一般来说,Java很新。我的代码中有3个Spinners,我的2个微调器将根据1个主旋转器(有2个选项)显示列表。在阅读了几个线程后,我读到了使用notifySetDataChanged()刷新列表的问题。但是微调器列表从未改变过。几个问题:
这是onCreate方法的代码。
public class MainActivity extends Activity {
private Spinner spinner1, spinner2, spinner3, spinner4;
private Button convertButton;
private EditText from;
private List <String> list1 = new ArrayList<String>();
private List <String> list2 = new ArrayList<String>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
from = (EditText) findViewById(R.id.amount);
//spinners for units
spinner1 = (Spinner) findViewById(R.id.spinner1);
spinner2 = (Spinner) findViewById(R.id.spinner2);
spinner4 = (Spinner) findViewById(R.id.spinner4_main);
List<String>list4 = new ArrayList<String>();
list4.add("Distance");
list4.add("Weight");
//adapter for main scale
ArrayAdapter<String> dataAdapter4 = new ArrayAdapter <String> (this,
android.R.layout.simple_spinner_dropdown_item, list4);
dataAdapter4.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner4.setAdapter(dataAdapter4);
//adapter for "from" currency
ArrayAdapter<String> dataAdapter1 = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list1);
dataAdapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner1.setAdapter(dataAdapter1);
//adapter for "to" currency
ArrayAdapter<String> dataAdapter2 = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, list2);
dataAdapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner2.setAdapter(dataAdapter2);
Object choice = spinner4.getSelectedItemPosition();
if (choice.equals("Weight")) {
//units to convert from
dataAdapter1.clear();
dataAdapter1.add("Milligrams");
dataAdapter1.add("Grams");
dataAdapter1.add("Kilograms");
dataAdapter1.add("Metric Ton");
//units to convert to
dataAdapter2.clear();
dataAdapter2.add("Milligrams");
dataAdapter2.add("Grams");
dataAdapter2.add("Kilograms");
dataAdapter2.add("Metric Ton");
}
else //(spinner4.getSelectedItem().toString().equals("Distance"))
{
//spinner1 = (Spinner) findViewById(R.id.spinner1);
dataAdapter1.clear();
dataAdapter1.add("Millimeter");
dataAdapter1.add("Centimeter");
dataAdapter1.add("Meter");
dataAdapter1.add("Kilometer");
dataAdapter2.clear();
dataAdapter2.add("Millimeter");
dataAdapter2.add("Centimeter");
dataAdapter2.add("Meter");
dataAdapter2.add("Kilometer");
}
dataAdapter1.notifyDataSetChanged();
dataAdapter2.notifyDataSetChanged();
}`
如果有人能解释什么是错的,请启发这个新手。 =)
答案 0 :(得分:0)
Object choice = spinner4.getSelectedItemPosition();
这不起作用。
getSelectedItemPosition()
返回int
(documentation),与
String
不等
if (choice.equals("Weight")
从来没有(除了在极少数情况下)使用Object
类作为参考,因为Java中的任何对象都是Object
(呃!)所以你可能比较苹果和橙子(哪两个都是水果)。好像你是来自一种更弱的类型语言,嗯? ;)
解决方案:比较职位:
if (spinnerX.getSelectedItemPosition == 0)...
此外,如果在spinner1
上选择了某些内容,您确定要更改spinner4
的内容吗?
答案 1 :(得分:0)
所以最初,spinner2和spinner3将没有任何内容。即使用户点击,下拉列表中也没有任何内容。但是一旦用户选择了Spinner1,spinner2和spinner3就会有下拉值。
请阅读setOnItemSelectedListener。有很多教程可供选择。您可以参考here开始。
如果这适合您,请接受我的回答。