自定义POI点，根据搜索半径进行POI搜索

接上一篇，即经纬度坐标文件已导入

最近这一个月才开始学习Java，所以拿到这个问题时从最基本的功能实现做起：

1. 实现txt文件的存入和读出；

2. 实现已知两点经纬度算出两点间距离；（这一步为了简单是把所有值存入数组做的）

3. 实现读入一组值就计算一组值；

MainActivity.java 文件代码

package com.example.distance;

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

import android.os.Bundle;
import android.os.SystemClock;
import android.R.integer;
import android.R.string;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {

@SuppressLint("SdCardPath")
String filepath = "/mnt/sdcard/android_txt1.txt";
//注意EditText初始化不要写在这里，会报unable to instantiate activity componentinfo nullpointerexception 错误
//EditText distanceEditText  = (EditText)findViewById(R.id.distance);
//EditText displaypoiText  = (EditText)findViewById(R.id.displaypoi);
//中心点 景山公园
double lat1 = 39.932221;
double lon1 = 116.403007;

String s1 = "";

//中心点
double lats = (Math.PI/180)*lat1;
double lons = (Math.PI/180)*lon1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.i("onCreat", "set");

}

private void getpoi(double s,int i) {
// TODO Auto-generated method stub

String s2[] = {"北海","故宫博物院","东城区政府"};
//比较计算出的两点间距离和用户输入的搜索半径
EditText distanceEditText  = (EditText)findViewById(R.id.distance);
double searchdistance = Double.parseDouble(distanceEditText.getText().toString());
if (s < searchdistance)
{

s1=s1+s2[i]+'\t'+Double.toString(s)+'\t';
}
}

private double  getdistance(double lon, double lat) {
// TODO Auto-generated method stub
//传入待计算的点
double latd = (Math.PI/180)*lat;
double lond = (Math.PI/180)*lon;
double a = lats-latd;
double b = lons-lond;
//地球半径
double R = 6378.137;
//已知两点经纬度计算距离的公式
double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2) +
Math.cos(lats)*Math.cos(latd)*Math.pow(Math.sin(b/2),2)));
s=s*R;
s= s*1000;
return s;
}

private void readF1(String filePath)  throws IOException{
// TODO Auto-generated method stub

BufferedReader br = new BufferedReader(new InputStreamReader(
new FileInputStream(filepath)));
int i =0;
double d1,d2,spoi;
String s1="";
for (String line = br.readLine(); line != null; line = br.readLine()) {
//因为txt文件中经纬度是按行写的，所以这里按行读出
d1= Double.parseDouble(line);

line = br.readLine();
d2= Double.parseDouble(line);
spoi = getdistance(d1, d2);
getpoi(spoi, i);

i++;
Log.i("d1",Double.toString(d1) );
Log.i("d2", Double.toString(d2));

}
br.close();

}

public void beginsearch(View v) {

EditText displaypoiText  = (EditText)findViewById(R.id.displaypoi);

try {
readF1(filepath);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

if (s1=="") {	displaypoiText.setText("未找到结果");

}
else {
displaypoiText.setText(s1);}
s1= "";

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}

activity_main.xml 文件代码

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<!-- 搜索后text会被替换掉 -->

<EditText
android:id="@+id/displaypoi"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/distance"
android:layout_marginTop="27dp"
android:cursorVisible="true"
android:editable="true"
android:ems="10"
android:text="正在查找" />

<!-- 设定搜索半径 -->
<EditText
android:id="@+id/distance"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"

android:layout_marginTop="32dp"
android:cursorVisible="true"
android:editable="true"
android:ems="10"
android:text="1000" />

</RelativeLayout>