使用 Spinner 使用来自 MySQL 的项目填充 Android ListView

Question

我是一个Android编程新手，标题中的问题一直困扰着我
我在本地主机的 MySQL 数据库中有一个 Groceries table：

id----name---------type
1     apple        fruit
2     banana       fruit
3     lettuce      vegetable
4     apricot      fruit
5     cauliflower  vegetable

我的 Android 应用程序中还有一个 Spinner 和一个 ListView。 Spinner 有一个字符串数组的条目，其中包含 fruit & vegetable.
我希望当用户从微调器中选择 fruit 或 vegetable 类型时，ListView 将填充 MySQL.

中相应类型的名称

这是我到目前为止所做的。

MainActivity class:

package com.example.mine.application;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Spinner;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

public Spinner groceryTypes;
public ListView groceries;

public static List<String> arrayGroceries;
ArrayAdapter<String> adapterGroceries;

@Override
protected void onCreate(Bundle savedInstanceState) {

    groceryTypes = (Spinner) findViewById(R.id.groceryTypes_spinner);
    groceries = (ListView) findViewById(R.id.groceries_listView);

    arrayGroceries = new ArrayList<>();
    adapterGroceries = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, arrayGroceries);
    groceries.setAdapter(adapterGroceries);

    groceryTypes.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            BackgroundWorker backgroundWorker = new BackgroundWorker(MainActivity.this);
            backgroundWorker.execute(groceryTypes.getItemAtPosition(position).toString());
            adapterGroceries.notifyDataSetChanged();
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {
            //TODO Auto-generated method stub
        }
    });
}

BackgroundWorker class:

package com.example.mine.application;
import android.content.Context;
import android.os.AsyncTask;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;

public class BackgroundWorker extends AsyncTask<String, Void, String> {
Context context;

BackgroundWorker(Context ctx){
    context = ctx;
}

@Override
protected String doInBackground(String... params) {
    String groceries_URL = "http://10.0.2.2/groceries.php";
    String groceryType = params[0];
    try {
        URL url = new URL(groceries_URL);
        HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
        httpURLConnection.setRequestMethod("POST");
        httpURLConnection.setDoOutput(true);
        httpURLConnection.setDoInput(true);

        OutputStream outputStream = httpURLConnection.getOutputStream();
        BufferedWriter bufferedWriter = new BufferedWriter
                (new OutputStreamWriter(outputStream, "UTF-8"));
        String post_data = URLEncoder.encode("grocery_type", "UTF-8")+"="+URLEncoder.encode(groceryType, "UTF-8");
        bufferedWriter.write(post_data);
        bufferedWriter.flush();
        bufferedWriter.close();
        outputStream.close();

        InputStream inputStream = httpURLConnection.getInputStream();
        BufferedReader bufferedReader = new BufferedReader
                (new InputStreamReader(inputStream, "iso-8859-1"));

        MainActivity.arrayGroceries.clear();
        String line;
        while ((line = bufferedReader.readLine()) != null) {
            MainActivity.arrayGroceries.add(line);
        }
        bufferedReader.close();
        inputStream.close();
        httpURLConnection.disconnect();

        return null;
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}
}

这是我的 groceries.php:

<?php
require "conn.php";

$grocery_type = $_POST["grocery_type"];
$qry = "SELECT name FROM groceries WHERE type LIKE '$grocery_type';";

$result = mysqli_query($conn, $qry);

while($row = mysqli_fetch_row($result)) {
    echo $row[1];
}

mysqli_free_result($result);

$conn->close();
?>

我认为问题在于我如何处理查询中的多个项目，但任何解释和帮助实现这一点都将受到高度重视。

Answer 1

假设您从服务器获取了正确的数据并且正在填充杂货数组，您需要将 onPostExecute 添加到 BackgroundWorker AsyncTask 并通知 adapterGroceries 数据已经改变。

您在 AysncTask.execute() 之后执行此操作，但它在那里没有任何好处，execute() returns 立即和通知运行s 但有还没有更新。数据returns.

后需要运行

使用 Spinner 使用来自 MySQL 的项目填充 Android ListView

Populate Android ListView with items from MySQL using Spinner

android

mysqli

listview

spinner