带有wifi扫描的广播接收器不起作用 [英] Broadcast receiver with wifi scan not working

问题描述

我在使用AlarmManager调用的服务中有以下代码(这很好用)，但是当我开始wifi扫描(返回true)时，我从未在创建的BroadcastReceiver中收到结果:

I have the following code in a service which is called with an AlarmManager (this works well) but when when I start the wifi scan (which returns true) I never receive the results in the BroadcastReceiver I created:

public class WifiCheckerService extends IntentService {

    WifiManager wifiManager;
    List<Wifi> savedWifis;
    List<Wifi> wifisInRange;
    List<ScanResult> wifisInRangeResults;
    BroadcastReceiver broadcastReceiver;

    public WifiCheckerService() {
        super("WifiCheckerService");
    }

    @Override
    public void onCreate() {
        super.onCreate();

        setScanAlwaysAvailable();
        if(broadcastReceiver == null)
            broadcastReceiver = new BroadcastReceiver() {
                @Override
                public void onReceive(Context context, Intent intent) {
                    check();
                }
            };
        if (wifiManager == null)
            wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
        registerReceiver(broadcastReceiver,
                new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));

    }

    @Override
    protected void onHandleIntent(Intent intent) {
        if (intent != null) {
            wifiManager.startScan();

        }
    }

    private void check() {
        // irrelevant stuff

            Intent intent = new Intent(Constants.BROADCAST_UPDATE_WIFI);
            intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            sendBroadcast(intent);
        }
    }

    public List<Wifi> getSavedWifisInRange(List<Wifi> savedWifis,
                                           List<ScanResult> wifisInRangeResults) {

        List<Wifi> wifisInRange = new ArrayList<Wifi>();

        for (Wifi wifi : savedWifis) {
            for (int i = 0; i < wifisInRangeResults.size(); i++) {
                if (wifi.getSsid().equals(wifisInRangeResults.get(i).SSID)) {
                    wifi.setRssi(String.valueOf(wifisInRangeResults.get(i).level));
                    wifisInRange.add(wifi);
                }

            }
        }

        return wifisInRange;
    }

    public void setScanAlwaysAvailable() {
        /* Set scan always available if it is turned off*/
        WifiManager wifiManager = (WifiManager) getSystemService(Context.WIFI_SERVICE);
        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN_MR2) {
            if (!wifiManager.isScanAlwaysAvailable()) {
                startActivity(new Intent(WifiManager.ACTION_REQUEST_SCAN_ALWAYS_AVAILABLE));
            }
        }
    }

    public boolean isTetheringActive() {
        //irrelevant stuff

        return false;
    }

    private boolean isAnySavedWifiInRange() {
        //irrelevant stuff
        return true;

    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        unregisterReceiver(wifiScanReceiver);
    }

}

我以前将BroadcastReceiver与wifi扫描一起使用，但是我不知道为什么这不起作用.

I have used BroadcastReceiver's with wifi scans before, but I don't know why this is not working.

怎么了?

AndroidManifest.xml

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

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="com.android.vending.BILLING" />

<application
    android:name=".WifiSentinelApp"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".activities.MainActivity"
        android:label="@string/app_name"
        android:screenOrientation="portrait"
        android:theme="@style/AppTheme.NoActionBar">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".activities.DonateActivity"
        android:label="@string/donate"
        android:screenOrientation="portrait"
        android:theme="@style/AppTheme.NoActionBar" />
    <activity
        android:name=".activities.SettingsActivity"
        android:label="@string/settings"
        android:screenOrientation="portrait" />

    <receiver android:name=".receivers.AlarmReceiver" />

    <receiver android:name=".receivers.BootReceiver"
        android:enabled="false">
        <intent-filter>
            <action android:name="android.intent.action.BOOT_COMPLETED" />
        </intent-filter>
    </receiver>
    <service android:name=".services.WifiCheckerService" />
</application>

推荐答案

我对IntentService的理解是，它仅在处理请求所需的时间(即运行onHandleIntent()所需的时间)内处于活动状态.我尚未测试您的代码，但我想是在交付扫描结果之前，当onDestroy()运行时，您的广播接收器将立即被注销.一个IntentService可能不合适.您可能需要创建常规"(长期存在的背景)服务.或者，可能更有意义的是在活动中使用BroadcastReceiver，在该活动中您将显示扫描结果并完全摆脱此IntentService.WifiManager :: startScan()是异步的，因此无论如何都不必在后台服务上调用它.

My understanding of the IntentService is that it will only be active for the time needed to handle the request (ie, the time needed to run onHandleIntent()). I haven't tested your code, but my guess is that your broadcast receiver is being unregistered right away when onDestroy() runs, before the scan results are delivered. Probably an IntentService is not right for this. You might need to create a "regular" (long living background) service. Or, maybe it just makes more sense to have your BroadcastReceiver in the activity where you will show the scan results and get rid of this IntentService altogether. WifiManager::startScan() is asynchronous so it shouldn't be necessary to call that on a background service anyway.

这篇关于带有wifi扫描的广播接收器不起作用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！