java - 无法从 SQLite 检索数据

Question

请看下面的代码

DatabaseHandler.java

用于检索数据的代码

public List<String> getAllBranches() {
        // TODO Auto-generated method stub

        String selectQuery = "select city from BranchNetwork";

        Cursor cursor = database.rawQuery(selectQuery, null);
        List <String>branches = new ArrayList<String>();

        if(cursor.isFirst())
        {
            do
            {

            }
            while(cursor.moveToNext());

            Toast.makeText(context, "Data Retrieved: "+branches.get(1), Toast.LENGTH_LONG).show();
        }

        return branches;
    }

用于插入数据的代码

public String insertData(String city, String streetAddress,String phoneNumber1, String phoneNumber2, String email) 
    {
        String insertQuery = "insert into BranchNetwork ('city','streetAddress','phoneNumber1','phoneNumber2','email') values('"+city+"','"+streetAddress+"','"+phoneNumber1+"','"+phoneNumber2+"','"+email+"');";




        try
        {  
            database.execSQL(insertQuery);


            return "Data Successfully Inserted";

        }
        catch(Exception e)
        {
            Toast.makeText(context, "Exception: "+e.getMessage(), Toast.LENGTH_LONG).show();
            return "Data Insertion Failed";
        }

    }

Form.java

第一个 Activity 。这里我检索数据并插入数据。以下是我检索数据的方法

public class Form extends Activity {
    private List<String>branches = new ArrayList<String>();
        private DatabaseConnector databaseConnector;
    String[]arr;


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

            databaseConnector = DatabaseHandler.getInstance(this);
            databaseConnector.createConnection();

            branches = databaseConnector.getAllBranches();

             arr = branches.toArray(new String[branches.size()]);
    }
}

但是，我什么也没得到!在 DatabaseHandler.java 中，我创建了一个 Toast，在检索代码时它应该生成一条消息。但它没有产生任何东西!我正在将数据加载到 ListView 中，但它也是空的!为什么是这样？请帮忙!

PS:以下是DatabaseConnector.java，DatabaseHandler的插入面

package com.example.esoftcallmanager;

import java.util.List;

import android.content.Context;

public interface DatabaseConnector 
{
    public void createConnection();
    public void closeConnection();
    public String getPhoneNumber();
    public String insertData(String city, String streetAddress, String phoneNumber1, String phoneNumber2, String email);
    public List<String>getAllBranches();

}

Answer 1

如果您确定数据库已有数据，请尝试将 if(cursor.isFirst()) 更改为 if(cursor.moveToFirst())