Android - 收听NFC适配器状态已更改

Question

我正在尝试构建一个使用NFC的应用程序.目标是显示包含按钮链接的DialogFragment以进行设置并手动更改它,并在启用该功能时禁用DialogFragment.

问题:如果用户使用下拉通知托盘中的图标启用/禁用NFC,则onPause/onResume不会被调用并完全错过该条件.我确信有一个接收器,我可以注册,并实时响应.任何想法,想法或参考将不胜感激!

以下代码检查状态是否已启用/禁用.我也在onResume事件中适当地回应它.

    NfcManager manager = (NfcManager) getSystemService(Context.NFC_SERVICE);
    NfcAdapter adapter = manager.getDefaultAdapter();

    if(adapter != null && adapter.isEnabled()) {
        detector = new NfcDetector(this);
        detector.setListener(this);
        onNfcFeatureFound();
    }
    else {
        onNfcFeatureNotFound();
    }

对于看过这篇文章的其他人,下面的代码将直接将用户带入设置以启用/禁用NFC:

startActivity(new Intent(android.provider.Settings.ACTION_NFC_SETTINGS));

Answer 1

以为我应该为寻找同样问题的其他人发布答案,因为我无法轻易找到.

将以下代码添加到您的活动onCreate()方法:

IntentFilter filter = new IntentFilter(NfcAdapter.ACTION_ADAPTER_STATE_CHANGED);
this.registerReceiver(mReceiver, filter);

在您的活动中(或您喜欢的任何其他地方)声明的内部私有类:

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();

        if (action.equals(NfcAdapter.ACTION_ADAPTER_STATE_CHANGED)) {
            final int state = intent.getIntExtra(NfcAdapter.EXTRA_ADAPTER_STATE,
                                                 NfcAdapter.STATE_OFF);
            switch (state) {
            case NfcAdapter.STATE_OFF:
                break;
            case NfcAdapter.STATE_TURNING_OFF:
                break;
            case NfcAdapter.STATE_ON:
                break;
            case NfcAdapter.STATE_TURNING_ON:
                break;
            }
        }
    }
};

@Override
public void onDestroy() {
    super.onDestroy();

    // Remove the broadcast listener
    this.unregisterReceiver(mReceiver);
}

  // The following check needs to also be added to the onResume
@Override
protected void onResume() 
    super.onResume();
    // Check for available NFC Adapter
    NfcAdapter adapter = NfcAdapter.getDefaultAdapter(this);

    if(adapter != null && adapter.isEnabled()) {
        createNfcDetector();
        //NFC is available on device, but disabled
    }
    else {
        //NFC Is available and enabled
    }
}