Question

我在举行第二个程序直到完成第一个程序时遇到问题。我正在使用AsyncTask。

我从MySql服务器获取数据。有时因为我使用共享服务器，所以花费更多的时间来获取数据。

因此，有时第二个进程在第一个进程之前运行。

这是代码。

这是我的ListView代码

 listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        MainItemListNotes invoiceNotes = (MainItemListNotes) parent.getItemAtPosition(position);if (shareactivitycode.equals("Quote"))
        {
            if (invoiceNotes.getItemType().equals("Labels"))
            {
                getLabelQualityID(invoiceNotes.getItemID());

                getLabelPrice(labelQualityID);

                if (labelNoOfColour.equals("0"))
                {
                    double a = Double.parseDouble(lPurchasePrice);
                    double b = Double.parseDouble(lLowRate);
                    double c = Double.parseDouble(lSellRate);

                    double d = Double.parseDouble(labelWidth);
                    double e = Double.parseDouble(labelHeight);

                    Double f = ((d * e) / 625.0000) * a;
                    Double g = Double.parseDouble(String.format("%.4f", f));
                    Log.e("0purchaseP", String.valueOf(g));
                    Log.e("0purchaseP", labelWidth + " * " + labelHeight + " / " + "625" + " * " + lPurchasePrice);

                    Double h = Double.parseDouble(String.format("%.4f", ((d * e) / 625.0000) * b));
                    Log.e("0LowP", String.valueOf(h));
                    Log.e("0LowP", labelWidth + " * " + labelHeight + " / " + "625" + " * " + lLowRate);

                    Double i = Double.parseDouble(String.format("%.4f", ((d * e) / 625.0000) * c));
                    Log.e("0SellP", String.valueOf(i));
                    Log.e("0SellP", labelWidth + " * " + labelHeight + " / " + "625" + " * " + lSellRate);

                    Intent intent = new Intent(ItemList.this, NewQuotation.class);
                    intent.putExtra("itemid", invoiceNotes.getItemID());
                    intent.putExtra("itemname", invoiceNotes.getItemName());
                    intent.putExtra("hsncode", invoiceNotes.getHSNCode());
                    intent.putExtra("itemtype", invoiceNotes.getItemType());
                    intent.putExtra("labelwidth", labelWidth);
                    intent.putExtra("labelheight", labelHeight);
                    intent.putExtra("packing", labelPacking);
                    intent.putExtra("purchaserate", String.valueOf(g));
                    intent.putExtra("lowrate", String.valueOf(h));
                    intent.putExtra("sellrate", String.valueOf(i));
                    setResult(3, intent);
                    finish();
                }
            }
        }
    }
});

这是getLabelQualityID(invoiceNotes.getItemID());代码

private void getLabelQualityID(String itemid) {
    String URL = "myserverurl.com";
    class VoucherDetails extends AsyncTask<Void, Void, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            try {
                JSONObject obj = new JSONObject(s);

                if (!obj.getBoolean("error")) {

                    JSONObject product = obj.getJSONObject("voucher");

                    labelQualityID = product.getString("id");
                    labelWidth = product.getString("width");
                    labelHeight = product.getString("height");
                    labelNoOfColour = product.getString("noofcolor");
                    labelPacking = product.getString("labelpacking");

                } else {
                    Toast.makeText(getApplicationContext(), "Invalid Voucher ID", Toast.LENGTH_SHORT).show();
                }
            } catch (JSONException e)
            {
                e.printStackTrace();
                Log.e("Sum Error ", e.toString());
                Toast.makeText(getApplicationContext(), "Error : "+e.toString(), Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        protected String doInBackground(Void... voids) {
            RequestHandler requestHandler = new RequestHandler();

            HashMap<String, String> params = new HashMap<>();
            params.put("itemid", itemid);

            return requestHandler.sendPostRequest(URL, params);
        }
    }

    VoucherDetails ul = new VoucherDetails();
    ul.execute();
}

这是getLabelPrice(labelQualityID);代码

private void getLabelPrice(String qualityid) {
    String URL = "myserverurl.com";
    class VoucherDetails extends AsyncTask<Void, Void, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            try {
                JSONObject obj = new JSONObject(s);

                if (!obj.getBoolean("error")) {

                    JSONObject product = obj.getJSONObject("voucher");

                    lPurchasePrice = product.getString("purchaserate");
                    lLowRate = product.getString("lowrate");
                    lSellRate = product.getString("sellrate");

                } else {
                    Toast.makeText(getApplicationContext(), "Invalid Voucher ID", Toast.LENGTH_SHORT).show();
                }
            } catch (JSONException e)
            {
                e.printStackTrace();
                Log.e("Sum Error ", e.toString());
                Toast.makeText(getApplicationContext(), "Error : "+e.toString(), Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        protected String doInBackground(Void... voids) {
            RequestHandler requestHandler = new RequestHandler();

            HashMap<String, String> params = new HashMap<>();
            params.put("id", qualityid);

            return requestHandler.sendPostRequest(URL, params);
        }
    }

    VoucherDetails ul = new VoucherDetails();
    ul.execute();
}

labelNoOfColour来自getLabelQualityID() ＆lPurchasePrice，lLowRate，lSellRate，labelWidth，labelHeight来自getLabelPrice()函数。

有时getLabelQualityID()和getLabelPrice()需要一些时间来获取数据。＆if (labelNoOfColour.equals("0"))，该过程将在获取数据之前执行。

有时getLabelPrice()进程在getLabelQualityID()完成之前运行。

请指导我如何进行第二个过程，直到第一个过程结束为止。

Answer 1

这是常见的，当您运行多个AsycTask时，一个线程可能先于另一个线程执行。因此，为了确保顺序处理，您需要在AsyncTask上放置一个侦听器，以跟踪线程是否完成。我想建议以下实现。

创建一个interface类，如下所示。

public interface ThreadFinishListener {
    void onThreadFinished();
}

现在为您的第一个线程VoucherDetails创建一个侦听器变量和一个构造函数。

private void getLabelQualityID(String itemid) {

    String URL = "myserverurl.com";

    class VoucherDetails extends AsyncTask<Void, Void, String> {

        // Create a listener
        ThreadFinishListener listener;

        // Create a constructor
        public VoucherDetails(ThreadFinishListener listener) {
            this.listener = listener;
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            try {
                JSONObject obj = new JSONObject(s);

                if (!obj.getBoolean("error")) {

                    JSONObject product = obj.getJSONObject("voucher");

                    labelQualityID = product.getString("id");
                    labelWidth = product.getString("width");
                    labelHeight = product.getString("height");
                    labelNoOfColour = product.getString("noofcolor");
                    labelPacking = product.getString("labelpacking");

                    // invoke the listener method here when you are done with your first thread
                    listener.onThreadFinished();

                } else {
                    Toast.makeText(getApplicationContext(), "Invalid Voucher ID", Toast.LENGTH_SHORT).show();
                }
            } catch (JSONException e) {
                e.printStackTrace();
                Log.e("Sum Error ", e.toString());
                Toast.makeText(getApplicationContext(), "Error : "+e.toString(), Toast.LENGTH_SHORT).show();
            }
        }

        @Override
        protected String doInBackground(Void... voids) {
            RequestHandler requestHandler = new RequestHandler();

            HashMap<String, String> params = new HashMap<>();
            params.put("itemid", itemid);

            return requestHandler.sendPostRequest(URL, params);
        }
    }

    VoucherDetails ul = new VoucherDetails(new ThreadFinishListener() {
        @Override
        public void onThreadFinished() {
            // Call the second thread here
        }
    });

    ul.execute();
}

希望有帮助！

Answer 2

您需要一个处理程序，通过该处理程序可以将第二个过程延迟到第一个过程完成为止。我给你一个简单的代码示例

       button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            firstProcess();

    // Now adding a delay for second process
    Handler handler = new Handler();
    handler.postDelayed(new Runnable() {
       @Override
       public void run() {
           secondProcess();
       }
}, 5000); //It means delay of 5 seconds as there are 5000 milliseconds in 5 seconds

   } //end onClickView
    });

如何在Android中完成第二个过程直到完成第一个过程？

2 个答案: