当所选项目发生变化时,如何为微调器设置事件侦听器?

基本上我想做的是类似这样的事情:

spinner1.onSelectionChange = handleSelectionChange;

void handleSelectionChange(Object sender){
    //handle event
}

当前回答

如果你想要一个true onChangedListener()。将初始值存储在处理程序中,并检查它是否已更改。它很简单,不需要全局变量。如果页面上有多个转轮,则有效。

String initialValue = // get from Database or your object
mySpinner.setOnItemSelectedListener(new SpinnerSelectedListener(initialValue));

...

protected class SpinnerSelectedListener implements AdapterView.OnItemSelectedListener {

        private SpinnerSelectedListener() {
            super();
        }

        public SpinnerSelectedListener(String initialValue) {
            this();
            this.initialValue = initialValue;
        }

        private String initialValue;

        // getter and setter removed.  

        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            final String newValue = (String) spinHeight.getItemAtPosition(position);
            if (newValue.equals(initialValue) == false) {
               // Add your code here.  The spinner has changed value. 

               // Maybe useful.   
               // initialValue = newValue;
            }

        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {
               // Maybe useful.   
               // initialValue = null; 
        }
    }

对象是你的朋友,使用它们。

其他回答

你在onCreate或onStart中设置OnItemSelectedListener并不重要——它仍然会在活动创建或启动期间被调用(分别)。 所以我们可以在onCreate中设置它(而不是在onStart中!) 只需添加一个标志来计算第一次初始化:

private Spinner mSpinner;
private boolean mSpinnerInitialized;

然后在onCreate(或onCreateView)中只需:

mSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                if (!mSpinnerInitialized) {
                    mSpinnerInitialized = true;
                    return;
                }

                // do stuff
            }

            public void onNothingSelected(AdapterView<?> adapterView) {
                return;
            }
        });
spinner1.setOnItemSelectedListener(
    new AdapterView.OnItemSelectedListener() {
        //add some code here
    }
);

对于kotlin,您可以使用:

spinner.onItemSelectedListener =  object : AdapterView.OnItemSelectedListener {
    override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
        
    }

    override fun onNothingSelected(p0: AdapterView<*>?) {
        
    }
}

注意:对于onItemSelected方法的参数,我使用自定义变量名

我认为最好的方法是让flagitemselected = 0;在onCreate()。在itemselected event上增加标志,即flagitemselected++;然后检查

if(flagitemselected!=1)
{
// do your work here
}

我想这会有帮助。

默认情况下,您将获得旋转器数组的第一项

value = spinner.getSelectedItem().toString();

无论何时你在旋转器中选择值,它都会给你选择的值

如果你想要选定项目的位置,然后这样做

pos = spinner.getSelectedItemPosition();

以上两个答案均为不应用监听器的情况