小编ami*_*ura的帖子

实际上我无法理解no-arg构造函数和默认构造函数之间的区别.

import javax.swing.*;

public class Test extends JFrame {
   public Test() {
     super();
     this.setSize(200,200);
     this.setVisible(true);
   }
   public static void main(Sting[] arg) {
       Test cFrame = new Test();
   }
}

这是否在创建名为cFrame的Test对象时调用此类的默认构造函数？

我是android开发的初学者。我使用实现LocationListener的Gps服务。我想使用按钮单击来停止onLocationChanged（）方法。我试图这样做，将空值分配给locationManager变量，但是它不起作用。

public class TabFragment1 extends Fragment implements LocationListener {
    ImageButton btnRUN;
    ImageButton btnSTOP;
    private LocationManager locationManager;
    Context ctx;
    private double lat_new, lon_new = 0.0;


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        ctx = container.getContext();
        View view = inflater.inflate(R.layout.tab_fragment_1, container, false);

        initializeApp(view);
        return view;
    }


    private void initializeApp(View view) {
        btnRUN = (ImageButton) view.findViewById(R.id.btnRun);
        btnSTOP= (ImageButton) view.findViewById(R.id.btnStop);


        btnRUN.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                runOnClick();
            }
        });

        btnSTOP.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) { …

我是vb.net的初学者.我尝试将字符串值和整数值添加到列表框中,但它会抛出无效的强制转换异常.我提到代码如下.

Public Class frmDetails

        Private Sub btnCompute_Click(sender As System.Object, e As System.EventArgs) Handles btnCompute.Click
            Listbox1.Items.Add("sum is " + (3 + 2))
            Listbox1.Items.Add("Substract is" + (3 - 2))
            Listbox1.Items.Add("Multiplication is " + (3 * 2))
            Listbox1.Items.Add("Division is " + (3 / 2))
            Listbox1.Items.Add("3 to power 2  " + (3 ^ 2))
        End Sub

        Private Sub btnExit_Click(sender As System.Object, e As System.EventArgs) Handles btnExit.Click
            Dispose()
        End Sub
    End Class

请帮我解决这个问题.