将Android中的POST数据发送到PHP

我正在寻找一种将POST数据发送到PHP脚本并显示结果的方法。我想将$username的POST数据发送到PHP。 这是我的php文件：

<?php

    ...// connect

            $username = $_POST['txtUsername'];// this data

    $mysqli->query("SET NAMES 'utf8'");
    $sql="SELECT * FROM $username";
    $result=$mysqli->query($sql);
    while($e=mysqli_fetch_assoc($result)){
    $output[]=$e; 
    }   

    print(json_encode($output)); 
    $mysqli->close();   

    ?>

和Downloader.class：

public class Downloader extends AsyncTask<Void,Void,String> {

Context c;
String urlAddress;
ListView lv;

ProgressDialog pd;
public Downloader(Context c, String urlAddress, ListView lv) {
    this.c = c;
    this.urlAddress = urlAddress;
    this.lv = lv;
}

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

    pd = new ProgressDialog(c);
    pd.setTitle("Fetch");
    pd.setMessage("Fetching...Please wait");
    pd.show();
}

@Override
protected String doInBackground(Void... voids) {
    return this.downloadData();
}

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

    pd.dismiss();

    if(s==null){
        Toast.makeText(c,"Unsuccessful,Null,returned",Toast.LENGTH_SHORT).show();
    }
    else {
    DataParser parser = new DataParser(c,lv,s);
        parser.execute();

    }

}


private String downloadData(){
    HttpURLConnection con = Connector.connect(urlAddress);
    if (con==null){
        return null;
    }
    InputStream is=null;
    try {

        is=new BufferedInputStream(con.getInputStream());
        BufferedReader br = new BufferedReader(new InputStreamReader(is));

    String line = null;
        StringBuffer response = new StringBuffer();

        if (br!=null){
            while ((line=br.readLine())!=null){
                response.append(line+"\n");
            }

            br.close();
        }
        else {return null;}
        return response.toString();

    } catch (IOException e) {
        e.printStackTrace();
    }
    finally {
        if(is != null){
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    return null;
}}

公共类下载程序扩展异步任务{
上下文c；
字符串地址；
ListView lv；
进展性帕金森病；
公共下载程序（上下文c、字符串URL地址、ListView lv）{
这个.c=c；
this.urlAddress=urlAddress；
this.lv=lv；
}
@凌驾
受保护的void onPreExecute（）{
super.onPreExecute（）；
pd=新进度对话框（c）；
pd.setTitle（“获取”）；
设置消息（“正在提取…请稍候”）；
pd.show（）；
}
@凌驾
受保护的字符串背景（无效…无效）{
返回此.downloadData（）；
}
@凌驾
受保护的void onPostExecute（字符串s）{
super.onPostExecute（s）；
pd.解散（）；
如果（s==null）{
Toast.makeText（c，“不成功，Null，返回”，Toast.LENGTH_SHORT.show（）；
}
否则{
DataParser=新的DataParser（c、lv、s）；
parser.execute（）；
}
}
私有字符串下载数据（）{
HttpURLConnection con=Connector.connect（urlAddress）；
如果（con==null）{
返回null；
}
InputStream=null；
试一试{
is=新的BufferedInputStream（con.getInputStream（））；
BufferedReader br=新的BufferedReader（新的InputStreamReader（is））；
字符串行=null；
StringBuffer响应=新的StringBuffer（）；
如果（br！=null）{
而（（line=br.readLine（））！=null）{
响应。追加（第+行“\n”）；
}
br.close（）；
}
else{return null；}
返回response.toString（）；
}捕获（IOE异常）{
e、 printStackTrace（）；
}
最后{
如果（is！=null）{
试一试{
is.close（）；
}捕获（IOE异常）{
e、 printStackTrace（）；
}
}
}
返回null；
}}

---

请帮帮我，谢谢

根据您提供的代码，您似乎正在下载数据，但似乎没有发布任何数据

有几种方法可以通过HTTP POST发送数据。您可以尝试使用，它可以为您处理许多网络呼叫的逻辑

例如：

RequestQueue queue = Volley.newRequestQueue(this);
String url = "https://myurl.com";
JsonRequest postRequest = new StringRequest(Request.Method.POST, url, 
    new Response.Listener<String>() 
    {
        @Override  
        public void onResponse(JSONObject response) 
        {
            Log.d(TAG, response.toString());
        }
    }, 
    new Response.ErrorListener() 
    {
        @Override
        public void onErrorResponse(VolleyError error)
        {
            Log.e(TAG, error.toString());
        }
    }) 
    {     
    @Override
    protected Map<String, String> getParams() 
    {  
        Map<String, String>  params = new HashMap<String, String>();  
        params.put("txtUsername", "mUsername");               
        return params;  
    }
    @Override
    public Map<String, String> getHeaders() throws AuthFailureError 
    {                
        Map<String, String> headers = new HashMap<String, String>();
        headers.put("Content-Type", "application/x-www-form-urlencoded");
        return headers;
    }
};
queue.add(postRequest);

RequestQueue queue=Volley.newRequestQueue（this）；
字符串url=”https://myurl.com";
JsonRequest postRequest=新的StringRequest（Request.Method.POST，url，
新的Response.Listener（）
{
@凌驾
公共void onResponse（JSONObject响应）
{
Log.d（TAG，response.toString（））；
}
}, 
新的Response.ErrorListener（）
{
@凌驾
公共无效onErrorResponse（截击错误）
{
Log.e（标记，error.toString（））；
}
}) 
{     
@凌驾
受保护的映射getParams（）
{  
Map params=新的HashMap（）；
参数put（“txtUsername”、“mUsername”）；
返回参数；
}
@凌驾
公共映射getHeaders（）引发AuthFailureError
{                
Map headers=newhashmap（）；
headers.put（“内容类型”、“应用程序/x-www-form-urlencoded”）；
返回标题；
}
};
添加（postRequest）；

您还可以编写自己的异步任务来执行post。以下是一个例子：

public class PostRequestAsyncTask extends AsyncTask<Void, Void, String
{
    Context context;
    Map<String, String> postParams;

    /**
     * Overridden constructor
     */
    public PostRequestAsyncTask(Context context, Map<String, String> postParams) 
    {
        this.context = context;
        this.postParams = new LinkedHashMap<String, String>(postParams);
    }

    /**
     * Default constructor
     */
    public PostRequestAsyncTask() {}

    public byte[] generatePostData() 
    {
        StringBuilder postData = new StringBuilder();
        for (Map.Entry<String, String> dParam : postParams.entrySet())
        {
            if (postData.length() != 0) 
                postData.append('&');
            try {
                postData.append(URLEncoder.encode(dParam.getKey(), "UTF-8"));
                postData.append('=');
                postData.append(URLEncoder.encode(String.valueOf(dParam.getValue()), "UTF-8"));
            } 
            catch (UnsupportedEncodingException e) 
            {
                e.printStackTrace();
            }
        }
        byte[] postDataBytes = null;
        try 
        {
            postDataBytes = postData.toString().getBytes("UTF-8");
        } 
        catch (UnsupportedEncodingException e) 
        {
            e.printStackTrace();
        }
        return postDataBytes;
    }

    @Override
    protected String doInBackground(Void... params) 
    {
        /* Set params */
        byte[] postDataBytes = generatePostData();

        /* Set headers and write */
        URL url = null;
        HttpURLConnection conn = null;
        try 
        {
            url = new URL("https://myurl.com");
            conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
            conn.setDoOutput(true);
            conn.getOutputStream().write(postDataBytes);
        } 
        catch (MalformedURLException | IOException e) 
        {
            e.printStackTrace();
        } 

        /* Retrieve response */
        Reader in = null;
        String response = new String();
        try 
        {
            in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
            response = "";
            for (int c = in.read(); c != -1; c = in.read()) 
            {
                response += (char) c;
            }
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }
        return response;
    }

    @Override
    protected void onPostExecute(String resp) {
        super.onPostExecute(resp);
        JSONObject jsonResponse = null;
        try 
        {
            jsonResponse = new JSONObject(resp);
            //do something with your json response
        } 
        catch (JSONException e) 
        {
            e.printStackTrace();
        }
    }
}

---

公共类PostRequestAsyncTask扩展了AsyncTask问题在哪里？在java代码或PHP代码中？对http请求使用改型。
RequestQueue queue = Volley.newRequestQueue(this);
String url = "https://myurl.com";
JsonRequest postRequest = new StringRequest(Request.Method.POST, url, 
    new Response.Listener<String>() 
    {
        @Override  
        public void onResponse(JSONObject response) 
        {
            Log.d(TAG, response.toString());
        }
    }, 
    new Response.ErrorListener() 
    {
        @Override
        public void onErrorResponse(VolleyError error)
        {
            Log.e(TAG, error.toString());
        }
    }) 
    {     
    @Override
    protected Map<String, String> getParams() 
    {  
        Map<String, String>  params = new HashMap<String, String>();  
        params.put("txtUsername", "mUsername");               
        return params;  
    }
    @Override
    public Map<String, String> getHeaders() throws AuthFailureError 
    {                
        Map<String, String> headers = new HashMap<String, String>();
        headers.put("Content-Type", "application/x-www-form-urlencoded");
        return headers;
    }
};
queue.add(postRequest);

public class PostRequestAsyncTask extends AsyncTask<Void, Void, String
{
    Context context;
    Map<String, String> postParams;

    /**
     * Overridden constructor
     */
    public PostRequestAsyncTask(Context context, Map<String, String> postParams) 
    {
        this.context = context;
        this.postParams = new LinkedHashMap<String, String>(postParams);
    }

    /**
     * Default constructor
     */
    public PostRequestAsyncTask() {}

    public byte[] generatePostData() 
    {
        StringBuilder postData = new StringBuilder();
        for (Map.Entry<String, String> dParam : postParams.entrySet())
        {
            if (postData.length() != 0) 
                postData.append('&');
            try {
                postData.append(URLEncoder.encode(dParam.getKey(), "UTF-8"));
                postData.append('=');
                postData.append(URLEncoder.encode(String.valueOf(dParam.getValue()), "UTF-8"));
            } 
            catch (UnsupportedEncodingException e) 
            {
                e.printStackTrace();
            }
        }
        byte[] postDataBytes = null;
        try 
        {
            postDataBytes = postData.toString().getBytes("UTF-8");
        } 
        catch (UnsupportedEncodingException e) 
        {
            e.printStackTrace();
        }
        return postDataBytes;
    }

    @Override
    protected String doInBackground(Void... params) 
    {
        /* Set params */
        byte[] postDataBytes = generatePostData();

        /* Set headers and write */
        URL url = null;
        HttpURLConnection conn = null;
        try 
        {
            url = new URL("https://myurl.com");
            conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
            conn.setDoOutput(true);
            conn.getOutputStream().write(postDataBytes);
        } 
        catch (MalformedURLException | IOException e) 
        {
            e.printStackTrace();
        } 

        /* Retrieve response */
        Reader in = null;
        String response = new String();
        try 
        {
            in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
            response = "";
            for (int c = in.read(); c != -1; c = in.read()) 
            {
                response += (char) c;
            }
        } 
        catch (IOException e) 
        {
            e.printStackTrace();
        }
        return response;
    }

    @Override
    protected void onPostExecute(String resp) {
        super.onPostExecute(resp);
        JSONObject jsonResponse = null;
        try 
        {
            jsonResponse = new JSONObject(resp);
            //do something with your json response
        } 
        catch (JSONException e) 
        {
            e.printStackTrace();
        }
    }
}

Map<String, String> postParams = new LinkedHashMap<>();
postParams.put("txtUserName", "mUsername");
new PostRequestAsyncTask(MyActivity.this, postParams).execute();