为什么我写的代码和老师的一样不行呢

我写的代码和老师的一样，只不过是用的动态注册，为什么不行呢

public class MainActivity extends AppCompatActivity {
    private Button button;
    private final  String CUSTOM_ACTION="com.sample.custom.action";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button=findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent=new Intent();
                intent.setAction(CUSTOM_ACTION);
                MainActivity.this.sendBroadcast(intent);
            }
        });

    }
}

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        IntentFilter filter=new IntentFilter();
        filter.addAction("com.sample.custom.action");
        registerReceiver(mBatter,filter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(mBatter);
    }

    private BroadcastReceiver mBatter = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            Log.d("wahaaaaa",intent.getAction());
            Intent intent1=new Intent();
            intent1.setClass(context,MainActivity.class);
            intent1.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            context.startActivity(intent1);
        }
    };
}