Cursor 数据库查询游标的应用

在建立数据库，输入数据的前提下，用db.rawQuery（sql，selectionArgs）联系接口Cursor c；

然后运用moveToFirst，isAfterLast，moveToNext等方法查询

在Curesor中index是从0开始查询列数的

例子：

1.新建数据库SQliteOpenHelper类

package com.example.CursorDemo;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by Anonymous on 2016/1/19.
 */
public class OpenHelpClass extends SQLiteOpenHelper {
      public OpenHelpClass(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
            super(context, name, factory, version);
      }

      @Override
      public void onCreate(SQLiteDatabase db) {

            db.execSQL("create table stu (id integer primary key autoincrement,name text not null,age text not null)");

      }

      @Override
      public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            db.execSQL("drop table if exists stu");

            onCreate(db);
      }
}

2.插入数据方法类：

package com.example.CursorDemo;

import android.database.sqlite.SQLiteDatabase;


public class MethodsClass {

      private SQLiteDatabase db;

      public MethodsClass(SQLiteDatabase db) {
            this.db = db;
      }

      public void DataInset(String name,int age){

            Object[] args = new Object[]{name, age};
            db.execSQL("insert into stu(name,age) values (?,?)",args);
      }

}

3.mainActivity类
package com.example.CursorDemo;

import android.app.Activity;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MyActivity extends Activity implements View.OnClickListener{
      private OpenHelpClass helper;
      private SQLiteDatabase db;
      private MethodsClass methods;
      private Button btn;

      @Override
      public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            helper = new OpenHelpClass(MyActivity.this, "stu.db", null, 1);
            db = helper.getWritableDatabase();
            createDatas();
            btn.setOnClickListener(this);

      }

      //创建数据，插入数据
      private void createDatas() {
            btn = (Button) findViewById(R.id.check);
            methods = new MethodsClass(db);
            for (int i = 0; i < 20; i++) {

                  methods.DataInset("tom"+i,10+i);
            }
            db.close();
      }

      // 转到新一个activity显示结果
      @Override
      public void onClick(View v) {

            startActivity(new Intent(MyActivity.this, ShowResult.class));

      }
}

4.显示结果的activity
package com.example.CursorDemo;

import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;


public class ShowResult extends Activity {

      private OpenHelpClass helper;
      private SQLiteDatabase db;
      private List<String> list;
      private ListView listView;

      @Override
      protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.items);
            helper = new OpenHelpClass(ShowResult.this, "stu.db", null, 1);
            db = helper.getReadableDatabase();
            GetDataFromDB();
            showInListView(list);
      }

      // 为listView添加适配器
      private void showInListView(List<String> list) {
            listView = (ListView) findViewById(R.id.listview);
            listView.setAdapter(new ArrayAdapter<String>(ShowResult.this, android.R.layout.simple_list_item_1, list));

      }

      //把数据库放到arrsylist中去
      private void GetDataFromDB() {

            list = new ArrayList<String>();
            Cursor c = db.rawQuery("select id,name,age from stu", null);
            for (c.moveToFirst();!c.isAfterLast();c.moveToNext()){

                  list.add("【" + c.getInt(0) + "】" + "   " + c.getString(1) + "   " + c.getInt(2));

            }
            db.close();
      }
}

结果：

来自为知笔记(Wiz)