NodeJS noob签入。我正在查看.listen方法的文档，该方法具有以下形式：
package com.example.bermud06.p036_1sqlitequery;
import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioGroup;
public class MainActivity extends Activity implements View.OnClickListener {
final String LOG_TAG="myLogs";
String name[]={"Китай","США","Бразилия","Россия",
"Япония","Германия","Египет","Италия","Франция","Канада"};
// String name[]={"China","USA","Brasil","Russia",
// "Japon","Germany","Egypt","Italy","France","Canade"};
int people[]={1400,311,195,142,128,82,80,60,66,35};
String region[]={"Азия","Америка","Америка","Европа","Азия","Европа","Африка","Европа","Европа","Америка"} ;
// String region[]={"Asia","America","America","Europe","Asia","Europe","Africa","Europe","Europe","America"};
Button btnAll,btnFunc,btnPeople,btnSort,btnGroup,btnHaving;
EditText etFunc,etPeople, etRegionPeople;
RadioGroup rgSort;
DBHelper dbHelper;
SQLiteDatabase db;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
btnAll =(Button) findViewById(R.id.btnAll);
btnFunc=(Button) findViewById(R.id.btnFunc);
btnGroup=(Button) findViewById(R.id.btnGroup);
btnHaving=(Button) findViewById(R.id.btnHaving);
btnPeople=(Button) findViewById(R.id.btnPeople);
btnSort=(Button) findViewById(R.id.btnSort);
btnAll.setOnClickListener(this);
btnFunc.setOnClickListener(this);
btnGroup.setOnClickListener(this);
btnHaving.setOnClickListener(this);
btnPeople.setOnClickListener(this);
btnSort.setOnClickListener(this);
etFunc=(EditText)findViewById(R.id.etFunc);
etRegionPeople=(EditText)findViewById(R.id.etRegionPeople);
etPeople=(EditText)findViewById(R.id.etPeople);
rgSort=(RadioGroup)findViewById(R.id.rgSort);
dbHelper=new DBHelper(this);
db=dbHelper.getWritableDatabase();
Cursor c=db.query("mytable",null,null,null,null,null,null);
if (c.getCount()==0)
{
ContentValues cv=new ContentValues();
for (int i=0;i<name.length;i++){
cv.put("name",name[i]);
cv.put("people",people[i]);
cv.put("region",region[i]);
Log.d(LOG_TAG,"id = "+db.insert("mytable",null,cv));
}
}
c.close();
dbHelper.close();
onClick(btnAll);
}
@Override
public void onClick(View v) {
db=dbHelper.getWritableDatabase();
String sFunc=etFunc.getText().toString();
String sPeople=etPeople.getText().toString();
String sRegionPeople=etRegionPeople.getText().toString();
String[] columns=null;
String selection=null;
String[] selectionargs=null;
String groupBy=null;
String having=null;
String orderBy=null;
Cursor c=null;
switch (v.getId())
{
case R.id.btnAll:
Log.d(LOG_TAG,"--- Проверка ---");
c=db.query("mytable",null,null,null,null,null,null);
break;
case R.id.btnFunc:
Log.d(LOG_TAG,"--- ??????? "+sFunc+" ---");
columns=new String[]{sFunc};
c=db.query("mytable",columns,null,null,null,null,null);
break;
case R.id.btnPeople:
Log.d(LOG_TAG,"--- ????????? ?????? "+sPeople+" ---");
selection="people > ?";
selectionargs=new String[]{sPeople};
c=db.query("mytable",null,selection,selectionargs,null,null,null);
break;
case R.id.btnGroup:
Log.d(LOG_TAG,"--- ????????? ?? ??????? ---");
columns=new String[]{"region","sum(people) as people"};
groupBy="region";
c=db.query("mytable",columns,null,null,groupBy,null,null);
break;
case R.id.btnHaving:
Log.d(LOG_TAG,"--- ?????? ? ?????????? ?????? "+sRegionPeople+" ---");
columns=new String[]{"region","sum(people) as people"};
groupBy="region";
having="sum(people) > "+sRegionPeople;
c=db.query("mytable",columns,null,null,groupBy,having,null);
break;
case R.id.btnSort:
switch (rgSort.getCheckedRadioButtonId())
{
case R.id.rName:
Log.d(LOG_TAG,"--- ?????????? ?? ???????????? ---");
orderBy="name";
break;
case R.id.rPeople:
Log.d(LOG_TAG,"--- ?????????? ?? ????????? ---");
orderBy="people";
break;
case R.id.rRegion:
Log.d(LOG_TAG,"--- ?????????? ?? ??????? ---");
orderBy="region";
break;
}
c=db.query("mytable",null,null,null,null,null,orderBy);
break;
}
if (c!=null)
{
if (c.moveToFirst())
{
String str;
do {
str="";
for (String cn : c.getColumnNames()){
str=str.concat(cn+" = "+
c.getString(c.getColumnIndex(cn))+"; ");
}
Log.d(LOG_TAG,str);
}while (c.moveToNext());
}
c.close();
} else {
Log.d(LOG_TAG,"Cursor is null");
dbHelper.close();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
class DBHelper extends SQLiteOpenHelper{
public DBHelper(Context cntx){
super(cntx,"myDB",null,1);
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.d(LOG_TAG,"--- onCreate database ---");
try{
db.execSQL("create table mytable (" +
"id integer primary key autoincrement,"+"name text," +
"people integer,"+"region text"+");");
}
catch (Exception e)
{
Log.d(LOG_TAG,e.toString());
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
}
port / hostname的解释说明：
开始接受指定端口和主机名上的连接。如果 hostname被省略，服务器将接受指向的连接 任何IPv4地址
我不完全理解＆＃39;如果省略主机名，服务器将接受指向任何IPv4地址的连接。部分。服务器如何接受与任何IP地址的连接？这是服务器接受的内容而不是它能接受的内容，这让我觉得这很奇怪吗？
答案 0 :(得分：0)
问题是运行服务器的当前主机有多个IP地址（多个网络或多个IP地址用于一个网卡）。见multihoming。
因此，该语句意味着如果不提供主机名，则无论连接的目标是哪个IP地址，都将接受到达此特定主机的任何传入连接。