我的 FirstActivity 包含此代码
mHandler.postDelayed(mLaunchTask,10000);
private Runnable mLaunchTask = new Runnable()
{
public void run()
{
Intent i = new Intent(getApplicationContext(),NearestPoint.class);
Bundle params = new Bundle();
params.putFloat("latiA", latA);
params.putFloat("longiA", longA);
params.putFloat("latiB", latB);
params.putFloat("longiB", longB);
params.putFloat("latiC", latC);
params.putFloat("longiC", longC);
i.putExtras(params);
startActivity(i);
}
};
NearestPoint 活动包含此代码
public float latA, longA, latB, longB, latC, longC;
Intent it = getIntent(); {
if (it != null)
{
Bundle params = it.getExtras();
if (params != null)
{
latA = params.getFloat("latiA");
longA = params.getFloat("longiA");
latB = params.getFloat("latiB");
longB = params.getFloat("longiB");
latC = params.getFloat("latiC");
longC = params.getFloat("longiC");
}
}}
我无法在 NearestPoint 活动中正确访问 latA、longA 等的值。我尝试使用 Toast 显示：
Toast.makeText(getApplicationContext(),"\nPoint A: \nLatitude: " + latA + "\nLongitude: " + longA, Toast.LENGTH_LONG).show();
在 FirstActivity 它给出了正确的值，但在 NearestPoint 我得到 0.0 作为纬度和经度。
这是我的清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.gpsdistance"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="16" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.gpsdistance.FirstActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.example.gpsdistance.NearestPoint"
android:label="@string/title_activity_nearest_point" >
</activity>
<activity
android:name="com.example.gpsdistance.MinimumDistance"
android:label="@string/title_activity_minimum_distance" >
</activity>
</application>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />
</manifest>
这是我完整的 FirstActivity 课程：
package com.example.gpsdistance;
import android.os.Bundle;
import android.os.Handler;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
public class FirstActivity extends Activity {
Button btnShowLocation, btnMinDis;
TextView display= null;
//private final Context mctx;
double latuser;
double longuser;
double dx1, dy1, delta_long1, delta_lat1, final_long1, final_lat1;
double dx2, dy2, delta_long2, delta_lat2, final_long2, final_lat2;
double dx3, dy3, delta_long3, delta_lat3, final_long3, final_lat3;
public float latA, longA, latB, longB, latC, longC;
public String latiA, longiA, latiB, longiB, latiC, longiC ;
// GPSTracker class
GPSTracker gps;
void getGPS()
{
gps = new GPSTracker(FirstActivity.this);
}
void points()
{
latuser = gps.getLatitude();
longuser = gps.getLongitude();
dx1 = 120*Math.cos(35);
dy1 = 120*Math.sin(35);
delta_long1 = dx1/(111320*Math.cos(latuser));
delta_lat1 = dy1/110540;
final_long1 = longuser + delta_long1;
final_lat1 = latuser + delta_lat1;
dx2 = 150*Math.cos(38);
dy2 = 150*Math.sin(38);
delta_long2 = dx2/(111320*Math.cos(latuser));
delta_lat2 = dy2/110540;
final_long2 = longuser + delta_long2;
final_lat2 = latuser + delta_lat2;
dx3 = 180*Math.cos(38);
dy3 = 180*Math.sin(38);
delta_long3 = dx3/(111320*Math.cos(latuser));
delta_lat3 = dy3/110540;
final_long3 = longuser + delta_long3;
final_lat3 = latuser + delta_lat3;
latA= (float)final_lat1;
longA= (float)final_long1;
latB= (float)final_lat2;
longB= (float)final_long2;
latC= (float)final_lat3;
longC= (float)final_long3;
}
private float getLatiA() {
return this.latA;
}
/*public FirstActivity(Context ctx)
{
this.mctx = ctx;
getGPS();
points();
} */
private float computeDistance(double lat1, double lon1,
double lat2, double lon2) {
// Based on http://www.ngs.noaa.gov/PUBS_LIB/inverse.pdf
// using the "Inverse Formula" (section 4)
int MAXITERS = 20;
// Convert lat/long to radians
lat1 *= Math.PI / 180.0;
lat2 *= Math.PI / 180.0;
lon1 *= Math.PI / 180.0;
lon2 *= Math.PI / 180.0;
double a = 6378137.0; // WGS84 major axis
double b = 6356752.3142; // WGS84 semi-major axis
double f = (a - b) / a;
double aSqMinusBSqOverBSq = (a * a - b * b) / (b * b);
double L = lon2 - lon1;
double A = 0.0;
double U1 = Math.atan((1.0 - f) * Math.tan(lat1));
double U2 = Math.atan((1.0 - f) * Math.tan(lat2));
double cosU1 = Math.cos(U1);
double cosU2 = Math.cos(U2);
double sinU1 = Math.sin(U1);
double sinU2 = Math.sin(U2);
double cosU1cosU2 = cosU1 * cosU2;
double sinU1sinU2 = sinU1 * sinU2;
double sigma = 0.0;
double deltaSigma = 0.0;
double cosSqAlpha = 0.0;
double cos2SM = 0.0;
double cosSigma = 0.0;
double sinSigma = 0.0;
double cosLambda = 0.0;
double sinLambda = 0.0;
double lambda = L;
for (int iter = 0; iter < MAXITERS; iter++) {
double lambdaOrig = lambda;
cosLambda = Math.cos(lambda);
sinLambda = Math.sin(lambda);
double t1 = cosU2 * sinLambda;
double t2 = cosU1 * sinU2 - sinU1 * cosU2 * cosLambda;
double sinSqSigma = t1 * t1 + t2 * t2;
sinSigma = Math.sqrt(sinSqSigma);
cosSigma = sinU1sinU2 + cosU1cosU2 * cosLambda;
sigma = Math.atan2(sinSigma, cosSigma);
double sinAlpha = (sinSigma == 0) ? 0.0 :
cosU1cosU2 * sinLambda / sinSigma;
cosSqAlpha = 1.0 - sinAlpha * sinAlpha;
cos2SM = (cosSqAlpha == 0) ? 0.0 :
cosSigma - 2.0 * sinU1sinU2 / cosSqAlpha;
double uSquared = cosSqAlpha * aSqMinusBSqOverBSq;
A = 1 + (uSquared / 16384.0) *
(4096.0 + uSquared *
(-768 + uSquared * (320.0 - 175.0 * uSquared)));
double B = (uSquared / 1024.0) *
(256.0 + uSquared *
(-128.0 + uSquared * (74.0 - 47.0 * uSquared)));
double C = (f / 16.0) *
cosSqAlpha *
(4.0 + f * (4.0 - 3.0 * cosSqAlpha));
double cos2SMSq = cos2SM * cos2SM;
deltaSigma = B * sinSigma *
(cos2SM + (B / 4.0) *
(cosSigma * (-1.0 + 2.0 * cos2SMSq) -
(B / 6.0) * cos2SM *
(-3.0 + 4.0 * sinSigma * sinSigma) *
(-3.0 + 4.0 * cos2SMSq)));
lambda = L +
(1.0 - C) * f * sinAlpha *
(sigma + C * sinSigma *
(cos2SM + C * cosSigma *
(-1.0 + 2.0 * cos2SM * cos2SM)));
double delta = (lambda - lambdaOrig) / lambda;
if (Math.abs(delta) < 1.0e-12) {
break;
}
}
float distance = (float) (b * A * (sigma - deltaSigma));
return distance;
}
/*public FirstActivity()
{
getGPS();
if(gps.canGetLocation())
points();
}*/
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.firstactivity);
final LinearLayout lView = new LinearLayout(this);
display= new TextView(this);
btnMinDis=new Button(this);
btnMinDis.setText("Nearest Point");
final Handler mHandler = new Handler();
btnShowLocation = (Button) findViewById(R.id.buttonLocation);
btnShowLocation.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0)
{
// TODO Auto-generated method stub
getGPS();
// check if GPS enabled
if(gps.canGetLocation())
{
points();
float initialdisA = computeDistance( latuser, longuser, latA, longA);
float initialdisB = computeDistance( latuser, longuser, latB, longB);
float initialdisC = computeDistance( latuser, longuser, latC, longC);
Toast.makeText(getApplicationContext(),"Point A: \nLatitude: " + latA + "\nLongitude: " + longA, Toast.LENGTH_LONG).show();
lView.addView(display);
setContentView(lView);
display.setText("Initial Location is - \nLatitude: " + latuser + " N" + "\nLongitude: " + longuser + " E"
+ "\n\n\nPoint A:\n" + "Latitude: " + latA + "N" + "\nLongitude: " + longA + "E"
+ "\nPoint B:\n" + "Latitude: " + latB + "N" + "\nLongitude: " + longB + "E"
+ "\nPoint C:\n" + "Latitude: " + latC + "N" + "\nLongitude: " + longC + "E"
+ "\n\n\nInitial Distance A: " + initialdisA + "m" + "\nInitial Distance B: " + initialdisB + "m" + "\nInitial Distance C: " + initialdisC + "m");
mHandler.postDelayed(mLaunchTask,10000);
}
else
{
// GPS or Network is not enabled
// Ask user to enable GPS/network in settings
gps.showSettingsAlert();
}
}
private Runnable mLaunchTask = new Runnable()
{
public void run()
{
Intent i = new Intent(getApplicationContext(),NearestPoint.class);
Bundle params = new Bundle();
params.putFloat("latiA", getLatiA());
params.putFloat("longiA", longA);
params.putFloat("latiB", latB);
params.putFloat("longiB", longB);
params.putFloat("latiC", latC);
params.putFloat("longiC", longC);
i.putExtras(params);
startActivity(i);
}
};
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.firstactivity, menu);
return true;
}
}
这是完整项目的链接： http ://www.filedropper.com/gpsdistance
请帮忙。