Android 4.0 支持wifi-p2p，从此p2p终于转正，一个便捷通信的革命来了。。

之前为了p2p应用调试而修改android 源码，业余的在Android添加了p2p功能，现在终于出现了官方支持版本，比预料中的早了很多。
从此android 系统在应用中会发生很多革命性变化，代表这一个便捷通信的时代来了。。。

官方wifi-p2p :api 如下：


package

android.net.wifi.p2p

Provides classes to create peer-to-peer (P2P) connections with Wi-Fi Direct.

Using these APIs, you can discover and connect to other devices when eachdevice supports Wi-Fi Direct, then communicate over a speedy connection across distances much longerthan a Bluetooth connection. The primary class you need to work with isWifiP2pManager, which you can acquire by callinggetSystemService(WIFI_P2P_SERVICE). TheWifiP2pManager includes APIs that allow you to:

• Initialize your application for P2P connections by calling initialize()
• Discover nearby devices by calling discoverPeers()
• Start a P2P connection by calling connect()
• And more

Several other interfaces and classes are necessary as well, such as:

• The WifiP2pManager.ActionListener interface allows you to receivecallbacks when an operation such as discovering peers or connecting to them succeeds or fails.
• WifiP2pManager.PeerListListener interface allows you to receiveinformation about discovered peers. The callback provides aWifiP2pDeviceList, from which you can retrieve aWifiP2pDevice object for each device within range and get information such asthe device name, address, device type, the WPS configurations the device supports, and more.
• The WifiP2pManager.GroupInfoListener interface allows you toreceive information about a P2P group. The callback provides aWifiP2pGroup object, which provides group information such as the owner, thenetwork name, and passphrase.
• WifiP2pManager.ConnectionInfoListener interface allows you toreceive information about the current connection. The callback provides a WifiP2pInfo object, which has information such as whether a group has beenformed and who is the group owner.

In order to use the Wi-Fi P2P APIs, your app must request the following user permissions:

• ACCESS_WIFI_STATE
• CHANGE_WIFI_STATE
• INTERNET (although your app doesn’t technically connectto the Internet, communicating to Wi-Fi Direct peers with standard java sockets requires Internetpermission).

For example code, see the Wi-FiDirect Demo sample application.

Note: Not all Android-powered devices support Wi-FiDirect. If your application uses Wi-Fi Direct, declare so with a<uses-feature>element in the manifest file:

<manifest ...>
    <uses-feature android:name="android.hardware.wifi.direct" />
    ...
</manifest>

Interfaces

WifiP2pManager.ActionListener	Interface for callback invocation on an application action
WifiP2pManager.ChannelListener	Interface for callback invocation when framework channel is lost
WifiP2pManager.ConnectionInfoListener	Interface for callback invocation when connection info is available
WifiP2pManager.GroupInfoListener	Interface for callback invocation when group info is available
WifiP2pManager.PeerListListener	Interface for callback invocation when peer list is available

Classes

WifiP2pConfig	A class representing a Wi-Fi P2p configuration for setting up a connection
WifiP2pDevice	A class representing a Wi-Fi p2p device
WifiP2pDeviceList	A class representing a Wi-Fi P2p device list
WifiP2pGroup	A class representing a Wi-Fi P2p group
WifiP2pInfo	A class representing connection information about a Wi-Fi p2p group
WifiP2pManager	This class provides the API for managing Wi-Fi peer-to-peer connectivity.
WifiP2pManager.Channel	A channel that connects the application to the Wifi p2p framework.