Question

我是Java，Android和SQLite的新手，所以我很惊讶我已经走到了这一步。

我正在尝试为我的盆景收藏创建一个简单的编目应用程序，该应用程序在MainActivity上的RecyclerView中显示我的收藏摘要。

我有数据库工作，因为我可以添加项目（通过DB Browser for SQLite检查）。我遇到的麻烦是在RecyclerView中显示这些数据。目前它只是显示laucher图标占位符图像，而不是使用来自DB的数据填充TextView。 RecyclerView中显示的视图数与数据库中的条目数相对应。

我不确定我做错了什么，所以非常感谢任何帮助。

MainActivity.java

Datasource mDataSource;
Button btnAddNew;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mDataSource = new Datasource(this);
    mDataSource.open();

    List<DataModel> listFromDB = mDataSource.getAllItems();
    DataItemAdapter adapter = new DataItemAdapter(this, listFromDB);

    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rvItems);
    recyclerView.setAdapter(adapter);

    btnAddNew = (Button) findViewById(R.id.btnInsert);
}

DataModel.Java

public class DataModel {

private String itemId;
private String itemName;
private String itemCommonName;

public DataModel() {
}

public String getItemId() {
    return itemId;
}

public void setItemId(String itemId) {
    this.itemId = itemId;
}

public String getItemName() {
    return itemName;
}

public void setItemName(String itemName) {
    this.itemName = itemName;
}

public String getItemCommonName() {
    return itemCommonName;
}

public void setItemCommonName(String itemCommonName) {
    this.itemCommonName = itemCommonName;
}

Datasource.java

public class Datasource {

private Context mContext;
private SQLiteDatabase mDatabase;
SQLiteOpenHelper mDbHelper;

public Datasource(Context context){
    this.mContext = context;
    mDbHelper = new DatabaseHelper(mContext);
    mDatabase = mDbHelper.getWritableDatabase();
}

public void open(){
    mDatabase = mDbHelper.getWritableDatabase();
}

public void close(){
    mDatabase.close();
}

public boolean insertData(String name, String commonName, String scientificName){
    SQLiteDatabase db = mDbHelper.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(COL_NAME, name);
    contentValues.put(COL_COMMON_NAME, commonName);
    contentValues.put(COL_SCI_NAME, scientificName);
    long result = db.insert(DATABASE_TABLE, null, contentValues);
    db.close();

    if(result == -1) {
        return false;
    }else{
        return true;
    }
}

public List<DataModel> getAllItems(){
    List<DataModel> dataModels = new ArrayList<>();
    Cursor cursor = mDatabase.query(DATABASE_TABLE, ItemsTable.ALL_COLUMNS,
            null, null, null, null, null);

    while (cursor.moveToNext()){
        DataModel item = new DataModel();
        item.setItemId(cursor.getString(
                cursor.getColumnIndex(ItemsTable.COL_ID)));
        item.setItemId(cursor.getString(
                cursor.getColumnIndex(ItemsTable.COL_NAME)));
        item.setItemId(cursor.getString(
                cursor.getColumnIndex(ItemsTable.COL_COMMON_NAME)));
        item.setItemId(cursor.getString(
                cursor.getColumnIndex(ItemsTable.COL_SCI_NAME)));
        dataModels.add(item);
    }
    return dataModels;
}

DataItemAdapter.java

public class DataItemAdapter extends RecyclerView.Adapter<DataItemAdapter.ViewHolder> {

private List<DataModel> mItems;
private Context mContext;

public DataItemAdapter(Context context, List<DataModel> items) {
    this.mContext = context;
    this.mItems = items;
}

@Override
public DataItemAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    LayoutInflater inflater = LayoutInflater.from(mContext);
    View itemView = inflater.inflate(R.layout.list_item, parent, false);
    ViewHolder viewHolder = new ViewHolder(itemView);
    return viewHolder;
}

@Override
public void onBindViewHolder(DataItemAdapter.ViewHolder holder, int position) {
    final DataModel item = mItems.get(position);

        holder.tvName.setText(item.getItemName());
        holder.tvCommonName.setText(item.getItemCommonName());
}

@Override
public int getItemCount() {
    return mItems.size();
}

public static class ViewHolder extends RecyclerView.ViewHolder {
    public TextView tvName, tvCommonName;
    public ImageView ivProfilePic;
    public View mView;
    public ViewHolder(View itemView){
        super(itemView);

        tvName = (TextView) itemView.findViewById(R.id.tvName);
        tvCommonName = (TextView) itemView.findViewById(R.id.tvCommonName);
        ivProfilePic = (ImageView) itemView.findViewById(R.id.ivProfilePic);
        mView = itemView;
    }
}

activity_main.xml中的RecyclerView对象

<android.support.v7.widget.RecyclerView
    android:id="@+id/rvItems"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layoutManager="LinearLayoutManager"/>

TextViews和图像视图list_item.xml

<ImageView
    android:id="@+id/ivProfilePic"
    android:layout_width="75dp"
    android:layout_height="75dp"
    app:srcCompat="@mipmap/ic_launcher_round"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"
    android:contentDescription="Profile Pic"
    tools:ignore="HardcodedText"/>

<TextView
    android:id="@+id/tvName"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    android:layout_marginStart="19dp"
    android:layout_toEndOf="@+id/ivProfilePic"
    android:text="TextView"
    android:textSize="18sp"
    android:visibility="visible"/>

<TextView
    android:id="@+id/tvCommonName"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:text="TextView"
    android:visibility="visible"/>

MainActivity目前的截图：

需要提供任何其他信息，只需询问，我会尝试发布。

Answer 1

对它进行排序，现在看起来很简单。

在Cursor中，在复制并粘贴第一行（仅列名称）之后，我没有将项目设置器更改为正确的项目设置器。

此外，我将ID列标识为字符串，它应该是一个整数 - 也在DataModel类中更新了

    while (cursor.moveToNext()){
        DataModel item = new DataModel();
        item.setItemId(cursor.getInt(
                cursor.getColumnIndex(ItemsTable.COL_ID)));
        item.setItemName(cursor.getString(
                cursor.getColumnIndex(ItemsTable.COL_NAME)));
        item.setItemCommonName(cursor.getString(
                cursor.getColumnIndex(ItemsTable.COL_COMMON_NAME)));
        item.setItemSciName(cursor.getString(
                cursor.getColumnIndex(ItemsTable.COL_SCI_NAME)));
        dataModels.add(item);
    }
    return dataModels;
}

TextViews没有填充RecyclerView中SQLite数据库的数据

1 个答案: