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>