系出名门Android(9) - 数据库支持(SQLite), 内容提供器(ContentProvider) - android

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系出名门Android(9) - 数据库支持(SQLite), 内容提供器(ContentProvider)

作者： webabcd

介绍
在 Android 中使用 SQLite, ContentProvider

数据库支持(SQLite)-Android 开发平台提供了操作 SQLite 数据库的相关 API
内容提供器(ContentProvider)-当数据需要在应用程序之间共享时，可以在某程序中使用 ContentProvider 定义 URI，以使其它应用程序可以通过此 URI 访问指定的数据

1、SQLite的 Demo
DatabaseHelper.java
代码 package com.webabcd.SQLite;

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

// 数据库操作的Helper类
public class DatabaseHelper extends SQLiteOpenHelper{

DatabaseHelper(Contextcontext,Stringname,CursorFactorycursorFactory, int version){
super (context,name,cursorFactory,version);
}

@Override
public void onCreate(SQLiteDatabasedb){
// TODO创建数据库后，对数据库的操作
}

@Override
public void onUpgrade(SQLiteDatabasedb, int oldVersion, int newVersion){
// TODO更改数据库版本的操作
}

@Override
public void onOpen(SQLiteDatabasedb){
super .onOpen(db);

// TODO每次成功打开数据库后首先被执行
}
}

Main.java
代码 package com.webabcd.SQLite;

import java.util.Random;

import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class Main extends Activity{

private DatabaseHelperdbHelper;

private static final StringDATABASE_NAME = " db.db " ;
private static final int DATABASE_VERSION = 1 ;
private static final StringTABLE_NAME = " employee " ;

TextViewtxtMsg;

/** Calledwhentheactivityisfirstcreated. */
@Override
public void onCreate(BundlesavedInstanceState){
super .onCreate(savedInstanceState);
setContentView(R.layout.main);

dbHelper = new DatabaseHelper( this ,DATABASE_NAME, null ,
DATABASE_VERSION);

txtMsg = (TextView) this .findViewById(R.id.txtMsg);

Buttonbtn1 = (Button) this .findViewById(R.id.btn1);
btn1.setText( " 创建表 " );
btn1.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
CreateTable();
}
});

Buttonbtn2 = (Button) this .findViewById(R.id.btn2);
btn2.setText( " 插入3条记录 " );
btn2.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
insertItem();
}
});

Buttonbtn3 = (Button) this .findViewById(R.id.btn3);
btn3.setText( " 删除全部记录 " );
btn3.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
deleteItem();
}
});

Buttonbtn4 = (Button) this .findViewById(R.id.btn4);
btn4.setText( " 更新指定数据 " );
btn4.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
updateItem();
}
});

Buttonbtn5 = (Button) this .findViewById(R.id.btn5);
btn5.setText( " 显示全部数据 " );
btn5.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
showItems();
}
});

Buttonbtn6 = (Button) this .findViewById(R.id.btn6);
btn6.setText( " 删除表 " );
btn6.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
dropTable();
}
});
}

// 创建数据表
private void CreateTable(){
SQLiteDatabasedb = dbHelper.getWritableDatabase();
Stringsql = " CREATETABLEIFNOTEXISTS " + TABLE_NAME
+ " (IDINTEGERPRIMARYKEY,NameVARCHAR,AgeINTEGER); " ;
try {
db.execSQL(sql);
txtMsg.append( " 数据表成功创建\n " );
} catch (SQLExceptionex){
txtMsg.append( " 数据表创建错误\n " + ex.toString() + " \n " );
}
}

// 插入数据
private void insertItem(){
SQLiteDatabasedb = dbHelper.getWritableDatabase();

try {
Randomrandom = new Random();
for ( int i = 0 ;i < 3 ;i ++ ){
Stringsql = " insertinto " + TABLE_NAME
+ " (name,age)values('name " + String.valueOf(i)
+ " ', " + random.nextInt() + " ) " ;
// execSQL()-执行指定的sql
db.execSQL(sql);
}
txtMsg.append( " 成功插入3条数据\n " );
} catch (SQLExceptionex){
txtMsg.append( " 插入数据失败\n " + ex.toString() + " \n " );
}
}

// 删除数据
private void deleteItem(){
try {
SQLiteDatabasedb = dbHelper.getWritableDatabase();
db.delete(TABLE_NAME, " id<999999 " , null );
txtMsg.append( " 成功删除数据\n " );
} catch (SQLExceptione){
txtMsg.append( " 删除数据失败\n " );
}
}

// 更新数据
private void updateItem(){
SQLiteDatabasedb = dbHelper.getWritableDatabase();

try {
ContentValuesvalues = new ContentValues();
values.put( " name " , " 批量更新后的名字 " );

db.update(TABLE_NAME,values, " id<? " , new String[]{ " 3 " });
txtMsg.append( " 成功更新数据\n " );
} catch (SQLExceptione){
txtMsg.append( " 更新数据失败\n " );
}
}

// 查询数据
private void showItems(){
SQLiteDatabasedb = dbHelper.getReadableDatabase();

try {
String[]column = { " id " , " name " , " age " };
Cursorcursor = db.query(TABLE_NAME,column, null , null , null ,
null , null );
Integernum = cursor.getCount();
txtMsg.append( " 共 " + Integer.toString(num) + " 条记录\n " );
cursor.moveToFirst();

while (cursor.getPosition() != cursor.getCount()){
txtMsg.append(Integer.toString(cursor.getPosition()) + " , "
+ String.valueOf(cursor.getString( 0 )) + " , "
+ cursor.getString( 1 ) + " , "
+ String.valueOf(cursor.getString( 2 )) + " \n " );
cursor.moveToNext();
}
} catch (SQLExceptionex){
txtMsg.append( " 读取数据失败\n " + ex.toString() + " \n " );
}
}

// 删除数据表
private void dropTable(){
SQLiteDatabasedb = dbHelper.getWritableDatabase();
Stringsql = " DROPTABLEIFEXISTS " + TABLE_NAME;
try {
db.execSQL(sql);
txtMsg.append( " 数据表删除成功\n " );
} catch (SQLExceptionex){
txtMsg.append( " 数据表删除错误\n " + ex.toString() + " \n " );
}
}
}

2、ContentProvider 的 Demo
MyUser.java
代码 package com.webabcd.contentprovider;

import android.net.Uri;
import android.provider.BaseColumns;

// 自定义ContentProvider所需的实体类
public class MyUser{

// 必须要有_id字段。本例中BaseColumn类中已经包含了_id字段
public static final class User implements BaseColumns{

// 定义CONTENT_URI
public static final UriCONTENT_URI = Uri.parse( " content://com.webabcd.MyContentProvider " );

// 表数据列
public static final StringUSER_NAME = " USER_NAME " ;
}
}

MyContentProvider.java
代码 package com.webabcd.contentprovider;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

import org.apache.http.util.EncodingUtils;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.net.Uri;

// 继承ContentProvider以实现自定义的ContentProvider（基于文件的信息存储）
public class MyContentProvider extends ContentProvider{

private Filefile;
private FileOutputStreamout;
private FileInputStreamin;

// ContentProvider的删除数据接口
@Override
public int delete(Uriuri,Stringselection,String[]selectionArgs){
// TODOAuto-generatedmethodstub
return 0 ;
}

@Override
public StringgetType(Uriuri){
// TODOAuto-generatedmethodstub
return null ;
}

// ContentProvider的插入数据接口
@Override
public Uriinsert(Uriuri,ContentValuesvalues){

try {
out = new FileOutputStream(file);
out.write(values.getAsString(MyUser.User.USER_NAME).getBytes());
out.close();

int rowId = 0 ;
UrirowUri = ContentUris.appendId(
MyUser.User.CONTENT_URI.buildUpon(),rowId).build();
getContext().getContentResolver().notifyChange(rowUri, null );

return rowUri;
} catch (Exceptione){
return null ;
}
}

// 创建用于保存信息的文件
@Override
public boolean onCreate(){
try {
// 每个包中应用程序的私有目录为：/data/data/包名/
// SD卡目录为：/sdcard
file = new File( " /data/data/com.webabcd.contentprovider/ " ,
" demo.txt " );
if ( ! file.exists())
file.createNewFile();

return true ;
} catch (Exceptionex){
return false ;
}
}

// ContentProvider的查询数据接口
@Override
public Cursorquery(Uriuri,String[]projection,Stringselection,
String[]selectionArgs,StringsortOrder){

Stringcontent;

try {
in = new FileInputStream(file);
int length = ( int )file.length();
byte []buffer = new byte [length];
in.read(buffer, 0 ,length);
content = EncodingUtils.getString(buffer, " UTF-8 " );
in.close();

String[]columns = new String[]{MyUser.User._ID,MyUser.User.USER_NAME};
MatrixCursorcur = new MatrixCursor(columns);
String[]values = new String[]{ " 0 " ,content};
cur.moveToFirst();
cur.addRow(values);

return cur;
} catch (Exceptione){
return null ;
}
}

// ContentProvider的更新数据接口
@Override
public int update(Uriuri,ContentValuesvalues,Stringselection,
String[]selectionArgs){
// TODOAuto-generatedmethodstub
return 0 ;
}
}

Main.java
代码 package com.webabcd.contentprovider;

import java.util.Random;

import android.app.Activity;
import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.Contacts;
import android.provider.Contacts.People;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

/*
*几个常用的系统内置的ContentProvider如下：
*content://media/internal/images这个URI将返回设备上存储的所有图片
*content://contacts/people/这个URI将返回设备上的所有联系人信息
*content://contacts/people/45这个URI返回单个结果（联系人信息中ID为45的联系人记录）
*/
public class Main extends Activity{
/** Calledwhentheactivityisfirstcreated. */
@Override
public void onCreate(BundlesavedInstanceState){
super .onCreate(savedInstanceState);
setContentView(R.layout.main);

Buttonbtn1 = (Button) this .findViewById(R.id.btn1);
btn1.setText( " 新增联系人记录 " );
btn1.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
Randomrandom = new Random();
insertRecords( " name " + String.valueOf(random.nextInt()),String
.valueOf(random.nextInt()));
}
});

Buttonbtn2 = (Button) this .findViewById(R.id.btn2);
btn2.setText( " 查看联系人记录 " );
btn2.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
displayRecords();
}
});

Buttonbtn3 = (Button) this .findViewById(R.id.btn3);
btn3.setText( " 清除联系人记录 " );
btn3.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
deleteRecords();
}
});

Buttonbtn4 = (Button) this .findViewById(R.id.btn4);
btn4.setText( " 更新联系人记录 " );
btn4.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
// 此处只是演示，id来自People._ID，可参见displayRecords()是如何获取id的
int id = 0 ;
updateRecord(id, " 修改后的name " );
}
});

Buttonbtn5 = (Button) this .findViewById(R.id.btn5);
btn5.setText( " 新增记录到MyContentProvider " );
btn5.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
insertRecord2MyContentProvider( " webabcd " );
}
});

Buttonbtn6 = (Button) this .findViewById(R.id.btn6);
btn6.setText( " 获取记录从MyContentProvider " );
btn6.setOnClickListener( new Button.OnClickListener(){
public void onClick(Viewv){
displayRecord2MyContentProvider();
}
});
}

// 调用ContentProvider的插入接口
private void insertRecords(Stringname,StringphoneNum){
ContentValuesvalues = new ContentValues();
values.put(People.NAME,name);
Uriuri = getContentResolver().insert(People.CONTENT_URI,values);
Log.d( " MyDebug " ,uri.toString());
UrinumberUri = Uri.withAppendedPath(uri,
People.Phones.CONTENT_DIRECTORY);
Log.d( " MyDebug " ,numberUri.toString());

values.clear();
values.put(Contacts.Phones.TYPE,People.Phones.TYPE_MOBILE);
values.put(People.NUMBER,phoneNum);
getContentResolver().insert(numberUri,values);
}

// 调用ContentProvider的查询接口
private void displayRecords(){
String[]columns = new String[]{People._ID,People.NAME,
People.NUMBER};
Uricontacts = People.CONTENT_URI;
Log.d( " MyDebug " ,contacts.toString());
Cursorcur = managedQuery(contacts,columns, // 要返回的数据字段
null , // WHERE子句
null , // WHERE子句的参数
null // Order-by子句
);

if (cur.moveToFirst()){
Stringid = null ;
Stringname = null ;
StringphoneNo = null ;
while (cur.getPosition() != cur.getCount()){
id = cur.getString(cur.getColumnIndex(People._ID));
name = cur.getString(cur.getColumnIndex(People.NAME));
phoneNo = cur.getString(cur.getColumnIndex(People.NUMBER));

Toast.makeText( this ,id + " / " + name + " / " + phoneNo,
Toast.LENGTH_SHORT).show();
cur.moveToNext();
}
}
}

// 调用ContentProvider的删除接口
private void deleteRecords(){
Uriuri = People.CONTENT_URI;
Log.d( " MyDebug " ,uri.toString());
getContentResolver().delete(uri, null , null );
// getContentResolver().delete(uri,"NAME="+"'name'",null);
}

// 调用ContentProvider的更新接口
private void updateRecord( int recordNo,Stringname){
Uriuri = ContentUris.withAppendedId(People.CONTENT_URI,recordNo);
Log.d( " MyDebug " ,uri.toString());
ContentValuesvalues = new ContentValues();
values.put(People.NAME,name);
getContentResolver().update(uri,values, null , null );
}

// 调用自定义ContentProvider的插入接口
private void insertRecord2MyContentProvider(Stringname){
ContentValuesvalues = new ContentValues();
values.put(MyUser.User.USER_NAME,name);
getContentResolver().insert(MyUser.User.CONTENT_URI,values);

}

// 调用自定义ContentProvider的查询接口
private void displayRecord2MyContentProvider(){
String[]columns = new String[]{MyUser.User.USER_NAME};
Uriuri = MyUser.User.CONTENT_URI;
Cursorcur = managedQuery(uri,columns, null , null , null );

while (cur.getPosition() != cur.getCount()){
Stringid = cur.getString(cur.getColumnIndex(People._ID));
Stringname = cur.getString(cur.getColumnIndex(MyUser.User.USER_NAME));
Toast.makeText( this ,
id + " / " + name,
Toast.LENGTH_SHORT).show();
cur.moveToNext();
}
}
}
AndroidManifest.xml
代码 <? xmlversion="1.0"encoding="utf-8" ?>
< manifest xmlns:android ="http://schemas.android.com/apk/res/android"
package ="com.webabcd.contentprovider"
android:versionCode ="1"
android:versionName ="1.0" >
< application android:icon ="@drawable/icon" android:label ="@string/app_name" >
< activity android:name =".Main"
android:label ="@string/app_name" >
< intent-filter >
< action android:name ="android.intent.action.MAIN" />
< category android:name ="android.intent.category.LAUNCHER" />
</ intent-filter >
</ activity >


< provider android:name ="MyContentProvider" android:authorities ="com.webabcd.MyContentProvider" />
</ application >
< uses-permission android:name ="android.permission.WRITE_CONTACTS" ></ uses-permission >
< uses-permission android:name ="android.permission.READ_CONTACTS" ></ uses-permission >
< uses-sdk android:minSdkVersion ="3" />
</ manifest >

OK
[源码下载]

系出名门Android(9) - 数据库支持(SQLite), 内容提供器(ContentProvider)

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