如何从单独的 AsyncTask 类更新 UI答案

【问题标题】：How to update UI from separate AsynkTask class如何从单独的 AsyncTask 类更新 UI
【发布时间】：2016-07-04 17:01:16
【问题描述】：

我有一个 CDealListing 类，我从那里执行 AsynkTask 类，它是一个单独的类，我想要更新 AsynkTask 类 onPost 方法上的 CDealListing 类的 UI。请帮助我.....

这是我的课程 CDealListing 的代码

public class CDealAppListing extends Fragment {
public static String m_DealListingURL = "http://192.166.0.110:8080/ireward/rest/json/metallica/getDealListInJSON";
public static String s_szresult = " ";
public static RecyclerView m_RecyclerView;
public static CDealAppListingAdapter m_oAdapter;
public static CDealAppDatastorage item;
public ArrayList<CDealAppDatastorage> s_oDataset;
public int[] m_n_FormImage;
public View m_Main;
public CRegistrationSessionManagement m_oSessionManagement;
public String m_szMobileNumber, m_szEncryptedPassword;
public LinearLayoutManager mLayoutManager;
public AppCompatButton m_showMore;
public ProgressBar mProgressBar;
public int m_n_DefaultRecordCount = 5;// intiallly record count is 5.
public int m_n_DeafalutLastCount = 0;//initally lastcount is 0.

public String sz_RecordCount, sz_LastCount;
//declare boolean
private CJsonsResponse m_oJsonsResponse;


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    m_Main = inflater.inflate(R.layout.deal_app_listing, container, false);//intialize mainLayout
    new CDealDataSent().execute(m_DealListingURL);
    init();//initialize method
    implementScroll();
    return m_Main;
}

public void init() {
    mProgressBar = (ProgressBar) m_Main.findViewById(R.id.progressBar1);
    mProgressBar.setVisibility(View.GONE);

    m_showMore = (AppCompatButton) m_Main.findViewById(R.id.show_more);
    m_showMore.setBackgroundColor(Color.TRANSPARENT);
    m_showMore.setVisibility(View.GONE);
    // Getting the string array from strings.xml
    m_n_FormImage = new int[]{
            R.drawable.amazon,
            R.drawable.whatsapp,
            R.drawable.zorpia,
            R.drawable.path,
            R.drawable.app_me,
            R.drawable.evernote,
            R.drawable.app_me};

    m_RecyclerView = (RecyclerView) m_Main.findViewById(R.id.my_recycler_view);//finding id of recyclerview
    m_RecyclerView.setItemAnimator(new DefaultItemAnimator());//setting default animation to recyclerview
    m_RecyclerView.setHasFixedSize(true);//fixing size of recyclerview
    mLayoutManager = new LinearLayoutManager(getActivity());
    m_RecyclerView.setLayoutManager(mLayoutManager);//showing odata vertically to user.
    m_oSessionManagement = new CRegistrationSessionManagement(getActivity());
    HashMap<String, String> user = m_oSessionManagement.getRegistrationDetails();
    m_szEncryptedPassword = user.get(m_oSessionManagement.s_szKEY_PASSWORD);
    m_szMobileNumber = user.get(m_oSessionManagement.s_szKEY_MOBILENUMBER);

    sz_RecordCount = String.valueOf(m_n_DefaultRecordCount);// increment of record count
    sz_LastCount = String.valueOf(m_n_DeafalutLastCount);
}

public void implementScroll() {
    m_RecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
            super.onScrollStateChanged(recyclerView, newState);
            if (newState ==  RecyclerView.SCROLL_STATE_IDLE){

            }
        }

        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);
            if (dy > 0) {

                m_showMore.setVisibility(View.VISIBLE);
                m_showMore.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        //change boolean value
                        m_showMore.setVisibility(View.GONE);
                        m_n_DefaultRecordCount = m_n_DefaultRecordCount + 5;
                        m_n_DeafalutLastCount = m_n_DeafalutLastCount + 5;

                        sz_RecordCount = String.valueOf(m_n_DefaultRecordCount);
                        sz_LastCount = String.valueOf(m_n_DeafalutLastCount);
                        new DealNext().execute(m_DealListingURL);
                    }
                });
            } else {
                m_showMore.setVisibility(View.GONE);
            }
        }
    });
}
//sending deal data to retreive response from server
public String DealListing(String url, CRegistrationDataStorage login) {
    InputStream inputStream = null;
    m_oJsonsResponse = new CJsonsResponse();
    try {
        // 1. create HttpClient
        HttpClient httpclient = new DefaultHttpClient();
        // 2. make POST request to the given URL
        HttpPost httpPost = new HttpPost(url);
        String json = "";
        // 3. build jsonObject
        JSONObject jsonObject = new JSONObject();
        jsonObject.put("agentCode", m_szMobileNumber);
        jsonObject.put("pin", m_szEncryptedPassword);
        jsonObject.put("recordcount", sz_RecordCount);
        jsonObject.put("lastcountvalue", sz_LastCount);
        //jsonObject.put("emailId", "nirajk1190@gmail.com");
        // 4. convert JSONObject to JSON to String
        json = jsonObject.toString();
        // 5. set json to StringEntity
        StringEntity se = new StringEntity(json);
        // 6. set httpPost Entity
        httpPost.setEntity(se);
        // 7. Set some headers to inform server about the type of the content
        httpPost.setHeader("Content-type", "application/json");
        // 8. Execute POST request to the given URL
        HttpResponse httpResponse = httpclient.execute(httpPost);
        HttpEntity entity = httpResponse.getEntity();
        // 9. receive response as inputStream
        inputStream = entity.getContent();
        System.out.println("InputStream....:" + inputStream.toString());
        System.out.println("Response....:" + httpResponse.toString());

        StatusLine statusLine = httpResponse.getStatusLine();
        System.out.println("statusLine......:" + statusLine.toString());
        ////Log.d("resp_body", resp_body.toString());
        int statusCode = statusLine.getStatusCode();
        // 10. convert inputstream to string
        if (statusCode == 200) {
            // 10. convert inputstream to string
            if (inputStream != null)
                s_szresult = m_oJsonsResponse.convertInputStreamToString(inputStream);
            //String resp_body =
            EntityUtils.toString(httpResponse.getEntity());
        } else
            s_szresult = "Did not work!";
    } catch (Exception e) {
        Log.d("InputStream", e.getLocalizedMessage());
    }
    System.out.println("resul.....:" + s_szresult);
    // 11. return s_szResult
    return s_szresult;
}

这是我的 AsynkTask 类

/   sending deal data to server and retreive response......
class CDealDataSent extends AsyncTask<String, Void, String> {
    public JSONObject m_oResponseobject;
    public ProgressDialog m_PDialog;
    public CRegistrationDataStorage oRegisterStorage;
    public CDealAppDatastorage item;

    //      @Override
    protected void onPreExecute() {
        super.onPreExecute();
        m_PDialog = new ProgressDialog(getActivity());
        m_PDialog.setMessage("Please wait while Loading Deals...");
        m_PDialog.setCancelable(false);
        m_PDialog.show();
    }
    @Override
    protected String doInBackground(String... urls) {
        return DealListing(urls[0], oRegisterStorage);// sending data to server...

    }
    // onPostExecute displays the results of the AsyncTask.
    @Override
    protected void onPostExecute(String result) {

        m_PDialog.dismiss();
        try {
            m_oResponseobject = new JSONObject(result);// getting response from server
            final JSONArray posts = m_oResponseobject.optJSONArray("dealList");

            s_oDataset = new ArrayList<CDealAppDatastorage>();
            for (int i = 0; i < posts.length(); i++) {
                JSONObject post = posts.getJSONObject(i);
                item = new CDealAppDatastorage();
                item.setM_szHeaderText(post.getString("dealname"));
                item.setM_szsubHeaderText(post.getString("dealcode"));
                item.setM_n_Image(m_n_FormImage[i]);
                s_oDataset.add(item);

            }
            getResponse();

        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    public void getResponse() throws JSONException {
        if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Transaction Successful")) {

            m_oAdapter = new CDealAppListingAdapter(s_oDataset);//creating object of adapter and addd setting odata to adapter for use.
            m_RecyclerView.setAdapter(m_oAdapter);//adding adapter to recyclerview
        } else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Connection Not Available")) {
            Toast.makeText(getActivity(), "Connection not avaliable", Toast.LENGTH_SHORT).show();
        }else if (m_oResponseobject.getString("resultdescription").equalsIgnoreCase("Deal List Not Found")){
            Toast.makeText(getActivity(),"No More Deals",Toast.LENGTH_SHORT).show();
        }
        System.out.println("agentCode...." + m_szMobileNumber);
        System.out.println("password...." + m_szEncryptedPassword);
        System.out.println("record////" + sz_RecordCount);
        System.out.println("last:........" + sz_LastCount);
    }

}

在asynkTask类中获取CDealListing类的Response方法更新UI

【问题讨论】：

标签： android

【解决方案1】：

一种方法是声明一个侦听器接口并将该接口的一个实例（或者可能是一个 Runnable）传递给 AsyncTask 的构造函数。

在您的片段代码中：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    ...        
    new CDealDataSent(new Runnable() {
        @Override
        public void run() {
            // perform update UI code here
        }
    }).execute(m_DealListingURL);
    ...
}

在您的 AsyncTask 代码中：

class CDealDataSent extends AsyncTask<String, Void, String> {
    private final Runnable mOnPostExecuteRunnable;
    CDealDataSent(Runnable onPostExecuteRunnable) {
        mOnPostExecuteRunnable = onPostExecuteRunnable;
    }

    ...

    @Override
    protected void onPostExecute(String result) {
        ...
        if (mPostExecuteRunnable != null) {
            mPostExecuteRunnable.run();
        }
        ...
    }
}

您还可以从片段中使用 AsyncTask 的匿名子类并覆盖 onPostExecute()：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    ...        
    new CDealDataSent() {
        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result); // be sure to call super first to do normal processing
            ... // update your UI here
        }
    }.execute(m_DealListingURL);
    ...
}

请注意，如果您不小心，这两种解决方案都容易出现 Activity/Fragment 泄漏，因为 Runnable/匿名子类的父类被保留为隐式引用。如果用户在 onDestroy() 中退出您的活动，请务必取消任何未完成的 AsyncTask。

您可以通过静态嵌套类缓解任何潜在的泄漏问题，或者可以将 Handler 实例传递给 AsyncTask，以便它在 onPostExecute() 完成其工作时发送消息。有关此问题的讨论，请参阅 What's the correct way to implement AsyncTask? static or non static nested class?。

【讨论】：

但是我怎样才能让progressdialog可见

【解决方案2】：

有3种方式

在onPostExecute() 中调用Fragment 的某些方法
在onPostExecute() 中使用BroadcastReceiver
使用EventBus 库将事件传递给您的Fragment。

【讨论】：