Android 12上BroadcastReceiver无法通过AndroidManifest.xml文件声明，需要通过代码动态注册。以下是一个示例：

public class MyReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // 处理接收到的广播
    }
}

public class MainActivity extends AppCompatActivity {
    private MyReceiver receiver;

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

        // 动态注册广播接收器
        receiver = new MyReceiver();
        IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(Intent.ACTION_SCREEN_ON);
        intentFilter.addAction(Intent.ACTION_SCREEN_OFF);
        registerReceiver(receiver, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // 取消注册广播接收器
        unregisterReceiver(receiver);
    }
}

以上示例将接收屏幕打开和关闭的广播。需要注意，在不需要使用时应该取消广播接收器的注册。