java安卓如何使用javaclass。这是一节零碎的课
我正在尝试在我的Android应用程序中使用GPS系统。我正在关注这个tutorial
当我试图调用我的javaclass时。这是我在如何做的上下文中遇到的一个错误
这是我的java课程
import 安卓.support.v4.app.Fragment;
import com.lifesymb.lifesymb.R;
import 安卓.os.Bundle;
import 安卓.view.LayoutInflater;
import 安卓.view.View;
import 安卓.view.ViewGroup;
import 安卓.widget.Button;
import 安卓.widget.RelativeLayout;
import 安卓.widget.Toast;
public class gps extends Fragment {
Button btnShowLocation;
// GPSTracker class
GPSTracker gps;
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (container == null) {
return null;
}
RelativeLayout mRelativeLayout = (RelativeLayout) inflater.inflate(R.layout.gps,
container, false);
// note that we're looking for a button with id="@+id/myButton" in your inflated layout
// Naturally, this can be any View; it doesn't have to be a button
// note that we're looking for a button with id="@+id/myButton" in your inflated layout
// Naturally, this can be any View; it doesn't have to be a button
btnShowLocation = (Button) mRelativeLayout.findViewById(R.id.gps1);
// show location button click event
btnShowLocation.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// create class object
gps = new GPSTracker(gps.this);
// check if GPS enabled
if(gps.canGetLocation()){
double latitude = gps.getLatitude();
double longitude = gps.getLongitude();
// \n is for new line
Toast.makeText(getActivity(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();
}else{
// can't get location
// GPS or Network is not enabled
// Ask user to enable GPS/network in settings
gps.showSettingsAlert();
}
}
});
我在以下几行有一个错误
gps = new GPSTracker(gps.this) ( The constructor GPSTracker(gps) is undefined)
这是我的GPSTracker。java文件
import 安卓.app.AlertDialog;
import 安卓.app.Service;
import 安卓.content.Context;
import 安卓.content.DialogInterface;
import 安卓.content.Intent;
import 安卓.location.Location;
import 安卓.location.LocationListener;
import 安卓.location.LocationManager;
import 安卓.os.Bundle;
import 安卓.os.IBinder;
import 安卓.provider.Settings;
import 安卓.util.Log;
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
// flag for GPS status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
// flag for GPS status
boolean canGetLocation = false;
Location location; // location
double latitude; // latitude
double longitude; // longitude
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute
// Declaring a Location Manager
protected LocationManager locationManager;
public GPSTracker(Context context) {
this.mContext = context;
getLocation();
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext
.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
// First get location from Network Provider
if (isNetworkEnabled) {
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return location;
}
/**
* Stop using GPS listener
* Calling this function will stop using GPS in your app
* */
public void stopUsingGPS(){
if(locationManager != null){
locationManager.removeUpdates(GPSTracker.this);
}
}
/**
* Function to get latitude
* */
public double getLatitude(){
if(location != null){
latitude = location.getLatitude();
}
// return latitude
return latitude;
}
/**
* Function to get longitude
* */
public double getLongitude(){
if(location != null){
longitude = location.getLongitude();
}
// return longitude
return longitude;
}
/**
* Function to check GPS/wifi enabled
* @return boolean
* */
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
* On pressing Settings button will lauch Settings Options
* */
public void showSettingsAlert(){
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
// Setting Dialog Title
alertDialog.setTitle("GPS is settings");
// Setting Dialog Message
alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");
// On pressing Settings button
alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int which) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// on pressing cancel button
alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}
@Override
public void onLocationChanged(Location location) {
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public IBinder onBind(Intent arg0) {
return null;
}
}
所以你可以告诉我怎么做。我在普通类中尝试过，但我无法理解片段类的用法
# 1 楼答案
首先，您的
GPSTracker类在扩展Service时已经表示它正在扩展Context。。。那么，为什么需要使用上下文作为参数的GPSTracker参数化构造函数呢？您可以直接在服务中调用getApplicationContext()，也可以使用this引用，因为服务是一个上下文其次，不建议（我认为这不是一种方法）为
Service（甚至对于Activity，BroadCastReceiver等）使用参数化构造函数。如果有参数化构造函数，那么必须定义默认构造函数第三，这不是手动为
Service创建对象（实例）的方法，即使Service是一个简单的Java类。系统将负责实例化Service最后，正如其他答案所说，
Fragment并不扩展Context。所以你应该使用getActivity()# 2 楼答案
Fragment不是从Context扩展而来的，因此不能将Fragment（或者因此将gps对象）传递到GPSTracker构造函数中。但是，您可以在Fragment上调用.getActivity()，以获取它的关联Activity，它是从^{# 3 楼答案
在片段类中使用
getActivity()getActivity()返回与此片段关联的活动this指当前上下文gps是一个片段。所以使用getActivity()和碎片
public class GPSTracker extends Service是一项服务你有这个
而是启动服务或将服务绑定到活动
你可以使用
getApplicationContext()为了给你一个更好的想法，请通过Commonware查看详细的答案
When to call activity context OR application context?