我想过一些不那么优雅的方法来解决这个问题,但我知道我一定遗漏了什么。

我的onItemSelected立即启动,没有与用户进行任何交互,这是不希望的行为。我希望UI能够等到用户选择某样东西后再执行任何操作。

我甚至尝试在onResume()中设置监听器,希望能有所帮助,但它没有。

我怎样才能阻止它在用户可以触摸控件之前发射?

public class CMSHome extends Activity { 

private Spinner spinner;

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

    // Heres my spinner ///////////////////////////////////////////
    spinner = (Spinner) findViewById(R.id.spinner);
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
            this, R.array.pm_list, android.R.layout.simple_spinner_item);
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(adapter);
    };

public void onResume() {
    super.onResume();
    spinner.setOnItemSelectedListener(new MyOnItemSelectedListener());
}

    public class MyOnItemSelectedListener implements OnItemSelectedListener {

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

     Intent i = new Intent(CMSHome.this, ListProjects.class);
     i.putExtra("bEmpID", parent.getItemAtPosition(pos).toString());
        startActivity(i);

        Toast.makeText(parent.getContext(), "The pm is " +
          parent.getItemAtPosition(pos).toString(), Toast.LENGTH_LONG).show();
    }

    public void onNothingSelected(AdapterView parent) {
      // Do nothing.
    }
}
}

当前回答

我需要在ViewHolder中使用mSpinner,因此标记mOldPosition在匿名内部类中设置。

mSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            int mOldPosition = mSpinner.getSelectedItemPosition();

            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long l) {
                if (mOldPosition != position) {
                    mOldPosition = position;
                    //Do something
                }
            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {
                //Do something
            }
        });

其他回答

我的小贡献是对上面的一些已经适合我几次的变化。

声明一个整型变量作为默认值(或保存在首选项中的最后使用值)。 使用spinner.setSelection(myDefault)在注册侦听器之前设置该值。 在onItemSelected中,在运行任何进一步的代码之前,检查新的spinner值是否等于您分配的值。

这样做的另一个好处是,如果用户再次选择相同的值,就不会运行代码。

不幸的是,解决这个问题的两个最常见的建议解决方案,即统计回调发生次数和发布Runnable以在稍后设置回调,在启用可访问性选项时都可能失败。下面是一个帮助类,它可以解决这些问题。进一步的解释在评论区。

import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.Spinner;
import android.widget.SpinnerAdapter;

/**
 * Spinner Helper class that works around some common issues 
 * with the stock Android Spinner
 * 
 * A Spinner will normally call it's OnItemSelectedListener
 * when you use setSelection(...) in your initialization code. 
 * This is usually unwanted behavior, and a common work-around 
 * is to use spinner.post(...) with a Runnable to assign the 
 * OnItemSelectedListener after layout.
 * 
 * If you do not call setSelection(...) manually, the callback
 * may be called with the first item in the adapter you have 
 * set. The common work-around for that is to count callbacks.
 * 
 * While these workarounds usually *seem* to work, the callback
 * may still be called repeatedly for other reasons while the 
 * selection hasn't actually changed. This will happen for 
 * example, if the user has accessibility options enabled - 
 * which is more common than you might think as several apps 
 * use this for different purposes, like detecting which 
 * notifications are active.
 * 
 * Ideally, your OnItemSelectedListener callback should be
 * coded defensively so that no problem would occur even
 * if the callback was called repeatedly with the same values
 * without any user interaction, so no workarounds are needed.
 * 
 * This class does that for you. It keeps track of the values
 * you have set with the setSelection(...) methods, and 
 * proxies the OnItemSelectedListener callback so your callback
 * only gets called if the selected item's position differs 
 * from the one you have set by code, or the first item if you
 * did not set it.
 * 
 * This also means that if the user actually clicks the item
 * that was previously selected by code (or the first item
 * if you didn't set a selection by code), the callback will 
 * not fire.
 * 
 * To implement, replace current occurrences of:
 * 
 *     Spinner spinner = 
 *         (Spinner)findViewById(R.id.xxx);
 *     
 * with:
 * 
 *     SpinnerHelper spinner = 
 *         new SpinnerHelper(findViewById(R.id.xxx))
 *         
 * SpinnerHelper proxies the (my) most used calls to Spinner
 * but not all of them. Should a method not be available, use: 
 * 
 *      spinner.getSpinner().someMethod(...)
 *
 * Or just add the proxy method yourself :)
 * 
 * (Quickly) Tested on devices from 2.3.6 through 4.2.2
 * 
 * @author Jorrit "Chainfire" Jongma
 * @license WTFPL (do whatever you want with this, nobody cares)
 */
public class SpinnerHelper implements OnItemSelectedListener {
    private final Spinner spinner;

    private int lastPosition = -1;
    private OnItemSelectedListener proxiedItemSelectedListener = null;  

    public SpinnerHelper(Object spinner) {
         this.spinner = (spinner != null) ? (Spinner)spinner : null;        
    }

    public Spinner getSpinner() {
        return spinner;
    }

    public void setSelection(int position) { 
        lastPosition = Math.max(-1, position);
        spinner.setSelection(position);     
    }

    public void setSelection(int position, boolean animate) {
        lastPosition = Math.max(-1, position);
        spinner.setSelection(position, animate);        
    }

    public void setOnItemSelectedListener(OnItemSelectedListener listener) {
        proxiedItemSelectedListener = listener;
        spinner.setOnItemSelectedListener(listener == null ? null : this);
    }   

    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        if (position != lastPosition) {
            lastPosition = position;
            if (proxiedItemSelectedListener != null) {
                proxiedItemSelectedListener.onItemSelected(
                        parent, view, position, id
                );
            }
        }
    }

    public void onNothingSelected(AdapterView<?> parent) {
        if (-1 != lastPosition) {
            lastPosition = -1;
            if (proxiedItemSelectedListener != null) {
                proxiedItemSelectedListener.onNothingSelected(
                        parent
                );
            }
        }
    }

    public void setAdapter(SpinnerAdapter adapter) {
        if (adapter.getCount() > 0) {
            lastPosition = 0;
        }
        spinner.setAdapter(adapter);
    }

    public SpinnerAdapter getAdapter() { return spinner.getAdapter(); } 
    public int getCount() { return spinner.getCount(); }    
    public Object getItemAtPosition(int position) { return spinner.getItemAtPosition(position); }   
    public long getItemIdAtPosition(int position) { return spinner.getItemIdAtPosition(position); }
    public Object getSelectedItem() { return spinner.getSelectedItem(); }
    public long getSelectedItemId() { return spinner.getSelectedItemId(); }
    public int getSelectedItemPosition() { return spinner.getSelectedItemPosition(); }
    public void setEnabled(boolean enabled) { spinner.setEnabled(enabled); }
    public boolean isEnabled() { return spinner.isEnabled(); }
}

设计一种通用的转轮,只需数据输入,由用户选择,优点: 1. 保持旋转样式相同的应用程序。 2. 在任何地方启动旋转器。 3.易于处理链接转轮(重新启动ReuseSpinner与不同的数据)。

我的演示示例:ReuseSpinner 传递数据到ReuseSpinner:

Intent intent = new Intent(MainActivity.this, SpinnerActivity.class);
intent.putExtra(SpinnerActivity.Extra_Resource, arrayList);
startActivityForResult(intent, mRequestCode_select_country_prompt);

获取用户选择:

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        // TODO Auto-generated method stub
        super.onActivityResult(requestCode, resultCode, data);

        if(requestCode == mRequestCode_select_country && resultCode == RESULT_OK){
            if(data != null){
                Map.Entry<String,String> entry = (Map.Entry<String,String>) data.getSerializableExtra(SpinnerActivity.Result_Data);
                if(entry != null){
                    Log.i(TAG, String.format("get result -> key:%s , value:%s", entry.getKey(), entry.getValue()));

                }
            }
        }
    }

这是我最后的简单易用的解决方案:

public class ManualSelectedSpinner extends Spinner {
    //get a reference for the internal listener
    private OnItemSelectedListener mListener;

    public ManualSelectedSpinner(Context context) {
        super(context);
    }

    public ManualSelectedSpinner(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public ManualSelectedSpinner(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public void setOnItemSelectedListener(@Nullable OnItemSelectedListener listener) {
        mListener = listener;
        super.setOnItemSelectedListener(listener);
    }

    public void setSelectionWithoutInformListener(int position){
        super.setOnItemSelectedListener(null);
        super.setSelection(position);
        super.setOnItemSelectedListener(mListener);
    }

    public void setSelectionWithoutInformListener(int position, boolean animate){
        super.setOnItemSelectedListener(null);
        super.setSelection(position, animate);
        super.setOnItemSelectedListener(mListener);
    }
}

使用默认的setSelection(…)作为默认行为,或者使用setSelectionWithoutInformListener(…)在旋转器中选择一个项目而不触发OnItemSelectedListener回调。

我需要在ViewHolder中使用mSpinner,因此标记mOldPosition在匿名内部类中设置。

mSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            int mOldPosition = mSpinner.getSelectedItemPosition();

            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long l) {
                if (mOldPosition != position) {
                    mOldPosition = position;
                    //Do something
                }
            }

            @Override
            public void onNothingSelected(AdapterView<?> adapterView) {
                //Do something
            }
        });