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我正在测试我的活动以获取 GPS 坐标(纬度、经度),但是当单击注册按钮时,日志猫显示错误。我打算测试这段代码

Log.d(ACCESSIBILITY_SERVICE, Double.toString(gps.getLatitude()));

这是我的代码。 MainActivity.java

public class MainActivity extends Activity {

    protected static final String PREFS_NAME = null;
    String prefName = "MyPref";
    EditText editText01, editText02;
    GPSTracker gps;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editText01 = (EditText) findViewById(R.id.EditText01);  //Trusted phone number
        editText02 = (EditText) findViewById(R.id.EditText02);  //Email address
        Button RegisterButton = (Button) findViewById(R.id.btnRegister);    //RegisterButton


        RegisterButton.setOnClickListener(new View.OnClickListener(){
            public void onClick(View v){

                SharedPreferences prefs = getSharedPreferences(PREFS_NAME, 0);
                SharedPreferences.Editor editor = prefs.edit();

                editor.putString("trustedNum", editText01.getText().toString());
                editor.putString("Email", editText02.getText().toString());

                TelephonyManager tm = (TelephonyManager) getApplicationContext().getSystemService(Context.TELEPHONY_SERVICE);
                editor.putString("storedSimSerial", tm.getSimSerialNumber());

                editor.commit();

                Log.d(ACCESSIBILITY_SERVICE, Double.toString(gps.getLatitude()));

                Toast.makeText(getApplicationContext(), "saved", 3000).show();

            }
    });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}

GPSTracker.java 包 com.example.sms;

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;
    }

}

清单.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.sms"
    android:versionCode="1"
    android:versionName="1.0" >

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

    <uses-permission android:name="android.permission.SEND_SMS" />
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    <uses-permission android:name="android.permission.READ_PHONE_STATE"/>
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <receiver android:name=".BootComplete">  
            <intent-filter>   
                <action android:name="android.intent.action.BOOT_COMPLETED"/>  
                <category android:name="android.intent.category.DEFAULT" />  
            </intent-filter> 
            <intent-filter>   
                <action android:name="android.intent.action.READ_PHONE_STATE"/>  
                <category android:name="android.intent.category.DEFAULT" />  
            </intent-filter> 
        </receiver>


        <activity
            android:name="com.example.sms.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>
    </application>

</manifest>

错误代码显示

03-12 18:10:56.200: E/AndroidRuntime(2368): FATAL EXCEPTION: main
03-12 18:10:56.200: E/AndroidRuntime(2368): java.lang.NullPointerException
03-12 18:10:56.200: E/AndroidRuntime(2368):     at com.example.sms.MainActivity$1.onClick(MainActivity.java:56)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at android.view.View.performClick(View.java:4211)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at android.view.View$PerformClick.run(View.java:17267)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at android.os.Handler.handleCallback(Handler.java:615)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at android.os.Handler.dispatchMessage(Handler.java:92)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at android.os.Looper.loop(Looper.java:137)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at android.app.ActivityThread.main(ActivityThread.java:4898)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at java.lang.reflect.Method.invokeNative(Native Method)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at java.lang.reflect.Method.invoke(Method.java:511)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
03-12 18:10:56.200: E/AndroidRuntime(2368):     at dalvik.system.NativeStart.main(Native Method)
4

3 回答 3

0

,天哪!你设置PREFS_NAME = null然后在你的代码中使用它!你忘记初始化了吗?

于 2013-03-12T18:24:39.087 回答
0

这里

Log.d(ACCESSIBILITY_SERVICE, Double.toString(gps.getLatitude()));
                                             ^^^

gps为 null 您必须先初始化gps实例,然后再将其用作:

gps=new GPSTracker(MainActivity.this);  //<<< initialize here
Log.d(ACCESSIBILITY_SERVICE, Double.toString(gps.getLatitude()));
于 2013-03-12T18:25:18.710 回答
0

GPSTracker gps 在哪里初始化?你直接使用它。

于 2013-03-12T18:25:54.360 回答