Question

我已经使用AsyncTask几天了。我的旧代码在带有runOnUIThred的API 8上工作，它不会在＆gt; API 18上工作。我想在doInBackground（）中使用JSON将数据发送到DB，并在onPostExecute（）中获取数据。如何将代码分成两部分？

class GetProductDetails extends AsyncTask<String, String, Integer> {

    @Override
    protected void onPreExecute() {
       //bla-bla-bla
    }

    protected Integer doInBackground(String... args) {
               int success = 0;
                try {
                    List<NameValuePair> params = new ArrayList<NameValuePair>();
                    params.add(new BasicNameValuePair("pid", pid));

                    JSONObject json = jsonParser.makeHttpRequest(
                            url_product_detials, "GET", params);
                    success = json.getInt(TAG_SUCCESS);

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

        return success;
    }

    protected void onPostExecute(Integer success) {
          pDialog.dismiss();
          JSONArray productObj = json.getJSONArray(TAG_PRODUCT); 
          JSONObject product = productObj.getJSONObject(0);

          if (success == 1) {

                txtName = (TextView) findViewById(R.id.tvName);
                txtPrice = (TextView) findViewById(R.id.tvPrice);
                txtDesc = (TextView) findViewById(R.id.tvDescription);
                txtCurrent = (TextView) findViewById(R.id.tvCurrent);
                txtTurn = (TextView) findViewById(R.id.tvTurn);

                txtName.setText(product.getString(TAG_NAME));
                txtPrice.setText(product.getString(TAG_PRICE));
                txtDesc.setText(product.getString(TAG_DESCRIPTION));
                txtCurrent.setText(product.getString("current"));
                txtTurn.setText(product.getString("turn"));

          }else{ }
       }
}

Answer 1

enter image description here 您可以让doInBackground返回JSONObject json并在onPostExecute中使用它。

然后检查一切是否正常，请在onPostExecute内进行检查。

类似的东西：

class GetProductDetails extends AsyncTask<String, String, JSONObject>
{

    @Override
    protected void onPreExecute() {
        //bla-bla-bla
    }

    protected JSONObject doInBackground(String... args) {
        JSONObject json = null;

        try {
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair("pid", pid));

            json = jsonParser.makeHttpRequest(
                    url_product_detials, "GET", params);

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

        return json;
    }

    protected void onPostExecute(JSONObject json) {

        pDialog.dismiss();
        if (json == null) return; // check if json is null too! if null something went wrong (handle it, i used return as example)

        int success = json.getInt(TAG_SUCCESS);;

        if (success == 1) {
            JSONArray productObj = json.getJSONArray(TAG_PRODUCT);
        JSONObject product = productObj.getJSONObject(0);
            txtName = (TextView) findViewById(R.id.tvName);
            txtPrice = (TextView) findViewById(R.id.tvPrice);
            txtDesc = (TextView) findViewById(R.id.tvDescription);
            txtCurrent = (TextView) findViewById(R.id.tvCurrent);
            txtTurn = (TextView) findViewById(R.id.tvTurn);

            txtName.setText(product.getString(TAG_NAME));
            txtPrice.setText(product.getString(TAG_PRICE));
            txtDesc.setText(product.getString(TAG_DESCRIPTION));
            txtCurrent.setText(product.getString("current"));
            txtTurn.setText(product.getString("turn"));

        }else{

        }
    }

Answer 2

在这里你不应该使用AsyncTask，试试这个库---- android-async-http，它由Instagram，Pinterest和其他着名的Android应用程序使用。有了这个库，你可以像这样完成你的工作：

RequestParams params = new RequestParams();
params.put("username", "james");
params.put("password", "123456");
params.put("email", "my@email.com");
params.put("profile_picture", new File("pic.jpg")); // Upload a File
params.put("profile_picture2", someInputStream); // Upload an InputStream
params.put("profile_picture3", new ByteArrayInputStream(someBytes)); // Upload some bytes
AsyncHttpClient client = new AsyncHttpClient();
client.post("http://youdomain.com", params, new AsyncHttpResponseHandler(){
    @Override
    public void onSuccess(String result) {
        // Do something here or change your ui according the result.
    }
});

Answer 3

Java提供的接口非常强大，可以为您的类添加行为，在您希望AsyncTask子类为1-retreive数据和db存储2-store的情况下，可以在后台线程上完成，没有任何问题。和你的活动来更新它的UI，所以你有三个行为，你的问题是第三种行为，你可以通过界面轻松克服这个问题。

UIUpdate.java

public interface UIUpdate
{
    public void updateFields(JSONObject json);
}

MainActivity.java

public class MainActivity extends Activity implements UIUpdate
{
    public void execute()
    {
         new GetProductDetails(this).execute("args"); 
    }
    ....
    @override
    public void updateFields(JSONObject json)
    {
            JSONArray productObj = json.getJSONArray(TAG_PRODUCT);
            JSONObject product = productObj.getJSONObject(0);
            txtName = (TextView) findViewById(R.id.tvName);
            txtPrice = (TextView) findViewById(R.id.tvPrice);
            txtDesc = (TextView) findViewById(R.id.tvDescription);
            txtCurrent = (TextView) findViewById(R.id.tvCurrent);
            txtTurn = (TextView) findViewById(R.id.tvTurn);
            txtName.setText(product.getString(TAG_NAME));
            txtPrice.setText(product.getString(TAG_PRICE));
            txtDesc.setText(product.getString(TAG_DESCRIPTION));
            txtCurrent.setText(product.getString("current"));
            txtTurn.setText(product.getString("turn"));
    }
}

GetProductDetails.java

class GetProductDetails extends AsyncTask<String, String, JSONObject>
{
    UIUpdate listener;

    public GetProductDetails( UIUpdate listener )
    {
        this.listener=listener;
    }

    protected JSONObject doInBackground(String... args)
    {
        JSONObject json = null;
        try {
            List<NameValuePair> params = new ArrayList<NameValuePair>();
            params.add(new BasicNameValuePair("pid", pid));
            json = jsonParser.makeHttpRequest(
                    url_product_detials, "GET", params);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return json;
    }

    protected void onPostExecute(JSONObject json)
    {
        pDialog.dismiss();
        if (json == null) return; // check if json is null too! if null something went wrong (handle it, i used return as example)
        int success = json.getInt(TAG_SUCCESS);
        if (success == 1)
        {
            listener.updateFields(json);
        }
        else{ }
    }
}

此外，您需要从doInBackGround（）中重新启动JSONObject以在postExecute（）中使用。

如何在AsyncTask中获得onPostExecute的结果？

3 个答案: