我没有在Android中找到最后一个位置

Question

我正在学习Android Google API。 我正在创建一个应用程序，以通过Google Play服务获取最新位置。 在尝试了许多教程之后，我的位置为空。 我正在我的手机上运行的应用程序是API23。我在手机上保持位置和数据设置。 下面是我的代码。

Gradle依赖项：

dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
compile 'com.android.support:appcompat-v7:23.1.1'
compile 'com.google.android.gms:play-services:7.5.0'
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />


<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <meta-data
        android:name="com.google.android.gms.version"
        android:value="@integer/google_play_services_version" />
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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


</application>

MainActivity代码

package com.lab.locationawareapp;

import android.location.Location;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks;
import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener;
import com.google.android.gms.location.LocationServices;


public class MainActivity extends AppCompatActivity implements
        ConnectionCallbacks, OnConnectionFailedListener {

    protected static final String TAG = "MainActivity";

    /**
     * Provides the entry point to Google Play services.
     */
    protected GoogleApiClient mGoogleApiClient;

    /**
     * Represents a geographical location.
     */
    protected Location mLastLocation;

    protected String mLatitudeLabel;
    protected String mLongitudeLabel;
    protected TextView mLatitudeText;
    protected TextView mLongitudeText;



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

        mLatitudeLabel = getResources().getString(R.string.latitude_label);
        mLongitudeLabel = getResources().getString(R.string.longitude_label);
        mLatitudeText = (TextView) findViewById((R.id.latitude_text));
        mLongitudeText = (TextView) findViewById((R.id.longitude_text));

        buildGoogleApiClient();
    }

    /**
     * Builds a GoogleApiClient. Uses the addApi() method to request the LocationServices API.
     */
    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
    }

    @Override
    protected void onStart() {
        super.onStart();
        mGoogleApiClient.connect();
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (mGoogleApiClient.isConnected()) {
            mGoogleApiClient.disconnect();
        }
    }

    /**
     * Runs when a GoogleApiClient object successfully connects.
     */
    @Override
    public void onConnected(Bundle connectionHint) {
        // Provides a simple way of getting a device's location and is well suited for
        // applications that do not require a fine-grained location and that do not need location
        // updates. Gets the best and most recent location currently available, which may be null
        // in rare cases when a location is not available.
        mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
        if (mLastLocation != null) {
            mLatitudeText.setText(String.format("%s: %f", mLatitudeLabel,
                    mLastLocation.getLatitude()));
            mLongitudeText.setText(String.format("%s: %f", mLongitudeLabel,
                    mLastLocation.getLongitude()));
        } else {
            Toast.makeText(this, R.string.no_location_detected, Toast.LENGTH_LONG).show();
        }
    }

    @Override
    public void onConnectionFailed(ConnectionResult result) {

        Log.i(TAG, "Connection failed: ConnectionResult.getErrorCode() = " + result.getErrorCode());
    }


    @Override
    public void onConnectionSuspended(int cause) {

        Log.i(TAG, "Connection suspended");
        mGoogleApiClient.connect();
    }
}

Answer 1

使用Android Marshmallow，即使您已在清单文件中指定了权限，也必须向用户明确请求权限。 因此，您必须通过以下方式请求位置权限：首先，创建位置请求代码

public static final int LOCATION_REQUEST_CODE = 1001; //Any number

然后检查是否已授予许可，否则代码将请求许可，该许可将显示一个本机弹出窗口，要求拒绝/允许位置许可

if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION}, LOCATION_REQUEST_CODE);
        } else {
            mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
        }

最好在活动的onCreate()中请求任何位置之前，应编写以上代码。 然后，根据用户在弹出窗口上执行的操作，您将获得一个回调，可以根据需要执行该回调。

@Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        switch (requestCode) {
            case LOCATION_REQUEST_CODE: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED
                        && (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED
                        || ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED)) {
                   mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
                }
            }
        }
    }

此外，无论您尝试获取位置的何处，都应检查是否已向应用程序授予了位置许可，然后再获取位置。

 if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED || ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
                          mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
                    }

您可以请求Manifest.permission.ACCESS_FINE_LOCATION或Manifest.permission.ACCESS_COARSE_LOCATION或两者都请求。 这取决于您的要求。

Answer 2

如果系统没有缓存位置，则getLastLocation将返回null。 这是另一个程序最近未请求该位置的任何时间。 您要么需要检查它是否为空，要么需要请求位置而不是获取最后一个位置（请注意，如果您无法获得GPS锁定并且想要高精度，那么请求位置会花费时间，并且可能永远不会调用您的回调）。

Answer 3

从我遇到的这个链接尝试，我也在那里放了一些代码，所以您可以尝试它 在棉花糖中获取当前位置0，其中23 API以下使用融合位置给出确切的当前位置

检查您在其中测试过应用的设备上是否已更新了Google Play服务？ 如果不更新，则应与您的gradle play服务版本匹配