我的 ArrayList 中的数据重复了数组最后输入的数据。这是什么原因？

Question

当我使用 ArrayList 使用自定义适配器在列表视图中列出图像时，代码没有显示任何错误。问题是，在使用代码时，只有我最后输入的数据在列表视图中显示。为什么之前输入的数据无法查看？

我的activityclass:

public class SocialActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_social);
        String json;
        ImageView babu = (ImageView) findViewById(R.id.babu);
        ListView lvsoc = (ListView) findViewById(R.id.list_social);
        LinearLayout l1 = (LinearLayout) findViewById(R.id.layhead);
        LayoutInflater inflater = null;
        ArrayList<SubjectData> arrayList = new ArrayList<SubjectData>();
        ArrayAdapter<SubjectData> a;
        /*ArrayList<String> allcategory = new ArrayList<>();
        ArrayList<String> allcategory1 = new ArrayList<>();
        ArrayList<String> img = new ArrayList<>();
        ArrayList<String> img1 = new ArrayList<>();*/
        arrayList.add(new SubjectData("JAVA", "https://www.tutorialspoint.com/java/", "https://s18955.pcdn.co/wp-content/uploads/2017/11/Facebook-share-icon.png"));
        arrayList.add(new SubjectData("Python", "https://www.tutorialspoint.com/python/", "https://www.tutorialspoint.com/python/images/python-mini.jpg"));
        /*arrayList.add(new SubjectData("Javascript", "https://www.tutorialspoint.com/javascript/", "https://www.tutorialspoint.com/javascript/images/javascript-mini-logo.jpg"));
        arrayList.add(new SubjectData("Cprogramming", "https://www.tutorialspoint.com/cprogramming/", "https://www.tutorialspoint.com/cprogramming/images/c-mini-logo.jpg"));
        arrayList.add(new SubjectData("Cplusplus", "https://www.tutorialspoint.com/cplusplus/", "https://www.tutorialspoint.com/cplusplus/images/cpp-mini-logo.jpg"));
        arrayList.add(new SubjectData("Android", "https://www.tutorialspoint.com/android/", "https://www.tutorialspoint.com/android/images/android-mini-logo.jpg"));*/

        //SocialAdapter customAdapter = new SocialAdapter(SocialActivity.this, arrayList);
        lvsoc.setAdapter((ListAdapter) arrayList);

        //arrayList.add(new SubjectData("JAVA", "https://www.tutorialspoint.com/java/", "https://www.tutorialspoint.com/java/images/java-mini-logo.jpg"));
        babu.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i;
                i = new Intent(SocialActivity.this, MainActivity.class);
                startActivity(i);
            }
        });






    }
    @Override
    public void onBackPressed() {
        Intent i = new Intent(SocialActivity.this, MainActivity.class);
        startActivity(i);
        super.onBackPressed();
    }
}

我的适配器class:

import java.util.ArrayList;

public class SocialAdapter implements ListAdapter {
    ArrayList<SubjectData> arrayList;
    Context context;
    public SocialAdapter(Context context, ArrayList<SubjectData> arrayList) {
        this.arrayList=arrayList;
        this.context=context;
    }

    @Override
    public boolean areAllItemsEnabled() {
        return false;
    }

    @Override
    public boolean isEnabled(int position) {
        return true;
    }

    @Override
    public void registerDataSetObserver(DataSetObserver observer) { }

    @Override
    public void unregisterDataSetObserver(DataSetObserver observer) { }

    @Override
    public int getCount() {
        return arrayList.size();
    }

    @Override
    public Object getItem(int position) {
        return position;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public boolean hasStableIds() {
        return false;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final SubjectData subjectData=arrayList.get(position);
        if(convertView==null){
            LayoutInflater layoutInflater = LayoutInflater.from(context);
            convertView=layoutInflater.inflate(R.layout.list_row, null);
            convertView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent i = new Intent(Intent.ACTION_VIEW);
                    i.setData(Uri.parse(subjectData.Link));
                    context.startActivity(i);
                    //Toast.makeText(context,subjectData.Link,Toast.LENGTH_LONG).show();
                }
            });
            TextView tittle=convertView.findViewById(R.id.title);
            ImageView imag=convertView.findViewById(R.id.list_image);
            tittle.setText(subjectData.SubjectName);
            Picasso.get()
                    .load(subjectData.Image)
                    .into(imag);

        }
        return convertView;
    }

    @Override
    public int getItemViewType(int position) {
        return position;
    }

    @Override
    public int getViewTypeCount() {
        return arrayList.size();
    }


    @Override
    public boolean isEmpty() {
        return false;
    }
}

我的 class 用于保存主题数据：

package com.gjinfotech.eschoolsolution.ClassAdapter;

public class SubjectData {
    public static  String SubjectName;
    public static String Link;
    public static String Image;
    public SubjectData(String subjectName, String link, String image) {
        this.SubjectName = subjectName;
        this.Link = link;
        this.Image = image;
    }
}

Answer 1

您的 SubjectData 具有所有静态字段。所以 SubjectData 的每个实例都有相同的信息。

改为：

public class SubjectData {
    public String SubjectName;
    public String Link;
    public String Image;
    public SubjectData(String subjectName, String link, String image) {
        this.SubjectName = subjectName;
        this.Link = link;
        this.Image = image;
    }
}

我的 ArrayList 中的数据重复了数组最后输入的数据。这是什么原因？

The data in my ArrayList repeats the last entered data of the array. What is the reason for this?

java

android

arraylist

adapter