Android5.0(Lollipop) BLE蓝牙4.0+浅析code（二）

作者：Bgwan
链接：https://zhuanlan.zhihu.com/p/23347612
来源：知乎
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Android5.0(Lollipop) BLE蓝牙4.0+浅析code说明（二）

Android4.4 启用蓝牙相关的操作方法主要是，BluetoothAdapter.startleScan();方法，最新的Android 5.0已经弃用了改方法，谷歌官方已经改用了android.bluetooth.le类來处理BLE的操作，所以我建议还是用最新的接口开发。但是为了兼容以前的版本改方法还是可以使用，上篇日志已经提到我们可以加一个SDK版本的判断，这里不过多说明，

这次更新总共在le下面添加了6个scan的相关类（4个advertise相关类），下面开始介绍这个类的作用。

1.BLE centrial的代码

mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();

利用adapter来得到一个scanner对象，这句代码和Peripheral的getBluetoothLeAdvertiser基本类似，一般手机支持BLE都会支持Central，除非是本身就只是外设设备。

advertiser = mBluetoothAdapter.getBluetoothLeAdvertiser();

如果是Peripheral 得到advertiser对象，那么我们可以广播设置一些参数，数据，加一个CallBack，如下：

advertiser.startAdvertising(settings, data, mAdvertiseCallback);

这里面的三个参数，不再本文导论范围，但是可以看一下

// TODO Auto-generated method stub
AdvertiseSettings settings = new AdvertiseSettings.Builder()
        .setAdvertiseMode(AdvertiseSettings.ADVERTISE_MODE_LOW_LATENCY)
        .setTxPowerLevel(AdvertiseSettings.ADVERTISE_TX_POWER_HIGH)
        .setConnectable(false).build();
ParcelUuid pUuid = new ParcelUuid(UUID.fromString("00001000-0000-1000-8000-00805f9b34fb"));
AdvertiseData data = new AdvertiseData.Builder()
        .setIncludeDeviceName(true)
        .addServiceUuid(pUuid)
        .addServiceData(pUuid,
"Data".getBytes(Charset.forName("UTF-8"))).build();
final AdvertiseCallback mAdvertiseCallback = new AdvertiseCallback() {
@Override
    public void onStartSuccess(AdvertiseSettings settingsInEffect) {
super.onStartSuccess(settingsInEffect);
if (settingsInEffect != null) {
            Log.d(TAG, "onStartSuccess TxPowerLv=" + settingsInEffect.getTxPowerLevel() + " mode=" + settingsInEffect.getMode()
                    + " timeout=" + settingsInEffect.getTimeout());
        } else {
            Log.e(TAG, "onStartSuccess, settingInEffect is null");
        }
        Log.e(TAG, "onStartSuccess settingsInEffect" + settingsInEffect);

    }

@Override
    public void onStartFailure(int errorCode) {
super.onStartFailure(errorCode);

if (errorCode == ADVERTISE_FAILED_DATA_TOO_LARGE) {
            Toast.makeText(mContext, "Operation failed due to an internal error", Toast.LENGTH_LONG).show();
            Log.e(TAG, "Failed to start advertising as the advertise data to be broadcasted is larger than 31 bytes.");
        } else if (errorCode == ADVERTISE_FAILED_TOO_MANY_ADVERTISERS) {
            Toast.makeText(mContext, "Operation failed due to an internal error", Toast.LENGTH_LONG).show();
            Log.e(TAG, "Failed to start advertising because no advertising instance is available.");
        } else if (errorCode == ADVERTISE_FAILED_ALREADY_STARTED) {
            Toast.makeText(mContext, "Operation failed due to an internal error", Toast.LENGTH_LONG).show();
            Log.e(TAG, "Failed to start advertising as the advertising is already started");
        } else if (errorCode == ADVERTISE_FAILED_INTERNAL_ERROR) {
            Toast.makeText(mContext, "Operation failed due to an internal error", Toast.LENGTH_LONG).show();
            Log.e(TAG, "Operation failed due to an internal error");
        } else if (errorCode == ADVERTISE_FAILED_FEATURE_UNSUPPORTED) {
            Toast.makeText(mContext, "This feature is not supported on this platform", Toast.LENGTH_LONG).show();
            Log.e(TAG, "This feature is not supported on this platform");
        } else {
            Toast.makeText(mContext, "onStartFailure errorCode", Toast.LENGTH_LONG).show();
            Log.e(TAG, "onStartFailure errorCode" + errorCode);
        }
    }
};

它主要的作用就是，假如说你有一个嵌入式的外设，蓝牙设备名字CTH-1001，这个蓝牙设备你可以通过设置这些参数去过滤你想要的蓝牙设备，如果周围还有其他的蓝牙外设你的手机可能就搜索不到，这也是在Android 后来新加入的功能，为了方便开发者使用。

2，接下来就是Scan的动作了，Scan新的接口动作把Scan分为了两类，

第一类：直接给一个callback

public void startScan(java.util.List<android.bluetooth.le.ScanFilter> filters, android.bluetooth.le.ScanSettings settings, android.bluetooth.le.ScanCallback callback)

/**
 * Start Bluetooth LE scan with default parameters and no filters. The scan results will be
 * delivered through {@code callback}.
 * <p>
 * Requires {@link android.Manifest.permission#BLUETOOTH_ADMIN} permission.
 *
 * @param callback Callback used to deliver scan results.
 * @throws IllegalArgumentException If {@code callback} is null.
 */
public void startScan(final ScanCallback callback) {
if (callback == null) {
throw new IllegalArgumentException("callback is null");
    }
    startScan(null, new ScanSettings.Builder().build(), callback);
}

直接搜索全部周围peripheral设备，当然这里你要填写callback，

第二类为这里加入了新的过滤条件。可以看到ScanFilter：

    /**
    * Start Bluetooth LE scan. The scan results will be delivered through {@code callback}.
    * <p>
* Requires {@link android.Manifest.permission#BLUETOOTH_ADMIN} permission.
*
* @param filters {@link ScanFilter}s for finding exact BLE devices.
* @param settings Settings for the scan.
* @param callback Callback used to deliver scan results.
* @throws IllegalArgumentException If {@code settings} or {@code callback} is null.
*/
public void startScan(List<ScanFilter> filters, ScanSettings settings,
    final ScanCallback callback) {
    startScan(filters, settings, callback, null);
    }

这一种明显属于定制化的函数了，因为他需要我们输入过滤条件。这里的ScanFilter和ScanSettings又是两个scan类，当然这两个类的目的主要是为了有些人想单独为某个产品开发应用，把过滤条件加上，比如DeviceName或者某个Service UUID等等，就可以搜索出只针对特定Peripheral特性的设备，就像我们公司的CTH-1001类型的设备。

单独看这两个新的接口，可能有些人会迷惑，本来不久应该是这样吗？其实Andoid L之前，scan接口不是这样的，就只有上面两种中的一种方法，suo'y。

3，OKay ，讲解了scanLeDevice，这里看一下回调mScanCallBack具体怎么实现的，其实在上篇文章已经贴出来了，

private ScanCallback mScanCallback = new ScanCallback() {
@Override
        public void onScanResult(int callbackType, ScanResult result) {
super.onScanResult(callbackType, result);
if (result == null || result.getDevice() == null
                    || TextUtils.isEmpty(result.getDevice().getName())) {
mText.setText("没有搜索到蓝牙设备");
//                return;
            }
//如果是外设则可能存在没有ServiceUuids
//            builder.append("/n").append(
//                    new String(result.getScanRecord().getServiceData(
//                            result.getScanRecord().getServiceUuids().get(0)),
//                            Charset.forName("UTF-8")));

            BluetoothDevice device = result.getDevice();
            Log.d(TAG, "Device name: " + device.getName());
            Log.d(TAG, "Device address: " + device.getAddress());
            Log.d(TAG, "Device service UUIDs: " + device.getUuids());
if (builder.toString().contains(device.getName())) {
            } else {
builder.append("\n" + device.getName() + "&" + device.getAddress() + "\n");
            }
            ScanRecord record = result.getScanRecord();
            Log.d(TAG, "Record advertise flags: 0x" + Integer.toHexString(record.getAdvertiseFlags()));
            Log.d(TAG, "Record Tx power level: " + record.getTxPowerLevel());
            Log.d(TAG, "Record device name: " + record.getDeviceName());
            Log.d(TAG, "Record service UUIDs: " + record.getServiceUuids());
            Log.d(TAG, "Record service data: " + record.getServiceData());

mLeDeviceListAdapter.addDevice(device);
mLeDeviceListAdapter.notifyDataSetChanged();

mText.setText("搜索结果，builder：" + builder.toString());
        }

看到没有，这里包含result就是onScanResult(int callbackType, ScanResult result)的返回值,而且对于如何解析的代码我也贴出来了，是不是应该感动一下。

最后，所有的操作完了，不要忘记stop一下，我们可以在OnDestory方法中停止，当然加一个postdelay，这里操作我写了一个方法直接在需要的地方调用。

mHandler.postDelayed(new Runnable() {
@Override
    public void run() {
        stopScanning();
    }
}, DEFAULT_SCAN_PERIOD);

停止方法，

 private void stopScanning() {
if (mBluetoothLeScanner != null) {
        Log.d(TAG, "Stop scanning.");
mBluetoothLeScanner.stopScan(mBleScanCallback);
    }
}

剩下的就是connectGatt了，下篇文章我会重点介绍，蓝牙之间如何连接，如果传递数据，可能会结合我们公司的项目来讲解，

对了，我猜大家肯定需要源码，等公司项目完了，就上传一个修改后的demo给大家，欢迎大家关注。