Question

我有以下基本适配器自定义类，创建列表视图和项目。但我想在单击重置按钮时从列表中删除所有项目。我的代码：

public class Scores extends Activity implements OnClickListener {

public static final String MY_PREFS_NAME = "PrefName";
SharedPreferences pref;
static String[] tempTime = new String[10];
static String[] tempScore = new String[10];

private static class EfficientAdapter extends BaseAdapter {
    private LayoutInflater mInflater;
    public EfficientAdapter(Context context) {
        mInflater = LayoutInflater.from(context);

    }

    public int getCount() {
        return tempTime.length;
    }

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

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

    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            convertView = mInflater.inflate(
                    R.layout.mathmatch_score_format, null);
            holder = new ViewHolder();
            holder.text1 = (TextView) convertView
                    .findViewById(R.id.time_text);
            holder.text2 = (TextView) convertView
                    .findViewById(R.id.score_text);
            /*final ImageView deleteButton = (ImageView) 
                    convertView.findViewById(R.id.score_reset);
            deleteButton.setOnClickListener(this);*/
            convertView.setTag(holder);
            //deleteButton.setTag(holder);

        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.text1.setText(tempTime[position]);
        holder.text2.setText(tempScore[position]);

        return convertView;
    }

    static class ViewHolder {
        TextView text1;
        TextView text2;
    }

}

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.mathmatch_score);
    setUpViews();
    pref = getSharedPreferences(MY_PREFS_NAME, 0);
    strTime = pref.getString("high_score_times", "");
    intScore = pref.getString("high_score_values", "");
    tempTime = strTime.split(",");
    tempScore = intScore.split(",");

    Comparator<String> comparator = new CustomArrayComparator<String, String>(tempScore, tempTime);
    Arrays.sort(tempTime, comparator);
    Arrays.sort(tempScore, Collections.reverseOrder());
    lv.setAdapter(new EfficientAdapter(this));
}

private void setUpViews() {
    lv = (ListView) findViewById(R.id.list);
    reset = (ImageView) findViewById(R.id.score_reset);
    reset.setOnClickListener(this);
}   

@Override
protected void onPause() {
    super.onPause();
    pref = getSharedPreferences(MY_PREFS_NAME, 0);
    SharedPreferences.Editor edit = pref.edit();
    edit.putString("high_score_times", strTime);
    edit.putString("high_score_values", intScore);
    edit.commit();
}
@Override
protected void onStop() {
    super.onStop();
}
@Override
public void onClick(View v) {
    switch (v.getId()) {
    case R.id.score_reset:
        AlertDialog.Builder alertbox = new AlertDialog.Builder(this);
        alertbox.setTitle("Reset");
        alertbox.setMessage("Are you sure all time ans score are reset?");

        alertbox.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                     public void onClick(DialogInterface arg0, int arg1) {
                         pref = getSharedPreferences(MY_PREFS_NAME, 0);
                        SharedPreferences.Editor edit = pref.edit();
                        /*edit.remove("high_score_times");
                        edit.remove("high_score_values");*/

                        /*edit.remove(intScore);
                        edit.remove(strTime);
                        */
                        //edit.clear();
                        edit.remove(MY_PREFS_NAME);
                        edit.commit();
                             }
        });
                    alertbox.setNegativeButton("No", new DialogInterface.OnClickListener() {
                     public void onClick(DialogInterface arg0, int arg1) {
                Toast.makeText(getApplicationContext(), "'No' button clicked", Toast.LENGTH_SHORT).show();
            }
        });
         alertbox.show();
           break;
      default:
        break;
}}}

我的重置按钮不包含在列表中。我在上面的代码中的是按钮点击事件中尝试了这个但是无法获得任何更新。那么该怎么办？提前谢谢。

Answer 1

使用listview实例获取列表适配器，如

urlist.setAdapter("pass your updated adapter with empty string array");

OR

你也可以调用notifyDataSetChanged（）;告诉列表视图其数据集已更改

Answer 2

清除列表：

将tempTime和tempScore设置为空数组

tempTime= new String[0]; 
adapter.notifyDataSetChanged();

添加/删除数据：

相应地更改数据源tempTime和tempScore并调用adapter.notifyDataSetChanged();

Answer 3

首先，您的适配器使用错误。您的适配器应该是数据的包装器，而不是用于公开代码中其他位置的数据的外观。

在您的情况下，您使用它来访问两个变量（非常糟糕的形式使这些变量静态）：

static String[] tempTime = new String[10];
static String[] tempScore = new String[10];

在您的共享偏好设置中创建填充这些变量。

然后在“是”上更新您的偏好设置，但无论您按下适配器上的“更新”按钮多少，它仍然会查看那些尚未更新的变量。

如果您希望“是”按钮清除列表，则需要更改支持适配器的数据，然后告诉适配器它已更改并重绘自己。

   alertbox.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface arg0, int arg1) {
            pref = getSharedPreferences(MY_PREFS_NAME, 0);
            SharedPreferences.Editor edit = pref.edit();
            /**/
            edit.remove(MY_PREFS_NAME);
            edit.commit();

            strTime = pref.getString("high_score_times", "");
            intScore = pref.getString("high_score_values", "");
            tempTime = strTime.split(",");
            tempScore = intScore.split(",");

            EfficientAdapter adapter = (EfficientAdapter)lv.getAdapter();
            adapter.notifyDataSetChanged();               
    });

如何使用共享首选项删除列表项或清除列表视图？

3 个答案: