android listview 点击事件

public class CheckActivity extends AppCompatActivity {
    private List<ExpressIn> expressInList= new ArrayList<>();
    private static String s_id;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_check);
        initExpressIns();
        ExpressAdapter adapter=new ExpressAdapter(CheckActivity.this,R.layout.expresslayout,expressInList);
        ListView listView=(ListView)findViewById(R.id.list_view);
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Intent intent = new Intent(CheckActivity.this,detailActivity.class);
                ExpressIn expressIn22 = expressInList.get(position);
                Toast.makeText(CheckActivity.this,""+expressIn22,Toast.LENGTH_SHORT).show();

            }
        });
    }
    private void initExpressIns(){
        List<ExpressIn> expressIns = DataSupport.findAll(ExpressIn.class);
        for(ExpressIn expressIn:expressIns){
            String R_address=expressIn.getR_address();
            String R_name=expressIn.getR_name();
            String R_se=expressIn.getSelect();
            ExpressIn expressIn1= new ExpressIn(R_name,R_address,R_se);
            expressInList.add(expressIn1);
        }
    }
}

为什么我点击事件里面 获得不到 expressIn22.getsid();

expressIn22的值可以拿到 但getsid就是空了

    private void initExpressIns(){
    List<ExpressIn> expressIns = DataSupport.findAll(ExpressIn.class);
    for(ExpressIn expressIn:expressIns){
        String R_address=expressIn.getR_address();
        String R_name=expressIn.getR_name();
        String R_se=expressIn.getSelect();
        String sid=expressIn.getS_id();
        ExpressIn expressIn1= new ExpressIn(R_name,R_address,R_se,sid);
        expressInList.add(expressIn1);
    }
}
    原来是下面的初始化没有创建sid的变量。。。。。。。。。。。。。。。。。。