php - 使用 PHP 从 MySQl 数据库中获取 SUM，然后在 android textview 中打印它

Question

我需要一些帮助。我想计算金额列的总和，然后在我的 Android 应用程序的 TextView 中显示它。 这是我到目前为止所做的。

import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class BalanceActivity extends SwipeFunctionActivity
{
private Boolean exit = false;
Button buttonExpense, buttonIncome, buttonSaving;
ImageView helpImageView;
TextView totalIncomeNumberTV;
String ftotalintv = "http://192.168.0.3/myapp/ftotalintv.php";
RequestQueue requestQueue;

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_balance);

    buttonExpense = (Button)findViewById(R.id.buttonExpense);
    buttonIncome = (Button)findViewById(R.id.buttonIncome);
    buttonSaving = (Button)findViewById(R.id.buttonSaving);

    helpImageView = (ImageView)findViewById(R.id.helpImageView);

    totalIncomeNumberTV = (TextView)findViewById(R.id.totalIncomeNumberTV);

    requestQueue = Volley.newRequestQueue(getApplicationContext());

    try
    {
        fetchTotalIncome();
    }

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

    buttonExpense.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            addExpenseMethod();
        }
    });

    buttonIncome.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            addIncomeMethod();
        }
    });

    buttonSaving.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            addSavingMethod();
        }
    });

    helpImageView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            instructionsMethod();
        }
    });

}

public void fetchTotalIncome() throws JSONException /*throws JSONException*/
{



    JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, ftotalintv, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response)
        {
            try {
                JSONArray jsonArray = response.getJSONArray("transactions");
                for(int i = 0; i<jsonArray.length(); i++)
                {
                    JSONObject test = jsonArray.getJSONObject(i);
                    String totalIncome = test.getString("TotalIncome");

                    totalIncomeNumberTV.append(totalIncome);
                }
            }

            catch (JSONException e)
            {
                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener()
    {
        @Override
        public void onErrorResponse(VolleyError error)
        {

        }
    });
    requestQueue.add(jsonObjectRequest);
//
//        String data = "http://192.168.0.3/myapp/ftotalintv.php";
//        JSONObject jObject;
//        jObject = new JSONObject(data);
//        String total = jObject.getString("TotalIncome");
//        totalIncomeNumberTV.setText(ftotalintv);


    //totalIncomeNumberTV.setText("troll");
}

public void addExpenseMethod()
{
    startActivity(new Intent(getApplicationContext(), AddExpenseActivity.class));
}

public void addIncomeMethod()
{
    startActivity(new Intent(getApplicationContext(), AddIncomeActivity.class));
}

public void addSavingMethod()
{
    startActivity(new Intent(getApplicationContext(), AddSavingActivity.class));
}

public void instructionsMethod()
{
    startActivity(new Intent(getApplicationContext(), InstructionsActivity.class));
    //finish();
}

@Override
public void onSwipeLeft()
{
    super.onSwipeLeft();
    startActivity(new Intent(getApplicationContext(), TransactionsActivity.class));
    finish();
}

@Override
public void onSwipeRight()
{
    super.onSwipeRight();
    startActivity(new Intent(getApplicationContext(), ExpenseCategoriesActivity.class));
    finish();
}

public void onSwipeTop()
{
    super.onSwipeRight();
    startActivity(new Intent(getApplicationContext(), ChartActivity.class));
    finish();
}

@Override
public void onBackPressed()
{
    if (exit)
    {
        finish(); // finish activity
    }

    else
    {
        Toast.makeText(this, "Press Back again to Exit.", Toast.LENGTH_SHORT).show();
        exit = true;

        new Handler().postDelayed(new Runnable()
        {
            @Override
            public void run()
            {
                exit = false;
            }
        }
                , 3 * 1000);

    }
}

这是我的带有 SUM 查询的 PHP 文件:

<?php
require "init.php";

$query = mysqli_query($con, "SELECT *, SUM(TransAmount) AS 'TotalIncome' FROM transactions WHERE TransType = 'income';");
$row = mysqli_fetch_assoc($query);
$sum = $row['TotalIncome'];

if($query)
{
    echo $sum;
}

myslqi_close($con);
?>

如您所见，我在代码中添加了一些注释。我试图用 Volley 库显示 SUM，但我失败了。有人可以帮我吗？我真的不知道此时该怎么办。我在 Android 应用程序方面需要的主要帮助是因为当我在浏览器中运行 PHP 文件时它可以正常工作，但也有可能出现一些问题。

Answer 1

在您的 php 脚本中，您没有在 json 中编码您的响应，您可能也没有在您的 php 代码中添加 json header 。所以你的 php 代码将是这样的

$sum = $row['TotalIncome'];
if($query)
{
   $data[]['TotalIncome'] = $sum;
   $result = array("transactions" => $data);
   echo json_encode($result);
}
myslqi_close($con);

不要忘记在 php 脚本的最顶部添加 json 类型的 header