如何在活动更改后获取当前活动

Question

我正在使用附近的连接在设备之间创建连接。建立连接后，活动将更改。现在，如果设备断开连接，则会调用回调，但在旧活动中收到回调。现在我想显示一个 AlertDialog，但该对话框永远不会显示，因为它显示在旧活动上。如何显示新活动的对话框？

我正在使用附近的连接，如下所示：网址

private Activity mActivity;
public RemoteConnection(Activity activity){
    mActivity = activity;
} 
  // For simplicity I did only include this method
  @Override
  public void onDisconnected(String endpointId) {
    // We've been disconnected from this endpoint. No more data can be
    // sent or received.
    new AlertDialog.Builder(mActivity)
      .setTitle("Disconnection")
      .setMessage("Other device is disconnected")
      .setIcon(android.R.drawable.ic_dialog_alert)
      .show();
  }

对话框应显示在当前活动上

Answer 1

在活动中编写方法如下：

public void showAlert(activity)
{
    new AlertDialog.Builder(activity)
  .setTitle("Disconnection")
  .setMessage("Other device is disconnected")
  .setIcon(android.R.drawable.ic_dialog_alert)
  .show();
}

并更改以下代码：

@Override
 public void onDisconnected(String endpointId) {
// We've been disconnected from this endpoint. No more data can be
// sent or received.
new AlertDialog.Builder(mActivity)
  .setTitle("Disconnection")
  .setMessage("Other device is disconnected")
  .setIcon(android.R.drawable.ic_dialog_alert)
  .show();

}

自：

@Override
 public void onDisconnected(String endpointId) {
// We've been disconnected from this endpoint. No more data can be
// sent or received.
if(((YourActivityA)activity) != null)
{
    ((YourActivityA)activity).showAlert(activity);
}
else if(((YourActivityB)activity) != null)
{
    ((YourActivityB)activity).showAlert(activity);
}
}

Answer 2

使用事件总线实现或使用 sendBroadcast() 发送回调，并让每个Activity在 onResume() 中注册一个BroadcastReceiver，并在 onPause() 中取消注册。