Android学习-----如何使用sqlite对于后台数据交换,sqlite使用例程入门
SQLite 这是一个非常流行的嵌入式数据库。它支持 SQL 查询,和只使用很少的内存。Android 在集成实施 SQLite,所以每 Android 应用程序能够使用 SQLite 数据库。对数熟悉 SQL 的开发者来时。使用 SQLite 相当简单。
能够。因为 JDBC 不适合手机这样的内存受限设备。所以 Android 开发者须要学习新的 API 来使用 SQLite。本文以一个注冊登录Demo简介一下sqlite入门使用。
先上一下执行结果:(请忽略丑陋的界面~~)
以下贴上主要代码,后面分析:
/** * 登录页面的activity * @author D_xiao * */ public class MainActivity extends Activity { SQLiteDatabase db; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button loginbtn = (Button)findViewById(R.id.loginbtn); Button regbtn = (Button)findViewById(R.id.regbtn); db = SQLiteDatabase.openOrCreateDatabase(this.getFilesDir().toString()+"/android1.db3", null); //创建或打开数据库 loginbtn.setOnClickListener(new OnClickListener(){ public void onClick(View sourse){ boolean flag = false; String userName = ((EditText)findViewById(R.id.userEditText)).getText().toString(); String userPassword = ((EditText)findViewById(R.id.passwordEditText)).getText().toString(); try{ Cursor cursor = db.rawQuery("select * from users where name = ? and password = ?",new String[]{userName,userPassword}); if(cursor.getCount()==0){ Intent intentE = new Intent(MainActivity.this,ErrorActivity.class); startActivity(intentE); }else{ Intent intentS = new Intent(MainActivity.this,HomeActivity.class); intentS.putExtra("name", userName); startActivity(intentS); } }catch(SQLiteException se){ Intent intentE = new Intent(MainActivity.this,ErrorActivity.class); startActivity(intentE); } } }); regbtn.setOnClickListener(new OnClickListener(){ public void onClick(View sourse){ Intent intentReg = new Intent(MainActivity.this,RegActivity.class); startActivity(intentReg); } }); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } }
/** * 注冊Activity * @author D_xiao * */ public class RegActivity extends Activity { SQLiteDatabase db; ListView listView; Button btn; protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_reg); db = SQLiteDatabase.openOrCreateDatabase(this.getFilesDir().toString()+"/android1.db3", null); final String a = this.getFilesDir().toString(); Button regOK = (Button)findViewById(R.id.regOK); Button backtologin = (Button)findViewById(R.id.backtologin); regOK.setOnClickListener(new OnClickListener(){ public void onClick(View sourse){ String name = ((EditText)findViewById(R.id.name)).getText().toString(); String password = ((EditText)findViewById(R.id.password)).getText().toString(); TextView suc = (TextView)findViewById(R.id.suc); try{ db.execSQL("insert into users values(null,?,?)",new String[]{name,password}); suc.setText("注冊成功。请点取消button返回到登录界面"); }catch(SQLiteException se){ db.execSQL("create table users(_id integer primary key autoincrement," +"name varchar(20) ," +"password varchar(200))"); db.execSQL("insert into users values(null,?,?)",new String[]{name,password}); suc.setText("注冊成功。请点取消button返回到登录界面"); } } }); backtologin.setOnClickListener(new OnClickListener(){ public void onClick(View sourse){ Intent intent = new Intent(RegActivity.this,MainActivity.class); startActivity(intent); } }); } public void onDestroy(){ super.onDestroy(); if(db!=null&&db.isOpen()){ db.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.main, menu); return true; } }
/** * 登录成功显示主页,能够发微博 并显示朋友圈 * @author D_xiao * */ public class HomeActivity extends Activity { SQLiteDatabase db; ListView listView; Button btn; protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_home); db = SQLiteDatabase.openOrCreateDatabase(this.getFilesDir().toString()+"/android1.db3", null); listView = (ListView)findViewById(R.id.show); btn = (Button)findViewById(R.id.send); btn.setOnClickListener(new OnClickListener(){ Cursor cursor = null; public void onClick(View sourse){ String weibo = ((EditText)findViewById(R.id.newtext)).getText().toString(); Intent intent = getIntent(); String name = intent.getStringExtra("name"); try{ insertData(db,name,weibo); //select * from weibo3 cursor = db.rawQuery("select * from weiboa", null); inflateList(cursor); }catch(SQLiteException se){ //primary key autoincrement db.execSQL("create table weiboa(_id integer primary key autoincrement," +"name varchar(20) ," +"weibo varchar(200))"); insertData(db,name,weibo); //查询 cursor = db.rawQuery("select * from weiboa", null); inflateList(cursor); }finally{ //cursor.close(); } } }); } private void insertData(SQLiteDatabase db,String name,String weibo){ //运行插入语句 db.execSQL("insert into weiboa values(null,?,?)",new String[]{name,weibo}); } private void inflateList(Cursor cursor){ //填充SimpleCursorAdapter SimpleCursorAdapter adapter = new SimpleCursorAdapter(HomeActivity.this,R.layout.line,cursor, new String[]{"name","weibo"}, new int[]{R.id.my_name,R.id.my_weibo}, CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER); listView.setAdapter(adapter); } public void onDestroy(){ super.onDestroy(); if(db!=null&&db.isOpen()){ db.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.main, menu); return true; } }
/** * username或password错误跳转 * @author D_xiao * */ public class ErrorActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_error); Button backbtn = (Button)findViewById(R.id.Ebackbtn); backbtn.setOnClickListener(new OnClickListener(){ public void onClick(View sourse){ Intent intentBack = new Intent(ErrorActivity.this,MainActivity.class); startActivity(intentBack); } }); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } }
通过此例,能够看出来sqlite和sql server 等数据库的差别联系:
sqlite没有图形界面,也不须要不论什么的配置安装打开连接等等的操作,几句简单的语句就能够完毕增删改查操作。使用起来还是非常方便的。并且sqlite和sql server ,MySQL是有非常多相似的地方的。除了大多数查询语句在sqlite里面都能够用以外,sqlite还有自己的api提供的方法进行查询,这个以后再叙。并且运行语句也非常相似。
比方db = SQLiteDatabase.openOrCreateDatabase(this.getFilesDir().toString()+"/android1.db3", null); 这句相当于sql server中的建立连接,所以在使用完以后要关闭连接,都是一样的。
Cursor cursor = db.rawQuery("select * from users where name = ? and password = ?",new String[]{userName,userPassword});这句中的cursor相当于sql server 中的resultSet结思集。
没有图形界面有一点还是比較麻烦的,就是不好操作查看数据表,必需要执行cmd查看,相对来说比較麻烦。请看下篇博文:http://blog.csdn.net/frightingforambition/article/details/24439981
完整Demo:
http://download.csdn.net/detail/u011250851/7248227
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