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Android App中各种数据保存方式的使用实例总结

程序员文章站 2024-02-28 21:36:46
少量数据保存之sharedpreferences接口实例 sharedpreferences数据保存主要是通过键值的方式存储在xml文件中 xml文件在data/此程序...

少量数据保存之sharedpreferences接口实例
sharedpreferences数据保存主要是通过键值的方式存储在xml文件中
xml文件在data/此程序的包名/xx.xml。
格式:

<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
<map>
<int name="count" value="3" />
<string name="time">写入日期:2013年10月07日,时间:11:28:09</string>
</map>

sharedpreferences读写的基本步骤:
读:
 1.通过context的getsharedpreferences获取sharedpreferences接口的对象share:sharedpreferences share = this.getsharedpreferences("share",context.mode_private);
"shre"保存的xml文件名 ,context.mode_private 保存的类型为只被本程序访问 (还有mode_world_readable表示其余的程序能够读不能写,mode
_world_writeble能读写 这两个都在api17的时候被废了)
2.通过share的getxxx的方法获取指定key的值 :  share.getint("count", 0);
写:
1.通过sharedpreferences对象的edit()方法获取edit对象:edit   editor = share.edit();
2.通过editor对象的putxxx方法来写入值 :editor.putint("count", 1);
3.调用editor的commit()方法提交修改值 :editor.commit();

访问其他程序的sharedpreferences
访问其他程序的sharedpreferences 的读写唯一不同的是先的获取该程序的context接口对象:this.createpackagecontext(packagename, flags)
packagename为要该目标程序的包名,flags访问类型
其余的就和上面的步骤差不多 就不再概叙

实例

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" 
 xmlns:tools="http://schemas.android.com/tools" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent" 
 
 android:orientation="vertical" 
 tools:context=".mainactivity" > 
 
 <button 
  android:id="@+id/write" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
   android:layout_gravity="center_horizontal" 
  android:text="写入数据" /> 
 
 <button 
  android:id="@+id/read" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" 
   android:layout_gravity="center_horizontal" 
  android:text="读入数据" /> 
 <textview 
  android:id="@+id/txtcount" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content"/> 
 
 <textview 
  android:id="@+id/txt1" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" /> 
 
</linearlayout> 

package com.android.xiong.sharepreferencestest; 
 
import java.text.simpledateformat; 
import java.util.date; 
 
import android.app.activity; 
import android.content.context; 
import android.content.sharedpreferences; 
import android.content.sharedpreferences.editor; 
import android.os.bundle; 
import android.view.menu; 
import android.view.view; 
import android.view.view.onclicklistener; 
import android.widget.button; 
import android.widget.textview; 
 
public class mainactivity extends activity { 
 
 private button write; 
 private button read; 
 
 private textview txt1; 
 private textview counttxt; 
  
 sharedpreferences share ; 
  
 editor editor; 
 
 int counto=0; 
 @override 
 protected void oncreate(bundle savedinstancestate) { 
  super.oncreate(savedinstancestate); 
  setcontentview(r.layout.activity_main); 
  //获取sharedpreferences对象 
  share = this.getsharedpreferences("share", 
    context.mode_private); 
  //获取editor对象 
  editor = share.edit(); 
  write = (button) findviewbyid(r.id.write); 
  read = (button) findviewbyid(r.id.read); 
  txt1 = (textview) findviewbyid(r.id.txt1); 
  counttxt=(textview)findviewbyid(r.id.txtcount); 
  //获取share中key为count的值 
  counto=share.getint("count", 0); 
  counto++; 
  //修改share中key为count的值 
  editor.putint("count", counto); 
  //提交修改 
  editor.commit(); 
  system.out.println("该应用程序使用了:"+counto+"次"); 
  counttxt.settext("该应用程序使用了:"+counto+"次"); 
   
  onclicklistener writelistener = new onclicklistener() { 
 
   @override 
   public void onclick(view v) { 
    // todo auto-generated method stub 
 
    simpledateformat data = new simpledateformat( 
      "写入日期:yyyy年mm月dd日,时间:hh:mm:ss"); 
    editor.putstring("time", 
      data.format(new date())); 
    editor.commit(); 
 
   } 
  }; 
  onclicklistener readlistener=new onclicklistener() { 
    
   @override 
   public void onclick(view v) { 
    // todo auto-generated method stub 
    if(!share.contains("share")){ 
     txt1.settext(share.getstring("time", null)); 
    } 
     
   } 
  }; 
  write.setonclicklistener(writelistener); 
  read.setonclicklistener(readlistener); 
 
 } 
 
 @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; 
 } 
 
} 


机身内存数据读写(internal storage)
1.机身内存读取主要用个两个类文件输入流(fileinputstream)和文件输出流(fileoutputstream): fileinputstream fileinput = this.openfileinput("test.txt") 第一个参数为 data/此程序包名/data/test.txt 文件下 的文件名 ;
fileoutputstream fileout = this.openfileoutput("test.txt",this.mode_append)第一个参数表示文件名 第二个参数表示打开的方式 
2.获取了文件输入输出流之后 其后的文件的读写和基本的io操作一样
机身内存数据读写实例

<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" 
 xmlns:tools="http://schemas.android.com/tools" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent" 
 android:layout_gravity="center_horizontal" 
 android:orientation="vertical" 
 tools:context=".mainactivity" > 
 <edittext 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  android:id="@+id/ed1" 
  android:inputtype="textmultiline"/> 
 <button 
  android:id="@+id/write" 
  android:text="写入" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content"/> 
 <button 
  android:id="@+id/read" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  android:text="读入"/> 
 <edittext 
  android:id="@+id/ed2" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  android:inputtype="textmultiline"/> 
 <button 
  android:id="@+id/delete" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  android:text="删除指定的文件" 
  /> 
 <edittext 
  android:id="@+id/ed3" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  /> 
 
</linearlayout> 
package com.android.xiong.fileiotest; 
 
import java.io.bufferedreader; 
import java.io.file; 
import java.io.fileinputstream; 
import java.io.fileoutputstream; 
import java.io.inputstreamreader; 
import java.lang.reflect.array; 
import java.util.arraylist; 
import java.util.arrays; 
import java.util.list; 
 
import android.app.activity; 
import android.os.bundle; 
import android.view.menu; 
import android.view.view; 
import android.view.view.onclicklistener; 
import android.widget.button; 
import android.widget.edittext; 
 
public class mainactivity extends activity { 
 
 private button read; 
 private button write; 
 private edittext ed1; 
 private edittext ed2; 
 private edittext ed3; 
 private button delete; 
 
 @override 
 protected void oncreate(bundle savedinstancestate) { 
  super.oncreate(savedinstancestate); 
  setcontentview(r.layout.activity_main); 
  read = (button) findviewbyid(r.id.read); 
  write = (button) findviewbyid(r.id.write); 
  delete = (button) findviewbyid(r.id.delete); 
  ed3 = (edittext) findviewbyid(r.id.ed3); 
  ed2 = (edittext) findviewbyid(r.id.ed2); 
  ed1 = (edittext) findviewbyid(r.id.ed1); 
  write.setonclicklistener(new onclicklistener() { 
   @override 
   public void onclick(view v) { 
    string str = ed1.gettext().tostring(); 
    if (!str.equals("")) { 
     write(str); 
    } 
 
   } 
  }); 
  read.setonclicklistener(new onclicklistener() { 
 
   @override 
   public void onclick(view v) { 
    read(); 
 
   } 
  }); 
  delete.setonclicklistener(new onclicklistener() { 
   @override 
   public void onclick(view v) { 
    string str = ed3.gettext().tostring(); 
    if (!str.equals("")) { 
     deletefiles(str); 
    } else { 
     ed3.settext(str + ":该文件输入错误或不存在!"); 
    } 
 
   } 
  }); 
 
 } 
 
 private void write(string content) { 
  try { 
   // 以追加的方式打开文件输出流 
   fileoutputstream fileout = this.openfileoutput("test.txt", 
     this.mode_append); 
   // 写入数据 
   fileout.write(content.getbytes()); 
   // 关闭文件输出流 
   fileout.close(); 
 
  } catch (exception e) { 
   e.printstacktrace(); 
  } 
 } 
 
 private void read() { 
  try { 
   ed2.settext(""); 
   // 打开文件输入流 
   fileinputstream fileinput = this.openfileinput("test.txt"); 
   bufferedreader br = new bufferedreader(new inputstreamreader( 
     fileinput)); 
   string str = null; 
   stringbuilder stb = new stringbuilder(); 
   while ((str = br.readline()) !=null ) { 
    stb.append(str); 
   } 
   ed2.settext(stb); 
  } catch (exception e) { 
   e.printstacktrace(); 
  } 
 
 } 
  
 //删除指定的文件 
 private void deletefiles(string filename) { 
  try { 
   // 获取data文件中的所有文件列表 
   list<string> name = arrays.aslist(this.filelist()); 
   if (name.contains(filename)) { 
    this.deletefile(filename); 
    ed3.settext(filename + ":该文件成功删除!"); 
   } else 
    ed3.settext(filename + ":该文件输入错误或不存在!"); 
 
  } catch (exception e) { 
   e.printstacktrace(); 
  } 
 } 
 
 @override 
 public boolean oncreateoptionsmenu(menu menu) { 
  getmenuinflater().inflate(r.menu.main, menu); 
  return true; 
 } 
 
} 


sdcard(external storage)读写数据实例
1.sdcard数据读写需要注定的先要在androidmainfest.xml文件中注册新建删除和读写的权限 : 

<!-- 在sd卡上创建与删除权限 -->
<uses-permission android:name="android.permission.mount_format_filesystems" />
<!-- 向sd卡上写入权限 -->
<uses-permission android:name="android.permission.write_external_storage" />

2.读写的基本流程就是:
2.1 通过environment类的getexternalstoragestate()方法来判断手机是否有sdcard: 

environment.getexternalstoragestate().equals(environment.media_mounted)

2.2 最通过getexternalstoragedirectory()方法来获取文件目录:

复制代码 代码如下:

file file = new file(environment.getexternalstoragedirectory().getcanonicalpath() + "/test.txt");

读写的文件都在sdcrad文件夹中 通过file explorer可以导出来
2.3 其后就和基本io操作相同了
2.4还有要注意一点的是 在运行的模拟器的时候要附带虚拟的sdcard时  要在run as->run configurations 中要关联一下 如下图
Android App中各种数据保存方式的使用实例总结
sdcard数据读写实例
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android" 
 xmlns:tools="http://schemas.android.com/tools" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent" 
 android:gravity="center_horizontal" 
 android:orientation="vertical" 
 tools:context=".mainactivity" > 
 <edittext 
  android:id="@+id/ed1" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  android:inputtype="textmultiline"/> 
 <button 
  android:id="@+id/write" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  android:text="写入sd卡中"/> 
 <button 
  android:id="@+id/read" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content" 
  android:text="读取sd文件"/> 
 <textview 
  android:id="@+id/txt1" 
  android:layout_width="match_parent" 
  android:layout_height="wrap_content"/> 
</linearlayout> 


<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
 package="com.android.xiong.sdcardtest" 
 android:versioncode="1" 
 android:versionname="1.0" > 
 
 <uses-sdk 
  android:minsdkversion="14" 
  android:targetsdkversion="17" /> 
 <!-- 在sd卡上创建与删除权限 --> 
 <uses-permission android:name="android.permission.mount_format_filesystems" /> 
 <!-- 向sd卡上写入权限 --> 
 <uses-permission android:name="android.permission.write_external_storage" /> 
 
 <application 
  android:allowbackup="true" 
  android:icon="@drawable/ic_launcher" 
  android:label="@string/app_name" 
  android:theme="@style/apptheme" > 
  <activity 
   android:name="com.android.xiong.sdcardtest.mainactivity" 
   android:label="@string/app_name" > 
   <intent-filter> 
    <action android:name="android.intent.action.main" /> 
 
    <category android:name="android.intent.category.launcher" /> 
   </intent-filter> 
  </activity> 
 </application> 
 
</manifest> 
package com.android.xiong.sdcardtest; 
 
import java.io.bufferedreader; 
import java.io.file; 
import java.io.fileinputstream; 
import java.io.fileoutputstream; 
import java.io.inputstreamreader; 
 
import android.app.activity; 
import android.os.bundle; 
import android.os.environment; 
import android.view.menu; 
import android.view.view; 
import android.view.view.onclicklistener; 
import android.widget.button; 
import android.widget.edittext; 
import android.widget.textview; 
 
public class mainactivity extends activity { 
 
 private button write; 
 private button read; 
 
 private edittext ed1; 
 private textview txt1; 
 
 @override 
 protected void oncreate(bundle savedinstancestate) { 
  super.oncreate(savedinstancestate); 
  setcontentview(r.layout.activity_main); 
  write = (button) findviewbyid(r.id.write); 
  read = (button) findviewbyid(r.id.read); 
  ed1 = (edittext) findviewbyid(r.id.ed1); 
  txt1 = (textview) findviewbyid(r.id.txt1); 
  write.setonclicklistener(new onclicklistener() { 
 
   @override 
   public void onclick(view v) { 
    // todo auto-generated method stub 
    writesdcard(ed1.gettext().tostring()); 
 
   } 
  }); 
  read.setonclicklistener(new onclicklistener() { 
 
   @override 
   public void onclick(view v) { 
    // todo auto-generated method stub 
 
    txt1.settext(readsdcard()); 
   } 
  }); 
 } 
 
 // 把数据写入sd卡 
 
 private void writesdcard(string str) { 
 
  try { 
   // 判断是否存在sd卡 
   if (environment.getexternalstoragestate().equals( 
     environment.media_mounted)) { 
    // 获取sd卡的目录 
    file file = environment.getexternalstoragedirectory(); 
    fileoutputstream filew = new fileoutputstream(file.getcanonicalpath() + "/test.txt"); 
    filew.write(str.getbytes()); 
    filew.close(); 
   } 
  } catch (exception e) { 
   e.printstacktrace(); 
  } 
 
 } 
 
 // 从sd卡中读取数据 
 private string readsdcard() { 
  stringbuffer str = new stringbuffer(); 
  try { 
   // 判断是否存在sd 
   if (environment.getexternalstoragestate().equals( 
     environment.media_mounted)) { 
    file file = new file(environment.getexternalstoragedirectory() 
      .getcanonicalpath() + "/test.txt");                 
    // 判断是否存在该文件 
    if (file.exists()) { 
     // 打开文件输入流 
     fileinputstream filer = new fileinputstream(file); 
     bufferedreader reads = new bufferedreader( 
       new inputstreamreader(filer)); 
     string st = null; 
     while ((st =reads.readline())!=null ) { 
      str.append(st); 
     } 
     filer.close(); 
    } else { 
     txt1.settext("该目录下文件不存在"); 
    } 
   } 
 
  } catch (exception e) { 
   e.printstacktrace(); 
  } 
  return str.tostring(); 
 } 
 
 @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; 
 } 
 
} 

sqlite简介和简单的登录与注册源代码
1.获取sqlitedatabase对象db创建数据库或连接数据库:sqlitedatabasedb = sqlitedatabase.openorcreatedatabase(mainactivity.this.getfilesdir().tostring()+ "/test.dbs", null);如果目录下有test.dbs数据库则是连接没有就是创建
2.用对象db的方法来执行sql语句:db.execsql(string sql) 此方法木有返回值 所以查询不好弄。查询一般用db.rawquery返回一个cursor对象(相当与jdbc中的resultset),cursor有如下几个方法来查询数据:
  2.1 move tofirst 将记录指针跳到第一行
  2.2 movetolast将记录指针跳到最后一行
  2.3 movenext将记录指针移到下一行
  2.4movetoposition( int ss)将记录指针跳到指定的ss行
  2.5movetoprevious将记录指针跳到上一行
将记录指针跳到指定的行之后就可以通过对象的getxxx方法来获取数据 :如 cursor cursor = db.rawquery("select  na,pw from user where na=? and pw=?", new string []{name,pwd});
3.回收资源close
当然以sqlitedatabase对象还可以调用许多方法来操作数据库,不过俺是觉得这几个方法基本够了

简单的登录与注册源代码:
(仅此来练习sqlite的操作  一般注册的信息都样上传到服务器而不会是存储在手机数据库)

Android App中各种数据保存方式的使用实例总结

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
  package="com.android.xiong.sqlitelogin" 
  android:versioncode="1" 
  android:versionname="1.0" > 
 
  <uses-sdk 
    android:minsdkversion="8" 
    android:targetsdkversion="14" /> 
 
  <application 
    android:allowbackup="true" 
    android:icon="@drawable/ic_launcher" 
    android:label="@string/app_name" 
    android:theme="@style/apptheme" > 
    <activity 
      android:name="com.android.xiong.sqlitelogin.mainactivity" 
      android:label="@string/app_name" > 
      <intent-filter> 
        <action android:name="android.intent.action.main" /> 
 
        <category android:name="android.intent.category.launcher" /> 
      </intent-filter> 
    </activity> 
    <activity 
      android:name="com.android.xiong.sqlitelogin.registersactivity" 
      android:label="@string/app_name" > 
    </activity> 
  </application> 
 
</manifest> 

<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" 
  xmlns:tools="http://schemas.android.com/tools" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" 
  tools:context=".mainactivity" > 
 
  <textview 
    android:id="@+id/login" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_margin="30dp" 
    android:gravity="center_horizontal" 
    android:textcolor="#8a2be2" 
    android:textsize="35dp" 
    android:text="登录界面" /> 
  <textview  
    android:id="@+id/txtname" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_below="@id/login" 
    android:layout_marginright="5dp" 
    android:layout_marginbottom="30dp" 
    android:textsize="28dp" 
    android:text="用户帐号:"/> 
  <edittext  
    android:id="@+id/edname" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_marginbottom="30dp" 
    android:layout_below="@id/login" 
    android:layout_torightof="@id/txtname" 
    android:layout_alignparentright="true" 
     android:hint="请输入用户帐号"/> 
    <textview  
    android:id="@+id/txtpassword" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_below="@id/txtname" 
    android:layout_marginright="5dp" 
    android:textsize="28dp" 
    android:text="用户密码:"/> 
  <edittext  
    android:id="@+id/edpassword" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_below="@id/edname" 
    android:layout_torightof="@id/txtpassword" 
    android:layout_alignparentright="true" 
    android:inputtype="textpassword" 
    android:hint="请输入用户密码"/> 
  <linearlayout  
    android:layout_below="@id/edpassword" 
    android:orientation="horizontal" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_margintop="30dp" 
    android:gravity="center_horizontal" > 
  <button  
    android:id="@+id/btregister" 
    android:layout_height="wrap_content" 
    android:layout_width="wrap_content" 
    android:layout_marginright="20dp" 
    android:text="用户注册"/> 
   <button  
    android:id="@+id/btlogin" 
    android:layout_height="wrap_content" 
    android:layout_width="wrap_content" 
    android:text="用户登录"/> 
   </linearlayout> 
 
</relativelayout> 


<?xml version="1.0" encoding="utf-8"?> 
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" 
  android:layout_width="match_parent" 
  android:layout_height="match_parent" > 
   
 
  <textview 
    android:id="@+id/txt1" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_margin="30dp" 
    android:gravity="center_horizontal" 
    android:text="注册界面" 
    android:textcolor="#8a2be2" 
    android:textsize="35dp" /> 
 
  <textview 
    android:id="@+id/txtname1" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_below="@id/txt1" 
    android:layout_marginbottom="30dp" 
    android:layout_marginright="5dp" 
    android:text="帐号:" 
    android:textsize="28dp" /> 
 
  <edittext 
    android:id="@+id/edname1" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignparentright="true" 
    android:layout_below="@id/txt1" 
     android:layout_torightof="@id/txtname1" 
    android:layout_marginbottom="30dp" /> 
 
  <textview 
    android:id="@+id/txtpassword1" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_below="@id/txtname1" 
    android:layout_marginright="5dp" 
    android:text="密码:" 
    android:textsize="28dp" /> 
 
  <edittext 
    android:id="@+id/edpassword1" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_alignparentright="true" 
    android:layout_below="@id/edname1" 
    android:layout_torightof="@id/txtpassword1" /> 
 
  <linearlayout 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_below="@id/edpassword1" 
    android:layout_margintop="30dp" 
    android:gravity="center_horizontal" 
    android:orientation="horizontal" > 
 
    <button 
      android:id="@+id/btregister1" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_marginright="20dp" 
      android:text="提交数据" /> 
  </linearlayout> 
</relativelayout> 


package com.android.xiong.sqlitelogin; 
 
import android.app.activity; 
import android.app.alertdialog; 
import android.content.intent; 
import android.database.cursor; 
import android.database.sqlite.sqlitedatabase; 
import android.database.sqlite.sqliteexception; 
import android.os.bundle; 
import android.view.menu; 
import android.view.view; 
import android.view.view.onclicklistener; 
import android.widget.button; 
import android.widget.edittext; 
 
public class mainactivity extends activity { 
 
  // 帐号和密码 
  private edittext edname; 
  private edittext edpassword; 
 
  private button btregister; 
  private button btlogin; 
  // 创建sqlite数据库 
  public static sqlitedatabase db; 
 
  @override 
  protected void oncreate(bundle savedinstancestate) { 
    super.oncreate(savedinstancestate); 
    setcontentview(r.layout.activity_main); 
    edname = (edittext) findviewbyid(r.id.edname); 
    edpassword = (edittext) findviewbyid(r.id.edpassword); 
    btregister = (button) findviewbyid(r.id.btregister); 
    btlogin = (button) findviewbyid(r.id.btlogin); 
    db = sqlitedatabase.openorcreatedatabase(mainactivity.this.getfilesdir().tostring() 
        + "/test.dbs", null); 
    // 跳转到注册界面 
    btregister.setonclicklistener(new onclicklistener() { 
 
      @override 
      public void onclick(view v) { 
        // todo auto-generated method stub 
        intent intent = new intent(); 
        intent.setclass(mainactivity.this, registersactivity.class); 
        startactivity(intent); 
      } 
    }); 
    btlogin.setonclicklistener(new loginlistener()); 
  } 
 
  @override 
  protected void ondestroy() { 
    // todo auto-generated method stub 
    super.ondestroy(); 
    db.close(); 
  } 
 
 
  class loginlistener implements onclicklistener { 
 
    @override 
    public void onclick(view v) { 
      // todo auto-generated method stub 
      string name = edname.gettext().tostring(); 
      string password = edpassword.gettext().tostring(); 
      if (name.equals("") || password.equals("")) { 
        // 弹出消息框 
        new alertdialog.builder(mainactivity.this).settitle("错误") 
            .setmessage("帐号或密码不能空").setpositivebutton("确定", null) 
            .show(); 
      } else { 
        isuserinfo(name, password); 
      } 
    } 
 
    // 判断输入的用户是否正确 
    public boolean isuserinfo(string name, string pwd) { 
      try{ 
        string str="select * from tb_user where name=? and password=?"; 
        cursor cursor = db.rawquery(str, new string []{name,pwd}); 
        if(cursor.getcount()<=0){ 
          new alertdialog.builder(mainactivity.this).settitle("错误") 
          .setmessage("帐号或密码错误!").setpositivebutton("确定", null) 
          .show(); 
          return false; 
        }else{ 
          new alertdialog.builder(mainactivity.this).settitle("正确") 
          .setmessage("成功登录").setpositivebutton("确定", null) 
          .show(); 
          return true; 
        } 
         
      }catch(sqliteexception e){ 
        createdb(); 
      } 
      return false; 
    } 
   
  } 
  // 创建数据库和用户表 
  public void createdb() { 
    db.execsql("create table tb_user( name varchar(30) primary key,password varchar(30))"); 
  } 
  @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; 
  } 
 
} 

package com.android.xiong.sqlitelogin; 
 
import android.app.activity; 
import android.app.alertdialog; 
import android.content.dialoginterface; 
import android.content.intent; 
import android.database.sqlite.sqlitedatabase; 
import android.os.bundle; 
import android.view.view; 
import android.view.view.onclicklistener; 
import android.widget.button; 
import android.widget.edittext; 
 
public class registersactivity extends activity { 
 
  private edittext edname1; 
  private edittext edpassword1; 
  private button btregister1; 
  sqlitedatabase db; 
 
  @override 
  protected void ondestroy() { 
    // todo auto-generated method stub 
    super.ondestroy(); 
    db.close(); 
  } 
 
  @override 
  protected void oncreate(bundle savedinstancestate) { 
    // todo auto-generated method stub 
    super.oncreate(savedinstancestate); 
    setcontentview(r.layout.register); 
    edname1 = (edittext) findviewbyid(r.id.edname1); 
    edpassword1 = (edittext) findviewbyid(r.id.edpassword1); 
    btregister1 = (button) findviewbyid(r.id.btregister1); 
    btregister1.setonclicklistener(new onclicklistener() { 
 
      @override 
      public void onclick(view v) { 
        // todo auto-generated method stub 
        string name = edname1.gettext().tostring(); 
        string password = edpassword1.gettext().tostring(); 
        if (!(name.equals("") && password.equals(""))) { 
          if (adduser(name, password)) { 
            dialoginterface.onclicklistener ss = new dialoginterface.onclicklistener() { 
              @override 
              public void onclick(dialoginterface dialog, 
                  int which) { 
                // todo auto-generated method stub 
                // 跳转到登录界面 
                intent in = new intent(); 
                in.setclass(registersactivity.this, 
                    mainactivity.class); 
                startactivity(in); 
                // 销毁当前activity 
                registersactivity.this.ondestroy(); 
              } 
            }; 
            new alertdialog.builder(registersactivity.this) 
                .settitle("注册成功").setmessage("注册成功") 
                .setpositivebutton("确定", ss).show(); 
 
          } else { 
            new alertdialog.builder(registersactivity.this) 
                .settitle("注册失败").setmessage("注册失败") 
                .setpositivebutton("确定", null); 
          } 
        } else { 
          new alertdialog.builder(registersactivity.this) 
              .settitle("帐号密码不能为空").setmessage("帐号密码不能为空") 
              .setpositivebutton("确定", null); 
        } 
 
      } 
    }); 
 
  } 
 
  // 添加用户 
  public boolean adduser(string name, string password) { 
    string str = "insert into tb_user values(?,?) "; 
    mainactivity main = new mainactivity(); 
    db = sqlitedatabase.openorcreatedatabase(this.getfilesdir().tostring() 
        + "/test.dbs", null); 
    main.db = db; 
    try { 
      db.execsql(str, new string[] { name, password }); 
      return true; 
    } catch (exception e) { 
      main.createdb(); 
    } 
    return false; 
  } 
 
}