Question

我有服务，它从API获取数据并将此数据发送到BroadcastReceiver类。另外，我创建了在Activity中使用的接口OnReceiveListener。看看这里的代码：

的活动：

public class StartActivity extends AppCompatActivity
    implements MyBroadcastReceiver.OnReceiveListener {

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

    MyBroadcastReceiver receiver = new MyBroadcastReceiver();
    receiver.setOnReceiveListener(this);
    LocalBroadcastManager.getInstance(this).registerReceiver(receiver,
            new IntentFilter(MyBroadcastReceiver.START));
    ...
}

@Override
public void onReceive(Intent intent) {
    // Do smth here
}
}

MyBroadcastReceiver：

public class MyBroadcastReceiver extends BroadcastReceiver {
public static final String START = "com.example.myapp.START";
public static final String GET_LINKS = "com.example.myapp.GET_LINKS";

private OnReceiveListener onReceiveListener = null;

public interface OnReceiveListener {
    void onReceive(Intent intent);
}

public void setOnReceiveListener(Context context) {
    this.onReceiveListener = (OnReceiveListener) context;
}

@Override
public void onReceive(Context context, Intent intent) {
    if(onReceiveListener != null) {
        onReceiveListener.onReceive(intent);
    }
}
}

服务对这个问题并不重要。

----问题----

那么，问题是什么：我想在片段中使用这个接收器，但是当它设置上下文时 - 我得到异常＆＃34;启用强制转换＆＃34;。我应该怎么做这个案子？

这是片段中的代码：

public class MainFragment extends Fragment
    implements MyBroadcastReceiver.OnReceiveListener {

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);

    MyBroadcastReceiver myBroadcastReceiver = new MyBroadcastReceiver();
    myBroadcastReceiver.setOnReceiveListener(getContext());
    LocalBroadcastManager.getInstance(getContext()).registerReceiver(myBroadcastReceiver,
            new IntentFilter(MyBroadcastReceiver.GET_LINKS));
}

@Override
public void onReceive(Intent intent) {
    // Do smth here
}
}

Answer 1

您的MainFragment课程实现了OnReceiveListener界面，而不是Context返回的getContext()界面。不要将Context对象传递到setOnReceiveListener()，而是尝试直接传递OnReceiveListener实例。然后，您的片段和活动都可以调用setOnReceiveListener(this)。

Answer 2

您不需要动态注册接收器。我相信您必须使用<receiver>标记在清单中注册它。

这不是必需的：

LocalBroadcastManager.getInstance（的getContext（））。registerReceiver（myBroadcastReceiver，新的IntentFilter（MyBroadcastReceiver.GET_LINKS））;

关于回调注册监听器，而不是使用getContext()使用MainFragment.this这样：

myBroadcastReceiver.setOnReceiveListener(MainFragment.this);

Answer 3

在寻找合适的方法来实现此问题的解决方案数小时后，我终于找到了一种方法。它基于 RussHWolf 的回答。完整的代码解决方案如下：

通过这种方式，setListener() 方法被公开，以便 Fragment 或 Activity 可以通过发送 IStatusChangeListener 的实例来设置侦听器。

public class StatusChangeReceiver extends BroadcastReceiver {
    private IStatusChangeListener listener;

    public void setListener(IStatusChangeListener listener) {
        this.listener = listener;
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        if (NetworkUtil.isNetworkConnected()) {
            listener.onConnected();
        } else {
            listener.onDisconnected();
        }
    }
}

这是界面：

public interface IStatusChangeListener {
    void onConnected(String status);
    void onDisonnected(String status);
}

现在，需要有一个 IStatusChangeListener 接口的实例，而不是实现 IStatusChangeListener 接口。然后，将此 IStatusChangeListener 实例传递给 setListener() 方法。

public class MainFragment extends Fragment { //Not implementing the interface

    private IStatusChangeListener listener = new IStatusChangeListener() {
        @Override
        void onConnected(String status) {
            //some log here
        }

        @Override
        void onDisonnected(String status) {
            //some log here
        }
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        StatusChangeReceiver r = new StatusChangeReceiver();
        r.setListener(listener); // pass the IStatusChangeListener instance
        LocalBroadcastManager.getInstance(getContext()).registerReceiver(r, new IntentFilter("connectionStatus"));
    }
}

注意：如果您从 LocalBroadcastManager 注册 BroadcastReceiver，请始终使用 Fragment。

如何在片段中设置广播监听器接口？

3 个答案: