多选微调器清除所有按钮android

Question

我正在创建多选微调器，并且“全部清除”按钮出现问题 http://postimg.org/image/eoyq5jpib/但“全选”工作相当不错，但点击“全部清除”时没有任何反应。为什么我会遇到“全部清除”的问题？

protected CharSequence[] _options = { "One", "Two", "Three", "Four", "Five" };
protected boolean[] _selections =  new boolean[ _options.length ];
protected Button _optionsButton;

 public class ButtonClickHandler implements View.OnClickListener {
    public void onClick( View view ) {
        showDialog( 0 );
    }
}

@Override
protected Dialog onCreateDialog( int id )
{
    return
            new AlertDialog.Builder( this )
                    .setTitle( "Students" )
                    .setMultiChoiceItems(_options, _selections, new DialogSelectionClickHandler())
                    .setPositiveButton("OK", new DialogButtonClickHandler())
                    .setNeutralButton("Select All",
                            new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    selectAllStudents();
                                }
                            })
                    .setNegativeButton("Clear All",
                            new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    clearAllStudents();
                                }
                            })
                    .create();

}


public class DialogSelectionClickHandler implements DialogInterface.OnMultiChoiceClickListener
{
    public void onClick( DialogInterface dialog, int clicked, boolean selected )
    {
        Log.i("ME", _options[clicked] + " selected: " + selected);
    }
}


public class DialogButtonClickHandler implements DialogInterface.OnClickListener
{
    public void onClick( DialogInterface dialog, int clicked )
    {
        checkAllStudents();
        switch( clicked )
        {
            case DialogInterface.BUTTON_POSITIVE:
                printSelectedStudents();
                break;
            case DialogInterface.BUTTON_NEUTRAL:
                printSelectedStudents();
                break;
            case DialogInterface.BUTTON_NEGATIVE:
                printSelectedStudents();
                break;
        }
    }
}

protected void clearAllStudents(){
    for (int i = 0; i<_options.length; i++) {
        _selections[i] = false;
    }
}

protected  void selectAllStudents(){
    for (int i = 0; i<_options.length; i++) {
        _selections[i] = true;
    }
}
protected void printSelectedStudents(){
    for( int i = 0; i < _options.length; i++ ){
        Log.i( "ME", _options[ i ] + " selected: " + _selections[i] );