蓝牙开关

最新推荐文章于 2022-03-28 21:50:48 发布

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本文主要探讨了Android系统设置中的蓝牙开关功能，详细分析了`BluetoothSettings`类的作用，以及`BluetoothEnabler`如何控制蓝牙的开启。在`BluetoothEnabler`的构造方法中，`LocalBluetoothManager`用于封装蓝牙API接口，并通过单例模式管理。`handleStateChanged`方法在界面恢复时获取蓝牙状态，确保界面与实际蓝牙状态同步。此外，蓝牙开启后会显示已配对和可用设备列表。

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BluetoothSettings

设置选项中蓝牙开关的按钮。在settings代码中。
代码路径（packages\apps\Settings\src\com\android\settings\bluetooth\）

BluetoothSettings

//android8.0\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothSettings.java

public final class BluetoothSettings extends DeviceListPreferenceFragment implements Indexable {
    ...
}

这个类，是蓝牙设置中的主界面。
我们通过这个类来完善对settings中蓝牙相关代码以及类的认识。

蓝牙开关

我们分析一下蓝牙开关按钮都做了什么操作。

//android8.0\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothSettings.java

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        /* Don't auto start scan if screen reconstructs due to frozen screen*/
        mInitialScanStarted = (savedInstanceState != null);
        mInitiateDiscoverable = true;

        final SettingsActivity activity = (SettingsActivity) getActivity();
        mSwitchBar = activity.getSwitchBar();
        //打开开关
        mBluetoothEnabler = new BluetoothEnabler(activity, new SwitchBarController(mSwitchBar),
            mMetricsFeatureProvider, Utils.getLocalBtManager(activity),
            MetricsEvent.ACTION_BLUETOOTH_TOGGLE);
        mBluetoothEnabler.setupSwitchController();
    }

BluetoothSettings.java是settings中蓝牙相对比较重要的类。在初始化（onActivityCreated）的时候，进行打开开关操作。

调用BluetoothEnabler来开启开关。

BluetoothEnabler构造方法

我们进入BluetoothEnabler的构造方法来看看都做了什么操作。

E:\android8.0\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothEnabler.java

public BluetoothEnabler(Context context, SwitchWidgetController switchWidget,
            MetricsFeatureProvider metricsFeatureProvider, LocalBluetoothManager manager,
            int metricsEvent, RestrictionUtils restrictionUtils) {
        mContext = context;
        mMetricsFeatureProvider = metricsFeatureProvider;
        //ui选择控件
        mSwitchWidget = switchWidget;
        mSwitch = mSwitchWidget.getSwitch();
        mSwitchWidget.setListener(this);
        mValidListener = false;
        mMetricsEvent = metricsEvent;

        if (manager == null) {
            // 蓝牙不支持。通过判断manager是否为空。
            mLocalAdapter = null;
            mSwitchWidget.setEnabled(false);
        } else {
            //1.1
            //支持蓝牙的时候，是通过manager获取.
            //这个manger是LocalBluetoothManager，这个类是为本地的蓝牙接口适配器，为应用提供接口，同时调用BluetoothAdapter的接口，起到应用和底层的适配作用。
            mLocalAdapter = manager.getBluetoothAdapter();
        }
        mIntentFilter = new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED);
        mRestrictionUtils = restrictionUtils;
    }

1.1 LocalBluetoothManager

LocalBluetoothManager类将bluetooth api的接口封装。


public class LocalBluetoothManager {
    private static final String TAG = "LocalBluetoothManager";

    /** Singleton instance. */
    private static LocalBluetoothManager sInstance;

    private final Context mContext;

    /** If a BT-related activity is in the foreground, this will be it. */
    private Context mForegroundActivity;

    private final LocalBluetoothAdapter mLocalAdapter;

    private final CachedBluetoothDeviceManager mCachedDeviceManager;

    /** The Bluetooth profile manager. */
    private final LocalBluetoothProfileManager mProfileManager;

    /** The broadcast receiver event manager. */
    private final BluetoothEventManager mEventManager;

    /**
        获取一个示例
    */
    public static synchronized LocalBluetoothManager getInstance(Context context,
            BluetoothManagerCallback onInitCallback) {
        if (sInstance == null) {
            LocalBluetoothAdapter adapter = LocalBluetoothAdapter.getInstance();
            if (adapter == null) {
                return null;
            }
            // This will be around as long as this process is
            Context appContext = context.getApplicationContext();
            sInstance = new LocalBluetoothManager(adapter, appContext);
            if (onInitCallback != null) {
                onInitCallback.onBluetoothManagerInitialized(appContext, sInstance);
            }
        }

        return sInstance;
    }

    //构造方法中new 了几个相关的manager来得到getxxxmanager。
    private LocalBluetoothManager(LocalBluetoothAdapter adapter, Context context) {
        mContext = context;
        mLocalAdapter = adapter;
        //负责管理蓝牙的缓存（已配对的设备和搜索到的设备）主要都保存在List<CachedBluetoothDevice> mCachedDevices中
        mCachedDeviceManager = new CachedBluetoothDeviceManager(context, this);
        //接收广播，分发底层发出的event。一般android中定义eventxxx类其实就是传递的类。
        mEventManager = new BluetoothEventManager(mLocalAdapter,
                mCachedDeviceManager, context);
        //蓝牙配置协议管理 例如A2dpProfile HeadsetProfile OppProfile PbapClientProfile有个印象即可。后续会进行详细讲解。
        mProfileManager = new LocalBluetoothProfileManager(context,
                mLocalAdapter, mCachedDeviceManager, mEventManager);
    }

   ...

}

这个类的代码很少，用一个单例模式。构造方法中new出3个相应的xxxmanager。并且提供了3个方法来获取xxxmanager。
getCachedDeviceManager，getProfileManager，getEventManager。

获取mLocalAdapter有什么用？

BluetoothEnabler的handleStateChanged方法

我们先看看bluetootheabler的的handleStateChanged方法

// BluetoothEnabler.java
    void handleStateChanged(int state) {
        switch (state) {
            case BluetoothAdapter.STATE_TURNING_ON:
                mSwitchWidget.setEnabled(false);
                break;
            case BluetoothAdapter.STATE_ON:
                setChecked(true);
                mSwitchWidget.setEnabled(true);
                break;
            case BluetoothAdapter.STATE_TURNING_OFF:
                mSwitchWidget.setEnabled(false);
                break;
            case BluetoothAdapter.STATE_OFF:
                setChecked(false);
                mSwitchWidget.setEnabled(true);
                break;
            default:
                setChecked(false);
                mSwitchWidget.setEnabled(true);
        }
    }

这个方法在onresume中被调用

BluetoothEnabler.java

    public void resume(Context context) {
        if (mContext != context) {
            mContext = context;
        }

        maybeEnforceRestrictions();

        if (mLocalAdapter == null) {
            mSwitchWidget.setEnabled(false);
            return;
        }

        // Bluetooth state is not sticky, so set it manually
        handleStateChanged(mLocalAdapter.getBluetoothState());

        mSwitchWidget.startListening();
        mContext.registerReceiver(mReceiver, mIntentFilter);
        mValidListener = true;
    }

我们也就清楚了，进入这个bluetoothEnabler类后。onresume方法来进行获取状态。

传入的参数是

mLocalAdapter.getBluetoothState()

也就是我们之前分析的构造方法中 //1.1

//1.1
mLocalAdapter = manager.getBluetoothAdapter();

的用处。

已配对设备，可用设备

蓝牙打开后，会出现已经配对设备，可用设备。

//android8.0\packages\apps\Settings\src\com\android\settings\bluetooth\BluetoothSettings.java

    @Override
    void addPreferencesForActivity() {
        addPreferencesFromResource(R.xml.bluetooth_settings);
        final Context prefContext = getPrefContext();
        //已经配对设备列表
        mPairedDevicesCategory = new PreferenceCategory(prefContext);
        mPairedDevicesCategory.setKey(KEY_PAIRED_DEVICES);
        mPairedDevicesCategory.setOrder(1);
        //可用设备列表
        getPreferenceScreen().addPreference(mPairedDevicesCategory);

        mAvailableDevicesCategory = new BluetoothProgressCategory(prefContext);
        mAvailableDevicesCategory.setSelectable(false);
        mAvailableDevicesCategory.setOrder(2);
        getPreferenceScreen().addPreference(mAvailableDevicesCategory);

        mMyDevicePreference = mFooterPreferenceMixin.createFooterPreference();
        mMyDevicePreference.setSelectable(false);

        setHasOptionsMenu(true);
    }