Question

我有MainActivty和MyLocationListener类。

MyLocationListener扩展AsyncTask实现LocationListener ..

以下是位置监听器类的代码：

私有类MyLocationListener extends AsyncTask实现了LocationListener {

    @Override
    public void onLocationChanged(Location location) {
            // convert coords from double to string
            String lat = Double.toString(location.getLatitude());
            String lon = Double.toString(location.getLongitude());

            Log.i(AppHelper.APP_LOG_NAMESPACE, "lat " + lat);
            Log.i(AppHelper.APP_LOG_NAMESPACE, "lon " + lon);

            // save actual position into shared preferences storage
            _appPrefs = new AppPreferences(activityContext);
            _appPrefs.saveSomeString("lat", lat);
            _appPrefs.saveSomeString("lon", lon);

            getAddressByCoords(location.getLatitude(),
                    location.getLongitude());
            setPositionToView(activityContext, mView);
    }

    /**
     * Method get string representation of the place in given coords
     * 
     * @param lat
     *            double
     * @param lon
     *            double
     * @return List <Address>
     * @throws Exception
     */

    public List<Address> getAddressByCoords(double lat, double lon) {

        Geocoder gCoder = new Geocoder(activityContext);
        try {
            addresses = gCoder.getFromLocation(lat, lon, 1);
            if (addresses != null && addresses.size() > 0) {
                Log.d("APP",
                        "LOCATION " + addresses.get(0).getAddressLine(0));
                Log.d("APP",
                        "LOCATION " + addresses.get(0).getAddressLine(1));
                Log.d("APP",
                        "LOCATION " + addresses.get(0).getAddressLine(2));

            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return addresses;
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        Toast.makeText(MainActivity.this,
                provider + "'s status changed to " + status + "!",
                Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onProviderEnabled(String provider) {
        Toast.makeText(MainActivity.this,
                "Provider " + provider + " enabled!", Toast.LENGTH_SHORT)
                .show();

    }

    @Override
    public void onProviderDisabled(String provider) {
        Toast.makeText(MainActivity.this,
                "Provider " + provider + " disabled!", Toast.LENGTH_SHORT)
                .show();
    }

    @Override
    protected Object doInBackground(Object... params) {

        try {
            // Define the criteria how to select the location provider
            criteria = new Criteria();
            criteria.setAccuracy(Criteria.ACCURACY_COARSE); // default
            criteria.setCostAllowed(false);

            // get the best provider depending on the criteria
            provider = locationManager.getBestProvider(criteria, false);

            // the last known location of this provider
            Location location = locationManager
                    .getLastKnownLocation(provider);

            // request single update
            this.onLocationChanged(location);
        } catch (Exception e) {
            Log.e(AppHelper.APP_LOG_NAMESPACE,
                    "doInBackground method cannot be processed", e);
            e.printStackTrace();
        }

        return null;
    }
}

如果我试图使用以下方法获取GPS坐标：

// Get the location manager
                locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
                mView = view;
                boolean isGPSEnabled = locationManager
                        .isProviderEnabled(LocationManager.GPS_PROVIDER);
                boolean isNetworkEnabled = locationManager
                        .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            // get values from user settings
            SharedPreferences sharedPrefs = PreferenceManager
                    .getDefaultSharedPreferences(this);
            Boolean prefferNativeGPs = sharedPrefs.getBoolean(
                    "prefNativeGps", false);

            Log.i("APP", "GPS enabled " + isGPSEnabled); // false
            Log.i("APP", "NETWORK enabled " + isNetworkEnabled); // true
            Log.i("APP", "USE native " + prefferNativeGPs); // true

            // blink textview
            TextView stateTv = (TextView) findViewById(R.id.state);
            stateTv.setTextColor(getResources().getColor(R.color.black));
            startBlinkText();
    Log.i("APP", "GPS POSITION USING GPS_PROVIDER");
    Toast.makeText(this,R.string.parking_car_using_gps_it_can_take_more_time,
    Toast.LENGTH_LONG).show();
    // calling doInBackground
    new MyLocationListener().execute("");

我在doInBackground中遇到以下异常：

无法在未调用looper.prepare的线程内创建处理程序

我想问一下，如何修改我的代码来正确处理？

非常感谢您的帮助。

Answer 1

在AsyncTask的构造函数中创建处理程序。您必须在具有活动消息循环的线程上创建它，例如UI线程。

Answer 2

获取位置已经是异步操作...

您需要做的就是在UI线程上调用它，并且很快就会得到新的结果（取决于许多事情）。

这就是为什么它有一个听众。否则它只会在阻止你时给你回复...

Android在Async方法中获取GPS坐标

2 个答案: