android - 在 Android 上，我可以注册一个回调来告诉我蓝牙是打开还是关闭吗？

Question

我需要在我的应用程序内部知道蓝牙是打开还是关闭。或者，如果蓝牙已打开或关闭，例如从操作系统设置下拉菜单。我认为我可以在 Activity 的 onResume() 中执行此操作。但事实证明，当打开 Android 操作系统的设置“下拉菜单”(用手指从屏幕顶部边缘下拉访问的菜单)时， Activity 不会暂停。

当蓝牙可用或不可用时，我需要更新我的用户界面。

我可以注册回调(例如 BroadcastReceiver)或任何其他回调，让系统在蓝牙可用性发生变化时通知我吗？

Answer 1

您可以使用 Intent 过滤器注册接收器:

<receiver
        android:name="com.example.BluetoothReceiver"
        android:enabled="true">
    <intent-filter>
        <action android:name="android.bluetooth.adapter.action.STATE_CHANGED"/>
    </intent-filter>
</receiver>

这是广播接收器:

public class BluetoothReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();

        if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
            int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1);

            switch (state){
                case BluetoothAdapter.STATE_OFF:
                    //Indicates the local Bluetooth adapter is off.
                break;

                case BluetoothAdapter.STATE_TURNING_ON:
                    //Indicates the local Bluetooth adapter is turning on. However local clients should wait for STATE_ON before attempting to use the adapter.
                break;

                case BluetoothAdapter.STATE_ON:
                    //Indicates the local Bluetooth adapter is on, and ready for use.
                break;

                case BluetoothAdapter.STATE_TURNING_OFF:
                    //Indicates the local Bluetooth adapter is turning off. Local clients should immediately attempt graceful disconnection of any remote links.
                break;
            }
        }
    }
};

或者如果你想直接在 Activity 中添加:

public class ExampleActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_example);
    }

    @Override
    protected void onResume() {
        super.onResume();
        registerReceiver(mReceiver, new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED));
    }

    @Override
    protected void onPause() {
        super.onPause();
        unregisterReceiver(mReceiver);
    }

    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {

        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();

            if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
                int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1);

                switch (state) {
                    case BluetoothAdapter.STATE_OFF:
                        //Indicates the local Bluetooth adapter is off.
                        break;

                    case BluetoothAdapter.STATE_TURNING_ON:
                        //Indicates the local Bluetooth adapter is turning on. However local clients should wait for STATE_ON before attempting to use the adapter.
                        break;

                    case BluetoothAdapter.STATE_ON:
                        //Indicates the local Bluetooth adapter is on, and ready for use.
                        break;

                    case BluetoothAdapter.STATE_TURNING_OFF:
                        //Indicates the local Bluetooth adapter is turning off. Local clients should immediately attempt graceful disconnection of any remote links.
                        break;
                }
            }
        }
    };
}