Android SQLiteDatabase

SQLiteOpenHelper是SQLiteDatabse的一个帮助类，用来管理数据的创建和版本更新。一般的用法是定义一个类继承SQLiteOpenHelper，并实现两个回调方法，OnCreate(SQLiteDatabase db)和onUpgrade(SQLiteDatabse, int oldVersion, int newVersion)来创建和更新数据库，我利用数据库做了一个类似电话本的功能，插入数据，查询数据，和删除数据，界面很丑，主要是讲解SQLiteOpenHelper类的用法，截图如下

 

首先我们创建一个DBHelper继承SQLiteOpenHelper，这个是数据库的一个帮助类

 package com.example.utils;

 import android.content.ContentValues;
 import android.content.Context;
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteDatabase.CursorFactory;
 import android.database.sqlite.SQLiteOpenHelper;

 public class DBHelper extends SQLiteOpenHelper {
     private final static int VERSION = 1;
     private final static String DB_NAME = "phones.db";
     private final static String TABLE_NAME = "phone";
     private final static String CREATE_TBL = "create table phone(_id integer primary key autoincrement, name text, sex text, number text, desc text)";
     private SQLiteDatabase db;

     //SQLiteOpenHelper子类必须要的一个构造函数
     public DBHelper(Context context, String name, CursorFactory factory,int version) {
         //必须通过super 调用父类的构造函数
         super(context, name, factory, version);
     }

     //数据库的构造函数，传递三个参数的
     public DBHelper(Context context, String name, int version){
         this(context, name, null, version);
     }

     //数据库的构造函数，传递一个参数的， 数据库名字和版本号都写死了
     public DBHelper(Context context){
         this(context, DB_NAME, null, VERSION);
     }

     // 回调函数，第一次创建时才会调用此函数，创建一个数据库
     @Override
     public void onCreate(SQLiteDatabase db) {
         this.db = db;
         System.out.println("Create Database");
         db.execSQL(CREATE_TBL);
     }

     //回调函数，当你构造DBHelper的传递的Version与之前的Version调用此函数
     @Override
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
         System.out.println("update Database");

     }

     //插入方法
     public void insert(ContentValues values){
         //获取SQLiteDatabase实例
         SQLiteDatabase db = getWritableDatabase();
         //插入数据库中
         db.insert(TABLE_NAME, null, values);
         db.close();
     }

     //查询方法
     public Cursor query(){
         SQLiteDatabase db = getReadableDatabase();
         //获取Cursor
         Cursor c = db.query(TABLE_NAME, null, null, null, null, null, null, null);
         return c;

     }

     //根据唯一标识_id  来删除数据
     public void delete(int id){
         SQLiteDatabase db = getWritableDatabase();
         db.delete(TABLE_NAME, "_id=?", new String[]{String.valueOf(id)});
     }


     //更新数据库的内容
     public void update(ContentValues values, String whereClause, String[]whereArgs){
         SQLiteDatabase db = getWritableDatabase();
         db.update(TABLE_NAME, values, whereClause, whereArgs);
     }

     //关闭数据库
     public void close(){
         if(db != null){
             db.close();
         }
     }

 }

第一个MainActivity

 package com.example.phonebooks;

 import android.app.Activity;
 import android.content.ContentValues;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.RadioButton;
 import android.widget.RadioGroup;
 import android.widget.RadioGroup.OnCheckedChangeListener;
 import android.widget.Toast;

 import com.example.utils.DBHelper;

 public class MainActivity extends Activity implements OnClickListener{
     private DBHelper dbHelper;
     //定义三个输入框
     private EditText name, number, desc;
     //定义两个按钮
     private Button submit ,look;
     //定义一个RadioGroup
     private RadioGroup radio;
     private String nameStr, numberStr, descStr;
     private String sexStr = "男";

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         //实例化DBHelper
         dbHelper = new DBHelper(this);

         //根据id 获取到相对应的控件
         name = (EditText)findViewById(R.id.editText1);
         number = (EditText)findViewById(R.id.editText2);
         desc = (EditText)findViewById(R.id.editText3);
         submit = (Button)findViewById(R.id.button1);
         look = (Button)findViewById(R.id.button2);
         radio = (RadioGroup)findViewById(R.id.radioGroup1);


         //按钮设置点击监听
         submit.setOnClickListener(this);
         look.setOnClickListener(this);

         //单选群组的监听
         radio.setOnCheckedChangeListener(new OnCheckedChangeListener() {

             @Override
             public void onCheckedChanged(RadioGroup group, int checkedId) {
                 if(checkedId == R.id.radio0){
                     RadioButton r = (RadioButton) group.findViewById(checkedId);
                     sexStr = r.getText().toString();
                 }
                 if(checkedId == R.id.radio1){
                     RadioButton r = (RadioButton) group.findViewById(checkedId);
                     sexStr = r.getText().toString();
                 }

             }
         });
     }

     @Override
     public void onClick(View v) {
         switch (v.getId()) {
         case R.id.button1:
             if(name.getText().toString().length() != 0){
                 nameStr = name.getText().toString();
             }else{
                 Toast.makeText(getApplication(), "姓名不能为空", Toast.LENGTH_SHORT).show();
                 return;
             }
             if(number.getText().toString().length() != 0){
                 numberStr = number.getText().toString();
             }else{
                 Toast.makeText(getApplication(), "电话号码不能为空", Toast.LENGTH_SHORT).show();
                 return;
             }
             if(desc.getText().toString().length() != 0){
                 descStr = desc.getText().toString();
             }else{
                 Toast.makeText(getApplication(), "备注不能为空", Toast.LENGTH_SHORT).show();
                 return;
             }

             //实例化一个ContentValues， ContentValues是以键值对的形式，键是数据库的列名，值是要插入的值
             ContentValues values = new ContentValues();
             values.put("name", nameStr);
             values.put("sex", sexStr);
             values.put("number", numberStr);
             values.put("desc", descStr);

             //调用insert插入数据库
             dbHelper.insert(values);

             //将三个输入框重置下
             reset();
             break;
         case R.id.button2:
             Intent intent = new Intent();
             intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
             intent.setClass(this, ResultActivity.class);
             startActivity(intent);
             break;
         default:
             break;
         }




     }

     //重置edittext
     private void reset(){
         name.setText("");
         number.setText("");
         desc.setText("");
     }


 }

activity_main.xml

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:background="#000000" >

     <TextView
         android:id="@+id/textView1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentTop="true"
         android:text="姓名"
         android:textSize="15dp" />

     <EditText
         android:id="@+id/editText1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentRight="true"
         android:layout_below="@+id/textView1"
         android:ems="10" >

         <requestFocus />
     </EditText>

     <RadioGroup
         android:id="@+id/radioGroup1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_below="@+id/editText1" >

         <RadioButton
             android:id="@+id/radio0"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:checked="true"
             android:text="男" />

         <RadioButton
             android:id="@+id/radio1"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_alignTop="@+id/radioGroup1"
             android:layout_toRightOf="@+id/textView2"
             android:text="女" />
     </RadioGroup>

     <TextView
         android:id="@+id/textView2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_below="@+id/radioGroup1"
         android:text="电话号码" />

     <EditText
         android:id="@+id/editText2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentRight="true"
         android:layout_below="@+id/textView2"
         android:ems="10" />

     <TextView
         android:id="@+id/textView3"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_below="@+id/editText2"
         android:text="备注" />

     <EditText
         android:id="@+id/editText3"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentRight="true"
         android:layout_below="@+id/textView3"
         android:lines="5"
         android:ems="10"
         android:inputType="textMultiLine" />

     <Button
         android:id="@+id/button2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentBottom="true"
         android:layout_alignParentLeft="true"
         android:layout_alignParentRight="true"
         android:text="查看" />

     <Button
         android:id="@+id/button1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentRight="true"
         android:layout_below="@+id/editText3"
         android:text="插入" />

 </RelativeLayout>
 用一个Person类来封装姓名，性别，电话，备注这些数据。里面只有get()和set()方法

 package com.example.mode;

 public class Person {
     private String name;
     private String sex;
     private String number;
     private String desc;
     private int _id;

     public int get_id() {
         return _id;
     }
     public void set_id(int _id) {
         this._id = _id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public String getSex() {
         return sex;
     }
     public void setSex(String sex) {
         this.sex = sex;
     }
     public String getNumber() {
         return number;
     }
     public void setNumber(String number) {
         this.number = number;
     }
     public String getDesc() {
         return desc;
     }
     public void setDesc(String desc) {
         this.desc = desc;
     }


 }

 查看数据的ResultActivity

 package com.example.phonebooks;

 import java.util.ArrayList;
 import java.util.List;

 import android.app.Activity;
 import android.app.AlertDialog;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.content.DialogInterface.OnClickListener;
 import android.database.Cursor;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.AdapterView;
 import android.widget.AdapterView.OnItemClickListener;
 import android.widget.BaseAdapter;
 import android.widget.ListView;
 import android.widget.TextView;

 import com.example.mode.Person;
 import com.example.utils.DBHelper;

 public class ResultActivity extends Activity implements OnItemClickListener{
     private ListView listView;
     private DbAdapter adapter;
     DBHelper dbHelper;
     List<Person> bookList = new ArrayList<Person>();

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.result);

         //获取ListView
         listView = (ListView)findViewById(R.id.listView1);
         bookList = queryData();
         //实例化DbAdapter
         adapter = new DbAdapter(getApplication(), bookList);
         listView.setAdapter(adapter);
         listView.setOnItemClickListener(this);

     }


     //查询数据库，将每一行的数据封装成一个person 对象，然后将对象添加到List中
     private List<Person> queryData(){
         List<Person> list = new ArrayList<Person>();
         dbHelper = new DBHelper(this);

         //调用query()获取Cursor
         Cursor c = dbHelper.query();
         while (c.moveToNext()){
             int _id = c.getInt(c.getColumnIndex("_id"));
             String name = c.getString(c.getColumnIndex("name"));
             String sex = c.getString(c.getColumnIndex("sex"));
             String number = c.getString(c.getColumnIndex("number"));
             String desc = c.getString(c.getColumnIndex("desc"));

             //用一个Person对象来封装查询出来的数据
             Person p = new Person();
             p.set_id(_id);
             p.setName(name);
             p.setSex(sex);
             p.setNumber(number);
             p.setDesc(desc);

             list.add(p);
         }
         return list;
     }


     //自定义DbAdapter
     public class DbAdapter extends BaseAdapter{
         private List<Person> list;
         private Context context;
         private LayoutInflater layoutInflater;

         public DbAdapter(Context context, List<Person> list){
             layoutInflater = LayoutInflater.from(context);
             this.context = context;
             this.list = list;
         }

         //刷新适配器
         public void refresh(List<Person> list){
             this.list = list;
             notifyDataSetChanged();
         }

         @Override
         public int getCount() {
             return list.size();
         }

         @Override
         public Object getItem(int position) {
             return list.get(position);
         }

         @Override
         public long getItemId(int position) {
             return position;
         }

         @Override
         public View getView(int position, View convertView, ViewGroup parent) {
             Person p = list.get(position);
             ViewHolder holder;

             if(convertView == null){
                 holder = new ViewHolder();
                 convertView = layoutInflater.inflate(R.layout.item, null);
                 holder.name = (TextView)convertView.findViewById(R.id.textView1);
                 holder.sex = (TextView)convertView.findViewById(R.id.textView2);
                 holder.number = (TextView)convertView.findViewById(R.id.textView3);
                 holder.desc = (TextView)convertView.findViewById(R.id.textView4);

                 convertView.setTag(holder);

             }else{
                 holder = (ViewHolder) convertView.getTag();
             }

             holder.name.setText(p.getName());
             holder.sex.setText(p.getSex());
             holder.number.setText(p.getNumber());
             holder.desc.setText(p.getDesc());

             return convertView;
         }


         public class ViewHolder {
             public TextView name;
             public TextView sex;
             public TextView number;
             public TextView desc;
             public TextView id;
         }

     }


     @Override
     public void onItemClick(AdapterView<?> parent, View view, final int position, long id) {
         final Person p = bookList.get(position);
         final long temp = id;
         AlertDialog.Builder builder = new AlertDialog.Builder(this);
         builder.setMessage("真的要删除该记录？").setPositiveButton("是", new OnClickListener() {
             @Override
             public void onClick(DialogInterface dialog, int which) {
                 //调用delete（）删除某条数据
                 dbHelper.delete(p.get_id());
                 //重新刷新适配器
                 adapter.refresh(queryData());
             }
         }).setNegativeButton("否", new OnClickListener() {

             @Override
             public void onClick(DialogInterface dialog, int which) {

             }
         }).create().show();


         // 关闭数据库
         dbHelper.close();
     }
 }

 显示数据的布局result.xml,里面只有一个ListView

 <?xml version="1.0" encoding="UTF-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent" >

     <ListView
         android:id="@+id/listView1"
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
         android:layout_alignParentLeft="true"
         android:cacheColorHint="#00000000"
         android:layout_alignParentTop="true" >
     </ListView>

 </RelativeLayout>

ListView 的item

 <?xml version="1.0" encoding="UTF-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent" >

     <TextView
         android:id="@+id/textView1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentTop="true"
         android:text="TextView" />

     <TextView
         android:id="@+id/textView3"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_above="@+id/textView4"
         android:layout_alignParentRight="true"
         android:text="TextView" />

     <TextView
         android:id="@+id/textView2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_above="@+id/textView4"
         android:layout_centerHorizontal="true"
         android:text="TextView" />

     <TextView
         android:id="@+id/textView4"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentRight="true"
         android:layout_below="@+id/textView1"
         android:layout_marginTop="19dp"
         android:text="TextView" />

 </RelativeLayout>

 主要不要忘了在AndroidManifest.xml 注册ResultActivity