如何创建序列化对象，并传递给bundle.putSerializable（键，值） [英] How to create Serializable object and pass to bundle.putSerializable(key, value)

问题描述

我也有类型的对象的活动 mqttQndroidClient 。这个对象我想将它传递给另一个活动。为了实现这一点，我阅读有关如何解决这样的问题，我发现soltion是创建一个类实现序列化如下图所示，和我做了以下内容：

 客户端=新mqttAndroidClient（..，...，...，..，）;
意图I =新意图（act_1.this，act_2.class）
clientObject = clientObj =新（CLIENT_OBJ_KEY，客户端）;
束B =新包（）;
b.putSerializable（CLIENT_OBJ_KEY，clientOb.getObjValue（））;
 

但是Eclipse强调 b.putSerializable（CLIENT_OBJ_KEY，clientObjValue（））; 有红色，看来我没cretae一个序列化对象正确。

和 clientObject 类，它实现序列化，看上去如下：

 公共类ClientObject实现Serializable {    私人字符串objectKey;
    私人MqttAndroidClient objectValue;    公共ClientObject（字符串objectKey，MqttAndroidClient objectValue）{        this.objectKey = objectKey;
        this.objectValue = objectValue;
    }    公共无效setObjKey（字符串objectKey）{        this.objectKey = objectKey;
    }    公共字符串getObjKey（）{        返回this.objectKey;
    }    公共无效setObjValue（MqttAndroidClient objValue）{        this.objectValue = objValue;
    }    公共MqttAndroidClient getObjValue（）{        返回this.objectValue;
    }
}
 

解决方案

我看到你解决很多问题。最大的一个是：你不能封装一个序列化的1个内没有一个序列化对象，并希望事情会工作。可序列化，每一个字段必须是可序列化，请阅读使用说明书。

问题是什么，你在这里解决？

1. 是它昂贵创建客户端的每个活动（时间/内存方面）？


2. 请你不想每次都重新配置客户端？


3. 你想在你的应用程序中的单个实例？

我对第一种情况的观点是，不昂贵创建一个客户端在您需要时（每个活动我猜想之一），通过阅读<一href=\"http://www.eclipse.org/paho/files/android-javadoc/org/eclipse/paho/android/service/MqttAndroidClient.html\">documentation有关MqttAndroidClient据我所知，客户端使用长时间运行的服务。此服务负责客户端/服务器通信，所以，我认为，客户端是一个非常小的包装，以简化服务/活动的通信。这意味着，只要你想，你可以创建任意多个客户端。

这使我们的第二点：你不希望每次都重新配置客户端。
该解决方案是创建一个工厂。基本上是这样的：

 公共final类MqttClientFactory {
  公共静态MqttAndroidClient createClientInstance（上下文的背景下，...）{
    MqttAndroidClient客户端=新MqttAndroidClient（背景下，....）;
    //这里配置客户端
    返回客户端;
  }
}
 

现在您可以创建一个配置实例的<一个href=\"http://developer.android.com/reference/android/app/Activity.html#onCreate%28android.os.Bundle%29\">Activity.onCreate(...)

  @覆盖
保护无效的onCreate（捆绑savedInstanceState）{
  super.onCreate（savedInstanceState）;
  ...
  mMqttClient = MqttClientFactory.createClientInstance（此，...）;
  ...
}
 

如果你想你的整个应用程序客户端的一个实例，有很多的解决方案，这通常涉及使用的单。我个人preFER避免单身，所以我建议重写应用程序类用自己，创造你的客户的实例有，并从活动得到引用。

 公共类MyApplication的扩展应用{
  私人MqttAndroidClient mClient;  公共无效的onCreate（）{
    super.onCreate（）;    mClient =新MqttAndroidClient（此，...）;    ...
  }  公众最终MqttAndroidClient getClient（）{
    返回mClient;
  }
}
 

您现在可以使用<一个href=\"http://developer.android.com/reference/android/content/Context.html#getApplicationContext()\">Context.getApplicationContext()或<一个href=\"http://developer.android.com/reference/android/app/Activity.html#getApplication%28%29\">Acticity.getAppliaction()去你的自定义应用程序的参考。即：

  MqttAndroidClient sharedClient =（（所有MyApplication）getApplication（））getClient（）。
 

您需要将您的自定义应用程序添加到清单，请参阅文档这里

I have an activity which has an object of type mqttQndroidClient. this object i would like to pass it to another activity. To achieve this i read about how to solve such issue and the soltion i found was to create a class that implements serializable as shown below, and i did the following:

client = new mqttAndroidClient(..,...,..,..,);
Intent i = new Intent(act_1.this, act_2.class)
clientObject = clientObj = new (CLIENT_OBJ_KEY, client);
Bundle b = new Bundle();
b.putSerializable(CLIENT_OBJ_KEY, clientOb.getObjValue());

But eclipse underscore the b.putSerializable(CLIENT_OBJ_KEY, clientObjValue()); with red, it seems i did not cretae a serializable object correctly.

and the clientObject class that implements serializable, looks as below:

public class ClientObject implements Serializable {

    private String objectKey;
    private MqttAndroidClient objectValue;

    public ClientObject(String objectKey, MqttAndroidClient objectValue) {

        this.objectKey = objectKey;
        this.objectValue = objectValue;
    }

    public void setObjKey(String objectKey) {

        this.objectKey = objectKey;
    }

    public String getObjKey() {

        return this.objectKey;
    }

    public void setObjValue(MqttAndroidClient objValue) {

        this.objectValue = objValue;
    }

    public MqttAndroidClient getObjValue() {

        return this.objectValue;
    }
}

解决方案

I see many problems in your solution. The biggest one is: you can not encapsulate a not serializable object inside a serializable one and hope that thing will work. To be serializable every single field must be serializable, please read the manual.

What problem are you addressing here?

1. Is it expensive to create a client for every activity (in terms of time/memory)?
2. Do you not want to reconfigure the client every time?
3. Do you want a single instance around your application?

My opinion about the first case is that is not to expensive to create a client when you need one (one per activity I suppose), by reading the documentation about MqttAndroidClient I understand that the client is using a long running service. This service is responsible for the client/server communications, so, I assume, the client is a very tiny wrapper to simplify service/activity communications. This imply you can create as many client as you want.

This leads us to the second point: you don't want to reconfigure the client every time. The solution is to create a factory. Basically something like this:

public final class MqttClientFactory {
  public static MqttAndroidClient createClientInstance(Context context, ...) {
    MqttAndroidClient client = new MqttAndroidClient(context, ....);
    // Configure your client here
    return client;
  }
}

Now you can create a configured instance your Activity.onCreate(...)

@Override
protected void onCreate (Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  ...
  mMqttClient = MqttClientFactory.createClientInstance(this, ...);
  ...
}

If you want a single instance of you client for the entire app, there are many solutions, that generally involve the use of a singleton. I personally prefer to avoid singletons, so I suggest to override the Application class with your own, create an instance of your client there and get the reference to it from your activity.

public class MyApplication extends Application {
  private MqttAndroidClient mClient;

  public void onCreate () {
    super.onCreate();

    mClient = new MqttAndroidClient(this, ...);

    ...
  }

  public final MqttAndroidClient getClient() {
    return mClient;
  }
}

You can now use Context.getApplicationContext() or Acticity.getAppliaction() to get a reference to your custom Application. I.E.:

MqttAndroidClient sharedClient = ((MyApplication) getApplication()).getClient();

You need to add your custom application to the manifest, please see the docs here

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