Android开发实现读取assets目录下db文件的方法示例

本文实例讲述了android开发实现读取assets目录下db文件的方法。分享给大家供大家参考，具体如下：

最近准备打算写一个关于天气预报的app，偶然的机会在一大神的博客上看到了一个获取天气的api，获取天气是通过城市的cityid，项目中准备通过读取weather_city.db数据库来查询cityid，这篇文章写怎么读取assets目录下的db文件，其实方法也挺简单的就是把assets目录下的db文件复制一份到”/data/data/” + packname + “/”目录下而已。

public class dbmanager {
  private string db_name = "weather_city.db";
  private context mcontext;
  public dbmanager(context mcontext) {
    this.mcontext = mcontext;
  }
  //把assets目录下的db文件复制到dbpath下
  public sqlitedatabase dbmanager(string packname) {
    string dbpath = "/data/data/" + packname
        + "/databases/" + db_name;
    if (!new file(dbpath).exists()) {
      try {
        fileoutputstream out = new fileoutputstream(dbpath);
        inputstream in = mcontext.getassets().open("weather_city.db");
        byte[] buffer = new byte[1024];
        int readbytes = 0;
        while ((readbytes = in.read(buffer)) != -1)
          out.write(buffer, 0, readbytes);
        in.close();
        out.close();
      } catch (ioexception e) {
        e.printstacktrace();
      }
    }
    return sqlitedatabase.openorcreatedatabase(dbpath, null);
  }
  //查询
  public city query(sqlitedatabase sqlitedb, string[] columns, string selection, string[] selectionargs) {
    city city = null;
    try {
      string table = "city";
      cursor cursor = sqlitedb.query(table, columns, selection, selectionargs, null, null, null);
      if (cursor.movetofirst()) {
        string parentcity = cursor.getstring(cursor
            .getcolumnindex("parent"));
        string phonecode = cursor.getstring(cursor.getcolumnindex("phone_code"));
        string name = cursor.getstring(cursor.getcolumnindex("name"));
        string pinyin = cursor.getstring(cursor.getcolumnindex("pinyin"));
        string cityid = cursor.getstring(cursor.getcolumnindex("posid"));
        string areacode = cursor.getstring(cursor.getcolumnindex("area_code"));
        city = new city(parentcity, name, pinyin, phonecode, cityid, areacode);
        cursor.movetonext();
        cursor.close();
      }
    } catch (exception e) {
      e.printstacktrace();
    }
    return city;
  }
}

为了方便数据的使用，我们建一个city类，对应city表中的字段，如下：

public class city {
  private string parentcity;
  private string childcity;
  private string pinyin;
  private string phonecode;
  private string cityid;
  private string areacode;
  public city(string parentcity, string childcity, string pinyin, string phonecode, string cityid, string areacode) {
    this.parentcity = parentcity;
    this.childcity = childcity;
    this.pinyin = pinyin;
    this.phonecode = phonecode;
    this.cityid = cityid;
    this.areacode = areacode;
  }
  public string getparentcity() {
    return parentcity;
  }
  public void setparentcity(string parentcity) {
    this.parentcity = parentcity;
  }
  public string getareacode() {
    return areacode;
  }
  public void setareacode(string areacode) {
    this.areacode = areacode;
  }
  public string getcityid() {
    return cityid;
  }
  public void setcityid(string cityid) {
    this.cityid = cityid;
  }
  public string getphonecode() {
    return phonecode;
  }
  public void setphonecode(string phonecode) {
    this.phonecode = phonecode;
  }
  public string getpinyin() {
    return pinyin;
  }
  public void setpinyin(string pinyin) {
    this.pinyin = pinyin;
  }
  public string getchildcity() {
    return childcity;
  }
  public void setchildcity(string childcity) {
    this.childcity = childcity;
  }
}

测试代码：

@override
protected void oncreate(bundle savedinstancestate) {
    super.oncreate(savedinstancestate);
    setcontentview(r.layout.activity_main);
    contenttextview = (textview) findviewbyid(r.id.content);
    dbmanager = new dbmanager(this);
    sqlitedatabase = dbmanager.initdbmanager(getpackagename());
    string[] columns = new string[]{"parent", "name", "posid", "pinyin", "phone_code", "area_code"};
    string selection = "parent=?" + "and" + " name=?";
    string[] selectionargs = new string[]{"北京", "丰台"};
    city city = dbmanager.query(sqlitedatabase, columns, selection, selectionargs);
    contenttextview.settext("邮编：" + city.getareacode() + "拼音：" + city.getpinyin() + "电话区号" + city.getphonecode() + "cityid:" + city.getcityid());
}

读取的数据与表中的数据一致

更多关于android相关内容感兴趣的读者可查看本站专题：《android文件操作技巧汇总》、《android操作sqlite数据库技巧总结》、《android视图view技巧总结》、《android编程之activity操作技巧总结》、《android布局layout技巧总结》、《android开发入门与进阶教程》、《android资源操作技巧汇总》及《android控件用法总结》

希望本文所述对大家android程序设计有所帮助。