13 获取外部数据库 以及数据库游标适配器(SimpleCursorAdapter)

时间：2023-03-08 19:02:25
13 获取外部数据库 以及数据库游标适配器(SimpleCursorAdapter)

获取外部数据库

  • API

    SQLiteDatabase db = SQLiteDatabase.openDatabase(path, factory, flags);
  • 参数详解:
    • path:数据库路径
    • factory:游标工厂
    • flags：以什么模式打开
      • SQLiteDatabase.OPEN_READWRITE 可读可写
      • SQLiteDatabase.OPEN_READONLY 可读
  • 代码例子:
File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "info.db");

        SQLiteDatabase db = SQLiteDatabase.openDatabase(file.toString(), null, SQLiteDatabase.OPEN_READONLY);

SimpleCursorAdapter

  • API:
SimpleCursorAdapter adapter = new SimpleCursorAdapter(context, layout, c, from, to, flags);

  • 参数详解

    • context:上下文
    • layout：需要填充的山下文
    • c:数据库游标
    • from:从游标中某一列名（数据库某列名，用于待会填充如布局文件中）
    • to:填充到layout的控件中 控件ID
    • flasg：SimpleCursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER 内容观察者
    • 注意使用此方法主键名必须_id

    • cursor更新时可以用cursor.requery();刷新填充的ListView或者其他控件

    • 代码例子:

package com.fmy.dsas;

import java.io.File;

import android.app.Activity;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.os.Bundle;

import android.os.Environment;

import android.support.v4.widget.SimpleCursorAdapter;

import android.widget.ListView;

import android.widget.Toast;

public class SecondActivity extends Activity {

    private ListView lv;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        lv = (ListView) findViewById(R.id.lv);

        set();

    }

    public void set() {

        File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "info.db");

        SQLiteDatabase db = SQLiteDatabase.openDatabase(file.toString(), null, SQLiteDatabase.OPEN_READONLY);

        Cursor cursor = db.query("person", null, null, null, null, null, null);

        SimpleCursorAdapter adpter = new SimpleCursorAdapter(this, R.layout.item, cursor, new String[] { "name" },

                new int[] { R.id.tv }, SimpleCursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);

        lv.setAdapter(adpter);

    }

}
  • 自定义CursorAdapter
    • 代码例子:
package com.fmy.dsas;

import java.io.File;

import android.app.Activity;

import android.content.Context;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.os.Bundle;

import android.os.Environment;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.CursorAdapter;

import android.widget.ListView;

import android.widget.SimpleAdapter;

import android.widget.SimpleCursorAdapter;

import android.widget.TextView;

public class ThirdlyActivity extends Activity {

    private ListView lv;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        //一个ListView

        lv = (ListView) findViewById(R.id.lv);

        //获取一个数据库的文件地址

        File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "info.db");

        //获得数据库对象

        SQLiteDatabase db = SQLiteDatabase.openDatabase(file.toString(), null, SQLiteDatabase.OPEN_READWRITE);

        //得到游标

        Cursor cursor = db.query("person", null, null, null, null, null, null);

        //创建自定义游标

        MyCurAdpter adpter = new MyCurAdpter(this, cursor, CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);

        lv.setAdapter(adpter);

    }

    class MyCurAdpter extends CursorAdapter {

        public MyCurAdpter(Context context, Cursor c, int flags) {

            super(context, c, flags);

        }

        /**

         * 返回被填充的View

         */

        @Override

        public View newView(Context context, Cursor cursor, ViewGroup parent) {

            LayoutInflater inflater = LayoutInflater.from(context);

            View view = inflater.inflate(R.layout.item, parent, false);

            return view;

        }

        /**

         * 给被填充的view初始化

         */

        @Override

        public void bindView(View view, Context context, Cursor cursor) {

            TextView tv = (TextView) view.findViewById(R.id.tv);

            tv.setText(cursor.getString(cursor.getColumnIndex("name")));

        }

    }

}