如何添加android的下拉列表中选择默认值 [英] How to add a default selected value in android dropdown

问题描述

我有一个下拉从数据库中获取其价值，那么我想一个默认值添加到现有的下拉值。在这种情况下，缺省值将是选定的值。

I have a dropdown which takes its values from a database, I then want to add a default value to the existing drop down values. In this case the default value would be the selected value.

 StringBuilder strbuilder = new StringBuilder();
    ArrayList<String> arr_list = new ArrayList<String>();
    List<String> m = new ArrayList<String>();

    //This get the data values from database
    m = db.getData();

    int ms = m.size();
    String str = strbuilder.toString();

    String[] str1 = str.split(",");


    try {
        if (ms > 1) {

            //This is my default value
             m.add("Default Value");

            for (int i = 0; i < ms; i++) {

                m.get(0);
            }
        } else {
            m.get(0);

        }
    } catch (Exception e) {
        e.printStackTrace();

    }


    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_spinner_dropdown_item, m);
    dropdown.setAdapter(adapter);

上面的codeS能够从数据库中添加值的下拉和默认值加入，但它似乎没有被选中值。

The codes above is able to add the values from the database to the dropdown and the Default Value is added but it doesn't appear to be the selected value.

例如，如果从数据库中苹果，芒果，菠萝和默认值的值是所有的水果。

For instance if the values from the database are "Apple, Mango,Pineapple" and the default value is "ALL FRUITS".

预期DROPDOWN

EXPECTED DROPDOWN

所有的水果
 苹果
 芒果
 菠萝

请我该怎么办做出的默认值选定的价值？先谢谢了。

Please how can I do make the default value the selected value? Thanks in advance.

推荐答案

我想你需要低于code。

I think you need below code.

    List<String> categories = new ArrayList<String>();
    categories = db.getData();
    categories.add(0,"your_default_value");
    ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, categories);
    dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);     
    spinner.setAdapter(dataAdapter);
    spinner.setSelection(0);

记住，当你想增加任何价值的第一ArrayList的你只是做

Remember when you want to add any value to the very first of Arraylist you just do

 arraylist.add(0,"value");

这将值添加到ArrayList的的第一指标，推动所有其他的元素了。

This will add the value to the very first index of arraylist and push all other element down.

如果您需要任何其他元素将被选择不是第一个

 Spinner spinner = (Spinner) findViewById(R.id.spinner);
    List<String> categories = new ArrayList<String>();
    categories.add("Automobile");
    categories.add("Business Services");
    categories.add("Computers");
    categories.add("Education");
    categories.add("Personal");
    categories.add("Travel");
    ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, categories);
    dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner.setAdapter(dataAdapter);
    int i=categories.indexOf("Education");
    spinner.setSelection(i);

这篇关于如何添加android的下拉列表中选择默认值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！