解释代码private final BroadcastReceiver receiver = new BroadcastReceiver() { public void onReceive(Context context, Intent intent) { boolean f = true; String action = intent.getAction(); BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); if (BluetoothDevice.ACTION_FOUND.equals(action) && f) { addDeviceList(new BleDevice(device, 20, device.getName())); } } };
时间: 2023-07-14 15:13:21 浏览: 65
这段代码定义了一个私有的BroadcastReceiver对象,当接收到蓝牙设备发现的广播时,会执行onReceive()方法。其中,通过getAction()方法获取广播的action,通过getParcelableExtra()方法获取BluetoothDevice对象,判断广播的action是否为ACTION_FOUND,如果是则将获取到的设备信息添加到设备列表中。此外,f变量的作用是控制只有第一次接收到广播时才添加设备信息。
相关问题
public abstract class BaseFragment extends Fragment { static final String TAG = "tag"; public final String ACTION = "NIGHT_SWITCH"; protected BroadcastReceiver receiver; protected IntentFilter filter; @Override protected void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); setNightMode(); filter = new IntentFilter(); filter.addAction(ACTION); receiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { Log.d(TAG, "onReceive: needRefresh"); needRefresh(); } }; registerReceiver(receiver, filter); } public boolean isNightMode(){ SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext()); return sharedPreferences.getBoolean("nightMode", false); } public void setNightMode(){ if(isNightMode()) { SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext()); Log.d(TAG, "setNightMode: " + sharedPreferences.getBoolean("nightMode", false)); this.setTheme(R.style.NightTheme); } else setTheme(R.style.DayTheme); } @Override protected void onDestroy() { super.onDestroy(); unregisterReceiver(receiver); } protected abstract void needRefresh(); }这段代码有问题,怎么改
这段代码中的问题在于 `setTheme()` 方法不能在 Fragment 中使用,而应该在 Activity 中使用。因此,我们需要将设置主题的代码移到 Activity 中。以下是修改后的代码:
```
public abstract class BaseFragment extends Fragment {
static final String TAG = "tag";
public final String ACTION = "NIGHT_SWITCH";
protected BroadcastReceiver receiver;
protected IntentFilter filter;
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
filter = new IntentFilter();
filter.addAction(ACTION);
receiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
Log.d(TAG, "onReceive: needRefresh");
needRefresh();
}
};
requireActivity().registerReceiver(receiver, filter);
}
public boolean isNightMode(){
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(requireContext());
return sharedPreferences.getBoolean("nightMode", false);
}
@Override
public void onDestroy() {
super.onDestroy();
requireActivity().unregisterReceiver(receiver);
}
protected abstract void needRefresh();
}
```
请注意,我们将 `registerReceiver()` 和 `unregisterReceiver()` 方法中的 `getContext()` 改为了 `requireContext()`,这是因为在 Fragment 中使用 `getContext()` 可能会返回 null,而 `requireContext()` 可以确保返回非 null 的 Context。
BroadcastReceiver如何正确处理网络状态变化的事件
要正确地处理网络状态变化的事件,需要使用Android提供的ConnectivityManager和NetworkInfo类。
1. 首先,在AndroidManifest.xml文件中声明一个具有网络状态变化意图过滤器的广播接收器。例如:
```
<receiver android:name=".NetworkStateReceiver">
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
</intent-filter>
</receiver>
```
2. 在NetworkStateReceiver类中覆盖onReceive()方法,并通过ConnectivityManager和NetworkInfo类检查网络状态。例如:
```
public class NetworkStateReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean isConnected = activeNetwork != null && activeNetwork.isConnectedOrConnecting();
if (isConnected) {
// 处理网络已连接的情况
} else {
// 处理网络未连接的情况
}
}
}
```
3. 在onCreate()方法中注册NetworkStateReceiver广播接收器。例如:
```
IntentFilter filter = new IntentFilter();
filter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
NetworkStateReceiver receiver = new NetworkStateReceiver();
registerReceiver(receiver, filter);
```
这样,当网络状态变化时,系统会自动调用NetworkStateReceiver的onReceive()方法,根据网络状态的变化来处理相应的事件。
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