android - 在 RecyclerView 中显示 SQLite 数据

Question

我搜索了很多，但没有找到任何有关如何在 RecyclerView 中显示 SQLite 数据的分步指南。谁能向我解释我该怎么做？

我的DataBaseAdapter:

public class DataBaseAdapter {

DataBaseHelper helper;

public DataBaseAdapter(Context context) {
    helper = new DataBaseHelper(context);
    }

public long insertData(String name, String card, String code) {

    SQLiteDatabase db = helper.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(DataBaseHelper.NAME, name);
    contentValues.put(DataBaseHelper.CARD, card);
    contentValues.put(DataBaseHelper.CODE, code);
    long id = db.insert(DataBaseHelper.TABLE_NAME, null, contentValues);
    return id;
}

public String getData(String name){
    //select _id,Name,Card,Code
    SQLiteDatabase db = helper.getWritableDatabase();
    String[] columns = {DataBaseHelper.NAME, DataBaseHelper.CARD, DataBaseHelper.CODE};
    Cursor cursor = db.query(DataBaseHelper.TABLE_NAME, columns,DataBaseHelper.NAME+" = '"+name+"'", null, null, null, null);
    StringBuffer buffer = new StringBuffer();
    while (cursor.moveToNext()) {
        int index2 = cursor.getColumnIndex(DataBaseHelper.NAME);
        int index3 = cursor.getColumnIndex(DataBaseHelper.CARD);
        int index4 = cursor.getColumnIndex(DataBaseHelper.CODE);

        String personName = cursor.getString(index2);
        String card = cursor.getString(index3);
        String code = cursor.getString(index4);
        buffer.append(name + " " + card + " " + code + "\n");

    }
    return buffer.toString();
}

public String getAllData() {
    //select _id,Name,Card,Code
    SQLiteDatabase db = helper.getWritableDatabase();
    String[] columns = {DataBaseHelper.UID, DataBaseHelper.NAME, DataBaseHelper.CARD, DataBaseHelper.CODE};
    Cursor cursor = db.query(DataBaseHelper.TABLE_NAME, columns, null, null, null, null, null);
    StringBuffer buffer = new StringBuffer();
    while (cursor.moveToNext()) {
        int index1 = cursor.getColumnIndex(DataBaseHelper.UID);
        int index2 = cursor.getColumnIndex(DataBaseHelper.NAME);
        int index3 = cursor.getColumnIndex(DataBaseHelper.CARD);
        int index4 = cursor.getColumnIndex(DataBaseHelper.CODE);

        int cid = cursor.getInt(index1);
        String name = cursor.getString(index2);
        String card = cursor.getString(index3);
        String code = cursor.getString(index4);
        buffer.append(cid + " " + name + " " + card + " " + code + "\n");
    }
    return buffer.toString();

}

static class DataBaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "cardsdatabase";
    private static final String TABLE_NAME = "CARDSTABLE";
    private static final String UID = "_id";
    private static final String NAME = "Name";
    private static final String CARD = "Card";
    private static final String CODE = "Code";
    private static final int DATABASE_VERSION = 1;
    private static final String CREATE_TABLE = "create table "
            + TABLE_NAME + " (" + UID
            + " integer primary key autoincrement, " + NAME
            + " text not null, " + CARD + " ext not null, " + CODE
            + " text not null);";
    private static final String DROP_TABLE = "DROP TABLE IF EXISTS "
            + TABLE_NAME;
    private Context context;

    public DataBaseHelper(Context context) {

        super(context, DataBaseHelper.DATABASE_NAME, null, DataBaseHelper.DATABASE_VERSION);
        this.context = context;
        Toast toast = Toast.makeText(context, "constructor called", Toast.LENGTH_LONG);
        toast.show();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        //CREATE TABLE CARDSTABLE(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(255));
        try {
            db.execSQL(CREATE_TABLE);
            Toast toast = Toast.makeText(context, "onCreate called", Toast.LENGTH_LONG);
            toast.show();

        } catch (SQLException e) {
            Toast toast = Toast.makeText(context, "" + e, Toast.LENGTH_SHORT);
            toast.show();
        }


    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        try {
            Toast toast = Toast.makeText(context, "onUpgrade called", Toast.LENGTH_LONG);
            toast.show();
            db.execSQL(DROP_TABLE);
            onCreate(db);
        } catch (SQLException e) {
            Toast toast = Toast.makeText(context, "" + e, Toast.LENGTH_LONG);
            toast.show();
        }

    }
}

你的回答对我很有帮助，谢谢

编辑:

DataBean 类:

public class DataBean {
//private variables
int _id;
String _name;
String _card_value;
String _card_code;

// Empty constructor
public DataBean(){

}
// constructor
public DataBean(int id, String name, String _card_value, String _card_code){
    this._id = id;
    this._name = name;
    this._card_value = _card_value;
    this._card_code = _card_code;
}

// constructor
public DataBean(String name, String _card_value, String _card_code){
    this._name = name;
    this._card_value = _card_value;
    this._card_code = _card_code;
}
// getting ID
public int getID(){
    return this._id;
}

// setting id
public void setID(int id){
    this._id = id;
}

// getting name
public String getName(){
    return this._name;
}

// setting name
public void setName(String name){
    this._name = name;
}

// getting CardValue
public String getCardValue(){
    return this._card_value;
}

// setting CardValue
public void setCardValue(String _card_value){
    this._card_value = _card_value;
}
// getting CardCode
public String getCardCode(){
    return this._card_code;
}

// setting CardCode
public void setCardCode(String _card_code){
    this._card_code = _card_code;
}

我将这些行添加到我的DataBaseAdapter:

public DataBean getDat(String name){
        DataBean bean=null;
        SQLiteDatabase db=this.getReadableDatabase();
        String[] columns = {DataBaseHelper.NAME, DataBaseHelper.CARD, DataBaseHelper.CODE};
        Cursor cursor = db.query(DataBaseHelper.TABLE_NAME, columns,DataBaseHelper.NAME+" = '"+name+"'", null, null, null, null);
        if (cursor.moveToFirst()) {
            int index = cursor.getColumnIndex(DataBaseHelper.UID);
            int index2 = cursor.getColumnIndex(DataBaseHelper.NAME);
            int index3 = cursor.getColumnIndex(DataBaseHelper.CARD);
            int index4 = cursor.getColumnIndex(DataBaseHelper.CODE);
            int id = cursor.getInt(index);
            String personName = cursor.getString(index2);
            String card = cursor.getString(index3);
            String code = cursor.getString(index4);
            bean = new DataBean(id, name, card, code);
        }
        return bean;
    }
    public List<DataBean> gelAllDat(){
        List<DataBean> list = new ArrayList<>();
        SQLiteDatabase db=this.getReadableDatabase();
        String[] columns = {DataBaseHelper.NAME, DataBaseHelper.CARD, DataBaseHelper.CODE};
        Cursor cursor = db.query(DataBaseHelper.TABLE_NAME, columns,DataBaseHelper.NAME, null, null, null, null);
        while (cursor.moveToNext()) {
            int index = cursor.getColumnIndex(DataBaseHelper.UID);
            int index2 = cursor.getColumnIndex(DataBaseHelper.NAME);
            int index3 = cursor.getColumnIndex(DataBaseHelper.CARD);
            int index4 = cursor.getColumnIndex(DataBaseHelper.CODE);
            int cid = cursor.getInt(index);
            String name = cursor.getString(index2);
            String card = cursor.getString(index3);
            String code = cursor.getString(index4);
            DataBean bean = new DataBean(cid, name, card, code);
            list.add(bean);
        }
        return list;

    }

最后一个问题？我需要在 DataBaseAdapter 中更改我的插入数据？

编辑 2:

我将这段代码添加到我的 DataBaseAdapter 中:

public List<DataBean> getAllCards(){
    List<DataBean> list=new ArrayList<>();
    String query = "SELECT  * FROM " + DataBaseHelper.TABLE_NAME;
    SQLiteDatabase db = helper.getReadableDatabase();
    Cursor cursor = db.rawQuery(query, null);
    while (cursor.moveToNext()) {
        //int index = cursor.getColumnIndex(DataBaseHelper.UID);
        int index2 = cursor.getColumnIndex(DataBaseHelper.NAME);
        int index3 = cursor.getColumnIndex(DataBaseHelper.CARD);
        int index4 = cursor.getColumnIndex(DataBaseHelper.CODE);
        //int cid = cursor.getInt(index);
        String name = cursor.getString(index2);
        String card = cursor.getString(index3);
        String code = cursor.getString(index4);
        DataBean bean = new DataBean(name, card, code);
        list.add(bean);
    }

    return list;

}

public DataBean getData(String name) {
    //select _id,Name,Card,Code
    SQLiteDatabase db = helper.getReadableDatabase();
    String[] columns = {DataBaseHelper.NAME, DataBaseHelper.CARD, DataBaseHelper.CODE};
    DataBean bean=null;
    Cursor cursor = db.query(DataBaseHelper.TABLE_NAME, columns, DataBaseHelper.NAME + " = '" + name + "'", null, null, null, null);
    StringBuffer buffer = new StringBuffer();
    while (cursor.moveToNext()) {
        int index2 = cursor.getColumnIndex(DataBaseHelper.NAME);
        int index3 = cursor.getColumnIndex(DataBaseHelper.CARD);
        int index4 = cursor.getColumnIndex(DataBaseHelper.CODE);

        String personName = cursor.getString(index2);
        String card = cursor.getString(index3);
        String code = cursor.getString(index4);
        //buffer.append(name + " " + card + " " + code + "\n");
        bean = new DataBean( name,card, code);

    }
    return bean;
}

Answer 1

您可以从一个 Bean 开始，以包含和建模信息并使其更易于实现。

public class DataBean{
    protected int id;
    protected String name;
    protected String card;
    protected String code;
    //Setter, Getters and constructor
    ...
}

创建 DataBean 后，您可以将方法的返回类型更改为 DataBean 或 List 并在每个方法中填充，而不是返回包含所有字段的字符串。

public DataBean getData(String name){
    ...
    DataBean bean = null;
    if (cursor.moveToFirst()) {
        int index = cursor.getColumnIndex(DataBaseHelper.UID);
        int index2 = cursor.getColumnIndex(DataBaseHelper.NAME);
        int index3 = cursor.getColumnIndex(DataBaseHelper.CARD);
        int index4 = cursor.getColumnIndex(DataBaseHelper.CODE);
        int id = cursor.getInt(index);
        String personName = cursor.getString(index2);
        String card = cursor.getString(index3);
        String code = cursor.getString(index4);
        bean = new DataBean(id, name, card, code);    
    }
    return bean;
}

public List<DataBean> getAllData() {
    List<DataBean> list = new ArrayList<>();
    ...
    while (cursor.moveToNext()) {
        int index = cursor.getColumnIndex(DataBaseHelper.UID);
        int index2 = cursor.getColumnIndex(DataBaseHelper.NAME);
        int index3 = cursor.getColumnIndex(DataBaseHelper.CARD);
        int index4 = cursor.getColumnIndex(DataBaseHelper.CODE);
        int cid = cursor.getInt(index);
        String name = cursor.getString(index2);
        String card = cursor.getString(index3);
        String code = cursor.getString(index4);
        DataBean bean = new DataBean(cid, name, card, code);
        list.add(bean);
    }
    return list;
}

现在当你调用你的方法时你有一个 DataBean 对象，现在你需要编写你的适配器来在 RecyclerView 中显示信息。

首先需要在您的 Activity 中链接并设置 RecyclerView。

mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.setAdapter(new DataBeanAdapter(dbAdapter.getAllData(), R.layout.item));

在您需要创建 DataBeanAdapter 和 ViewHolder 之后.

public class DataBeanAdapter extends RecyclerView.Adapter<DataBeanAdapter.ViewHolder>{
    private List<DataBean> items;
    private int itemLayout;

    public DataBeanAdapter(List<DataBean> items, int itemLayout){
        this.items = items;
        this.itemLayout = itemLayout;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(itemLayout, parent, false);
        return new ViewHolder(v);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        DataBean item = items.get(position);
        holder.name.setText(item.getName());
        holder.card.setText(item.getCard());
        //All the thing you gonna show in the item
    }

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

    public static class ViewHolder extends RecyclerView.ViewHolder {
        public TextView name;
        public TextView card;

        public ViewHolder(View itemView) {
            super(itemView);
            name = (TextView) itemView.findViewById(R.id.name);
            card = (TextView) itemView.findViewById(R.id.card);
        }
    }
}

ViewHolder 的 ID、布局和属性取决于您要在 RecyclerView 中显示每个项目的对象。