同步思想：
先介绍客户端为最新数据的数据同步问题，这种机制常常应用在云笔记，随手记类似的app。
这里我建了一个listview，对listview上item的增删改，来代替实际项目中的情况。
1.对listview 和本地数据表datatable表(使用id作为数据唯一表示)映射，实现增删改。
2.每次将对本地数据表的操作记录在operation表中，在表中记录该操作的时间戳。
3.将operation 表中内容封装成json数据发送给服务器（从服务器获取上次同步时间戳，只提交在这次更新以后的操作）。
4.服务器更新完成，返回success,表示同步成功，在时候可以清空operation表
MainActivity.java
package com.example.sqllitcache;import java.text.SimpleDateFormat;import java.util.Date;import android.app.Activity;import android.app.AlertDialog;import android.content.ContentValues;import android.content.DialogInterface;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.AdapterView;import android.widget.AdapterView.OnItemClickListener;import android.widget.AdapterView.OnItemLongClickListener;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.EditText;import android.widget.ImageButton;import android.widget.ListView;import android.widget.Toast;public class MainActivity extends Activity { ListView lv; Button submit; EditText et; SQLiteDatabase dbwrite ; Dbhelper dbhelper; ArrayAdapter <String> adapter; ImageButton upload; Cursor c; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); lv=(ListView) findViewById(R.id.listView1); submit=(Button) findViewById(R.id.button1); upload=(ImageButton) findViewById(R.id.imageButton1); et=(EditText) findViewById(R.id.autoCompleteTextView1); adapter=new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1); lv.setAdapter(adapter); dbhelper=new Dbhelper(this); dbwrite=dbhelper.getWritableDatabase(); getData(); //点击提交 submit.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub String newData=et.getText().toString(); addData(newData); } }); //点击了同步 upload.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub getOp(); } }); //长按列表项，修改数据 lv.setOnItemLongClickListener(new OnItemLongClickListener() { @Override public boolean onItemLongClick(AdapterView<?> arg0, View arg1, final int position, long arg3) { // TODO Auto-generated method stub new AlertDialog.Builder(MainActivity.this).setPositiveButton("我确定修改",new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { // TODO Auto-generated method stub updateData(position); } }).show(); return false; } }); //短按列表项删除数据 lv.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> arg0, View arg1, int position, long arg3) { // TODO Auto-generated method stub Toast.makeText(MainActivity.this, position+"", 0).show(); deleteData(position); } }); } //添加数据的执行函数，添加到本地数据库，并提示更新listtview void addData(String newData) { //添加到本地数据库 ContentValues content=new ContentValues(); String putdata=et.getText().toString(); content.put("data", putdata); dbwrite.insert("datatable",null, content); //下面将操作保存到operation表 getData(); c.moveToLast(); int id=c.getInt(c.getColumnIndex("_id")); ContentValues content2=new ContentValues(); content2.put("data", putdata); content2.put("op", 0); content2.put("dataid",id ); long time=System.currentTimeMillis(); SimpleDateFormat sdf=new SimpleDateFormat("yyyy/MM/dd HH:mm:ss"); Date date=new Date(time); String formattime=sdf.format(date); content2.put("timestamp", formattime); dbwrite.insert("operation", null, content2); } //删除一条数据 void deleteData(int position) { c.moveToPosition(position); int id=c.getInt(c.getColumnIndex("_id")); dbwrite.delete("datatable", "_id=?", new String[]{id+""} ); getData(); //记录到operation表 ContentValues content2=new ContentValues(); content2.put("data", ""); content2.put("op", 1); content2.put("dataid",id ); long time=System.currentTimeMillis(); SimpleDateFormat sdf=new SimpleDateFormat("yyyy/MM/dd HH:mm:ss"); Date date=new Date(time); String formattime=sdf.format(date); content2.put("timestamp", formattime); dbwrite.insert("operation", null, content2); } //修改一条数据 void updateData(int position) { c.moveToPosition(position); ContentValues cv=new ContentValues(); cv.put("data", "changed"); int id=c.getInt(c.getColumnIndex("_id")); dbwrite.update("datatable", cv, "_id=?", new String [] {id+""}); getData(); ContentValues content2=new ContentValues(); content2.put("data", "changed"); content2.put("op", 2); content2.put("dataid",id ); long time=System.currentTimeMillis(); SimpleDateFormat sdf=new SimpleDateFormat("yyyy/MM/dd HH:mm:ss"); Date date=new Date(time); String formattime=sdf.format(date); content2.put("timestamp", formattime); dbwrite.insert("operation", null, content2); } //获取数据 void getData() { c= dbwrite.query("datatable", null, null, null, null, null, null); adapter.clear(); //读取本地数据库 while(c.moveToNext()) { String data=c.getString(c.getColumnIndex("data")); int id=c.getInt(c.getColumnIndex("_id")); adapter.add(data+":"+id); System.out.println(data+": "+id); } adapter.notifyDataSetChanged(); } //从日志表获得操作记录 void getOp() { c= dbwrite.query("operation", null, null, null, null, null, null); while(c.moveToNext()) { String data=c.getString(c.getColumnIndex("data")); int id=c.getInt(c.getColumnIndex("dataid")); int op=c.getInt(c.getColumnIndex("op")); String timestamp=c.getString(c.getColumnIndex("timestamp")); Toast.makeText(MainActivity.this, id+": "+op+" "+timestamp, 0).show(); System.out.println(id+": "+op+" "+timestamp); } dbwrite.delete("operation", "1", null); }}Dbhelper.java
package com.example.sqllitcache;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;public class Dbhelper extends SQLiteOpenHelper { public Dbhelper(Context context ) { super(context, "mydb",null, 1); // TODO Auto-generated constructor stub } @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub db.execSQL("CREATE TABLE datatable ("+ "_id INTEGER PRIMARY KEY AUTOINCREMENT,"+ "data String DEFAULT \"\")" ); //创建一个操作表作为日志，dataid为数据项id,opt=0,1,2,3为对数据的增删改查 db.execSQL("CREATE TABLE operation ("+ "_id INTEGER PRIMARY KEY AUTOINCREMENT,"+ "dataid INTEGER ,"+ "op INTEGER,"+ "data String DEFAULT \"\","+ "timestamp String"+")"); } @Override public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) { // TODO Auto-generated method stub }}