Question

我想在sqlite数据库中保存自定义arraylist对象，当我在互联网上搜索它时，我知道我需要让我的课程序列化。但问题是我的那个班级是 Parcelable 而我是在 Parcelable 的帮助下将值从一个活动发送到另一个活动。

Medicine.class

public class Medicine implements Parcelable {

// Private Variables

int _id;
String _product_Code;
String _product_name;
String _type;
int _price;
int _quantity;

//empty constructor
public Medicine(){

}

//constructor
public Medicine(int id, String product_code,String product_name, String type, int price, int quantity){
    this._id = id;
    this._product_Code = product_code;
    this._product_name = product_name;
    this._type = type;
    this._price = price;
    this._quantity = quantity;
}

public Medicine(String product_code,String product_name, String type, int price, int quantity){
    this._product_Code = product_code;
    this._product_name = product_name;
    this._type = type;
    this._price = price;
    this._quantity = quantity;
}

public String get_product_Code() {
    return _product_Code;
}

public void set_product_Code(String _product_Code) {
    this._product_Code = _product_Code;
}

public Medicine(Parcel p){
    set_id(p.readInt());
    set_product_name(p.readString());
    set_type(p.readString());
    set_price(p.readInt());
    set_quantity(p.readInt());
}

public int get_id() {
    return _id;
}

public void set_id(int _id) {
    this._id = _id;
}

public String get_product_name() {
    return _product_name;
}

public void set_product_name(String _product_name) {
    this._product_name = _product_name;
}

public String get_type() {
    return _type;
}

public void set_type(String _type) {
    this._type = _type;
}

public int get_price() {
    return _price;
}

public void set_price(int _price) {
    this._price = _price;
}

public int get_quantity() {
    return _quantity;
}

public void set_quantity(int _quantity) {
    this._quantity = _quantity;
}

@Override
public int describeContents() {
    // TODO Auto-generated method stub
    return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
    // TODO Auto-generated method stub

    dest.writeInt(get_id());
    dest.writeString(get_product_name());
    dest.writeString(get_type());
    dest.writeInt(get_price());
    dest.writeInt(get_quantity());
}

public static final Parcelable.Creator<Medicine> CREATOR  = new Creator<Medicine>() {

    public Medicine createFromParcel(Parcel source) {

        return new Medicine(source);
    }

    public Medicine[] newArray(int size) {

        return new Medicine[size];
    }

};

}

在此类 ShowMedicineList i中，将值保存在名为“nextValuesOf”的arraylist中，并传递给下一个活动 SelectedMedicineList

    Button btnAddMedicine = (Button) findViewById(R.id.buttonAddSelectedMed);
    btnAddMedicine.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            Intent intent = new Intent(ShowMedicineList.this, SelectedMedicineList.class);
            //intent.putExtra("ccode", o._product_name);
            //intent.putExtra("cname", o._quantity);
            //intent.putExtra("caddress", amount);
            intent.putParcelableArrayListExtra("myArrayL", nextValuesOf);
            startActivity(intent);

        }
    });

这是 SelectedMedicineList类的onCreate方法，其中i，m接收意图。现在我想在我的数据库中使用 selectedProducts arraylist。请告诉我解决方案或代码

public ArrayList<Medicine> selectedProducts = new ArrayList<Medicine>();

DatabaseHandler db = new DatabaseHandler(this);

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

     selectedProducts = getIntent().getParcelableArrayListExtra("myArrayL");
     LinkedHashSet<Medicine> hs = new LinkedHashSet<Medicine>();
     hs.addAll(selectedProducts);
     selectedProducts.clear();
     selectedProducts.addAll(hs);
}

Answer 1

您可以使用Gson库来保存和检索任何数据结构中的数据。想法是库将对象转换（序列化和反序列化）为JSON格式

因此，创建一个字段类型为TEXT的数据库列，并将您的arraylist转换为JSON对象

Gson gson = new Gson();
String arrayList = gson.toJson(yourArraylist);

并将此字符串保存到数据库中。

并且在检索时从数据库中取一个字符串并将其转换为原始列表

Type listType = new TypeToken<ArrayList<YourClass>>() {
                    }.getType();
 List<YourClass> yourClassList = new Gson().fromJson(jsonArray, listType);

希望这个帮助

如何序列化自定义arraylist对象并将其保存到sqlite数据库？

1 个答案: