【发布时间】：2017-03-17 10:10:03
【问题描述】：
使用 Android-7.1.1、SDK-25.3.0
我的 WiFi 广播接收器有问题。直到 Android-7.0.x 一切正常。但是现在，已经更新到 Android-7.1.1。使用最新的 SDK，我的 WiFi-broadcast-receiver 不再返回任何值。
List<ScanResult> resultList = wifi.getScanResults(); 返回 0（而不是像之前的一些有价值的值）。为什么是这样 ？？？ Android更新可能导致什么或我的代码中有任何错误？任何帮助表示赞赏！
下面是我的代码：
在 Fragment 内设置 WiFi-broadcast-receiver（不是完整的 Fragment，而是 excerts...）：
public class ScanTeachingFragment extends Fragment implements MyWifiReceiver.OnWiFiResultListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// set up WiFi Manager
this.wifiManager = (WifiManager) getActivity().getSystemService(Context.WIFI_SERVICE);
if (wifiManager.isWifiEnabled()) {
// register Broadcast-Receiver for WiFi
receiverWifi = new MyWifiReceiver(this.context);
IntentFilter filterWiFi = new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION);
getActivity().registerReceiver(receiverWifi, filterWiFi);
}
// setListener necessary otherwise null-pointer occurs in WiFiReceiver
receiverWifi.setListener(this);
}
private void ScanWifi() {
if (!IndoorNavHelpers.inEmulator()) {
wifiManager.setWifiEnabled(true);
wifiManager.startScan();
}
}
}
这里是 WiFi-broadcast-receiver 实现：
package com.xxxx.yyyy.broadcast_receiver;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiManager;
import java.util.List;
public class MyWifiReceiver extends BroadcastReceiver {
private Context context;
OnWiFiResultListener resultListener;
// ScanFragment must implement this interface
public interface OnWiFiResultListener {
void scanWiFireceived(List<ScanResult> resultList);
}
// create setListener class (otherwise null-pointer occurs)
public void setListener(OnWiFiResultListener listener) {
this.resultListener = listener;
}
public MyWifiReceiver(Context context)
{
this.context = context;
}
// This method call when number of wifi connections changed
public void onReceive(final Context context, Intent intent) {
WifiManager wifi = (WifiManager)this.context.getSystemService(Context.WIFI_SERVICE);
List<ScanResult> resultList = wifi.getScanResults();
// ???????????????????????????????????????????????????????????
// Here resultList returns 0, WHY ????????????????????????????
// ???????????????????????????????????????????????????????????
// append newly found WiFi-scanResults to WiFiSniffing_File by calling callback-method in MainActivity
if(resultListener != null) {
resultListener.scanWiFireceived(resultList);
}
}
}
这是我的 gradle 文件：
apply plugin: 'com.android.application'
android {
compileSdkVersion 25
buildToolsVersion "25.0.2"
defaultConfig {
applicationId "com.xxxx.yyyy"
minSdkVersion 25
targetSdkVersion 25
versionCode 1
versionName "0.0.2(26)"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
testCompile 'junit:junit:4.12'
compile 'com.android.support:appcompat-v7:25.3.0'
compile 'com.android.support:support-v4:25.3.0'
compile 'com.android.support:design:25.3.0'
compile files('libs/ftp4j-1.7.2.jar')
compile 'org.greenrobot:eventbus:3.0.0'
compile 'com.github.johnkil.print:print:1.2.2'
compile 'com.github.bmelnychuk:atv:1.2.+'
}
这是我的清单文件：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.xxxx.yyyy">
<uses-permission android:name="android.permission.USE_FINGERPRINT" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<application
android:allowBackup="true"
android:icon="@mipmap/yyyy_icon"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme"
android:largeHeap="true">
<activity
android:name=".activity.MainActivity"
android:launchMode="singleTop"
android:label="@string/app_name"
android:theme="@style/AppTheme.NoActionBar"
android:screenOrientation="portrait"
android:excludeFromRecents="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
<action android:name="android.hardware.usb.action.USB_DEVICE_DETATCHED" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" android:resource="@xml/device_filter" />
<meta-data android:name="android.hardware.usb.action.USB_DEVICE_DETACHED" android:resource="@xml/device_filter" />
</activity>
</application>
</manifest>
【问题讨论】：
标签： android android-fragments broadcastreceiver wifi