android - 从微调器中删除最后一项会删除整个列表

Question

我正在尝试使用微调器控件，使用户能够删除任何列表元素。我有一个“添加”按钮可以将元素添加到列表中，还有一个“删除”按钮可以从列表中删除当前显示的项目。

它按预期工作除了当用户删除列表中的最后一项时。届时，列表中的所有项目都将被删除。

我的代码如下:

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

    // grab our UI elements so we can manipulate them (for the Spinner)
    // or add listeners to them (in the case of the buttons)
    m_myDynamicSpinner = (Spinner)findViewById(R.id.dynamicSpinner);
    m_addItemText = (EditText)findViewById(R.id.newSpinnerItemText);
    Button addButton = (Button)findViewById(R.id.AddBtn);
    Button clearButton = (Button)findViewById(R.id.ClearBtn);

    // create an arrayAdapter an assign it to the spinner
    m_adapterForSpinner = new ArrayAdapter(this, android.R.layout.simple_spinner_item);
        ((ArrayAdapter)m_adapterForSpinner).setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    m_myDynamicSpinner.setAdapter(m_adapterForSpinner);

    // add listener for addButton
    addButton.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            addNewSpinnerItem();
        }
    });

    clearButton.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
            clearSpinnerItems();
        }
    });
}

// add listener for addButton
private void addNewSpinnerItem() {
    if (m_addItemText.getText().length() == 0) {
        Toast.makeText(getApplicationContext(), "The textView is empty", Toast.LENGTH_LONG).show();
    } else {
        CharSequence textHolder = "" + m_addItemText.getText();
        ((ArrayAdapter) m_adapterForSpinner).add(textHolder);
    }
    m_addItemText.setText("");
}

private void clearSpinnerItems() {
    m_myDynamicSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {

        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
            Object t = m_adapterForSpinner.getItem(pos);
            ((ArrayAdapter) m_adapterForSpinner).remove((CharSequence) t);
        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO
        }
    });
}

有人对如何使这项工作有任何想法或建议吗？

Answer 1

您的代码的问题在于删除是在 onItemSelected 回调中进行的，每次您删除条目时都会调用该回调，从而递归删除，直到您实际上没有更多条目可供选择为止。如果您在该方法中添加日志:

Log.d("Spinner", "Count: " + m_adapterForSpinner.getCount());

你会明白我的意思。我相信您可以想出更优雅的代码，但一个快速而肮脏的 hack 是设置一个 bool 标志以在第一次删除后停止递归。请参阅下面的代码段并将注释行添加到您自己的代码中:

public class SpinnerTest extends Activity {
    Spinner m_myDynamicSpinner;
    EditText m_addItemText;
    ArrayAdapter m_adapterForSpinner;

    public static boolean cleared = false;  //   <--- set up a static boolean here

       @Override
        public void onCreate(Bundle savedInstanceState) {
// all your code unchanged

        clearButton.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {

                cleared=false;   //   <--- nope, we did not clear the value yet

                clearSpinnerItems();
            }
        });
    }

// code unchanged

    private void clearSpinnerItems() {
        m_myDynamicSpinner.setOnItemSelectedListener(new OnItemSelectedListener() {

            public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
                Object t = m_adapterForSpinner.getItem(pos);
                Log.d("Spinner", "Count: " + m_adapterForSpinner.getCount());

                if (!cleared)  //   <--- did I do it already?

                    ((ArrayAdapter) m_adapterForSpinner).remove((CharSequence) t);

                Log.d("Spinner", "Count: " + m_adapterForSpinner.getCount());

                cleared=true;  // I did it!

            }

// code unchanged