Android 4.0新增WiFiDirect功能

Android 4.0引入了一项很重要的技术就是 WiFiDirect (WiFi直连) ，它可以让WiFi设备无需热点即可实现两个WiFi设备的P2P数据交换。使用最新的Android 4.0 SDK，最低API Level 14才支持此项技术，在SDK的例子中我们可以看到很多界面用到了Android 3.0时代的Fragment容器。

  首先我们需要实现android.net.wifi.p2p.WifiP2pManager.ChannelListener 接口来获取支持WiFi直连的Android设备。

  public class WiFiDirectActivity extends Activity implements ChannelListener, DeviceActionListener {

    public static final String TAG = "wifidirectdemo";
    private WifiP2pManager manager;
    private boolean isWifiP2pEnabled = false;
    private boolean retryChannel = false;

    private final IntentFilter intentFilter = new IntentFilter();
    private Channel channel;
    private BroadcastReceiver receiver = null;

    public void setIsWifiP2pEnabled(boolean isWifiP2pEnabled) {   //设置一个标记是否启用WiFi直连
        this.isWifiP2pEnabled = isWifiP2pEnabled;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

      //注册所需要处理的action，比如WiFi连接、状态改变等。

        intentFilter.addAction(WifiP2pManager.WIFI_P2P_STATE_CHANGED_ACTION);
        intentFilter.addAction(WifiP2pManager.WIFI_P2P_PEERS_CHANGED_ACTION);
        intentFilter.addAction(WifiP2pManager.WIFI_P2P_CONNECTION_CHANGED_ACTION);
        intentFilter.addAction(WifiP2pManager.WIFI_P2P_THIS_DEVICE_CHANGED_ACTION);

        manager = (WifiP2pManager) getSystemService(Context.WIFI_P2P_SERVICE);
        channel = manager.initialize(this, getMainLooper(), null); //实例化WifiP2pManager对象
    }

    @Override
    public void onResume() {
        super.onResume();
        receiver = new WiFiDirectBroadcastReceiver(manager, channel, this);
        registerReceiver(receiver, intentFilter);
    }

    @Override
    public void onPause() {
        super.onPause();
        unregisterReceiver(receiver);
    }

    public void resetData() {
        DeviceListFragment fragmentList = (DeviceListFragment) getFragmentManager()
                .findFragmentById(R.id.frag_list);
        DeviceDetailFragment fragmentDetails = (DeviceDetailFragment) getFragmentManager()
                .findFragmentById(R.id.frag_detail);
        if (fragmentList != null) {
            fragmentList.clearPeers();
        }
        if (fragmentDetails != null) {
            fragmentDetails.resetViews();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.action_items, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.atn_direct_enable:
                if (manager != null && channel != null) {

                    startActivity(new Intent(Settings.ACTION_WIRELESS_SETTINGS));
                } else {
                    Log.e(TAG, "channel or manager is null");
                }
                return true;

            case R.id.atn_direct_discover:
                if (!isWifiP2pEnabled) {
                    Toast.makeText(WiFiDirectActivity.this, R.string.p2p_off_warning,
                            Toast.LENGTH_SHORT).show();
                    return true;
                }
                final DeviceListFragment fragment = (DeviceListFragment) getFragmentManager()
                        .findFragmentById(R.id.frag_list);
                fragment.onInitiateDiscovery();
                manager.discoverPeers(channel, new WifiP2pManager.ActionListener() {

                    @Override
                    public void onSuccess() {
                        Toast.makeText(WiFiDirectActivity.this, "Discovery Initiated",
                                Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onFailure(int reasonCode) {
                        Toast.makeText(WiFiDirectActivity.this, "Discovery Failed : " + reasonCode,
                                Toast.LENGTH_SHORT).show();
                    }
                });
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    @Override
    public void showDetails(WifiP2pDevice device) {
        DeviceDetailFragment fragment = (DeviceDetailFragment) getFragmentManager()
                .findFragmentById(R.id.frag_detail);
        fragment.showDetails(device);

    }

    @Override
    public void connect(WifiP2pConfig config) {
        manager.connect(channel, config, new ActionListener() {

            @Override
            public void onSuccess() {
                // WiFiDirectBroadcastReceiver will notify us. Ignore for now.
            }

            @Override
            public void onFailure(int reason) {
                Toast.makeText(WiFiDirectActivity.this, "Connect failed. Retry.",
                        Toast.LENGTH_SHORT).show();
            }
        });
    }

    @Override
    public void disconnect() {
        final DeviceDetailFragment fragment = (DeviceDetailFragment) getFragmentManager()
                .findFragmentById(R.id.frag_detail);
        fragment.resetViews();
        manager.removeGroup(channel, new ActionListener() {

            @Override
            public void onFailure(int reasonCode) {
                Log.d(TAG, "Disconnect failed. Reason :" + reasonCode);

            }

            @Override
            public void onSuccess() {
                fragment.getView().setVisibility(View.GONE);
            }

        });
    }

    @Override
    public void onChannelDisconnected() {
        // we will try once more
        if (manager != null && !retryChannel) {
            Toast.makeText(this, "Channel lost. Trying again", Toast.LENGTH_LONG).show();
            resetData();
            retryChannel = true;
            manager.initialize(this, getMainLooper(), this);
        } else {
            Toast.makeText(this,
                    "Severe! Channel is probably lost premanently. Try Disable/Re-Enable P2P.",
                    Toast.LENGTH_LONG).show();
        }
    }

    @Override
    public void cancelDisconnect() {

        if (manager != null) {
            final DeviceListFragment fragment = (DeviceListFragment) getFragmentManager()
                    .findFragmentById(R.id.frag_list);
            if (fragment.getDevice() == null
                    || fragment.getDevice().status == WifiP2pDevice.CONNECTED) {
                disconnect();
            } else if (fragment.getDevice().status == WifiP2pDevice.AVAILABLE
                    || fragment.getDevice().status == WifiP2pDevice.INVITED) {

                manager.cancelConnect(channel, new ActionListener() {

                    @Override
                    public void onSuccess() {
                        Toast.makeText(WiFiDirectActivity.this, "Aborting connection",
                                Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onFailure(int reasonCode) {
                        Toast.makeText(WiFiDirectActivity.this,
                                "Connect abort request failed. Reason Code: " + reasonCode,
                                Toast.LENGTH_SHORT).show();
                    }
                });
            }
        }

    }
}