Android LocationManager 标准答案

【问题标题】：Android LocationManager CriteriaAndroid LocationManager 标准
【发布时间】：2013-03-18 17:39:13
【问题描述】：

我需要接收来自网络和 GPS 提供商的位置更改。

如果 GPS 供应商不可用或没有位置（卫星能见度差），我会从网络供应商那里收到位置，否则从 GPS 供应商那里获得位置。

是否可以根据我的需要使用标准选择提供者？

【问题讨论】：

如果您使用 Criteria 类根据配置查找可用的最佳提供程序，那么将导致来自 GPS PROVIDER、NETWORK PROVIDER 或 PASSIVE 的任何人。在没有 Criteria 类的情况下，使用 requestLocationUpdates 获取与提供者一致的位置
LocationManager 不会在一次回调中通知我有关网络和 GPS 的信息？我需要使用两个具有不同回调的 requestLocation() 吗？
要注册您的位置经理以获取更新，您必须提供一个提供商，您想从该提供商那里获取更新。喜欢mgr.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 10 * 1000, 50, this);

标签： android location criteria locationmanager

【解决方案1】：

其实Android Developers - Making Your App Location Aware 有一个很好的示例代码可以满足您的需求。

在其代码中，如果您同时使用两个提供商（来自 GPS 和来自网络），它将进行比较：

...
} else if (mUseBoth) {
    // Get coarse and fine location updates.
    mFineProviderButton.setBackgroundResource(R.drawable.button_inactive);
    mBothProviderButton.setBackgroundResource(R.drawable.button_active);
    // Request updates from both fine (gps) and coarse (network) providers.
    gpsLocation = requestUpdatesFromProvider(
            LocationManager.GPS_PROVIDER, R.string.not_support_gps);
    networkLocation = requestUpdatesFromProvider(
            LocationManager.NETWORK_PROVIDER, R.string.not_support_network);

    // If both providers return last known locations, compare the two and use the better
    // one to update the UI.  If only one provider returns a location, use it.
    if (gpsLocation != null && networkLocation != null) {
        updateUILocation(getBetterLocation(gpsLocation, networkLocation));
    } else if (gpsLocation != null) {
        updateUILocation(gpsLocation);
    } else if (networkLocation != null) {
        updateUILocation(networkLocation);
    }
}
...

它实现了最佳位置提供者的想法（通过确定指定时间段内的准确性，例如：

/** Determines whether one Location reading is better than the current Location fix.
  * Code taken from
  * http://developer.android.com/guide/topics/location/obtaining-user-location.html
  *
  * @param newLocation  The new Location that you want to evaluate
  * @param currentBestLocation  The current Location fix, to which you want to compare the new
  *        one
  * @return The better Location object based on recency and accuracy.
  */
protected Location getBetterLocation(Location newLocation, Location currentBestLocation) {
    if (currentBestLocation == null) {
        // A new location is always better than no location
        return newLocation;
    }

    // Check whether the new location fix is newer or older
    long timeDelta = newLocation.getTime() - currentBestLocation.getTime();
    boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
    boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
    boolean isNewer = timeDelta > 0;

    // If it's been more than two minutes since the current location, use the new location
    // because the user has likely moved.
    if (isSignificantlyNewer) {
        return newLocation;
    // If the new location is more than two minutes older, it must be worse
    } else if (isSignificantlyOlder) {
        return currentBestLocation;
    }

    // Check whether the new location fix is more or less accurate
    int accuracyDelta = (int) (newLocation.getAccuracy() - currentBestLocation.getAccuracy());
    boolean isLessAccurate = accuracyDelta > 0;
    boolean isMoreAccurate = accuracyDelta < 0;
    boolean isSignificantlyLessAccurate = accuracyDelta > 200;

    // Check if the old and new location are from the same provider
    boolean isFromSameProvider = isSameProvider(newLocation.getProvider(),
            currentBestLocation.getProvider());

    // Determine location quality using a combination of timeliness and accuracy
    if (isMoreAccurate) {
        return newLocation;
    } else if (isNewer && !isLessAccurate) {
        return newLocation;
    } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
        return newLocation;
    }
    return currentBestLocation;
}

完整代码请查看上面提供的链接。

【讨论】：

【解决方案2】：

对于搜索最佳位置提供商，请使用以下代码：请参考https://developer.android.com/reference/android/location/Criteria.html 为了理解，标准将如何发挥作用？

public  String getProviderName() {
    LocationManager locationManager =(LocationManager)this.getSystemService(Context.LOCATION_SERVICE);
    Criteria criteria = new Criteria();
    criteria.setPowerRequirement(Criteria.POWER_LOW);
    criteria.setAccuracy(Criteria.ACCURACY_FINE);
    criteria.setSpeedRequired(true);
    criteria.setAltitudeRequired(false);
    criteria.setBearingRequired(false);
    criteria.setCostAllowed(false);
    return locationManager.getBestProvider(criteria, true);
}

【讨论】：

【解决方案3】：

只是不给出任何标准，并尝试获得最佳提供者：

LocationManager mgr = (LocationManager) getSystemService(LOCATION_SERVICE);
Criteria criteria = new Criteria();
String best = mgr.getBestProvider(criteria, true);
//since you are using true as the second parameter, you will only get the best of providers which are enabled.
Location location = mgr.getLastKnownLocation(best);

【讨论】：