android - 为什么 FusedLoactionProvider.getLocationAvailability() 返回 null(虽然它不应该)？

Question

像这样启动我的 google play 服务客户端:

public class MyApplication  extends Application implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener

    protected synchronized GoogleApiClient buildGoogleApiClient() {
        return new GoogleApiClient.Builder(this)
            .addConnectionCallbacks(this)
            .addOnConnectionFailedListener(this)
            .addApi(LocationServices.API)
            .build();
    }


    /* GoogleApiClient.ConnectionCallbacks */
    @Override
    public void onConnected(Bundle bundle) {
        Log.v(TAG, "Google play services connected.");
        boolean isConnected = mGoogleApiClient.isConnected();    // - this is true
        boolean isLocAvailable = LocationServices.FusedLocationApi.getLocationAvailability(mGoogleApiClient).isLocationAvailable();
        // this causes NullPointerException because getLocationAvailabality() returns null. WHY ????
        .
        .
        .
    }

}

Google Play 服务库版本为 Rev.24。为什么会发生这个空指针事件？ Google API 客户端已初始化、已连接，一切都按照文档的要求进行了吗？存在 WiFi 连接...

Answer 1

根据文档:https://developers.google.com/android/reference/com/google/android/gms/location/FusedLocationProviderApi.html#getLocationAvailability(com.google.android.gms.common.api.GoogleApiClient)

Note it's always possible for getLastLocation(GoogleApiClient) to return null even when this method returns true (e.g. location settings were disabled between calls).

因此，您可能会收到 null 的原因有很多。我的建议是您检查权限，并确保允许位置权限，而不仅仅是检查 GoogleClient 是否已连接以及位置是否可用。您可以使用以下功能。

public static boolean checkAppPermissions(Context context, String... strPermissions) {
    for (String permissions : strPermissions) {
        if (!FrameworkUtils.isStringEmpty(permissions)) {
            int result = ContextCompat.checkSelfPermission(context, permissions);
            if (result == PackageManager.PERMISSION_GRANTED) {
                return true;
            }
        }
    }
    return false;
}

你可以这样调用它

checkAppPermissions(mContext, Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION)