我正在尝试阻止displayDistance函数运行，直到我单击按钮。它继续运行该函数，我假设因为值被传递给它所以它会自动调用它我猜？我需要它在窗口加载时显示当前的纬度/经度，然后在按钮点击后显示到每个位置的距离。现在它在窗口加载
上显示所有内容 window.addEventListener("load", setupEventHandlers, false);
window.addEventListener("load", displayLocation, false);
function setupEventHandlers() {
console.log("Inside setupEventHandlers function that is fired on the window load event");
var displayButtonReference = document.getElementById("butCalculate");
displayButtonReference.addEventListener("click", displayDistance, false);
}
//-------------------------------------------------------------------------------
// Name: displayLocation()
// Description:
//-------------------------------------------------------------------------------
function displayLocation() {
console.log("displayLocation function called!");
//Call getCurrentPosition() method to retrieve current position data
//This is an asynchronous call.
//When completed it calls the cb_GetCurrentPosition_Success callback function
//navigator.geolocation.getCurrentPosition(cb_GetCurrentPosition_Success);
navigator.geolocation.getCurrentPosition(cb_GetCurrentPosition_Success,
cb_GetCurrentPosition_Error,
{
enableHighAccuracy: true,
maximumAge: 5000
}
);
}
//-------------------------------------------------------------------------------
// Name: cb_GetCurrentPosition_Success
// Description: Callback function if GeoLocation info retrieved successfully
//-------------------------------------------------------------------------------
function cb_GetCurrentPosition_Success(positionObject) {
console.log("cb_GetCurrentPosition_Success callback function called!");
//Show returned positionObject in Inspect Element Console
console.dir(positionObject);
//1. Declare variables
var accuracy,
distanceInKilometers,
distanceInFeet,
distanceInMiles,
displayString,
currentLat,
currentLong;
//Extract geolocation data from returned object
currentLat = positionObject.coords.latitude;
currentLong = positionObject.coords.longitude;
console.log("distanceInFeet = " + distanceInFeet);
distanceInFeet = calculateDistanceInFeet(currentLat, currentLong)
//Display retrieved Geolocation data
document.getElementById("divLat").innerHTML = currentLat;
document.getElementById("divLon").innerHTML = currentLong;
}
//---------------------------------------------------------------------------------------
// Name: cb_GetCurrentPosition_Error
// Description: Callback function if there is a problem retrieving GeoLocation info
//---------------------------------------------------------------------------------------
function cb_GetCurrentPosition_Error(err) {
var errorMessage;
if (err.code == 1) {
errorMessage = "You chose not to share your location info.";
}
else if (err.code == 2) {
errorMessage = "Location information currently unavailable!";
}
else if (err.code == 3) {
errorMessage = "Timed out waiting to receive location information!";
}
else {
errorMessage = "Unknown error occured";
}
}
// ---------------------------------------------------------------------------------------
// name: calculateDistanceInFeet
// source: http://www.codecodex.com/wiki/Calculate_distance_between_two_points_on_a_globe
// ---------------------------------------------------------------------------------------
function calculateDistanceInFeet(parcurrentLat, parcurrentLon) {
console.log("calculateDistanceInFeet function called!");
console.log("parcurrentLat = " + parcurrentLat);
console.log("parcurrentLon = " + parcurrentLon);
var distanceInKilometersToRamsey,
distanceInKilometersToPicnic,
distanceInFeetToRamsey,
distanceInFeetToPicnic,
Lat1 = 35.303209, //Ramsey Coordinates
Lon1 = -83.182745,
Lat2 = 35.314455, //Picnic Shelter Coordinates
Lon2 = -83.188011;
//Distance to Ramsey
//Code retrieved from source shown above - don't modify
//-------------------------------------------------------
var R1 = 6371; // km
var dLat1 = (Lat1 - parcurrentLat) * Math.PI / 180;
var dLon1 = (Lon1 - parcurrentLon) * Math.PI / 180;
var a1 = Math.sin(dLat1 / 2) * Math.sin(dLat1 / 2) +
Math.cos(parcurrentLat * Math.PI / 180) * Math.cos(Lat1 * Math.PI / 180) *
Math.sin(dLon1 / 2) * Math.sin(dLon1 / 2);
var c1 = 2 * Math.asin(Math.sqrt(a1));
distanceInKilometersToRamsey = R1 * c1;
//---------------------------------------------------------
//end of code to not modify
//Distance to Picnic
//Code retrieved from source shown above - don't modify
//-------------------------------------------------------
var R2 = 6371; // km
var dLat2 = (Lat2 - parcurrentLat) * Math.PI / 180;
var dLon2 = (Lon2 - parcurrentLon) * Math.PI / 180;
var a2 = Math.sin(dLat2 / 2) * Math.sin(dLat2 / 2) +
Math.cos(parcurrentLat * Math.PI / 180) * Math.cos(Lat2 * Math.PI / 180) *
Math.sin(dLon2 / 2) * Math.sin(dLon2 / 2);
var c2 = 2 * Math.asin(Math.sqrt(a2));
distanceInKilometersToPicnic = R2 * c2;
//---------------------------------------------------------
//end of code to not modify
//3. Do calculations
distanceInFeetToRamsey = distanceInKilometersToRamsey * 1000 * 3.2808;
distanceInFeetToPicnic = distanceInKilometersToPicnic * 1000 * 3.2808;
var passedDistance = displayDistance(distanceInFeetToRamsey, distanceInFeetToPicnic);
console.log("distanceInFeetToRamsey = " + distanceInFeetToRamsey);
console.log("distanceInFeetToPicnic = " + distanceInFeetToPicnic);
}
function displayDistance(parRamsey, parPicnic) {
if (parRamsey >= 5280) {
var distanceInMilesToRamsey = parRamsey / 5280;
document.getElementById("divDistance1").innerHTML = distanceInMilesToRamsey.toFixed(2) + "miles";
}
else {
document.getElementById("divDistance1").innerHTML = parPicnic.toFixed(2) + "feet";
}
if (parPicnic >= 5280) {
var distanceInMilesToPicnic = distanceInFeetToPicnic / 5280;
document.getElementById("divDistance2").innerHTML = distanceInMilesToPicnic.toFixed(2) + "miles";
}
else {
document.getElementById("divDistance2").innerHTML = parPicnic.toFixed(2) + "feet";
}
}
答案 0 :(得分：0)
displayDistance由load事件间接调用：
加载调用displayLocation：
window.addEventListener("load", displayLocation, false);
displayLocation调用cb_GetCurrentPosition_Success（通过回调）：
navigator.geolocation.getCurrentPosition(cb_GetCurrentPosition_Success,
cb_GetCurrentPosition_Error,
{
enableHighAccuracy: true,
maximumAge: 5000
}
);
cb_GetCurrentPosition_Success调用calculateDistanceInFeet：
distanceInFeet = calculateDistanceInFeet(currentLat, currentLong)
calculateDistanceInFeet调用displayDistance：
var passedDistance = displayDistance(distanceInFeetToRamsey, distanceInFeetToPicnic);