Android - 从应用程序类更改活动 UI

Question

我扩展了Application类，以创建Android中的单例对象。

在这个对象中，我处理与我的服务器的所有HTTP工作，所有其他活动都可以访问它并调用GET、POST等方法。

代码：

public class HttpManagerInstance extends Application {
    private HttpClient httpClient;
    private HttpGet get;

    @Override
    public void onCreate() {
        httpClient = new DefaultHttpClient();
        get = new HttpGet("http://10.100.102.9:8000/users/");
        super.onCreate();

    }


    public Void getUsers() throws Exception {
        new executeRequest().execute(get);
        return null;
    }

    private class executeRequest extends AsyncTask<HttpRequest, Void, Integer> {

        @Override
        protected Integer doInBackground(HttpRequest... params) {
            // TODO Auto-generated method stub
            HttpRequest request = params[0];
            HttpResponse response;
            String result="";
            try {
                response = httpClient.execute((HttpUriRequest) request);
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return responseCode;
        }

        @Override
        protected void onPostExecute(Integer result) {
            // TODO Auto-generated method stub
            switch (result) {
            case HttpStatus.SC_OK:
                // request was fine

                // Here I want to updated the GUI of the activity that called this method.
                break;
            }
        }

    }

}

这是我从Activity中调用方法的方式：

HttpManagerInstance sampleApp = (HttpManagerInstance)getApplicationContext();
sampleApp.getUsers();

再次强调 - 我想访问调用放置 REQUEST ACCEPTED 消息方法的 Activity 的 UI。

或者传递一个上下文？有什么想法吗？

- Ofek Agmon

Answer 1

我会创建一个监听器：

public class HttpManagerInstance extends Application {
    private HttpClient httpClient;
    private HttpGet get;

    public interface ResponseListener{
      public void onSuccess(Object data);
    }


    @Override
    public void onCreate() {
        httpClient = new DefaultHttpClient();
        get = new HttpGet("http://10.100.102.9:8000/users/");
        super.onCreate();

    }


    public Void getUsers(ResponseListener listener) throws Exception {
        new executeRequest(listener).execute(get);
        return null;
    }

    private class executeRequest extends AsyncTask<HttpRequest, Void, Integer> {

        private ResponseListener mListener;

        public executeRequest(ResponseListener listener){
         this.mListener = listener;
        }

        @Override
        protected Integer doInBackground(HttpRequest... params) {
            // TODO Auto-generated method stub
            HttpRequest request = params[0];
            HttpResponse response;
            String result="";
            try {
                response = httpClient.execute((HttpUriRequest) request);
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return responseCode;
        }

        @Override
        protected void onPostExecute(Integer result) {
            // TODO Auto-generated method stub
            switch (result) {
            case HttpStatus.SC_OK:
                // request was fine

                // Here I want to updated the GUI of the activity that called this method.
                if(this.mListener != null) mListener.onSuccess(whatEverDataYouWant);
                break;
            }
        }

    }

}

然后，在你的活动中：

    HttpManagerInstance sampleApp = (HttpManagerInstance)getApplicationContext();
    sampleApp.getUsers(new ResponseListener(){
       public void onSuccess(Object data){
         //update your ui!
       }

});

- mmark

---

谢谢你的回答，看起来非常好，我会尝试它。顺便说一句 - 我认为你犯了一个小错误 - 在Activity代码中，有一个ResponseListener接口，在AsyncTask中，你写了不存在的RequestListener。再次感谢！ - Ofek Agmon

@OfekAgmon 感谢您的纠正！我已经修复了它！请告诉我它的运行情况。不用客气！ - mmark

Answer 2

简短的回答是你不能直接从另一个活动引用UI。我的建议是在你的Application类上设置一个回调，在executeRequest#onPostExecute上调用它，然后在你的Activity上实现该回调并从那里更新你的UI。

如果你需要帮助来实现回调，请查看this question。

- Carlos J

Answer 3

如果您需要显示消息，Dialog类或Toast类是不错的选择，您可以在这里查看更多信息： 对话框：http://developer.android.com/guide/topics/ui/dialogs.html Toast：http://developer.android.com/guide/topics/ui/notifiers/toasts.html

但是，如果您想要访问或修改实际活动中的控件，则使用Runnable类，并使用context.runOnUiThread()方法（如果您在AsyncTask内工作）。真正的问题是您无法使用控件的声明在AsyncTask中更改UI。您需要抛出一个Runnable进程来与活动通信！！例如：

context.runOnUiThread(new Runnable() {
                public void run() {
                    //Declaration of variables
                    TextView MyTextView = (TextView) context.findViewById(R.id.txtvMyControl);

                    MyTextView.setText("My title");
                }
}

如果我能帮到你，请告诉我，祝你好运！

- Merlí Escarpenter Pérez