Question

我是Android的新手。尝试获取微调框的选定项目时，我得到的值为空。

我尝试设计两个微调器，然后单击按钮，将微调器的选定项之一写入文本字段。但是我越来越空了。您能解释一下原因吗？

public class EERActivity extends AppCompatActivity implements  
OnItemSelectedListener {
private Spinner spinner1; 
private Spinner spinner2; 
private String[] array1= {"xx","yy"};
private String[] array2= {"x2", "y2"};
private ArrayAdapter<String> dataAdapterForArray1;
private ArrayAdapter<String> dataAdapterForArray2;
String selected1;
String selected2;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_eer);

    spinner1 = (Spinner)findViewById(R.id.spinner2);
    spinner2 = (Spinner)findViewById(R.id.spinner3);

    dataAdapterForArray1 = new ArrayAdapter<String>(this, 
    android.R.layout.simple_spinner_item, array1);
    //and 2 is here..//

    spinner1.setAdapter(dataAdapterForArray1);
    spinner2.setAdapter(...filled...);

@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, 
long id) {
    if(parent.getId() == R.id.spinner2) {
        selected1 = spinner1.getSelectedItem().toString();
    }

    else if(parent.getId() == R.id.spinner3){
        selected2 = spinner2.getSelectedItem().toString();
    }
    selectedSpinner1 = spinner1.getSelectedItem().toString();
    selectedSpinner2 = spinner2.getSelectedItem().toString();
}

public void onNothingSelected(AdapterView<?> arg0) {

}


public void run (View view){
textView.setText("Result: " + selected1);  }

我希望从spinner1中选择输出，但结果为空。

Answer 1

最有可能在微调器组件中实际更改值之前触发了事件。为了解决这个问题，您可以添加一个空检查。尝试在“ onItemSelected”方法的第一行中添加以下内容：

if ((parent.getId() == R.id.spinner2 && spinner1.getSelectedItem() == null) || (parent.getId() == R.id.spinner3 && spinner2.getSelectedItem() == null)) {
    return ;
}

此外，我不确定您是否发布了整个代码，但这看起来是错误的：

spinner1 = (Spinner)findViewById(R.id.spinner2);
spinner2 = (Spinner)findViewById(R.id.spinner3);

为什么从微调器项目中获取空值？

1 个答案: