android - 为什么 isMultipleAdvertisementSupported() 在 getBluetoothLeAdvertiser 返回对象时返回 false？

Question

我正在尝试在我的设备上使用 BLE 传输。

这是我使用的代码和输出:

// check BLE support
Log.i(TAG, "BLE supported: " + getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)); // true

// check BLE transmission support
final BluetoothManager bluetoothManager =
        (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
BluetoothAdapter mBluetoothAdapter = bluetoothManager.getAdapter();

Log.i(TAG, "isMultipleAdvertisementSupported: " + mBluetoothAdapter.isMultipleAdvertisementSupported()); // false
Log.i(TAG, "isOffloadedFilteringSupported: " + mBluetoothAdapter.isOffloadedFilteringSupported()); // false
Log.i(TAG, "isOffloadedScanBatchingSupported: " + mBluetoothAdapter.isOffloadedScanBatchingSupported()); // false

BluetoothLeAdvertiser mBluetoothLeAdvertiser = mBluetoothAdapter.getBluetoothLeAdvertiser();
Log.i(TAG, mBluetoothLeAdvertiser.toString()); //android.bluetooth.le.BluetoothLeAdvertiser@1c51f789

// check BLE transmission support
// android-beacon-library, https://github.com/AltBeacon/android-beacon-library
int result = BeaconTransmitter.checkTransmissionSupported(getApplicationContext());
Log.i(TAG, "ABL checkTransmissionSupported: " + result); // 0

我不明白为什么 mBluetoothLeAdvertiser 不是 null，因为 mBluetoothLeAdvertiser 验证它不是 false:

package android.bluetooth;
// ...

public BluetoothLeAdvertiser getBluetoothLeAdvertiser() {
    if (getState() != STATE_ON) {
        return null;
    }
    if (!isMultipleAdvertisementSupported()) {
        return null;
    }
    synchronized(mLock) {
        if (sBluetoothLeAdvertiser == null) {
            sBluetoothLeAdvertiser = new BluetoothLeAdvertiser(mManagerService);
        }
    }
    return sBluetoothLeAdvertiser;
}

// ...

public boolean isMultipleAdvertisementSupported() {
    if (getState() != STATE_ON) return false;
    try {
        return mService.isMultiAdvertisementSupported();
    } catch (RemoteException e) {
        Log.e(TAG, "failed to get isMultipleAdvertisementSupported, error: ", e);
    }
    return false;
}

Answer 1

欢迎来到既开源又封闭源代码的 Android 世界!您对上述开源BluetoothLeAdvertiser 代码的分析是正确的。如果该代码在您的移动设备上运行，您将看不到顶部代码 fragment 中的测试显示的输出。 结论:第二个 fragment 中显示的代码一定不是设备上的代码。

Android 设备 OEM 可以自由 fork 源代码并对其进行修改以使其与他们的硬件一起使用。在这种情况下，我知道摩托罗拉在这段代码中为他们的 Moto X 和 Moto G 设备做了同样的事情。这些设备返回 BluetoothLeAdvertiser，尽管 isMultipleAdvertisementSupported() 返回 false。一位摩托罗拉工程师向我解释说，他们改变了这一点，因为他们想要支持广告，尽管使用一次只能支持一个广告的 BLE 芯片。事实上，我已经验证了摩托罗拉设备可以做广告，但是如果你试图让两个广告同时播放，它就会失败。