java - Spinner onItemSelected() 执行不当

Question

Possible Duplicate:
Android Spinner OnItemSelected Called Erroneously (without user action on opening spinner)

有谁知道在布局实例化时如何防止 onItemSelected()(OnItemSelectedListener 接口(interface))方法运行？我需要知道是否有办法做到这一点，因为我想将我的布局实例化方式与此监听器分开。

我已经尝试创建一个 if 语句，最初设置为 false 围绕被覆盖方法内的所有代码，但无法知道何时将其设置为 true，因为被覆盖的方法在 onCreate() 之后运行，onStart( ) 和 onResume() 方法。

我还没有找到任何明确的答案。任何明确的解决方案将不胜感激。

Answer 1

大卫，这是我为这个问题写的教程...

问题陈述

在 Gallery(或 Spinner)初始化时触发了不受欢迎的 onItemSelected()。 这意味着代码被过早地执行；仅在用户实际做出选择时才会执行的代码。

解决方案

1. 在 onCreate() 中，计算 View 中有多少个 Gallery(或 Spinner)小部件。 (mGalleryCount)
2. 在 onItemSelected() 中，计算它触发的频率。 (mGalleryInitializedCount)
3. 当 (mGalleryInitializedCount < mGalleryCount) == false 时，执行针对用户的代码

代码示例

public class myActivity extends Activity implements OnItemSelectedListener
{
    //this counts how many Gallery's are on the UI
    private int mGalleryCount=0;

    //this counts how many Gallery's have been initialized
    private int mGalleryInitializedCount=0;

    //UI reference
    private Gallery mGallery;


    @Override
    public void onCreate(Bundle savedInstanceState)
    {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.myxmllayout);

        //get references to UI components
        mGallery = (Gallery) findViewById(R.id.mygallery);

        //trap selection events from gallery
        mGallery.setOnItemSelectedListener(this);

        //trap only selection when no flinging is taking place
        mGallery.setCallbackDuringFling(false);

        //
        //do other stuff like load images, setAdapter(), etc
        //

        //define how many Gallery's are in this view
        //note: this could be counted dynamically if you are programmatically creating the view
        mGalleryCount=1;

    }


    public void onItemSelected(AdapterView<?> parent, View view, int position, long id)
    {

        if (mGalleryInitializedCount < mGalleryCount)
        {
            mGalleryInitializedCount++;
        }
        else
        {
            //only detect selection events that are not done whilst initializing
            Log.i(TAG, "selected item position = " + String.valueOf(position) );
        }

    }

}

为什么会这样

此解决方案之所以有效，是因为库在用户实际能够做出选择之前很久就完成了初始化。