概述
在最近开发过程中需要获取当前wifi的SSID，目前网上一般推荐 mWifiManager.getConnectionInfo() 这个方法来进行获取，但是发现在Android12上这个方法已经被标记为过时，本着用最新方法的想法，决定使用推荐的新方法试试。
问题分析
一言不合看源码，既然该方法被标记为过时，那么应该也会有推荐的方法来使用，源码如下：
/**
//path:packages/modules/Wifi/framework/java/android/net/wifi/WifiManager.java
* Return dynamic information about the current Wi-Fi connection, if any is active.
* <p>
*
* @return the Wi-Fi information, contained in {@link WifiInfo}.
*
* @deprecated Starting with {@link Build.VERSION_CODES#S}, WifiInfo retrieval is moved to
* {@link ConnectivityManager} API surface. WifiInfo is attached in
* {@link NetworkCapabilities#getTransportInfo()} which is available via callback in
* {@link NetworkCallback#onCapabilitiesChanged(Network, NetworkCapabilities)} or on-demand from
* {@link ConnectivityManager#getNetworkCapabilities(Network)}.
*
*</p>
* Usage example:
* <pre>{@code
* final NetworkRequest request =
* new NetworkRequest.Builder()
* .addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
* .build();
* final ConnectivityManager connectivityManager =
* context.getSystemService(ConnectivityManager.class);
* final NetworkCallback networkCallback = new NetworkCallback() {
* ...
* {@literal @}Override
* void onAvailable(Network network) {}
*
* {@literal @}Override
* void onCapabilitiesChanged(Network network, NetworkCapabilities networkCapabilities) {
* WifiInfo wifiInfo = (WifiInfo) networkCapabilities.getTransportInfo();
* }
* // etc.
* };
* connectivityManager.requestNetwork(request, networkCallback); // For request
* connectivityManager.registerNetworkCallback(request, networkCallback); // For listen
* }</pre>
* <p>
* <b>Compatibility Notes:</b>
* <li>Apps can continue using this API, however newer features
* such as ability to mask out location sensitive data in WifiInfo will not be supported
* via this API. </li>
* <li>On devices supporting concurrent connections (indicated via
* {@link #isStaConcurrencyForLocalOnlyConnectionsSupported()}, etc) this API will return
* the details of the internet providing connection (if any) to all apps, except for the apps
* that triggered the creation of the concurrent connection. For such apps, this API will return
* the details of the connection they created. e.g. apps using {@link WifiNetworkSpecifier} will
* trigger a concurrent connection on supported devices and hence this API will provide
* details of their peer to peer connection (not the internet providing connection). This
* is to maintain backwards compatibility with behavior on single STA devices.</li>
* </p>
*/
@Deprecated
public WifiInfo getConnectionInfo() {
try {
return mService.getConnectionInfo(mContext.getOpPackageName(),
mContext.getAttributionTag());
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
根据注释里的提示，谷歌推荐使用NetworkCallback监听网络状态的方法来获取wifi 的ssid，照着写一下，如下：
final NetworkRequest request =
new NetworkRequest.Builder()
.addTransportType(NetworkCapabilities.TRANSPORT_WIFI)
.build();
final ConnectivityManager.NetworkCallback mNetworkCallback = new ConnectivityManager.NetworkCallback() {
@Override
public void onAvailable(@NonNull Network network) {
super.onAvailable(network);
}
@Override
public void onCapabilitiesChanged(@NonNull Network network, @NonNull NetworkCapabilities networkCapabilities) {
super.onCapabilitiesChanged(network, networkCapabilities);
WifiInfo wifiInfo = (WifiInfo) networkCapabilities.getTransportInfo();
if (wifiInfo != null) {
String ssid = wifiInfo.getSSID().replace("\"", "").replace("<", "").replace(">", ""));
}
}
};
private void requestNetwork() {
mConnectivityManager.registerNetworkCallback(mRequest, mNetworkCallback);
}
private void unrequestNetwork() {
mConnectivityManager.unregisterNetworkCallback(mNetworkCallback);
}
本以为万事大吉，一切OK，没想到install以后拿到的ssid 一直是 unknow ssid。对于这种情况，第一想法是应用是否缺少权限？查看WifiInfo源码，发现在应用没有"Manifest.permission.ACCESS_FINE_LOCATION"权限时，ssid的确会返回Unknown Ssid。难道这就解决了？看了一下应用的清单文件，发现该有的权限配置都是有的。这~ 给我整不会了！
纠结了好几天，始终没有找到解决问题的办法。
偶然在查看NetworkCallback源码的时候好像发现了新大陆。
//path:packages/modules/Connectivity/framework/src/android/net/ConnectivityManager.java
/**
* Base class for {@code NetworkRequest} callbacks. Used for notifications about network
* changes. Should be extended by applications wanting notifications.
*
* A {@code NetworkCallback} is registered by calling
* {@link #requestNetwork(NetworkRequest, NetworkCallback)},
* {@link #registerNetworkCallback(NetworkRequest, NetworkCallback)},
* or {@link #registerDefaultNetworkCallback(NetworkCallback)}. A {@code NetworkCallback} is
* unregistered by calling {@link #unregisterNetworkCallback(NetworkCallback)}.
* A {@code NetworkCallback} should be registered at most once at any time.
* A {@code NetworkCallback} that has been unregistered can be registered again.
*/
public static class NetworkCallback {
/**
* No flags associated with this callback.
* @hide
*/
public static final int FLAG_NONE = 0;
/**
* Use this flag to include any location sensitive data in {@link NetworkCapabilities} sent
* via {@link #onCapabilitiesChanged(Network, NetworkCapabilities)}.
* <p>
* These include:
* <li> Some transport info instances (retrieved via
* {@link NetworkCapabilities#getTransportInfo()}) like {@link android.net.wifi.WifiInfo}
* contain location sensitive information.
* <li> OwnerUid (retrieved via {@link NetworkCapabilities#getOwnerUid()} is location
* sensitive for wifi suggestor apps (i.e using {@link WifiNetworkSuggestion}).</li>
* </p>
* <p>
* Note:
* <li> Retrieving this location sensitive information (subject to app's location
* permissions) will be noted by system. </li>
* <li> Without this flag any {@link NetworkCapabilities} provided via the callback does
* not include location sensitive info.
* </p>
*/
// Note: Some existing fields which are location sensitive may still be included without
// this flag if the app targets SDK < S (to maintain backwards compatibility).
public static final int FLAG_INCLUDE_LOCATION_INFO = 1 << 0;
/** @hide */
@Retention(RetentionPolicy.SOURCE)
@IntDef(flag = true, prefix = "FLAG_", value = {
FLAG_NONE,
FLAG_INCLUDE_LOCATION_INFO
})
public @interface Flag {
}
/**
* All the valid flags for error checking.
*/
private static final int VALID_FLAGS = FLAG_INCLUDE_LOCATION_INFO;
public NetworkCallback() {
this(FLAG_NONE);
}
public NetworkCallback(@Flag int flags) {
if ((flags & VALID_FLAGS) != flags) {
throw new IllegalArgumentException("Invalid flags");
}
mFlags = flags;
}
...
发现NetworkCallback的构造方法中是可以传参数的，并且根据注释可知 FLAG_INCLUDE_LOCATION_INFO 这个flag就是控制onCapabilitiesChanged时 NetworkCapabilities#getTransportInfo() 可以传递一些敏感的位置信息，而获取WifiInfo中的ssid的确需要位置信息。似乎？这就是正解？赶紧加进去试试。
final ConnectivityManager.NetworkCallback mNetworkCallback = new ConnectivityManager.NetworkCallback(ConnectivityManager.NetworkCallback.FLAG_INCLUDE_LOCATION_INFO) {
@Override
public void onAvailable(@NonNull Network network) {
super.onAvailable(network);
}
@Override
public void onCapabilitiesChanged(@NonNull Network network, @NonNull NetworkCapabilities networkCapabilities) {
super.onCapabilitiesChanged(network, networkCapabilities);
WifiInfo wifiInfo = (WifiInfo) networkCapabilities.getTransportInfo();
if (wifiInfo != null) {
String ssid = wifiInfo.getSSID().replace("\"", "").replace("<", "").replace(">", ""));
}
}
};
方法相同就是在创建NetworkCallback 时传入FLAG_INCLUDE_LOCATION_INFO。
编译，install，打开应用，ssid完美呈现。
至此问题解决，这就是正解。
总结
遇事不决阅读源码，百思不解可读源码。