学步园

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

package com.webabcd.SQLite;<br /> import android.content.Context;<br /> import android.database.sqlite.SQLiteDatabase;<br /> import android.database.sqlite.SQLiteOpenHelper;<br /> import android.database.sqlite.SQLiteDatabase.CursorFactory;<br /> // 数据库操作的 Helper 类<br /> public class DatabaseHelper extends SQLiteOpenHelper {<br /> DatabaseHelper(Context context, String name, CursorFactory cursorFactory, int version) {<br /> super(context, name, cursorFactory, version);<br /> }<br /> @Override<br /> public void onCreate(SQLiteDatabase db) {<br /> // TODO 创建数据库后，对数据库的操作<br /> }<br /> @Override<br /> public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {<br /> // TODO 更改数据库版本的操作<br /> }<br /> @Override<br /> public void onOpen(SQLiteDatabase db) {<br /> super.onOpen(db);</p> <p> // TODO 每次成功打开数据库后首先被执行<br /> }<br /> }

Main.java

package com.webabcd.SQLite;<br /> import java.util.Random;<br /> import android.app.Activity;<br /> import android.content.ContentValues;<br /> import android.database.Cursor;<br /> import android.database.SQLException;<br /> import android.database.sqlite.SQLiteDatabase;<br /> import android.os.Bundle;<br /> import android.view.View;<br /> import android.widget.Button;<br /> import android.widget.TextView;<br /> public class Main extends Activity {<br /> private DatabaseHelper dbHelper;<br /> private static final String DATABASE_NAME="db.db";<br /> private static final int DATABASE_VERSION=1;<br /> private static final String TABLE_NAME="employee";<br /> TextView txtMsg;<br /> /** Called when the activity is first created. */<br /> @Override<br /> public void onCreate(Bundle savedInstanceState) {<br /> super.onCreate(savedInstanceState);<br /> setContentView(R.layout.main);<br /> dbHelper=new DatabaseHelper(this, DATABASE_NAME, null,<br /> DATABASE_VERSION);<br /> txtMsg=(TextView) this.findViewById(R.id.txtMsg);<br /> Button btn1=(Button) this.findViewById(R.id.btn1);<br /> btn1.setText("创建表");<br /> btn1.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> CreateTable();<br /> }<br /> });<br /> Button btn2=(Button) this.findViewById(R.id.btn2);<br /> btn2.setText("插入 3 条记录");<br /> btn2.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> insertItem();<br /> }<br /> });<br /> Button btn3=(Button) this.findViewById(R.id.btn3);<br /> btn3.setText("删除全部记录");<br /> btn3.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> deleteItem();<br /> }<br /> });<br /> Button btn4=(Button) this.findViewById(R.id.btn4);<br /> btn4.setText("更新指定数据");<br /> btn4.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> updateItem();<br /> }<br /> });<br /> Button btn5=(Button) this.findViewById(R.id.btn5);<br /> btn5.setText("显示全部数据");<br /> btn5.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> showItems();<br /> }<br /> });<br /> Button btn6=(Button) this.findViewById(R.id.btn6);<br /> btn6.setText("删除表");<br /> btn6.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> dropTable();<br /> }<br /> });<br /> }<br /> // 创建数据表<br /> private void CreateTable() {<br /> SQLiteDatabase db=dbHelper.getWritableDatabase();<br /> String sql="CREATE TABLE IF NOT EXISTS " + TABLE_NAME<br /> + " (ID INTEGER PRIMARY KEY, Name VARCHAR, Age INTEGER);";<br /> try {<br /> db.execSQL(sql);<br /> txtMsg.append("数据表成功创建/n");<br /> } catch (SQLException ex) {<br /> txtMsg.append("数据表创建错误/n" + ex.toString() + "/n");<br /> }<br /> }<br /> // 插入数据<br /> private void insertItem() {<br /> SQLiteDatabase db=dbHelper.getWritableDatabase();</p> <p> try {<br /> Random random=new Random();<br /> for (int i=0; i < 3; i++) {<br /> String sql="insert into " + TABLE_NAME<br /> + " (name, age) values ('name" + String.valueOf(i)<br /> + "', " + random.nextInt() + ")";<br /> // execSQL() - 执行指定的 sql<br /> db.execSQL(sql);<br /> }<br /> txtMsg.append("成功插入 3 条数据/n");<br /> } catch (SQLException ex) {<br /> txtMsg.append("插入数据失败/n" + ex.toString() + "/n");<br /> }<br /> }<br /> // 删除数据<br /> private void deleteItem() {<br /> try {<br /> SQLiteDatabase db=dbHelper.getWritableDatabase();<br /> db.delete(TABLE_NAME, " id < 999999", null);<br /> txtMsg.append("成功删除数据/n");<br /> } catch (SQLException e) {<br /> txtMsg.append("删除数据失败/n");<br /> }<br /> }<br /> // 更新数据<br /> private void updateItem() {<br /> SQLiteDatabase db=dbHelper.getWritableDatabase();<br /> try {<br /> ContentValues values=new ContentValues();<br /> values.put("name", "批量更新后的名字");<br /> db.update(TABLE_NAME, values, "id<?", new String[] { "3" });<br /> txtMsg.append("成功更新数据/n");<br /> } catch (SQLException e) {<br /> txtMsg.append("更新数据失败/n");<br /> }<br /> }<br /> // 查询数据<br /> private void showItems() {<br /> SQLiteDatabase db=dbHelper.getReadableDatabase();<br /> try {<br /> String[] column={ "id", "name", "age" };<br /> Cursor cursor=db.query(TABLE_NAME, column, null, null, null,<br /> null, null);<br /> Integer num=cursor.getCount();<br /> txtMsg.append("共 " + Integer.toString(num) + " 条记录/n");<br /> cursor.moveToFirst();<br /> while (cursor.getPosition() != cursor.getCount()) {<br /> txtMsg.append(Integer.toString(cursor.getPosition()) + ","<br /> + String.valueOf(cursor.getString(0)) + ","<br /> + cursor.getString(1) + ","<br /> + String.valueOf(cursor.getString(2)) + "/n");<br /> cursor.moveToNext();<br /> }<br /> } catch (SQLException ex) {<br /> txtMsg.append("读取数据失败/n" + ex.toString() + "/n");<br /> }<br /> }<br /> // 删除数据表<br /> private void dropTable() {<br /> SQLiteDatabase db=dbHelper.getWritableDatabase();<br /> String sql="DROP TABLE IF EXISTS " + TABLE_NAME;<br /> try {<br /> db.execSQL(sql);<br /> txtMsg.append("数据表删除成功/n");<br /> } catch (SQLException ex) {<br /> txtMsg.append("数据表删除错误/n" + ex.toString() + "/n");<br /> }<br /> }<br /> }

2、ContentProvider 的 Demo

MyUser.java

package com.webabcd.contentprovider;<br /> import android.net.Uri;<br /> import android.provider.BaseColumns;<br /> // 自定义 ContentProvider 所需的实体类<br /> public class MyUser {<br /> // 必须要有 _id 字段。本例中 BaseColumn 类中已经包含了 _id 字段<br /> public static final class User implements BaseColumns {</p> <p> // 定义 CONTENT_URI<br /> public static final Uri CONTENT_URI=Uri.parse("content://com.webabcd.MyContentProvider");<br /> // 表数据列<br /> public static final String USER_NAME="USER_NAME";<br /> }<br /> }

MyContentProvider.java

package com.webabcd.contentprovider;<br /> import java.io.File;<br /> import java.io.FileInputStream;<br /> import java.io.FileOutputStream;<br /> import org.apache.http.util.EncodingUtils;<br /> import android.content.ContentProvider;<br /> import android.content.ContentUris;<br /> import android.content.ContentValues;<br /> import android.database.Cursor;<br /> import android.database.MatrixCursor;<br /> import android.net.Uri;<br /> // 继承 ContentProvider 以实现自定义的 ContentProvider（基于文件的信息存储）<br /> public class MyContentProvider extends ContentProvider {<br /> private File file;<br /> private FileOutputStream out;<br /> private FileInputStream in;<br /> // ContentProvider 的删除数据接口<br /> @Override<br /> public int delete(Uri uri, String selection, String[] selectionArgs) {<br /> // TODO Auto-generated method stub<br /> return 0;<br /> }<br /> @Override<br /> public String getType(Uri uri) {<br /> // TODO Auto-generated method stub<br /> return null;<br /> }<br /> // ContentProvider 的插入数据接口<br /> @Override<br /> public Uri insert(Uri uri, ContentValues values) {<br /> try {<br /> out=new FileOutputStream(file);<br /> out.write(values.getAsString(MyUser.User.USER_NAME).getBytes());<br /> out.close();<br /> int rowId=0;<br /> Uri rowUri=ContentUris.appendId(<br /> MyUser.User.CONTENT_URI.buildUpon(), rowId).build();<br /> getContext().getContentResolver().notifyChange(rowUri, null);<br /> return rowUri;<br /> } catch (Exception e) {<br /> return null;<br /> }<br /> }<br /> // 创建用于保存信息的文件<br /> @Override<br /> public boolean onCreate() {<br /> try {<br /> // 每个包中应用程序的私有目录为：/data/data/包名/<br /> // SD 卡目录为：/sdcard<br /> file=new File("/data/data/com.webabcd.contentprovider/",<br /> "demo.txt");<br /> if (!file.exists())<br /> file.createNewFile();<br /> return true;<br /> } catch (Exception ex) {<br /> return false;<br /> }<br /> }<br /> // ContentProvider 的查询数据接口<br /> @Override<br /> public Cursor query(Uri uri, String[] projection, String selection,<br /> String[] selectionArgs, String sortOrder) {</p> <p> String content;<br /> try {<br /> in=new FileInputStream(file);<br /> int length=(int) file.length();<br /> byte[] buffer=new byte[length];<br /> in.read(buffer, 0, length);<br /> content=EncodingUtils.getString(buffer, "UTF-8");<br /> in.close();<br /> String[] columns=new String[] { MyUser.User._ID, MyUser.User.USER_NAME };<br /> MatrixCursor cur=new MatrixCursor(columns);<br /> String[] values=new String[] { "0", content };<br /> cur.moveToFirst();<br /> cur.addRow(values);<br /> return cur;<br /> } catch (Exception e) {<br /> return null;<br /> }<br /> }<br /> // ContentProvider 的更新数据接口<br /> @Override<br /> public int update(Uri uri, ContentValues values, String selection,<br /> String[] selectionArgs) {<br /> // TODO Auto-generated method stub<br /> return 0;<br /> }<br /> }

Main.java

package com.webabcd.contentprovider;<br /> import java.util.Random;<br /> import android.app.Activity;<br /> import android.content.ContentUris;<br /> import android.content.ContentValues;<br /> import android.database.Cursor;<br /> import android.net.Uri;<br /> import android.os.Bundle;<br /> import android.provider.Contacts;<br /> import android.provider.Contacts.People;<br /> import android.util.Log;<br /> import android.view.View;<br /> import android.widget.Button;<br /> import android.widget.Toast;<br /> /*<br /> * 几个常用的系统内置的 ContentProvider 如下：<br /> * content://media/internal/images 这个URI将返回设备上存储的所有图片<br /> * content://contacts/people/ 这个URI将返回设备上的所有联系人信息<br /> * 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）<br /> */<br /> public class Main extends Activity {<br /> /** Called when the activity is first created. */<br /> @Override<br /> public void onCreate(Bundle savedInstanceState) {<br /> super.onCreate(savedInstanceState);<br /> setContentView(R.layout.main);<br /> Button btn1=(Button) this.findViewById(R.id.btn1);<br /> btn1.setText("新增联系人记录");<br /> btn1.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> Random random=new Random();<br /> insertRecords("name" + String.valueOf(random.nextInt()), String<br /> .valueOf(random.nextInt()));<br /> }<br /> });<br /> Button btn2=(Button) this.findViewById(R.id.btn2);<br /> btn2.setText("查看联系人记录");<br /> btn2.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> displayRecords();<br /> }<br /> });<br /> Button btn3=(Button) this.findViewById(R.id.btn3);<br /> btn3.setText("清除联系人记录");<br /> btn3.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> deleteRecords();<br /> }<br /> });<br /> Button btn4=(Button) this.findViewById(R.id.btn4);<br /> btn4.setText("更新联系人记录");<br /> btn4.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> // 此处只是演示，id 来自 People._ID ，可参见 displayRecords() 是如何获取 id 的<br /> int id=0;<br /> updateRecord(id, "修改后的name");<br /> }<br /> });<br /> Button btn5=(Button) this.findViewById(R.id.btn5);<br /> btn5.setText("新增记录到 MyContentProvider");<br /> btn5.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> insertRecord2MyContentProvider("webabcd");<br /> }<br /> });<br /> Button btn6=(Button) this.findViewById(R.id.btn6);<br /> btn6.setText("获取记录从 MyContentProvider");<br /> btn6.setOnClickListener(new Button.OnClickListener() {<br /> public void onClick(View v) {<br /> displayRecord2MyContentProvider();<br /> }<br /> });<br /> }<br /> // 调用 ContentProvider 的插入接口<br /> private void insertRecords(String name, String phoneNum) {<br /> ContentValues values=new ContentValues();<br /> values.put(People.NAME, name);<br /> Uri uri=getContentResolver().insert(People.CONTENT_URI, values);<br /> Log.d("MyDebug", uri.toString());<br /> Uri numberUri=Uri.withAppendedPath(uri,<br /> People.Phones.CONTENT_DIRECTORY);<br /> Log.d("MyDebug", numberUri.toString());<br /> values.clear();<br /> values.put(Contacts.Phones.TYPE, People.Phones.TYPE_MOBILE);<br /> values.put(People.NUMBER, phoneNum);<br /> getContentResolver().insert(numberUri, values);<br /> }<br /> // 调用 ContentProvider 的查询接口<br /> private void displayRecords() {<br /> String[] columns=new String[] { People._ID, People.NAME,<br /> People.NUMBER };<br /> Uri contacts=People.CONTENT_URI;<br /> Log.d("MyDebug", contacts.toString());<br /> Cursor cur=managedQuery(contacts, columns, // 要返回的数据字段<br /> null, // WHERE子句<br /> null, // WHERE 子句的参数<br /> null // Order-by子句<br /> );<br /> if (cur.moveToFirst()) {<br /> String id=null;<br /> String name=null;<br /> String phoneNo=null;<br /> while (cur.getPosition() != cur.getCount()) {<br /> id=cur.getString(cur.getColumnIndex(People._ID));<br /> name=cur.getString(cur.getColumnIndex(People.NAME));<br /> phoneNo=cur.getString(cur.getColumnIndex(People.NUMBER));<br /> Toast.makeText(this, id + " / " + name + " / " + phoneNo,<br /> Toast.LENGTH_SHORT).show();<br /> cur.moveToNext();<br /> }<br /> }<br /> }<br /> // 调用 ContentProvider 的删除接口<br /> private void deleteRecords() {<br /> Uri uri=People.CONTENT_URI;<br /> Log.d("MyDebug", uri.toString());<br /> getContentResolver().delete(uri, null, null);<br /> // getContentResolver().delete(uri, "NAME=" + "'name'", null);<br /> }<br /> // 调用 ContentProvider 的更新接口<br /> private void updateRecord(int recordNo, String name) {<br /> Uri uri=ContentUris.withAppendedId(People.CONTENT_URI, recordNo);<br /> Log.d("MyDebug", uri.toString());<br /> ContentValues values=new ContentValues();<br /> values.put(People.NAME, name);<br /> getContentResolver().update(uri, values, null, null);<br /> }</p> <p> // 调用自定义 ContentProvider 的插入接口<br /> private void insertRecord2MyContentProvider(String name) {<br /> ContentValues values=new ContentValues();<br /> values.put(MyUser.User.USER_NAME, name);<br /> getContentResolver().insert(MyUser.User.CONTENT_URI, values);<br /> }<br /> // 调用自定义 ContentProvider 的查询接口<br /> private void displayRecord2MyContentProvider() {<br /> String[] columns=new String[] { MyUser.User.USER_NAME };<br /> Uri uri=MyUser.User.CONTENT_URI;<br /> Cursor cur=managedQuery(uri, columns, null, null, null);<br /> while (cur.getPosition() != cur.getCount()) {<br /> String id=cur.getString(cur.getColumnIndex(People._ID));<br /> String name=cur.getString(cur.getColumnIndex(MyUser.User.USER_NAME));<br /> Toast.makeText(this,<br /> id + " / " + name,<br /> Toast.LENGTH_SHORT).show();<br /> cur.moveToNext();<br /> }<br /> }<br /> }

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?><br /> <manifest xmlns:android="http://schemas.android.com/apk/res/android"<br /> package="com.webabcd.contentprovider"<br /> android:versionCode="1"<br /> android:versionName="1.0"><br /> <application android:icon="@drawable/icon" android:label="@string/app_name"><br /> <activity android:name=".Main"<br /> android:label="@string/app_name"><br /> <intent-filter><br /> <action android:name="android.intent.action.MAIN" /><br /> <category android:name="android.intent.category.LAUNCHER" /><br /> </intent-filter><br /> </activity></p> <p> <!--<br /> 配置一个自定义的 ContentProvider"<br /> --><br /> <provider android:name="MyContentProvider" android:authorities="com.webabcd.MyContentProvider" /><br /> </application><br /> <uses-permission android:name="android.permission.WRITE_CONTACTS"></uses-permission><br /> <uses-permission android:name="android.permission.READ_CONTACTS"></uses-permission><br /> <uses-sdk android:minSdkVersion="3" /><br /> </manifest>