我想使用一个微调器,最初(当用户还没有做出选择时)显示文本“Select One”。当用户单击微调器时,将显示项目列表,用户可以选择其中一个选项。用户做出选择后,所选项目将显示在微调器中,而不是“Select One”。

我有以下代码来创建一个旋转器:

String[] items = new String[] {"One", "Two", "Three"};
Spinner spinner = (Spinner) findViewById(R.id.mySpinner);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_spinner_item, items);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);

使用这段代码,最初会显示项目“One”。我可以在项目中添加一个新项目“Select One”,但“Select One”也会作为第一项显示在下拉列表中,这不是我想要的。

我该如何解决这个问题?


当前回答

我试过的方法如下。取一个按钮并将单击事件赋予它。通过改变按钮背景,它似乎是一个旋转器。

声明为全局变量alertdialog和默认值..

AlertDialog d;
static int default_value = 0;
final Button btn = (Button) findViewById(R.id.button1);
btn .setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v)
{
    //c.show();
    final CharSequence str[] = {"Android","Black Berry","Iphone"};
        AlertDialog.Builder builder =
          new AlertDialog.Builder(TestGalleryActivity.this).setSingleChoiceItems(
            str, default_value,new  DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int position)
            {
                Toast.makeText(TestGalleryActivity.this,
                               "" + position,
                               Toast.LENGTH_SHORT).show();
                default_value = position;
                btn.setText(str[position]);
                if(d.isShowing())
                    d.dismiss();
            }
        }).setTitle("Select Any");
        d = builder.create();
        d.show();
    }
});

其他回答

你可以把它变成一个文本视图,并使用这个:

android:style="@android:style/Widget.DeviceDefault.Light.Spinner"

然后定义android:text属性。

我最终使用了Button。虽然Button不是旋转器,但其行为很容易自定义。

首先像往常一样创建适配器:

String[] items = new String[] {"One", "Two", "Three"};
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
        android.R.layout.simple_spinner_dropdown_item, items);

注意,我使用simple_spinner_dropdown_item作为布局id。这将有助于创建一个更好的外观时,创建警报对话框。

在onClick处理我的按钮,我有:

public void onClick(View w) {
  new AlertDialog.Builder(this)
  .setTitle("the prompt")
  .setAdapter(adapter, new DialogInterface.OnClickListener() {

    @Override
    public void onClick(DialogInterface dialog, int which) {

      // TODO: user specific action

      dialog.dismiss();
    }
  }).create().show();
}

就是这样!

对此,我找到了很多好的解决方案。大多数是通过在适配器的末尾添加一个项来工作的,并且不在下拉列表中显示最后一个项。 对我来说最大的问题是旋转器下拉列表将从列表的底部开始。所以用户看到的最后一个项目,而不是第一个项目(在情况下有许多项目显示),触摸转轮后,第一次。

所以我把提示项放在列表的开头。并在下拉列表中隐藏第一项。

private void loadSpinner(){

    HintArrayAdapter hintAdapter = new HintArrayAdapter<String>(context, 0);

    hintAdapter.add("Hint to be displayed");
    hintAdapter.add("Item 1");
    hintAdapter.add("Item 2");
            .
            .
    hintAdapter.add("Item 30");

    spinner1.setAdapter(hintAdapter);

    //spinner1.setSelection(0); //display hint. Actually you can ignore it, because the default is already 0
    //spinner1.setSelection(0, false); //use this if don't want to onItemClick called for the hint

    spinner1.setOnItemSelectedListener(yourListener);
}

private class HintArrayAdapter<T> extends ArrayAdapter<T> {

    Context mContext;

    public HintArrayAdapter(Context context, int resource) {
        super(context, resource);
        this.mContext = context
    }

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) {

        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        View view = inflater.inflate(android.R.layout.simple_spinner_item, parent, false);
        TextView texview = (TextView) view.findViewById(android.R.id.text1);

        if(position == 0) {
            texview.setText("");
            texview.setHint(getItem(position).toString()); //"Hint to be displayed"
        } else {
            texview.setText(getItem(position).toString());
        }

        return view;
    }

    @Override
    public View getDropDownView(int position, View convertView, ViewGroup parent) {

        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        View view;

        if(position == 0){
            view = inflater.inflate(R.layout.spinner_hint_list_item_layout, parent, false); // Hide first row
        } else {
            view = inflater.inflate(android.R.layout.simple_spinner_dropdown_item, parent, false);
            TextView texview = (TextView) view.findViewById(android.R.id.text1);
            texview.setText(getItem(position).toString());
        } 

        return view;
    }
}

在@Override getDropDownView()中设置下面的布局,当position为0时,隐藏第一个提示行。

R.layout.spinner_hint_list_item_layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

</LinearLayout>

首先,您可能对Spinner类的prompt属性感兴趣。如下图所示,“Choose a Planet”是可以用android在XML中设置的提示符:prompt=""。

我建议子类化Spinner,在这里您可以在内部维护两个适配器。一个适配器有“选择一个”选项,另一个真正的适配器(有实际的选项),然后使用OnClickListener在选项对话框显示之前切换适配器。然而,在尝试实现这个想法后,我得出的结论是,你不能接收小部件本身的OnClick事件。

您可以将旋转器包装在不同的视图中,拦截视图上的单击,然后告诉CustomSpinner切换适配器,但这似乎是一种糟糕的hack。

你真的需要显示“选择一”吗?

When extending SpinnerAdapter, you override two View-producing methods, getView(int, View, ViewGroup) and getDropDownView(int, View, ViewGroup). The first one supplies the View inserted into the Spinner itself; the second supplies the View in the drop-down list (as the name suggests). You can override the getView(...) so that, until an item has been selected, it displays a TextView containing a prompt; then, when you detect an item has been selected, you change it to display a TextView corresponding to that.

public class PromptingAdapter extends SpinnerAdapter {

    //... various code ...

    private boolean selectionmade = false;

    //call this method from the OnItemSelectedListener for your Spinner
    public setSelectionState(boolean b) {
        selectionmade = b;
    }

    @Override
    public View getView(int position, View recycle, ViewGroup container) {
        if(selectionmade) {
            //your existing code to supply a View for the Spinner
            //you could even put "return getDropDownView(position, recycle, container);"
        }
        else {
            View output;
            if(recycle instanceof TextView) {
                 output = recycle;
            }
            else {
                 output = new TextView();
                 //and layout stuff
            }
            output.setText(R.string.please_select_one);
            //put a string "please_select_one" in res/values/strings.xml
            return output;
        }
    }

//...
}