在 Android 中获取位置更新

Question

您好 AM，使用以下代码：How to get current location in Android 这里我使用 TextView 显示位置坐标一次。 现在，一旦位置不断变化，我如何才能不断更新 TextView 中的位置。

我现在使用的代码：这是我的主要活动

package com.example.locationtests;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.TextView;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    GPSTracker mGPS = new GPSTracker(this);

    TextView text = (TextView) findViewById(R.id.texts);
    if(mGPS.canGetLocation ){
    mGPS.getLocation();
    text.setText("Lat"+mGPS.getLatitude()+"Lon"+mGPS.getLongitude());
    }else{
        text.setText("Unabletofind");
        System.out.println("Unable");
    }
}

@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;
}
}

This is the class im using for Tracking:

package com.example.locationtests;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.provider.Settings;
import android.util.Log;

public final class GPSTracker implements LocationListener {

    private final Context mContext;

    // flag for GPS status
    public 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 = 1; // 10 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 1; // 1 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;

    public GPSTracker(Context context) {
        this.mContext = context;
        getLocation();
    }

    /**
     * Function to get the user's current location
     * 
     * @return
     */
    public Location getLocation() {
        try {
            locationManager = (LocationManager) mContext
                    .getSystemService(Context.LOCATION_SERVICE);

            // getting GPS status
            isGPSEnabled = locationManager
                    .isProviderEnabled(LocationManager.GPS_PROVIDER);

            Log.v("isGPSEnabled", "=" + isGPSEnabled);

            // getting network status
            isNetworkEnabled = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            Log.v("isNetworkEnabled", "=" + isNetworkEnabled);

            if (isGPSEnabled == false && isNetworkEnabled == false) {
                // no network provider is enabled
            } else {
                this.canGetLocation = true;
                if (isNetworkEnabled) {
                    location=null;
                    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) {
                    location=null;
                    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) {
    }

}
This is my AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.locationtests"
    android:versionCode="1"
    android:versionName="1.0" >
    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" /> 
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.VIBRATE" />
    <uses-feature android:name="android.hardware.camera" />
    <uses-feature android:name="android.hardware.location" android:required="true" />
    <uses-feature android:name="android.hardware.location.gps" android:required="false" />

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.locationtests.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

Answer 1

当您在 locationManger 上调用 requestLocationUpdates 方法时，您将 'this' 指定为 LocationListener：

locationManager.requestLocationUpdates(..., ..., ..., this);

这很好，因为该类实现了 LocationListener。位置更改时进行的回调是方法“onLocationChanged”。你的类中有这个方法，但它没有代码，所以什么都不做：

@Override
public void onLocationChanged(Location location) {
}

添加适当的代码以从“位置”参数中获取新的纬度和经度，并在您的 Activity 中更新 TextView。有很多方法可以做到这一点。想到的两个：

1) 在 GPSTracker 类构造函数中传递对 TextView 的引用，以便您可以从类中访问它。 2) 在 GPSTracker 类构造函数中传递对 Activity 的引用，以便您可以在 Activity 中调用一个方法（接受要显示的值），然后更新 TextView。

编辑：

您已经有了我在上面第 2 点中提到的参考资料。当您在 Activity 中实例化 GPSTracker 实例时，您已经传递了“this”：

GPSTracker mGPS = new GPSTracker(this);

在这种情况下，'this' 是 MainActivity 类的实例，而 Activity 类也恰好是 Context。在 GPSTracker 的构造函数中，您将此上下文存储在一个变量中：

public GPSTracker(Context context) {
    this.mContext = context;

因此，您可以使用它来访问 TextView。将您拥有的上下文投射到一个 Activity 上，然后您可以在其上使用 findViewById 方法：

@Override
public void onLocationChanged(Location location)
{
    TextView text = (TextView) ((Activity)mContext).findViewById(R.id.texts);
    text.setText("Lat"+location.getLatitude()+"Lon"+location.getLongitude());
}

Answer 2

做这样的事情：

示例代码：

@Override
public void onLocationChanged(Location location) {
Log.d(TAG, "GPS LocationChanged");
double lat = location.getLatitude();
double lng = location.getLongitude();
Log.d(TAG, "Received GPS request for " + String.valueOf(lat) + "," + String.valueOf(lng)       + " , ready to rumble!");

// Do clever stuff here
}