WifiP2pSettings工作流程

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Android平台中，P2P操作用户只需执行如下三个步骤：
1)进入WifiP2pSettings界面；
2)搜索周围的P2P设备。搜索到的设备将显示在WifiP2pSettings中。
3)用户选择其中的某个设备以发起连接。
首先来看WifiP2pSettings的onActivityCreate函数。
1.WifiP2pSettings创建

Android-5.1/packages/apps/Settings/src/com/android/settings/wifi/p2p/WifiP2pSettings.Java

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public void onActivityCreated(Bundle savedInstanceState) {
addPreferencesFromResource(R.xml.wifi_p2p_settings);//加载界面元素
/*WifiP2pSettings也是通过监听广播的方式来了解系统中Wi-Fi P2P相关的信息及变化情况。下面这几个广播属于P2P特有的，其作用如下：
WIFI_P2P_STATE_CHANGED_ACTION:用于通知系统中P2P功能的启用情况，如该功能是enable还是disable。
WIFI_P2P_PEERS_CHANGED_ACTION:系统内部将保存搜索到的其他P2P设备信息，如果这些信息有变化，则系统将发送该广播。接收者需要通过WifiP2PManager的requestPeers函数重新获取这些P2P设备的信息。
WIFI_P2P_CONNECTION_CHANGED_ACTION:用于通知P2P连接情况，该广播可携带WifiP2pInfo和NetworkInfo两个对象。相关信息可从这两个对象中获取。
WIFI_P2P_THIS_DEVICE_CHANGED_ACTION:用于通知本机P2P设备信息发生了变化。
WIFI_P2P_DISCOVERY_CHANGED_ACTION:用于通知P2P Device Discovery的工作状态，如启动或停止。
WIFI_P2P_PERSISTENT_GROUPS_CHANGED_ACTION:用于通知persistent group信息发生了变化。
mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);
mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_DISCOVERY_CHANGED_ACTION);
mIntentFilter.addAction(WifiP2pManager.WIFI_P2P_PERSISTENT_GROUPS_CHANGED_ACTION);
final Activity activity = getActivity();
//创建WifiP2pManager对象，它将和WifiP2pService交互
mWifiP2pManager = (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
if (mWifiP2pManager != null) {
//初始化WifiManager并建立和WiFiService的联系
mChannel = mWifiP2pManager.initialize(activity, getActivity().getMainLooper(), null);
if (mChannel == null) {
//Failure to set up connection
Log.e(TAG, "Failed to set up connection with wifi p2p service");
mWifiP2pManager = null;
}
} else {
Log.e(TAG, "mWifiP2pManager is null !");
}
if (savedInstanceState != null && savedInstanceState.containsKey(SAVE_DIALOG_PEER)) {
WifiP2pDevice device = savedInstanceState.getParcelable(SAVE_DIALOG_PEER);
mSelectedWifiPeer = new WifiP2pPeer(getActivity(), device);
}
if (savedInstanceState != null && savedInstanceState.containsKey(SAVE_DEVICE_NAME)) {
mSavedDeviceName = savedInstanceState.getString(SAVE_DEVICE_NAME);
}
if (savedInstanceState != null && savedInstanceState.containsKey(SAVE_SELECTED_GROUP)) {
mSelectedGroupName = savedInstanceState.getString(SAVE_SELECTED_GROUP);
}
//创建UI中按钮对应的onClickListener
mRenameListener = new OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (which == DialogInterface.BUTTON_POSITIVE) {
if (mWifiP2pManager != null) {
mWifiP2pManager.setDeviceName(mChannel,
mDeviceNameText.getText().toString(),
new WifiP2pManager.ActionListener() {
public void onSuccess() {
if (DBG) Log.d(TAG, " device rename success");
}
public void onFailure(int reason) {
Toast.makeText(getActivity(),
R.string.wifi_p2p_failed_rename_message,
Toast.LENGTH_LONG).show();
}
});
}
}
}
};
//disconnect dialog listener
mDisconnectListener = new OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (which == DialogInterface.BUTTON_POSITIVE) {
if (mWifiP2pManager != null) {
mWifiP2pManager.removeGroup(mChannel, new WifiP2pManager.ActionListener() {
public void onSuccess() {
if (DBG) Log.d(TAG, " remove group success");
}
public void onFailure(int reason) {
if (DBG) Log.d(TAG, " remove group fail " + reason);
}
});
}
}
}
};
//cancel connect dialog listener
mCancelConnectListener = new OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (which == DialogInterface.BUTTON_POSITIVE) {
if (mWifiP2pManager != null) {
mWifiP2pManager.cancelConnect(mChannel,
new WifiP2pManager.ActionListener() {
public void onSuccess() {
if (DBG) Log.d(TAG, " cancel connect success");
}
public void onFailure(int reason) {
if (DBG) Log.d(TAG, " cancel connect fail " + reason);
}
});
}
}
}
};
//delete persistent group dialog listener
mDeleteGroupListener = new OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (which == DialogInterface.BUTTON_POSITIVE) {
if (mWifiP2pManager != null) {
if (mSelectedGroup != null) {
if (DBG) Log.d(TAG, " deleting group " + mSelectedGroup.getGroupName());
mWifiP2pManager.deletePersistentGroup(mChannel,
mSelectedGroup.getNetworkId(),
new WifiP2pManager.ActionListener() {
public void onSuccess() {
if (DBG) Log.d(TAG, " delete group success");
}
public void onFailure(int reason) {
if (DBG) Log.d(TAG, " delete group fail " + reason);
}
});
mSelectedGroup = null;
} else {
if (DBG) Log.w(TAG, " No selected group to delete!" );
}
}
} else if (which == DialogInterface.BUTTON_NEGATIVE) {
if (DBG) {
Log.d(TAG, " forgetting selected group " + mSelectedGroup.getGroupName());
}
mSelectedGroup = null;
}
}
};
setHasOptionsMenu(true);
final PreferenceScreen preferenceScreen = getPreferenceScreen();
preferenceScreen.removeAll();
preferenceScreen.setOrderingAsAdded(true);
mThisDevicePref = new Preference(getActivity());
mThisDevicePref.setPersistent(false);
mThisDevicePref.setSelectable(false);
preferenceScreen.addPreference(mThisDevicePref);
mPeersGroup = new PreferenceCategory(getActivity());
mPeersGroup.setTitle(R.string.wifi_p2p_peer_devices);
preferenceScreen.addPreference(mPeersGroup);
mPersistentGroup = new PreferenceCategory(getActivity());
mPersistentGroup.setTitle(R.string.wifi_p2p_remembered_groups);
preferenceScreen.addPreference(mPersistentGroup);
super.onActivityCreated(savedInstanceState);
}

2.WifiP2pSettings工作流程
1)WIFI_P2P_STATE_CHANGED_ACTION处理流程
打开WifiP2pSettings后，首先要等待 WIFI_P2P_STATE_CHANGED_ACTION广播以判断P2P功能是否正常启动。相应的处理函数如下所示：
android-5.1/packages/apps/Settings/src/com/android/settings/wifi/p2p/WifiP2pSettings.java

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private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION.equals(action)) {
//从 WIFI_P2P_STATE_CHANGED_ACTION广播中获取相关状态信息以判断P2P功能是否打开
mWifiP2pEnabled = intent.getIntExtra(WifiP2pManager.EXTRA_WIFI_STATE,
WifiP2pManager.WIFI_P2P_STATE_DISABLED) == WifiP2pManager.WIFI_P2P_STATE_ENABLED;
handleP2pStateChanged();
/如果搜索到新的P2P设备，则WIFI_P2P_PEERS_CHANGED_ACTION将被发送
} else if (WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION.equals(action)) {
mPeers = (WifiP2pDeviceList) intent.getParcelableExtra(
WifiP2pManager.EXTRA_P2P_DEVICE_LIST);
handlePeersChanged();
} else if (WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION.equals(action)) {
if (mWifiP2pManager == null) return;
NetworkInfo networkInfo = (NetworkInfo) intent.getParcelableExtra(
WifiP2pManager.EXTRA_NETWORK_INFO);
WifiP2pInfo wifip2pinfo = (WifiP2pInfo) intent.getParcelableExtra(
WifiP2pManager.EXTRA_WIFI_P2P_INFO);
if (networkInfo.isConnected()) {
if (DBG) Log.d(TAG, "Connected");
} else if (mLastGroupFormed != true) {
//start a search when we are disconnected
//but not on group removed broadcast event
startSearch(); //如果没有加入某个P2P组，则重新发起设备扫描
}
mLastGroupFormed = wifip2pinfo.groupFormed;
} else if (WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION.equals(action)) {
mThisDevice = (WifiP2pDevice) intent.getParcelableExtra(
WifiP2pManager.EXTRA_WIFI_P2P_DEVICE);
if (DBG) Log.d(TAG, "Update device info: " + mThisDevice);
updateDevicePref();
} else if (WifiP2pManager.WIFI_P2P_DISCOVERY_CHANGED_ACTION.equals(action)) {
int discoveryState = intent.getIntExtra(WifiP2pManager.EXTRA_DISCOVERY_STATE,
WifiP2pManager.WIFI_P2P_DISCOVERY_STOPPED);
if (DBG) Log.d(TAG, "Discovery state changed: " + discoveryState);
if (discoveryState == WifiP2pManager.WIFI_P2P_DISCOVERY_STARTED) {
updateSearchMenu(true);//更新SEARCH按钮显示的名称
} else {
updateSearchMenu(false);
}
} else if (WifiP2pManager.WIFI_P2P_PERSISTENT_GROUPS_CHANGED_ACTION.equals(action)) {
if (mWifiP2pManager != null) {
mWifiP2pManager.requestPersistentGroupInfo(mChannel, WifiP2pSettings.this);
}
}
}
};

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private void handleP2pStateChanged() {
updateSearchMenu(false);//该函数将触发WifiP2pSettings的onCreateOptionsMenu被调用
mThisDevicePref.setEnabled(mWifiP2pEnabled);
mPeersGroup.setEnabled(mWifiP2pEnabled);
mPersistentGroup.setEnabled(mWifiP2pEnabled);
}

用户下一步要做的事情就是主动搜索周围的P2P设备。Android原生代码中的WifiP2pSettings界面下方有两个按钮，分别是SEARCH和RENAME，分别用于搜索周围的P2P Device和更改本机的P2P设备名。
当P2P功能正常启用后(即上述代码中的mWifiP2pEnabled为true时)，这两个按钮将被使能。此后，用户就可单击SEARCH按钮以搜索周围的P2P设备。该按钮对应的函数是startSearch。

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private void startSearch() {
if (mWifiP2pManager != null && !mWifiP2pSearching) {
//discoverPeers将搜索周围的P2P设备
mWifiP2pManager.discoverPeers(mChannel, new WifiP2pManager.ActionListener() {
public void onSuccess() {
}
public void onFailure(int reason) {
if (DBG) Log.d(TAG, " discover fail " + reason);
}
});
}
}

当WPAS完成搜索后， WIFI_P2P_PEERS_CHANGED_ACTION广播将被发送。对该广播的处理参考onReceive函数。startSearch还将触发系统发送 WIFI_P2P_DISCOVERY_CHANGED_ACTION广播，WifiP2pSettings将根据该广播携带的信息来更新SEARCH按钮的界面:如果P2P Discovery启动成功(即状态变为 WIFI_P2P_DISCOVERY_STARTED)，则SEARCH按钮名称显示为Searching，否则该按钮显示为Search For Devices。
当系统搜索到新的P2P设备后，WIFI_P2P_PEERS_CHANGED_ACTION广播将被发送，而WifiP2pSettings对于该广播的处理就是调用WifiP2pManager的requestPeers来获取系统保存的P2P设备信息列表
系统中所有的P2P设备信息将通过PeerListener接口类的onPeersAvailable函数返回给WifiP2pSettings：

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public void onPeersAvailable(WifiP2pDeviceList peers) {
if (DBG) Log.d(TAG, "Requested peers are available");
//系统中所有的P2P设备信息都保存在这个类型为WifiP2pDeviceList的peers对象中
mPeers = peers;
handlePeersChanged();
}

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private void handlePeersChanged() {
mPeersGroup.removeAll();//mPeersGroup类型为PreferenceGroup，属于UI相关的类
mConnectedDevices = 0;
if (DBG) Log.d(TAG, "List of available peers");
for (WifiP2pDevice peer: mPeers.getDeviceList()) {
if (DBG) Log.d(TAG, "-> " + peer);
//WifiP2pPeer是Preference的子类，它和UI相关
mPeersGroup.addPreference(new WifiP2pPeer(getActivity(), peer));
if (peer.status == WifiP2pDevice.CONNECTED) mConnectedDevices++;
}
if (DBG) Log.d(TAG, " mConnectedDevices " + mConnectedDevices);
}

在该函数中，WifiP2pDeviceList中保存的每一个WifiP2pDevice信息将作为一个Preference项添加到mPeersGroup中并显示在UI界面上。
接下来用户就可在界面中选择某个P2P设备并与之连接，这个步骤由onPreferenceTreeClick函数来完成。

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public boolean onPreferenceTreeClick(PreferenceScreen screen, Preference preference) {
if (preference instanceof WifiP2pPeer) {
mSelectedWifiPeer = (WifiP2pPeer) preference;//获取用户指定的那一个WifiP2pPeer项
if (mSelectedWifiPeer.device.status == WifiP2pDevice.CONNECTED) {
showDialog(DIALOG_DISCONNECT);//如果已经和该设备连接，则判断是否需要与之断开连接
} else if (mSelectedWifiPeer.device.status == WifiP2pDevice.INVITED) {
showDialog(DIALOG_CANCEL_CONNECT);
} else {//向对端P2P设备发起连接
WifiP2pConfig config = new WifiP2pConfig();
config.deviceAddress = mSelectedWifiPeer.device.deviceAddress;
//判断系统是否强制使用了某种WSC配置方法
int forceWps = SystemProperties.getInt("wifidirect.wps", -1);
if (forceWps != -1) {
config.wps.setup = forceWps;
} else {
//获取对端P2P设备支持的WSC配置方法，优先考虑PBC
if (mSelectedWifiPeer.device.wpsPbcSupported()) {
config.wps.setup = WpsInfo.PBC;
} else if (mSelectedWifiPeer.device.wpsKeypadSupported()) {
config.wps.setup = WpsInfo.KEYPAD;
} else {
config.wps.setup = WpsInfo.DISPLAY;
}
}
//通过WifiP2pManager的connect函数向对端P2P设备发起连接。注意，目标设备信息保存在config对象中
mWifiP2pManager.connect(mChannel, config,
new WifiP2pManager.ActionListener() {
public void onSuccess() {
if (DBG) Log.d(TAG, " connect success");
}
public void onFailure(int reason) {
Log.e(TAG, " connect fail " + reason);
Toast.makeText(getActivity(),
R.string.wifi_p2p_failed_connect_message,
Toast.LENGTH_SHORT).show();
}
});
}
} else if (preference instanceof WifiP2pPersistentGroup) {
mSelectedGroup = (WifiP2pPersistentGroup) preference;
showDialog(DIALOG_DELETE_GROUP);
}
return super.onPreferenceTreeClick(screen, preference);
}

当系统完成和P2P设备的连接后，WifiP2pSettings将收到 WIFI_P2P_CONNECTION_CHANGED_ACTION 广播，对应的代码见onReceive

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