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

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;

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(Context context, String name, CursorFactory cursorFactory, int version) {

super(context, name, cursorFactory, version);

}

@Override

public void onCreate(SQLiteDatabase db) {

// TODO 创建数据库后，对数据库的操作

public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

// TODO 更改数据库版本的操作

public void onOpen(SQLiteDatabase db) {

super.onOpen(db);

// TODO 每次成功打开数据库后首先被执行

}

Main.java

import java.util.Random;

import android.app.Activity;

import android.content.ContentValues;

import android.database.Cursor;

import android.database.SQLException;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.TextView;

public class Main extends Activity {

private DatabaseHelper dbHelper;

private static final String DATABASE_NAME = "db.db";

private static final int DATABASE_VERSION = 1;

private static final String TABLE_NAME = "employee";

TextView txtMsg;

/** Called when the activity is first created. */

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

dbHelper = new DatabaseHelper(this, DATABASE_NAME, null,

DATABASE_VERSION);

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

Button btn1 = (Button) this.findViewById(R.id.btn1);

btn1.setText("创建表");

btn1.setOnClickListener(new Button.OnClickListener() {

public void onClick(View v) {

CreateTable();

}

});

Button btn2 = (Button) this.findViewById(R.id.btn2);

btn2.setText("插入 3 条记录");

btn2.setOnClickListener(new Button.OnClickListener() {

insertItem();

Button btn3 = (Button) this.findViewById(R.id.btn3);

btn3.setText("删除全部记录");

btn3.setOnClickListener(new Button.OnClickListener() {

deleteItem();

Button btn4 = (Button) this.findViewById(R.id.btn4);

btn4.setText("更新指定数据");

btn4.setOnClickListener(new Button.OnClickListener() {

updateItem();

Button btn5 = (Button) this.findViewById(R.id.btn5);

btn5.setText("显示全部数据");

btn5.setOnClickListener(new Button.OnClickListener() {

showItems();

Button btn6 = (Button) this.findViewById(R.id.btn6);

btn6.setText("删除表");

btn6.setOnClickListener(new Button.OnClickListener() {

dropTable();

// 创建数据表

private void CreateTable() {

SQLiteDatabase db = dbHelper.getWritableDatabase();

String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME

+ " (ID INTEGER PRIMARY KEY, Name VARCHAR, Age INTEGER);";

try {

db.execSQL(sql);

txtMsg.append("数据表成功创建\n");

} catch (SQLException ex) {

txtMsg.append("数据表创建错误\n" + ex.toString() + "\n");

}

// 插入数据

private void insertItem() {

Random random = new Random();

for (int i = 0; i < 3; i++) {

String sql = "insert into " + 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");

txtMsg.append("插入数据失败\n" + ex.toString() + "\n");

// 删除数据

private void deleteItem() {

SQLiteDatabase db = dbHelper.getWritableDatabase();

db.delete(TABLE_NAME, " id < 999999", null);

txtMsg.append("成功删除数据\n");

} catch (SQLException e) {

txtMsg.append("删除数据失败\n");

// 更新数据

private void updateItem() {

ContentValues values = 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");

txtMsg.append("更新数据失败\n");

// 查询数据

private void showItems() {

SQLiteDatabase db = dbHelper.getReadableDatabase();

String[] column = { "id", "name", "age" };

Cursor cursor = db.query(TABLE_NAME, column, null, null, null,

null, null);

Integer num = 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();

txtMsg.append("读取数据失败\n" + ex.toString() + "\n");

// 删除数据表

private void dropTable() {

String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;

txtMsg.append("数据表删除成功\n");

txtMsg.append("数据表删除错误\n" + ex.toString() + "\n");

2、ContentProvider 的 Demo

MyUser.java

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 Uri CONTENT_URI = Uri.parse("content://com.webabcd.MyContentProvider");

// 表数据列

public static final String USER_NAME = "USER_NAME";

MyContentProvider.java

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.database.MatrixCursor;

// 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 File file;

private FileOutputStream out;

private FileInputStream in;

// ContentProvider 的删除数据接口

public int delete(Uri uri, String selection, String[] selectionArgs) {

// TODO Auto-generated method stub

return 0;

public String getType(Uri uri) {

return null;

// ContentProvider 的插入数据接口

public Uri insert(Uri uri, ContentValues values) {

out = new FileOutputStream(file);

out.write(values.getAsString(MyUser.User.USER_NAME).getBytes());

out.close();

int rowId = 0;

Uri rowUri = ContentUris.appendId(

MyUser.User.CONTENT_URI.buildUpon(), rowId).build();

getContext().getContentResolver().notifyChange(rowUri, null);

return rowUri;

} catch (Exception e) {

return null;

// 创建用于保存信息的文件

public boolean onCreate() {

// 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 (Exception ex) {

return false;

// ContentProvider 的查询数据接口

public Cursor query(Uri uri, String[] projection, String selection,

String[] selectionArgs, String sortOrder) {

String content;

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 };

MatrixCursor cur = new MatrixCursor(columns);

String[] values = new String[] { "0", content };

cur.moveToFirst();

cur.addRow(values);

return cur;

// ContentProvider 的更新数据接口

public int update(Uri uri, ContentValues values, String selection,

String[] selectionArgs) {

import android.provider.Contacts;

import android.provider.Contacts.People;

import android.util.Log;

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）

btn1.setText("新增联系人记录");

Random random = new Random();

insertRecords("name" + String.valueOf(random.nextInt()), String

.valueOf(random.nextInt()));

btn2.setText("查看联系人记录");

displayRecords();

btn3.setText("清除联系人记录");

deleteRecords();

btn4.setText("更新联系人记录");

// 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");

btn5.setText("新增记录到 MyContentProvider");

insertRecord2MyContentProvider("webabcd");

btn6.setText("获取记录从 MyContentProvider");

displayRecord2MyContentProvider();

// 调用 ContentProvider 的插入接口

private void insertRecords(String name, String phoneNum) {

ContentValues values = new ContentValues();

values.put(People.NAME, name);

Uri uri = getContentResolver().insert(People.CONTENT_URI, values);

Log.d("MyDebug", uri.toString());

Uri numberUri = 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 };

Uri contacts = People.CONTENT_URI;

Log.d("MyDebug", contacts.toString());

Cursor cur = 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()) {

String id = null;

String name = null;

String phoneNo = 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() {

Uri uri = People.CONTENT_URI;

getContentResolver().delete(uri, null, null);

// getContentResolver().delete(uri, "NAME=" + "'name'", null);

// 调用 ContentProvider 的更新接口

private void updateRecord(int recordNo, String name) {

Uri uri = ContentUris.withAppendedId(People.CONTENT_URI, recordNo);

getContentResolver().update(uri, values, null, null);

// 调用自定义 ContentProvider 的插入接口

private void insertRecord2MyContentProvider(String name) {

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 };

Uri uri = MyUser.User.CONTENT_URI;

Cursor cur = managedQuery(uri, columns, null, null, null);

while (cur.getPosition() != cur.getCount()) {

String id = cur.getString(cur.getColumnIndex(People._ID));

String name = cur.getString(cur.getColumnIndex(MyUser.User.USER_NAME));

Toast.makeText(this,

id + " / " + name,

Toast.LENGTH_SHORT).show();

cur.moveToNext();

AndroidManifest.xml

<?xml version="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">

<activity android:name=".Main"

android:label="@string/app_name">

<intent-filter>

</intent-filter>

</activity>

<!--

配置一个自定义的 ContentProvider"

-->

</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>

本文转自webabcd 51CTO博客，原文链接：http://blog.51cto.com/webabcd/342098，如需转载请自行联系原作者

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

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