Question

我是Android开发的初学者。它可能看起来非常基本，但我真的很难让它在我的项目中运行。

我正在为教授开发一个应用程序，以查看所有在数据库中试用的学生名单。

在我们将帐户登录到应用程序后的进度中，数据库中的所有学生都将以ListView形式显示

这是我的活动代码

UPDATE1：我管理以使项目可点击并显示名为Profile.class的新活动（我希望它能显示出来学生姓名：显示姓名 学生ID：显示身份 但它显示为NULL）

这是我的更新代码

public class MainPage extends Activity {

TextView name,email;
private String jsonResult;
private String url = "http://192.168.254.106/notificationapp/students.php";
private ListView listView;
String stud_name, stud_id;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.mainpage_layout);
    name = (TextView)findViewById(R.id.name);
    email = (TextView)findViewById(R.id.email);
    Bundle bundle = getIntent().getExtras();
    name.setText("Welcome "+bundle.getString("name"));
    email.setText("Email: "+bundle.getString("email"));
    listView = (ListView) findViewById(R.id.listView);
    accessWebService();
}



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}
// Async Task to access the web
private class JsonReadTask extends AsyncTask<String, Void, String> {
    @Override
    protected String doInBackground(String... params) {
        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(params[0]);
        try {
            HttpResponse response = httpclient.execute(httppost);
            jsonResult = inputStreamToString(
                    response.getEntity().getContent()).toString();
        }

        catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
    private StringBuilder inputStreamToString(InputStream is) {
        String rLine = "";
        StringBuilder answer = new StringBuilder();
        BufferedReader rd = new BufferedReader(new InputStreamReader(is));

        try {
            while ((rLine = rd.readLine()) != null) {
                answer.append(rLine);
            }
        }

        catch (IOException e) {
            // e.printStackTrace();
            Toast.makeText(getApplicationContext(),
                    "Error..." + e.toString(), Toast.LENGTH_LONG).show();
        }
        return answer;
    }

    @Override
    protected void onPostExecute(String result) {
        ListDrawer();
    }
}// end async task

public void accessWebService() {
    JsonReadTask task = new JsonReadTask();
    task.execute(new String[] { url });
}


public void ListDrawer() {
    final List<Map<String, String>> studentList = new ArrayList<Map<String, String>>();

    try {
        JSONObject jsonResponse = new JSONObject(jsonResult);
        JSONArray jsonMainNode = jsonResponse.optJSONArray("student_info");

        for (int i = 0; i < jsonMainNode.length(); i++) {
            JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
            String name = jsonChildNode.optString("student_name");
            String number = jsonChildNode.optString("student_id");
            String outPut = name + "-" + number;
            studentList.add(createStudent("Students", outPut));
        }
    } catch (JSONException e) {
        Toast.makeText(getApplicationContext(), "Error" + e.toString(),
                Toast.LENGTH_SHORT).show();
    }
 ////////////////////////////////// UPDATE LISTVIEW ITEMS ONCLICK
    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
             studentList.get(position);
            //Do your logic for getting the student variables here
            Intent intent = new Intent(MainPage.this,Profile.class);
            Bundle b = new Bundle();
            b.putString("student_name", stud_name);
            b.putString("student_id", stud_id);
            intent.putExtras(b);
            startActivity(intent);
        }
    });
//////////////////////////////////////UPDATE END
    SimpleAdapter simpleAdapter = new SimpleAdapter(this, studentList,
            android.R.layout.simple_list_item_1,
            new String[] { "Students" }, new int[] { android.R.id.text1 });
    listView.setAdapter(simpleAdapter);
    Toast.makeText(getApplication(), "Logged in Successfully", Toast.LENGTH_SHORT).show();

}

private HashMap<String, String> createStudent(String name, String number) {
    HashMap<String, String> Students = new HashMap<String, String>();
    Students.put(name, number);
    return Students;
}

}

我的个人资料活动

public class Profile extends Activity {

TextView stud_name,stud_id;

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

    stud_name = (TextView)findViewById(R.id.student_name);
    stud_id = (TextView)findViewById(R.id.student_id);
    Bundle bundle = getIntent().getExtras();
    stud_name.setText("Student name: "+bundle.getString("student_name"));
    stud_id.setText("Student ID: "+bundle.getString("student_id"));
}

}

我认为我的问题是在我的php中如何配置它如果我使用捆绑方法？从ListView中单击一个项目后，从mysql获取字符串数据并将其发送到Profile活动？

<?php
$host="localhost";
$username="thesis"; 
$password="thesis123"; 
$db_name="professor_db";
$con=mysql_connect("$host", "$username", "$password")or die("cannot      connect"); 
mysql_select_db("$db_name")or die("cannot select DB");
$sql = "select * from student_info"; 
$result = mysql_query($sql);
$json = array();
if(mysql_num_rows($result)){
while($row=mysql_fetch_assoc($result)){
$json['student_info'][]=$row;
}
}
mysql_close($con);
echo json_encode($json); 
?>

Answer 1

您可以为listview的每个元素创建一个customListView附加clickListener，clickListener将通过INTENT将您带到另一个活动，您也可以使用INTENT发送一些数据，以便您的新活动将被填充。

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
public class CustomAdapter extends BaseAdapter{   
    String [] result;
    Context context;
 int [] imageId;
      private static LayoutInflater inflater=null;
    public CustomAdapter(MainActivity mainActivity, String[] prgmNameList, int[] prgmImages) {
        // TODO Auto-generated constructor stub
        result=prgmNameList;
        context=mainActivity;
        imageId=prgmImages;
         inflater = ( LayoutInflater )context.
                 getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }
    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return result.length;
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    public class Holder
    {
        TextView tv;
        ImageView img;
    }
    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        Holder holder=new Holder();
        View rowView;       
             rowView = inflater.inflate(R.layout.program_list, null);
             holder.tv=(TextView) rowView.findViewById(R.id.textView1);
             holder.img=(ImageView) rowView.findViewById(R.id.imageView1);       
         holder.tv.setText(result[position]);
         holder.img.setImageResource(imageId[position]);         
         rowView.setOnClickListener(new OnClickListener() {            
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Toast.makeText(context, "You Clicked "+result[position], Toast.LENGTH_LONG).show();
            }
        });   
        return rowView;
    }

}

https://www.caveofprogramming.com/guest-posts/custom-listview-with-imageview-and-textview-in-android.html

Answer 2

您可以在ListView上设置onItemClickListener。在onClick方法中，您可以根据所选位置从阵列中获取学生。使用该数据，您可以创建一个Intent with extras并启动它。例如：

listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            ... studentList.get(position); //Do your logic for getting the student variables here

            Intent intent = new Intent(MainPage.this, TargetActivity.class);
            intent.putExtra("name", studentName);
            intent.putExtra("id", studentId);
            startActivity(intent);
        }
});

在TargetActivity（或项目中调用的内容）中，在onCreate方法中添加：

Intent intent = getIntent();
String studentName = intent.getStringExtra("name");
int studentId = intent.getIntExtra("id",-1);

Answer 3

您可以为所有可用的学生的基本和常见信息创建一个班级，创建其get()＆amp; set()方法。您从json获取的数据使用它的set()方法存储它喜欢：

public class StudentInfo{
    public String stud_name, stud_id ,stud_roll_num ,stud_add;

    // get Student Name with this method
    public String getName() {
        return stud_name;
    }

    // set Student Name with this method
    public void setName(String name) {
        this.stud_name = name;
    }

    public String getRollNum() {
        return stud_roll_num;
    }

    public void setRollNum(String rollNum) {
        this.stud_roll_num = rollNum;
    }
}

然后像这样使用它：

 public ArraryList<StudentInfo> studinfo = new ArraryList<StudentInfo>();

 String name = studinfo.get(position).stud_name;
 String roll_num = studinfo.get(position).stud_roll_num;

从我的listview添加ItemOnClick，使用MYSQL中的JSON获取数据

3 个答案: