataSetObserver(DataSetObserver observer) 
    adapter.registerDataSetObserver(observer);


@Override
public void unregisterDataSetObserver(DataSetObserver observer) 
    adapter.unregisterDataSetObserver(observer);


@Override
public boolean areAllItemsEnabled() 
    return false;


@Override
public boolean isEnabled(int position) 
    return position == 0 ? false : true; // Don't allow the 'nothing selected'
    // item to be picked.

更新： 我尝试执行下面的代码（没有自定义适配器）但仍然给我错误

mPresenter.observerPersonTypes().observe(this, personTypes -> 

        mPersonTypeList.addAll(personTypes);
        mPersonTypeAdapter = new ArrayAdapter<>(this, R.layout.spinner_item_textview, mPersonTypeList);
        mPersonTypeAdapter.setDropDownViewResource(R.layout.spinner_dropdown_item);
        mSpinnerPersonType.setAdapter(mPersonTypeAdapter);
        mSpinnerPersonType.setOnItemSelectedListener(mSpinnerPersonTypeOnItemSelectedListener);
    );

【问题讨论】：

您可以使用适配器并将列表中的值设置到该适配器中...***.com/questions/47690279/…

@DroiDev 已经完成了mSpinnerPersonType.setAdapter(new NothingSelectedSpinnerAdapter(mPersonTypeAdapter, R.layout.spinner_row_nothing_selected, PERSON_TYPE_PROMPT, this));

什么是PERSON_TYPE_PROMPT？这是决赛吗？

什么是 NothingSelectedSpinnerAdapter... 这有什么用？您的适配器可能是错误的。您不需要自定义适配器（大部分情况下）。

查看@DroiDev上方的更新编辑。

【参考方案1】：

这对我有用。

这也是假设您已经正确实现了一个包含字符串项目的列表。

public class MainActivity extends AppCompatActivity 

    Spinner spinner;
    List<String> spinnerList;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        spinner = findViewById(R.id.spinner);
        spinnerList = new ArrayList<>();

        //For you, you may have a method that gets the information from Firebase. 
        //Either way, you need to make sure your list has items in it.    

        spinnerList.add("test 1");
        spinnerList.add("test 2");
        spinnerList.add("test 3");
        spinnerList.add("test 4");
        spinnerList.add("test 5");

        ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>
                (this, android.R.layout.simple_spinner_item, spinnerList);

        spinner.setAdapter(spinnerArrayAdapter);


    

这就是我的结果。

您必须对其进行样式设置...但这将帮助您入门。

来自 Firebase 文档。

public static class Post 

  public String author;
  public String title;

  public Post(String author, String title) 
    // ...
  



// Get a reference to our posts
final FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("server/saving-data/fireblog/posts");

// Attach a listener to read the data at our posts reference
ref.addValueEventListener(new ValueEventListener() 
  @Override
  public void onDataChange(DataSnapshot dataSnapshot) 
    Post post = dataSnapshot.getValue(Post.class);
    System.out.println(post);
  

  @Override
  public void onCancelled(DatabaseError databaseError) 
    System.out.println("The read failed: " + databaseError.getCode());
  
);

如果System.out.println(post);，你可以做spinnerList.add(post.getTitle());，这会将帖子标题添加到列表中。希望这是有道理的....

【讨论】：

我明白你的意思，但我的问题在于 firebase 数据库，我不确定mPersonTypeList（相当于你的spinnerList）是否正确实施，因为参数说它可能为空，但当我调试它时，它显示它有 size=17 所以我假设它有项目。

为什么不遍历该列表并将值打印到控制台以查看？您从 Firebase 获取字符串值的 ID 图像？我不使用firebase，所以我无法帮助，但我可能可以查看文档并弄清楚。如果