我正在使用 this tutorial 在我的 Android 项目中实现 SQLite 功能.
我有这个 SQLiteOpenHelper 代码:
public class HHSSQLiteHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "HHS.db";
private static final String TABLE_VENDORS = "vendors";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_VENDORID = "vendorId";
public static final String COLUMN_COMPANYNAME = "companyName";
public HHSSQLiteHandler(Context context, String vendor,
SQLiteDatabase.CursorFactory factory, int company) {
super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}
. . .
...但尝试以这种方式实例化该类:
protected void onPostExecute(String result) {
try {
JSONArray jsonArr = new JSONArray(result);
for (int i = 0; i < jsonArr.length(); i++) {
JSONObject jsonObj = jsonArr.getJSONObject(i);
String vendorId = jsonObj.getString("vendorId");
String companyName = jsonObj.getString("companyName");
// Prepare for writing to db
Vendor vend = new Vendor();
vend.setVendorId(vendorId);
vend.setCompanyName(companyName);
HHSSQLiteHandler sqliteHandler = new HHSSQLiteHandler(this, null, null, 1);
sqliteHandler.addVendor(vend);
}
} catch (JSONException j) {
System.out.println(j.getMessage());
Log.i("jsonEx", j.getMessage());
}
}
...在“HHSSQLiteHandler sqliteHandler = new HHSSQLiteHandler(this, null, null, 1);”上给我“错误:类型不兼容:MainActivity.GetVendorsTask 无法转换为上下文”行。
它到底在期待什么?我拿什么来安抚它?
最佳答案
嵌套类中的
this
指的是嵌套类实例 (GetVendorsTask
),而不是外部类实例 (MainActivity
)。用例如限定它MainActivity.this
引用外部类实例,如果它是 Context
(例如 Activity
),它将起作用。
关于java - 为什么我的 SQLiteOpenHelper 构造函数中出现 "incompatible types: Bla cannot be converted to Context"?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22874726/