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    文件類型: .zip
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    發布日期: 2021-01-22
  • 語言: Java
  • 標簽: GeoHash??

資源簡介

傳統數據庫索引

存儲用戶登入字段主要包括 userId，lat，lng。分別代表用戶 ID、最近一次 check-in 的經度、緯度。
lat/lng 建立復合索引。

然后通過手機的定位，得到自己的位置，比如記為 myLat，myLng。
代碼如下，先做一個計算，算出 1km 所對應的經緯度范圍：
double range = 180 / Math.PI * 1 / 6372.797; //里面的 1 就代表搜索 1km 之內，單位km
double lngR = range / Math.cos(myLat * Math.PI / 180.0);
double maxLat = myLat range;
double minLat = myLat - range;
double maxLng = myLng lngR;
double minLng = myLng - lngR;

然后執行 SQL ：
SELECT xxxx FROM checkinTable WHERE ((lat BETWEEN ? AND ?) AND (lng BETWEEN ? AND ?)) LIMIT 100
這四個問號，分別代入變量
minLat、maxLat、minLng、maxLng

然后就可以查詢得到結果
但是，這樣得到的結果不是有序的。
如果要排序，在程序代碼（比如 app 客戶端）執行。
不建議在 SQL 層上執行，因為上述的那個 SQL 是可以用到索引進行查詢的，一旦引入排序后，索引就無法發揮作用，從而會影響效率。

資源截圖

代碼片段和文件信息 

package?com.andieguoe.locationdemo;

import?java.util.Iterator;

import?android.app.Activity;
import?android.location.GpsSatellite;
import?android.location.GpsStatus;
import?android.location.Location;
import?android.location.LocationListener;
import?android.location.LocationManager;
import?android.os.Bundle;
import?android.util.Log;
import?android.widget.Toast;

public?class?GpsActivity?extends?Activity?{
	private?LocationManager?locationManager;
	private?GpsStatus?gpsstatus;
	private?static?final?String?TAG?=?“GpsActivity“;
	@Override
	protected?void?onCreate（Bundle?savedInstanceState）?{
		//?TODO?Auto-generated?method?stub
		super.onCreate（savedInstanceState）;
		setContentView（R.layout.gps）;

		//?獲取到LocationManager對象
		locationManager?=?（LocationManager）?getSystemService（LOCATION_SERVIC

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\
?????文件?????????474??2014-10-22?15:13??nearbydemo-master\.gitignore
?????文件?????????648??2014-10-22?15:13??nearbydemo-master\GETDISTANCE.sql
?????文件???????11515??2014-10-22?15:13??nearbydemo-master\LICENSE
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\
?????文件?????????356??2014-10-22?15:13??nearbydemo-master\LocationDemo\.classpath
?????文件?????????815??2014-10-22?15:13??nearbydemo-master\LocationDemo\.project
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\.settings\
?????文件?????????173??2014-10-22?15:13??nearbydemo-master\LocationDemo\.settings\org.eclipse.jdt.core.prefs
?????文件????????1359??2014-10-22?15:13??nearbydemo-master\LocationDemo\AndroidManifest.xml
?????文件???????51394??2014-10-22?15:13??nearbydemo-master\LocationDemo\ic_launcher-web.png
?????文件?????????781??2014-10-22?15:13??nearbydemo-master\LocationDemo\proguard-project.txt
?????文件?????????563??2014-10-22?15:13??nearbydemo-master\LocationDemo\project.properties
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\drawable-hdpi\
?????文件????????7658??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\drawable-hdpi\ic_launcher.png
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\drawable-mdpi\
?????文件????????3777??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\drawable-mdpi\ic_launcher.png
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\drawable-xhdpi\
?????文件???????12516??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\drawable-xhdpi\ic_launcher.png
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\drawable-xxhdpi\
?????文件???????24777??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\drawable-xxhdpi\ic_launcher.png
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\layout\
?????文件?????????618??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\layout\gps.xml
?????文件????????1218??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\layout\main.xml
?????文件?????????621??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\layout\network.xml
?????文件?????????621??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\layout\telepony.xml
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\menu\
?????文件?????????253??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\menu\main.xml
?????目錄???????????0??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\values-sw600dp\
?????文件?????????195??2014-10-22?15:13??nearbydemo-master\LocationDemo\res\values-sw600dp\dimens.xml
............此處省略186個文件信息

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