问题描述
我要做的就是让用户获得他喜欢的类型的地方的列表.例如,如果输入是医院,我的应用程序将使用搜索字符串医院"打开谷歌地图.但正如使用地理编码的文档中所建议的那样 geo:0,0?q=hospital
uri 显示坐标 0 纬度附近的所有医院 &0 经度.因此,当我尝试使用以下代码首先获取用户坐标时.
All I am trying to do is let the user get a list of the places of types he likes. For example if the input was hospital my application would open google maps with the search string "Hospital". But as suggested in the documentation using the geocode like geo:0,0?q=hospital
uri shows all the hospitals near the coordinates 0 latitude & 0 longitude. So when I tried to get the users coordinates first by using the following code.
地方 Decoder.java
Places Decoder.java
package com.kkze.Mappy;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationManager;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.provider.Settings;
import android.text.TextUtils;
import android.util.Log;
import android.widget.Toast;
public class PlacesDecoder extends Activity {
Intent intentThatCalled;
public double latitude;
public double longitude;
public LocationManager locationManager;
public Criteria criteria;
public String bestProvider;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
intentThatCalled = getIntent();
String voice2text = intentThatCalled.getStringExtra("v2txt");
getLocation(voice2text);
}
public static boolean isLocationEnabled(Context context)
{
int locationMode = 0;
String locationProviders;
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT)
{
try
{
locationMode = Settings.Secure.getInt(context.getContentResolver(), Settings.Secure.LOCATION_MODE);
} catch (Settings.SettingNotFoundException e) {
e.printStackTrace();
}
return locationMode != Settings.Secure.LOCATION_MODE_OFF;
}
else
{
locationProviders = Settings.Secure.getString(context.getContentResolver(), Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
return !TextUtils.isEmpty(locationProviders);
}
}
public void getLocation(String voice2txt) {
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
criteria = new Criteria();
bestProvider = String.valueOf(locationManager.getBestProvider(criteria, true)).toString();
Location location = locationManager.getLastKnownLocation(bestProvider);
if (isLocationEnabled(PlacesDecoder.this)) {
Log.e("TAG", "GPS is on");
latitude = location.getLatitude();
longitude = location.getLongitude();
Toast.makeText(PlacesDecoder.this, "latitude:" + latitude + " longitude:" + longitude, Toast.LENGTH_SHORT).show();
searchNearestPlace(voice2txt);
}
else
{
AlertDialog.Builder notifyLocationServices = new AlertDialog.Builder(PlacesDecoder.this);
notifyLocationServices.setTitle("Switch on Location Services");
notifyLocationServices.setMessage("Location Services must be turned on to complete this action. Also please take note that if on a very weak network connection, such as 'E' Mobile Data or 'Very weak Wifi-Connections' it may take even 15 mins to load. If on a very weak network connection as stated above, location returned to application may be null or nothing and cause the application to crash.");
notifyLocationServices.setPositiveButton("Ok, Open Settings", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Intent openLocationSettings = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
PlacesDecoder.this.startActivity(openLocationSettings);
finish();
}
});
notifyLocationServices.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
notifyLocationServices.show();
}
}
public void searchNearestPlace(String v2txt) {
Log.e("TAG", "Started");
v2txt = v2txt.toLowerCase();
String[] placesS = {"accounting", "airport", "aquarium", "atm", "attraction", "bakery", "bakeries", "bank", "bar", "cafe", "campground", "casino", "cemetery", "cemeteries", "church", "courthouse", "dentist", "doctor", "electrician", "embassy", "embassies", "establishment", "finance", "florist", "food", "grocery", "groceries", "supermarket", "gym", "health", "hospital", "laundry", "laundries", "lawyer", "library", "libraries", "locksmith", "lodging", "mosque", "museum", "painter", "park", "parking", "pharmacy", "pharmacies", "physiotherapist", "plumber", "police", "restaurant", "school", "spa", "stadium", "storage", "store", "synagog", "synagogue", "university", "universities", "zoo"};
String[] placesM = {"amusement park", "animal care", "animal care", "animal hospital", "art gallery", "art galleries", "beauty salon", "bicycle store", "book store", "bowling alley", "bus station", "car dealer", "car rental", "car repair", "car wash", "city hall", "clothing store", "convenience store", "department store", "electronics store", "electronic store", "fire station", "funeral home", "furniture store", "gas station", "general contractor", "hair care", "hardware store", "hindu temple", "home good store", "homes good store", "home goods store", "homes goods store", "insurance agency", "insurance agencies", "jewelry store", "liquor store", "local government office", "meal delivery", "meal deliveries", "meal takeaway", "movie rental", "movie theater", "moving company", "moving companies", "night club", "pet store", "place of worship", "places of worship", "post office", "real estate agency", "real estate agencies", "roofing contractor", "rv park", "shoe store", "shopping mall", "subway station", "taxi stand", "train station", "travel agency", "travel agencies", "veterinary care"};
int index;
for (int i = 0; i <= placesM.length - 1; i++) {
Log.e("TAG", "forM");
if (v2txt.contains(placesM[i])) {
Log.e("TAG", "sensedM?!");
index = i;
Uri gmmIntentUri = Uri.parse("geo:" + latitude + "," + longitude + "?q=" + placesM[index]);
Intent mapIntent = new Intent(Intent.ACTION_VIEW, gmmIntentUri);
mapIntent.setPackage("com.google.android.apps.maps");
startActivity(mapIntent);
finish();
}
}
for (int i = 0; i <= placesS.length - 1; i++) {
Log.e("TAG", "forS");
if (v2txt.contains(placesS[i])) {
Log.e("TAG", "sensedS?!");
index = i;
Uri gmmIntentUri = Uri.parse("geo:" + latitude + "," + longitude + "?q=" + placesS[index]);
Intent mapIntent = new Intent(Intent.ACTION_VIEW, gmmIntentUri);
mapIntent.setPackage("com.google.android.apps.maps");
startActivity(mapIntent);
finish();
}
}
}
}
问题是位置总是返回空值.而且我知道一个事实,只要启用了位置,另一个应用程序 Jarvis 就可以轻松完成任务,如果不是,则只是要求用户这样做.但在相同条件下,我的应用程序总是崩溃.
The problem is that always and always location returns null. And I know for a fact that another application Jarvis easily does the task as long as location is enabled, if not is simply asks the user to. But under the same conditions my application always crashes.
我做了什么:
- 日以继夜地试图解决这个问题.
- 浏览了有关该主题的大量页面.
- 尝试了我自己的不同代码.
它仍然发生.我是 Android 的初学者.拜托,请帮帮我.没有办法解决我的问题吗?甚至认为其他应用程序以某种方式设法做到了.
And it still happens. I am a beginner in Android.And please, please do help me. Is there no possible way to solve my problem? even thought that other application somehow manages to do it.
这是我的 LogCat.
This my LogCat.
Process: com.kkze.Mappy, PID: 6742
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.kkze.Mappy/com.kkze.Mappy.PlacesDecoder}: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2658)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5832)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at com.kkze.Mappy.PlacesDecoder.getLocation(PlacesDecoder.java:62)
at com.kkze.Mappy.PlacesDecoder.onCreate(PlacesDecoder.java:32)
at android.app.Activity.performCreate(Activity.java:6221)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2611)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5832)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
还要检查位置!=null 需要 ACCESS_FINE_LOCATION 权限,这会弄乱我的应用程序,导致它始终返回为 null.
Also checking for location!=null requires ACCESS_FINE_LOCATION permission which messes up my app causing it to always return as null.
推荐答案
正如 Jon Skeet 在评论中提到的,getLastKnownLocation()
方法可以并且将会返回 null.主要问题是它不会向操作系统提示新的位置锁定请求,而只是检查是否存在来自其他应用程序的位置请求的最后一个已知位置.如果最近没有其他应用发出位置请求,则会返回一个空位置.
As Jon Skeet mentioned in the comments, the getLastKnownLocation()
method can and will return null. The main problem is that it doesn't prompt a request to the OS for a new location lock, instead it just checks if there was a last known location from some other app's location request. If no other app had recently made a location request, then you get a null location returned to you.
保证您实际获得位置的唯一方法是请求一个位置,这是通过调用 requestLocationUpdates()
.
The only way to guarantee that you actually get a location is to request one, and this is done with a call to requestLocationUpdates()
.
传入onLocationChanged()
回调方法的位置不会为空,因为回调只发生在成功的位置锁定.
The location passed into the onLocationChanged()
callback method will not be null, since the callback only occurs on a successful location lock.
请注意,在您的应用注册位置更新的整个过程中,这将导致额外的电池消耗,因此请务必尽快取消注册位置更新.在这里,您似乎可以在第一个位置进入后立即取消注册.
Just to note, the entire time your app is registered for location updates, it will be causing extra battery drain, so be sure to un-register for location updates as soon as possible. Here it looks like you can un-register as soon as the first location comes in.
此外,您可能需要考虑在此 Activity 等待位置锁定时显示进度对话框,以便向用户提供应用正在等待某事的反馈.
Also, you might want to consider showing a progress dialog in this Activity while it waits for a location lock in order to give the user some feedback that the app is waiting on something.
以下是您的代码的一般结构:
Here is the general structure of what your code should look like:
public class MainActivity extends Activity
implements LocationListener {
Intent intentThatCalled;
public double latitude;
public double longitude;
public LocationManager locationManager;
public Criteria criteria;
public String bestProvider;
String voice2text; //added
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
intentThatCalled = getIntent();
voice2text = intentThatCalled.getStringExtra("v2txt");
getLocation();
}
public static boolean isLocationEnabled(Context context)
{
//...............
return true;
}
protected void getLocation() {
if (isLocationEnabled(MainActivity.this)) {
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
criteria = new Criteria();
bestProvider = String.valueOf(locationManager.getBestProvider(criteria, true)).toString();
//You can still do this if you like, you might get lucky:
Location location = locationManager.getLastKnownLocation(bestProvider);
if (location != null) {
Log.e("TAG", "GPS is on");
latitude = location.getLatitude();
longitude = location.getLongitude();
Toast.makeText(MainActivity.this, "latitude:" + latitude + " longitude:" + longitude, Toast.LENGTH_SHORT).show();
searchNearestPlace(voice2text);
}
else{
//This is what you need:
locationManager.requestLocationUpdates(bestProvider, 1000, 0, this);
}
}
else
{
//prompt user to enable location....
//.................
}
}
@Override
protected void onPause() {
super.onPause();
locationManager.removeUpdates(this);
}
@Override
public void onLocationChanged(Location location) {
//Hey, a non null location! Sweet!
//remove location callback:
locationManager.removeUpdates(this);
//open the map:
latitude = location.getLatitude();
longitude = location.getLongitude();
Toast.makeText(MainActivity.this, "latitude:" + latitude + " longitude:" + longitude, Toast.LENGTH_SHORT).show();
searchNearestPlace(voice2text);
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
public void searchNearestPlace(String v2txt) {
//.....
}
}
这篇关于在空对象引用上调用虚拟方法“double android.location.Location.getLatitude()"时出错的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!