Question

我有一个自定义适配器和ListView活动。我需要实现全选/取消全选按钮。我使用MVC并有特殊的类来处理单词 - WordsHandler。因此，当用户按下按钮时，hendler将条件（布尔值 - 已选中/未选中）设置为单词并运行notifyDataSetChanged（）方法。但这并不奏效。你能看到我的课程并告诉我我的错误吗？我是初学者，不知道哪里出错... 有趣的是，方法isAllSelected（）返回不同的值，但适配器不会改变。

SettingsAdapter.java：

public class SettingsAdapter extends BaseAdapter {

private Context context;
private LayoutInflater layoutInflater;
private ArrayList<WordListModel> words;
private View view;

public SettingsAdapter(Context context, ArrayList<WordListModel> words) {
    this.context = context;
    this.words = words;
    layoutInflater = (LayoutInflater) this.context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

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

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

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    view = convertView;
    CompleteListViewHolder viewHolder;
    if (convertView == null) {
        view = layoutInflater.inflate(R.layout.item, parent, false);
        viewHolder = new CompleteListViewHolder(view);
        view.setTag(viewHolder);
    } else {
        viewHolder = (CompleteListViewHolder) view.getTag();
    }
    viewHolder.checkBox.setText(words.get(position).getWord().toString());
    if (words.get(position).isChecked())
        viewHolder.checkBox.setChecked(true);
    else
        viewHolder.checkBox.setChecked(false);

    return view;
}}

class CompleteListViewHolder {

public CheckBox checkBox;

public CompleteListViewHolder(View base) {
    checkBox = (CheckBox) base.findViewById(R.id.checkBox);
}}

SettingsActivity.java：

public class SettingsActivityRTG extends Activity  {

private WordsHandler wordsHandler;
private Context context;
private SettingsAdapter adapter;
private ListView listView;

private void enableActionBarBackButton() {
    getActionBar().setDisplayHomeAsUpEnabled(true);
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_settings);
    enableActionBarBackButton();
    context = getApplicationContext();
    wordsHandler = new WordsHandler(context);
    adapter = new SettingsAdapter(this, wordsHandler.getWordsList());
    listView = (ListView) findViewById(R.id.listView);
    listView.setAdapter(adapter);
}

@Override
public void onBackPressed() {
    try {
        wordsHandler.writeStringsToFile(wordsHandler.getWordsList());
    } catch (FileNotFoundException e) {
    } catch (IOException e) {
    }
    finish();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.activity_settings_action, menu);
    if(wordsHandler.isAllSelected())
        menu.findItem(R.id.action_select_all).setTitle(getString(R.string.deselall));

    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.action_select_all:
        if(wordsHandler.isAllSelected()) {
            wordsHandler.deselectAll();
            item.setTitle(getString(R.string.selall));
            } else {
            wordsHandler.selectAll();
            item.setTitle(getString(R.string.deselall));
        }
        adapter.notifyDataSetChanged();

        return true;
    default:
        return super.onOptionsItemSelected(item);
    }
}}

WordsHandler的一些方法：

    private Context ctx;
private ArrayList<WordListModel> wordsArray;
private SharedPreferences sharedPreferences;
private String filePath;
private File file;
private File dir;

public void selectAll() {
    for(WordListModel m : wordsArray)
        m.setChecked(true);
}

public void deselectAll() {
    for(WordListModel m : wordsArray)
        m.setChecked(false);
}

public boolean isAllSelected() {
    for(int i = 0; i < wordsArray.size(); i++)
        if(wordsArray.get(i).isChecked() == false)
            return false;
    return true;
}

public WordsHandler(Context ctx) {
    this.ctx = ctx;
    filePath = Environment.getExternalStorageDirectory()+Const.PATH_TO_FILE;
    dir = new File(filePath);
    dir.mkdirs();
    file = new File(dir,Const.FILE_NAME);
    sharedPreferences = ctx.getSharedPreferences(Const.SHARED_PREFERENCES_NAME, Context.MODE_PRIVATE);
    wordsArray = getWordsList();
}

Answer 1

在致电notifyDataSetChanged之前，您尚未更改适配器。您已更改wordsHandler。在致电SettingsAdapter

之前更改notifyDataSetChanged的内容

具有notifyDataSetChanged的自定义适配器无法正常工作

1 个答案: