Android由众多Activity组成，每个Activity对应不同的功能和UI，但是每个Activity都是一个单独的类，所以需要传递参数。一般来讲，Android中传递参数是在不同的Activity中。大致上有5类方案：
1 静态 static
定义方法：
1 public class MainActivity extends TabActivity {
2 public static DatabaseHelper mHelper;
3 public static SQLiteDatabase db;
4 }
使用方法：
1 public class QQList extends Activity{
2 try{
3 db=MainActivity.db;
4
5 }catch(Exception e){
6 e.printStackTrace();
7 }
8 }
2 单例 Singleton
定义方法：
Java代码
1 public class SingleSocket {
2 /*
3 * GG单例模式的第四个版本，既解决了“懒汉式的”多线程问题，又解决了资源浪费的现象，看上去是一种不错的选择
4 */
5 //Socket成员
6 private Socket socket=null;
7 //对单例本身引用的名称
8 private static SingleSocket sSocket;
9 public Socket getSocket() {
10 return socket;
11 }
12 public void initSocket(String ip,int port ) {
13 try{
14 socket=new Socket(ip,port);
15 }catch(Exception e){
16 e.printStackTrace();
17 }
18 }
19 //构造函数私有化
20 private SingleSocket() {
21 }
22 //提供一个全局的静态方法
23 public static SingleSocket getSingle() {
24 if(sSocket == null) {
25 synchronized (SingleSocket.class) {
26 if(sSocket == null) {
27 sSocket = new SingleSocket();
28 }
29 }
30 }
31 return sSocket;
32 }
33 }
使用方法：
Java代码
1 public class MainActivity extends TabActivity {
2 private SingleSocket olsocket=SingleSocket.getSingle();
3 private Socket socket=null;
4 }
3 通过Intent传递
Intent是Android的类，含有传递参数的方法，类似于jsp中的get，但可传的参数类型支持很少。
定义方法：
Java代码
1 public class ClientActivity extends Activity {
2 Intent intent = new Intent();
3 Bundle bundle = new Bundle();
4 bundle.putString("Usr", Usr);
5 bundle.putString("Psd", Psd);
6 intent.putExtras(bundle);
7 intent.setClass(ClientActivity.this, MainActivity.class);
8 }
使用方法：
Java代码
1 Bundle bundle = getIntent().getExtras();
2 Usr = bundle.getString("Usr");
3 Psd=bundle.getString("Psd");
Socket传递
这个无需多说，创建Socket和ServerSocket对，进行通信。
5 SQLite数据库
创建数据库方法：
Java代码
1 package com.android.client;
2 import android.content.Context;
3 import android.database.sqlite.SQLiteDatabase;
4 import android.database.sqlite.SQLiteOpenHelper;
5 import android.database.sqlite.SQLiteDatabase.CursorFactory;
6
7 public class DatabaseHelper extends SQLiteOpenHelper{
8 /*public static final String TB_XINLANGWEIBO="XINLANGWEIBO";
9 public static final String TB_QQGROUP="QQGROUP";
10 public static final String TB_WEB="WEB";
11 public static final String TB_QQLIST="QQLIST";
12 public static final String TB_CLIENTPUB="CLIENTPUB";
13
14 public static final String XINLANGWEIBO_ID="_id";
15 public static final String QQGROUP_ID="_id";
16 public static final String WEB_ID="_id";
17 public static final String CLIENTPUB_ID="_id";
18
19 public static final String QQLIST_ID="_id";
20 public static final String QQLIST_NICK="NICK";*/
21 public static final String TB_BUSINESS="BUSINESS";
22
23 public static final String ID="_id";
24 public static final String class="CLASS";
25 public static final String CONTENT="CONTENT";
26 public static final String FROM="FRM";
27 public static final String WHO="WHO";
28
29
30 public DatabaseHelper(Context context,String name,CursorFactory factory,int version){
31 super(context,name,factory,version);
32 }
33
34 @Override
35 public void onCreate(SQLiteDatabase arg0){
36 //arg0.execSQL("CREATE TABLE IF NOT EXISTS "+TB_XINLANGWEIBO+"(_id INTEGER PRIMARY KEY AUTOINCREMENT,CONTENT TEXT);");
37 //arg0.execSQL("CREATE TABLE IF NOT EXISTS "+TB_QQGROUP+"(_id INTEGER PRIMARY KEY AUTOINCREMENT,CONTENT TEXT);");
38 //arg0.execSQL("CREATE TABLE IF NOT EXISTS "+TB_WEB+"(_id INTEGER PRIMARY KEY AUTOINCREMENT,CONTENT TEXT);");
39
40 //arg0.execSQL("CREATE TABLE IF NOT EXISTS "+TB_QQLIST+"(_id TEXT PRIMARY KEY,NICK TEXT);");
41 //arg0.execSQL("CREATE TABLE IF NOT EXISTS "+TB_CLIENTPUB+"(_id INTEGER PRIMARY KEY AUTOINCREMENT,CONTENT TEXT);");
42 arg0.execSQL("CREATE TABLE IF NOT EXISTS "+TB_BUSINESS+"(_id INTEGER PRIMARY KEY AUTOINCREMENT,CLASS TEXT,CONTENT TEXT,FRM TEXT,WHO TEXT);");
43
44
45 }
46 @Override
47 public void onUpgrade(SQLiteDatabase db,int oldVertion,int newVersion){
48 //db.execSQL("DROP TABLE IF EXISTS"+TB_XINLANGWEIBO);
49 //db.execSQL("DROP TABLE IF EXISTS"+TB_QQGROUP);
50 //db.execSQL("DROP TABLE IF EXISTS"+TB_WEB);
51 //db.execSQL("DROP TABLE IF EXISTS"+TB_QQLIST);
52 onCreate(db);
53
54 }
55 }
调用之:
Java代码
1 try{
2
3 //创建数据库(如果数据库文件已经存在就不会再创建)
4 mHelper = new DatabaseHelper(this,DB_NAME,null,VERSION);
5 db=mHelper.getWritableDatabase();
6 }catch (Exception ee){
7 AlertDialog dlg1=new AlertDialog.Builder(this)
8 .setMessage(ee.getMessage())
9 .setPositiveButton("Ok", null)
10 .show();
11 }
使用方法,其实就是查询数据库：
Java代码
1 try{
2 cursor=db.query(TB_NAME, new String []{"_id","NICK"},null, null, null, null,null);
3 }catch(Exception ee){
4 ee.printStackTrace();
5 AlertDialog dlg=new AlertDialog.Builder(QQList.this)
6 .setMessage("没找到表")
7 .setPositiveButton("Ok", null)
8 .show();
9 }
