带有多个按钮的 Android 列表视图

Question

问题是，如果单击第一个按钮，那么第十二个按钮也仅在移动设备上运行此错误，如果在模拟器上运行，列表显示所有元素并完美运行。但在移动列表视图中显示 10 个项目，需要向下滚动才能查看更多`public class MyCustomAdapter 扩展 BaseAdapter 实现 ListAdapter { 私有 ArrayList 列表 = 新 ArrayList(); 私有上下文上下文；

public MyCustomAdapter(ArrayList<String> list, Context context) {
    this.list = list;
    this.context = context;

}

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

@Override
public Object getItem(int pos) {
    return list.get(pos);
}

@Override
public long getItemId(int pos) {
    return 0; //list.get(pos).getId();
    //just return 0 if your list items do not have an Id variable.
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    View view = convertView;
    if (view == null) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        view = inflater.inflate(R.layout.list, null);
    }

    //Handle TextView and display string from your list
    TextView listItemText = (TextView)view.findViewById(R.id.name);
    listItemText.setText(list.get(position));

    //Handle buttons and add onClickListeners
    final Button deleteBtn = (Button)view.findViewById(R.id.present);
    final Button addBtn = (Button)view.findViewById(R.id.absent);

    deleteBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //do something
           // list.remove(position); //or some other task
            Toast.makeText(context,"hello",Toast.LENGTH_SHORT).show();
            deleteBtn.setBackgroundColor(Color.GREEN);
            addBtn.setEnabled(false);
          //  notifyDataSetChanged();
        }
    });
    addBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //do something
            addBtn.setBackgroundColor(Color.GREEN);
            deleteBtn.setEnabled(false);
         //   notifyDataSetChanged();
        }
    });

    return view;
}

}`

这是添加列表项

 public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            str = sp1.getSelectedItem().toString();

            //handle listview and assign adapter
            if(str.equals("3rd year")) {
                Toast.makeText(getApplicationContext(), str, Toast.LENGTH_SHORT).show();

               for(int i=0;i<15;i++)
               {
                   list3.add("Item"+i);
               }
            }
            ListView lView = (ListView) findViewById(R.id.listView);
            lView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
            lView.setAdapter(adapter);

        }

Answer 1

自定义 LIstview 与 ViewHolder 完美配合。这里的问题是您的按钮状态使用 getView() 方法更改。如果您使用 ViewHolder 完成此操作，您的 ListView 项目将保持其状态。

Answer 2

发生这种情况是因为您的视图被重用了。模拟器很弱，它不重用视图，而是创建一个新的。

改一下

View view = convertView;    
    if (view == null) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        view = inflater.inflate(R.layout.list, null);
    }

到这里

ViewHolder holder = null;
 if (view == null) {
        view = LayoutInflater.from(context).inflate(R.layout.list, viewGroup, false);
        holder = new ViewHolder(view);
        // init your views here, f.e.:
        holder.listItemText = (TextView)view.findViewById(R.id.name);            
        // or just use Butterknife library
        view.setTag(holder);
    } else {
        holder = (ViewHolder) view.getTag();
    }
    // now you can set value
    holder.listItemText.setText(list.get(position));

ViewHolder 存放对象的位置，其中存储有关您的视图的信息

class ViewHolder {
    TextView listItemText ;
    Button deleteBtn;
    Button addBtn;
        public ViewHolder(View view) {
           // I would advice you to use Butterknife, it saves time. http://jakewharton.github.io/butterknife/ 
           //ButterKnife.inject(this, view);
        }
    }

Answer 3

问题在于列表视图布局被回收以提高性能，这意味着屏幕上的第一个可见单元格的位置为 0 并递增到最后一个可见单元格。因此，如果设备显示 10 个视图，那么每 10 个视图本质上是相同的视图。保留要修改的视图位置列表是一种快速简单的方法，可确保在正确的视图上绘制正确的方案。

解决方案

List<Integer> presentPositions = new ArrayList<>();
List<Integer> absentPositions = new ArrayList<>();

public View getView(int position, View convertView, ViewGroup parent) {

    if (convertView == null) {
        LayoutInflater inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.list, parent, false);
    }

    //Handle TextView and display string from your list
    TextView listItemText = (TextView)view.findViewById(R.id.name);
    listItemText.setText(list.get(position));

    //Handle buttons and add onClickListeners
    final Button deleteBtn = (Button)view.findViewById(R.id.present);
    final Button addBtn = (Button)view.findViewById(R.id.absent);

    deleteBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            presentPosition.add(position);
            Toast.makeText(context,"hello",Toast.LENGTH_SHORT).show();
            deleteBtn.setBackgroundColor(Color.GREEN);
            addBtn.setEnabled(true);
        }
    });

    addBtn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
            absentPositions.add(position);
            addBtn.setBackgroundColor(Color.GREEN);
            deleteBtn.setEnabled(false);
         //   notifyDataSetChanged();
        }
    });

    if (presentPositions.contains(position)) {
        deleteBtn.setBackgroundColor(Color.GREEN);
        addBtn.setEnabled(false);
    } else {
        deleteBtn.setBackgroundColor(Color.RED);
        addBtn.setEnabled(true);
    }

    if (absentPositions.contains(position)) {
        addBtn.setBackgroundColor(Color.GREEN);
        deleteBtn.setEnabled(false);
    } else {
        addBtn.setBackgroundColor(Color.RED);
        deleteBtn.setEnabled(true);
    }

    return convertView;
}