Php 回收器视图可以'；不显示mysql数据

请帮我查一下这个密码。 我想显示mysql中的数据并将其显示给android。我在mysql中插入数据并在android上显示mysql中有多少数据，这样我就知道我的android应用程序是否可以从mysql读取我的所有数据，但当我运行android应用程序时，它说没有数据。请帮帮我

Android代码

data_list = new ArrayList<>();
    load_data_from_server();
    gridLayoutManager = new GridLayoutManager(this, 2);
    recyclerView.setLayoutManager(gridLayoutManager);

    adapter = new CustomAdapter(this, data_list);
    recyclerView.setAdapter(adapter);

if (adapter.getItemCount() == 0){
        Toast.makeText(this, "Empty", Toast.LENGTH_SHORT).show();
    }

private void load_data_from_server() {
    AsyncTask<Integer, Void, Void> task = new AsyncTask<Integer, Void, Void>() {
        @Override
        protected Void doInBackground(Integer... integers) {
            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    .url("http://192.168.43.147/webapp/travelplanning.php")
                    .build();
            try {
                Response response = client.newCall(request).execute();
                JSONArray array = new JSONArray(response.body().string());

                for(int i = 0; i < array.length(); i++){
                    JSONObject object = array.getJSONObject(i);
                    MyData data = new MyData(object.getInt("ID"), object.getString("AttractionName"), object.getString("Location"));

                    data_list.add(data);
                }
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            adapter.notifyDataSetChanged();
        }
    };
}

}

布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".travelplanning"
android:background="@drawable/img_banner">

<FrameLayout
    android:layout_width="0dp"
    android:layout_height="0dp"
    android:layout_marginStart="10dp"
    android:layout_marginTop="120dp"
    android:layout_marginEnd="10dp"
    android:layout_marginBottom="60dp"
    android:background="@drawable/square"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <androidx.recyclerview.widget.RecyclerView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/recTravel">

        </androidx.recyclerview.widget.RecyclerView>

    </LinearLayout>
</FrameLayout>

<EditText
    android:id="@+id/etSearchAttraction"
    android:layout_width="0dp"
    android:layout_height="38dp"
    android:layout_marginStart="10dp"
    android:layout_marginTop="72dp"
    android:autofillHints=""
    android:background="@drawable/searchdestination"
    android:drawableStart="@drawable/icon_search1"
    android:ems="10"
    android:hint="@string/etsearchdestination"
    android:inputType="textPersonName"
    android:paddingStart="10dp"
    app:layout_constraintEnd_toStartOf="@+id/btnAddAttraction"
    app:layout_constraintHorizontal_bias="0.5"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    android:focusable="false"/>

<Button
    android:id="@+id/btnAddAttraction"
    android:layout_width="40dp"
    android:layout_height="40dp"
    android:layout_marginStart="5dp"
    android:layout_marginEnd="10dp"
    android:background="@drawable/icon_plus"
    app:layout_constraintBaseline_toBaselineOf="@+id/etSearchAttraction"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.5"
    app:layout_constraintStart_toEndOf="@+id/etSearchAttraction" />

<FrameLayout
    android:id="@+id/frameLayout2"
    android:layout_width="match_parent"
    android:layout_height="50dp"
    android:background="@drawable/navbar"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@drawable/nav_topborder"></LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="63dp"
        android:orientation="horizontal"
        android:paddingTop="1dp">

        <Button
            android:id="@+id/btnAttraction"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:background="@drawable/navbar"
            android:drawableTop="@drawable/icon_places"
            android:paddingTop="7dp"
            android:paddingBottom="18dp"
            android:text="@string/attract"
            android:textAllCaps="false"
            android:textColor="#2d3e52"
            android:textSize="9dp" />

        <Button
            android:id="@+id/btnTrips"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:background="@drawable/navbar"
            android:drawableTop="@drawable/icon_trips"
            android:paddingTop="7dp"
            android:paddingBottom="18dp"
            android:text="@string/trips"
            android:textAllCaps="false"
            android:textColor="#A6A3A3"
            android:textSize="9dp" />

        <Button
            android:id="@+id/btnWishlist"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:background="@drawable/navbar"
            android:drawableTop="@drawable/icon_wishlist"
            android:paddingTop="7dp"
            android:paddingBottom="18dp"
            android:text="@string/wishlist"
            android:textAllCaps="false"
            android:textColor="#A6A3A3"
            android:textSize="9dp" />
    </LinearLayout>


</FrameLayout>

<ImageView
    android:id="@+id/imgUser"
    android:layout_width="40dp"
    android:layout_height="40dp"
    android:layout_marginStart="10dp"
    android:layout_marginTop="15dp"
    android:src="@drawable/icon_mainuser"
    app:layout_constraintStart_toEndOf="@+id/imageView4"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<ImageView
    android:id="@+id/imageView6"
    android:layout_width="0dp"
    android:layout_height="25dp"
    android:layout_marginTop="20dp"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:srcCompat="@drawable/img_logowhite" />

卡片布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="wrap_content"
android:layout_width="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto">

<androidx.cardview.widget.CardView
    android:layout_width="match_parent"
    android:layout_height="400dp"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/imgAttraction"
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:scaleType="centerCrop"
        android:src="@mipmap/ic_launcher_round"
        android:layout_margin="10dp"/>

    <LinearLayout
        android:layout_marginLeft="10dp"
        android:layout_marginRight="10dp"
        android:layout_marginTop="320dp"
        android:layout_width="match_parent"
        android:layout_height="55dp"
        android:orientation="horizontal">

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <TextView
                android:id="@+id/tvAttractionName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Attraction Name"
                android:textSize="20dp"
                android:textColor="#000000"/>

            <TextView
                android:id="@+id/tvLocation"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Location"
                android:textSize="20dp"
                android:textColor="#000000"/>
        </LinearLayout>

        <TextView
            android:id="@+id/tvID"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="ID"
            android:textSize="26dp"
            android:textColor="#000000"
            android:layout_marginTop="7dp"
            android:textAlignment="textEnd"
            android:visibility="invisible"/>

        <TextView
            android:id="@+id/tvRate"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="7dp"
            android:text="Rating"
            android:textAlignment="textEnd"
            android:textColor="#000000"
            android:textSize="26dp" />

    </LinearLayout>

</androidx.cardview.widget.CardView>

PHP文件

<?php
require "init.php";

if(mysqli_connect_error($con))
{
    echo "Failed to connect";
}

$query = "Select id, attractionname, location from attraction";
$result = mysqli_query($con, $query);

if($result){
    while($row=mysqli_fetch_array($result)){
       $flag[]=$row;
    }

    print(json_encode($flag));
}
mysqli_close($con);
?>

---

你不能这样做。因为，您不会在AsyncTask中更改ui操作。试试这个

private void load_data_from_server() {
    AsyncTask<Integer, Void, Void> task = new AsyncTask<Integer, Void, Void>() {
        @Override
        protected Void doInBackground(Integer... integers) {
            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    .url("http://192.168.43.147/webapp/travelplanning.php")
                    .build();
            try {
                Response response = client.newCall(request).execute();
                JSONArray array = new JSONArray(response.body().string());
                List<MyData> list = new ArrayList<>();
                for(int i = 0; i < array.length(); i++){
                    JSONObject object = array.getJSONObject(i);
                    MyData data = new MyData(object.getInt("ID"), object.getString("AttractionName"), object.getString("Location"));

                    list.add(data);
                }
                setListData(list);
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
        }
    };
}

private void setListData(List<MyData> list) {
  data_list.addAll(list);
  adapter.notifyDataSetChanged();
}

private void从\u服务器（）加载\u数据{
AsyncTask任务=新建AsyncTask（）{
@凌驾
受保护的Void doInBackground（整数…整数）{
OkHttpClient=新的OkHttpClient（）；
Request Request=newrequest.Builder（）
.url（“http://192.168.43.147/webapp/travelplanning.php")
.build（）；
试一试{
Response=client.newCall（request.execute（）；
JSONArray数组=新的JSONArray（response.body（）.string（））；
列表=新的ArrayList（）；
对于（int i=0；i

谢谢您的回复，但仍然是空的。我的mysql中有3个示例数据，但它没有显示在recycler视图中。您检查响应数据了吗？如果有数据，我们检查客户端（android）。

<?php
require "init.php";

if(mysqli_connect_error($con))
{
    echo "Failed to connect";
}

$query = "Select id, attractionname, location from attraction";
$result = mysqli_query($con, $query);

if($result){
    while($row=mysqli_fetch_array($result)){
       $flag[]=$row;
    }

    print(json_encode($flag));
}
mysqli_close($con);
?>

private void load_data_from_server() {
    AsyncTask<Integer, Void, Void> task = new AsyncTask<Integer, Void, Void>() {
        @Override
        protected Void doInBackground(Integer... integers) {
            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    .url("http://192.168.43.147/webapp/travelplanning.php")
                    .build();
            try {
                Response response = client.newCall(request).execute();
                JSONArray array = new JSONArray(response.body().string());
                List<MyData> list = new ArrayList<>();
                for(int i = 0; i < array.length(); i++){
                    JSONObject object = array.getJSONObject(i);
                    MyData data = new MyData(object.getInt("ID"), object.getString("AttractionName"), object.getString("Location"));

                    list.add(data);
                }
                setListData(list);
            } catch (IOException e) {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
        }
    };
}

private void setListData(List<MyData> list) {
  data_list.addAll(list);
  adapter.notifyDataSetChanged();
}