测试字段是否为空并预防用户将空字段输入sqlite数据库

如何测试该字段不是空值呢? 我想让程序显示一个提示：用户已经完全填充好所有字段，但是下面这段代码还会显示其他情况，比如name值为null， number有值的情况。
public void onClick(View arg0)
{

switch(arg0.getId())
{
case R.id.bSQLUpdate:
    boolean diditwork = true;
    try
    {
    String name = sqlName.getText().toString();
    String number = sqlNumber.getText().toString();
    GroupDb entry = new GroupDb(ContactDb.this);
    entry.open();
    if(name != null && number != null)
    {
        if((!entry.hasDuplicateNameNumber(name, number)) )
        {
            entry.createEntry(name, number);

        }
        else
        {
            diditwork = false;
            Dialog d = new Dialog(this);
            d.setTitle("Error");
            TextView tv = new TextView(this);
            tv.setText("Duplicate name or number. Please try again.");
            d.setContentView(tv);
            d.show();
            sqlName.setText("");
            sqlNumber.setText("");
        }
    }
    else
    {
        diditwork = false;
        Dialog d = new Dialog(this);
        d.setTitle("Error");
        TextView tv = new TextView(this);
        tv.setText("Please fill up all fields. Please try again.");
        d.setContentView(tv);
        d.show();
        sqlName.setText("");
        sqlNumber.setText("");
    }

    entry.close();
    }
    catch(Exception e)
    {
        diditwork = false;
        String error = e.toString();
        Dialog d = new Dialog(this);
        d.setTitle("Update failed");
        TextView tv = new TextView(this);
        tv.setText(error);
        d.setContentView(tv);
        d.show();
        sqlName.setText("");
        sqlNumber.setText("");
    }
    finally
    {
        if(diditwork)
        {
            Dialog d = new Dialog(this);
            d.setTitle("Contact list updated");
            TextView tv = new TextView(this);
            tv.setText("Success");
            d.setContentView(tv);
            d.show();
            sqlName.setText("");
            sqlNumber.setText("");
        }
    }
    break;
case R.id.bSQLOpenView:
    Intent intent = new Intent();
    intent.setClass(ContactDb.this, CustomListView.class);

    startActivityForResult(intent, 0);
    break;

}

}// end onclick