Android5.0(Lollipop) BLE藍牙4.0+淺析demo鏈接（三）

做者：Bgwan
連接：https://zhuanlan.zhihu.com/p/23363591
來源：知乎
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Android5.0(Lollipop) BLE藍牙4.0+淺析demo鏈接（三）

上面的兩篇文章已經實現了藍牙之間的搜索和藍牙搜索的代碼的分析，這裏須要補充一點，在搜索的時候，咱們最好是跳轉到用戶的setting界面去開啓，關閉藍牙的操做，由於權限的問題，這是一個關乎到用戶隱私，而不單單是隱私，從技術角度，咱們調用bluetoothadapter.enable，也可能不一樣的手機啓動不了，形成很差的用戶體驗。

這篇文章主要講解，咱們搜索到藍牙之後如何和藍牙進行鏈接的問題，其實也看過一些博客，大多關於藍牙的文章都融合到一塊兒，我以爲這樣很差，我仍是喜歡分模塊來說解。

藍牙鏈接。

The First ：

兩個設備經過BLE通訊，首先須要創建GATT鏈接。這裏咱們講的是Android設備做爲client端，鏈接GATT Server。
鏈接GATT Server，你須要調用BluetoothDevice的connectGatt()方法。此函數帶三個參數：Context、autoConnect(boolean)和BluetoothGattCallback對象。調用示例：
這是官方的說明：

// We want to directly connect to the device, so we are setting the autoConnect
// parameter to false.
mBluetoothGatt = device.connectGatt(this, false, mGattCallback);

函數成功，返回BluetoothGatt對象，它是GATT profile的封裝。經過這個對象，咱們就能進行GATT Client端的相關操做。BluetoothGattCallback用於傳遞一些鏈接狀態及結果。

BluetoothGatt常規用到的幾個操做示例:

connect() ：鏈接遠程設備。
discoverServices() : 搜索鏈接設備所支持的service。
disconnect()：斷開與遠程設備的GATT鏈接。
close()：關閉GATT Client端。
readCharacteristic(characteristic) ：讀取指定的characteristic。
setCharacteristicNotification(characteristic, enabled) ：設置當指定characteristic值變化時，發出通知。
getServices() ：獲取遠程設備所支持的services。

The Second：

connectGatt()傳遞了三個參數，一個是context,還有一個是是否開啓自動鏈接，最後是一個mGattCallback，和mLeScanCallback很像。如今來看看mGattCallback。

private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
@Override
    public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
        String intentAction;
if (newState == BluetoothProfile.STATE_CONNECTED) {
            intentAction = ACTION_GATT_CONNECTED;
mConnectionState = STATE_CONNECTED;
            broadcastUpdate(intentAction);
            Log.i(TAG, "Connected to GATT server.");
// Attempts to discover services after successful connection.
            Log.i(TAG, "Attempting to start service discovery:" +
mBluetoothGatt.discoverServices());

        } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
            intentAction = ACTION_GATT_DISCONNECTED;
mConnectionState = STATE_DISCONNECTED;
            Log.i(TAG, "Disconnected from GATT server.");
            broadcastUpdate(intentAction);
        }
    }

@Override
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
            broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
        } else {
            Log.w(TAG, "onServicesDiscovered received: " + status);
        }
    }

@Override
    public void onCharacteristicRead(BluetoothGatt gatt,
                                     BluetoothGattCharacteristic characteristic,
int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        }
    }

@Override
    public void onCharacteristicChanged(BluetoothGatt gatt,
                                        BluetoothGattCharacteristic characteristic) {
        broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
    }
};

能夠看到裏面接口主要有藍牙鏈接的狀態改變，ServicesDiscovered方法等，從名字就知道幹嗎用的，可是須要特別注意 ，某些函數調用之間存在前後關係。例如首先須要connect上才能discoverServices，還有一些函數調用是異步的，須要獲得的值不會當即返回，而會在BluetoothGattCallback的回調函數中返回。例如discoverServices與onServicesDiscovered回調，readCharacteristic與onCharacteristicRead回調，setCharacteristicNotification與onCharacteristicChanged回調等。

The End : 在末尾想了一下，200多行Service代碼仍是貼出來，這樣其實很差，文章太長了。

Log.i(TAG, "Connected to GATT server.");

這樣就表明藍牙設備之間創建了鏈接，（我靠這個知乎怎麼打出字中間有橫線的）

不少人概念藍牙概念不是很理解的，能夠移步至-，Android5.0(Lollipop) BLE藍牙4.0+淺析Smack術語（五）

下篇文章會講解藍牙之間鏈接的設備如何傳遞信息（DATA）

----- BluetoothLeService

/**
 * Service for managing connection and data communication with a GATT server hosted on a
 * given Bluetooth LE device.
 */
public class BluetoothLeService extends Service {
private final static String TAG = BluetoothLeService.class.getSimpleName();

private BluetoothManager mBluetoothManager;
private BluetoothAdapter mBluetoothAdapter;
private String mBluetoothDeviceAddress;
private BluetoothGatt mBluetoothGatt;
private int mConnectionState = STATE_DISCONNECTED;

private static final int STATE_DISCONNECTED = 0;
private static final int STATE_CONNECTING = 1;
private static final int STATE_CONNECTED = 2;

public final static String ACTION_GATT_CONNECTED =
"com.example.bluetooth.le.ACTION_GATT_CONNECTED";
public final static String ACTION_GATT_DISCONNECTED =
"com.example.bluetooth.le.ACTION_GATT_DISCONNECTED";
public final static String ACTION_GATT_SERVICES_DISCOVERED =
"com.example.bluetooth.le.ACTION_GATT_SERVICES_DISCOVERED";
public final static String ACTION_DATA_AVAILABLE =
"com.example.bluetooth.le.ACTION_DATA_AVAILABLE";
public final static String EXTRA_DATA =
"com.example.bluetooth.le.EXTRA_DATA";

public final static UUID UUID_HEART_RATE_MEASUREMENT =
            UUID.fromString(SampleGattAttributes.HEART_RATE_MEASUREMENT);

// Implements callback methods for GATT events that the app cares about.  For example,
    // connection change and services discovered.
    private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
@Override
        public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            String intentAction;
if (newState == BluetoothProfile.STATE_CONNECTED) {
                intentAction = ACTION_GATT_CONNECTED;
mConnectionState = STATE_CONNECTED;
                broadcastUpdate(intentAction);
                Log.i(TAG, "Connected to GATT server.");
// Attempts to discover services after successful connection.
                Log.i(TAG, "Attempting to start service discovery:" +
mBluetoothGatt.discoverServices());

            } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                intentAction = ACTION_GATT_DISCONNECTED;
mConnectionState = STATE_DISCONNECTED;
                Log.i(TAG, "Disconnected from GATT server.");
                broadcastUpdate(intentAction);
            }
        }

@Override
        public void onServicesDiscovered(BluetoothGatt gatt, int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
                broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
            } else {
                Log.w(TAG, "onServicesDiscovered received: " + status);
            }
        }

@Override
        public void onCharacteristicRead(BluetoothGatt gatt,
                                         BluetoothGattCharacteristic characteristic,
int status) {
if (status == BluetoothGatt.GATT_SUCCESS) {
                broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
            }
        }

@Override
        public void onCharacteristicChanged(BluetoothGatt gatt,
                                            BluetoothGattCharacteristic characteristic) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        }
    };

private void broadcastUpdate(final String action) {
final Intent intent = new Intent(action);
        sendBroadcast(intent);
    }

private void broadcastUpdate(final String action,
final BluetoothGattCharacteristic characteristic) {
final Intent intent = new Intent(action);

// This is special handling for the Heart Rate Measurement profile.  Data parsing is
        // carried out as per profile specifications:
        // http://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml
        if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
int flag = characteristic.getProperties();
int format = -1;
if ((flag & 0x01) != 0) {
                format = BluetoothGattCharacteristic.FORMAT_UINT16;
                Log.d(TAG, "Heart rate format UINT16.");
            } else {
                format = BluetoothGattCharacteristic.FORMAT_UINT8;
                Log.d(TAG, "Heart rate format UINT8.");
            }
final int heartRate = characteristic.getIntValue(format, 1);
            Log.d(TAG, String.format("Received heart rate: %d", heartRate));
            intent.putExtra(EXTRA_DATA, String.valueOf(heartRate));
        } else {
// For all other profiles, writes the data formatted in HEX.
            final byte[] data = characteristic.getValue();
if (data != null && data.length > 0) {
final StringBuilder stringBuilder = new StringBuilder(data.length);
for(byte byteChar : data)
                    stringBuilder.append(String.format("%02X ", byteChar));
                intent.putExtra(EXTRA_DATA, new String(data) + "\n" + stringBuilder.toString());
            }
        }
        sendBroadcast(intent);
    }

public class LocalBinder extends Binder {
        BluetoothLeService getService() {
return BluetoothLeService.this;
        }
    }

@Override
    public IBinder onBind(Intent intent) {
return mBinder;
    }

@Override
    public boolean onUnbind(Intent intent) {
// After using a given device, you should make sure that BluetoothGatt.close() is called
        // such that resources are cleaned up properly.  In this particular example, close() is
        // invoked when the UI is disconnected from the Service.
        close();
return super.onUnbind(intent);
    }

private final IBinder mBinder = new LocalBinder();

/**
     * Initializes a reference to the local Bluetooth adapter.
     *
     * @return Return true if the initialization is successful.
     */
    public boolean initialize() {
// For API level 18 and above, get a reference to BluetoothAdapter through
        // BluetoothManager.
        if (mBluetoothManager == null) {
mBluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
if (mBluetoothManager == null) {
                Log.e(TAG, "Unable to initialize BluetoothManager.");
return false;
            }
        }

mBluetoothAdapter = mBluetoothManager.getAdapter();
if (mBluetoothAdapter == null) {
            Log.e(TAG, "Unable to obtain a BluetoothAdapter.");
return false;
        }

return true;
    }

/**
     * Connects to the GATT server hosted on the Bluetooth LE device.
     *
     * @param address The device address of the destination device.
     *
     * @return Return true if the connection is initiated successfully. The connection result
     *         is reported asynchronously through the
     *         {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
     *         callback.
     */
    public boolean connect(final String address) {
if (mBluetoothAdapter == null || address == null) {
            Log.w(TAG, "BluetoothAdapter not initialized or unspecified address.");
return false;
        }

// Previously connected device.  Try to reconnect.
        if (mBluetoothDeviceAddress != null && address.equals(mBluetoothDeviceAddress)
                && mBluetoothGatt != null) {
            Log.d(TAG, "Trying to use an existing mBluetoothGatt for connection.");
if (mBluetoothGatt.connect()) {
mConnectionState = STATE_CONNECTING;
return true;
            } else {
return false;
            }
        }

final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
if (device == null) {
            Log.w(TAG, "Device not found.  Unable to connect.");
return false;
        }
// We want to directly connect to the device, so we are setting the autoConnect
        // parameter to false.
        mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
        Log.d(TAG, "Trying to create a new connection.");
mBluetoothDeviceAddress = address;
mConnectionState = STATE_CONNECTING;
return true;
    }
/**
     * Disconnects an existing connection or cancel a pending connection. The disconnection result
     * is reported asynchronously through the
     * {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
     * callback.
     */
    public void disconnect() {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
return;
        }
mBluetoothGatt.disconnect();
    }

/**
     * After using a given BLE device, the app must call this method to ensure resources are
     * released properly.
     */
    public void close() {
if (mBluetoothGatt == null) {
return;
        }
mBluetoothGatt.close();
mBluetoothGatt = null;
    }

/**
     * Request a read on a given {@code BluetoothGattCharacteristic}. The read result is reported
     * asynchronously through the {@code BluetoothGattCallback#onCharacteristicRead(android.bluetooth.BluetoothGatt, android.bluetooth.BluetoothGattCharacteristic, int)}
     * callback.
     *
     * @param characteristic The characteristic to read from.
     */
    public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
return;
        }
mBluetoothGatt.readCharacteristic(characteristic);
    }

/**
     * Enables or disables notification on a give characteristic.
     *
     * @param characteristic Characteristic to act on.
     * @param enabled If true, enable notification.  False otherwise.
     */
    public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic,
boolean enabled) {
if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
return;
        }
mBluetoothGatt.setCharacteristicNotification(characteristic, enabled);

// This is specific to Heart Rate Measurement.
        if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
            BluetoothGattDescriptor descriptor = characteristic.getDescriptor(
                    UUID.fromString(SampleGattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
            descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mBluetoothGatt.writeDescriptor(descriptor);
        }
    }

/**
     * Retrieves a list of supported GATT services on the connected device. This should be
     * invoked only after {@code BluetoothGatt#discoverServices()} completes successfully.
     *
     * @return A {@code List} of supported services.
     */
    public List<BluetoothGattService> getSupportedGattServices() {
if (mBluetoothGatt == null) return null;

return mBluetoothGatt.getServices();
    }