Android之sqlite操作

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Android使用sqlite数据库不需要安装。
先创建一个名为DBTest 的项目：
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AndroidMainfest.xml的代码如下：

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.dbtest"    android:versionCode="1"    android:versionName="1.0" >    <uses-sdk        android:minSdkVersion="8"        android:targetSdkVersion="18" />    <application        android:allowBackup="true"        android:icon="@drawable/ic_launcher"        android:label="@string/app_name"        android:theme="@style/AppTheme" >        <activity            android:name="com.example.dbtest.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>

DBUtil的代码如下：

package com.example.dbtest;import java.util.ArrayList;import java.util.List;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;public class DBUtil {    static SQLiteDatabase sld;    public static void createOrOpenDatabase() throws Exception {        //目录是   /data/data/包名/数据库名        sld = SQLiteDatabase.openDatabase("/data/data/com.example.dbtest/dbtest", null, SQLiteDatabase.OPEN_READWRITE|SQLiteDatabase.CREATE_IF_NECESSARY);        String sql = "create table if not exists user(username varchar2(20),password varchar2(20))";        sld.execSQL(sql);    }    public static void closeDatabase() throws Exception {        try{            sld.close();        } catch(Exception e ){            e.printStackTrace();        }    }    public static List<String> searchuser(String username){        List<String> list = new ArrayList<String>();        try{            createOrOpenDatabase();            String sql = "select * from user where username='" +username + "'";            Cursor cur = sld.rawQuery(sql, new String[]{});            while(cur.moveToNext()){                list.add(cur.getString(0));                list.add(cur.getString(1));            }            cur.close();            closeDatabase();        } catch (Exception e ){            e.printStackTrace();        }        return list;    }    public static List<String> serchalluser(){        List<String> list = new ArrayList<String>();        try{            createOrOpenDatabase();            String sql = "select * from user";            Cursor cur = sld.rawQuery(sql, new String[]{});            while(cur.moveToNext()){                list.add(cur.getString(0));                list.add(cur.getString(1));            }            cur.close();            closeDatabase();        } catch(Exception e ){            e.printStackTrace();        }        return list;    }    public static void updatetable(String sql){        try{            createOrOpenDatabase();            sld.execSQL(sql);            closeDatabase();        } catch(Exception e){            e.printStackTrace();        }    }    public static void droptable(){        try{            String sql ="drop table user";            createOrOpenDatabase();            sld.execSQL(sql);            closeDatabase();        } catch(Exception e){            e.printStackTrace();        }    }}

MainActivity的代码如下：

package com.example.dbtest;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;import android.widget.TextView;import android.widget.Toast;public class MainActivity extends Activity {    Button btn_createdb,btn_insert,btn_show,btn_update,btn_showall,btn_deleteusertable;    EditText username,password;    TextView show;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        init();    }    public void init(){        username = (EditText) findViewById(R.id.username);        password = (EditText) findViewById(R.id.password);        btn_createdb = (Button) findViewById(R.id.btn_create);        btn_insert = (Button) findViewById(R.id.btn_insert);        btn_show = (Button) findViewById(R.id.btn_show);        btn_update = (Button) findViewById(R.id.btn_update);        btn_showall = (Button) findViewById(R.id.btn_showall);        btn_deleteusertable = (Button) findViewById(R.id.btn_delet);        show = (TextView) findViewById(R.id.showsomething);        btn_createdb.setOnClickListener(listener);        btn_insert.setOnClickListener(listener);        btn_show.setOnClickListener(listener);        btn_update.setOnClickListener(listener);        btn_showall.setOnClickListener(listener);        btn_deleteusertable.setOnClickListener(listener);    }    public OnClickListener listener = new OnClickListener(){        public void onClick(View v){            Button button = (Button)v;            if(button.getId() == btn_createdb.getId()){                try{                    DBUtil.createOrOpenDatabase();                    show.setText("用户表已经打开");                } catch(Exception e){                    e.printStackTrace();                }            } else if(button.getId() == btn_update.getId()){                try{                    String sql = "update user set username='" + username.getText() +"',password='" + password.getText() +"'";                    DBUtil.updatetable(sql);                    show.setText("update success");                } catch(Exception e ){                    e.printStackTrace();                }            } else if(button.getId() == btn_insert.getId()){                try{                    String sql = "insert into user values('" +username.getText() + "','" +password.getText()+"')";                    DBUtil.updatetable(sql);                    show.setText("insert success");                } catch(Exception e ){                    e.printStackTrace();                }            }  else if(button.getId() == btn_showall.getId()){                try{                    List<String> list = DBUtil.serchalluser();                    show.setText(list.toString());                } catch(Exception e ){                    e.printStackTrace();                }            } else if(button.getId() == btn_show.getId()){                try{                    List<String> user =DBUtil.searchuser(username.getText().toString());                    show.setText(user.toString());                } catch (Exception e ){                    e.printStackTrace();                }            } else if(button.getId() == btn_deleteusertable.getId()){                try{                    DBUtil.droptable();                    Toast.makeText(getApplicationContext(), "用户表删除成功", Toast.LENGTH_SHORT).show();                } catch (Exception e){                    e.printStackTrace();                }            }        }    };    @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;    }}

运行结果如图：
这里写图片描述

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