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

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 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. */
@Override
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() {
public void onClick(View v) {
insertItem();
}
});
Button btn3=(Button) this.findViewById(R.id.btn3);
btn3.setText("删除全部记录");
btn3.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
deleteItem();
}
});
Button btn4=(Button) this.findViewById(R.id.btn4);
btn4.setText("更新指定数据");
btn4.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
updateItem();
}
});
Button btn5=(Button) this.findViewById(R.id.btn5);
btn5.setText("显示全部数据");
btn5.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
showItems();
}
});
Button btn6=(Button) this.findViewById(R.id.btn6);
btn6.setText("删除表");
btn6.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
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() {
SQLiteDatabase db=dbHelper.getWritableDatabase();

try {
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");
} catch (SQLException ex) {
txtMsg.append("插入数据失败/n" + ex.toString() + "/n");
}
}
// 删除数据
private void deleteItem() {
try {
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() {
SQLiteDatabase db=dbHelper.getWritableDatabase();
try {
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");
} catch (SQLException e) {
txtMsg.append("更新数据失败/n");
}
}
// 查询数据
private void showItems() {
SQLiteDatabase db=dbHelper.getReadableDatabase();
try {
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();
}
} catch (SQLException ex) {
txtMsg.append("读取数据失败/n" + ex.toString() + "/n");
}
}
// 删除数据表
private void dropTable() {
SQLiteDatabase db=dbHelper.getWritableDatabase();
String sql="DROP TABLE IF EXISTS " + TABLE_NAME;
try {
db.execSQL(sql);
txtMsg.append("数据表删除成功/n");
} catch (SQLException ex) {
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

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 File file;
private FileOutputStream out;
private FileInputStream in;
// ContentProvider 的删除数据接口
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}
// ContentProvider 的插入数据接口
@Override
public Uri insert(Uri uri, ContentValues values) {
try {
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
@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 (Exception ex) {
return false;
}
}
// ContentProvider 的查询数据接口
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {

String content;
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 };
MatrixCursor cur=new MatrixCursor(columns);
String[] values=new String[] { "0", content };
cur.moveToFirst();
cur.addRow(values);
return cur;
} catch (Exception e) {
return null;
}
}
// ContentProvider 的更新数据接口
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
}

Main.java

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 {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btn1=(Button) this.findViewById(R.id.btn1);
btn1.setText("新增联系人记录");
btn1.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
Random random=new Random();
insertRecords("name" + String.valueOf(random.nextInt()), String
.valueOf(random.nextInt()));
}
});
Button btn2=(Button) this.findViewById(R.id.btn2);
btn2.setText("查看联系人记录");
btn2.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
displayRecords();
}
});
Button btn3=(Button) this.findViewById(R.id.btn3);
btn3.setText("清除联系人记录");
btn3.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
deleteRecords();
}
});
Button btn4=(Button) this.findViewById(R.id.btn4);
btn4.setText("更新联系人记录");
btn4.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
// 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");
}
});
Button btn5=(Button) this.findViewById(R.id.btn5);
btn5.setText("新增记录到 MyContentProvider");
btn5.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
insertRecord2MyContentProvider("webabcd");
}
});
Button btn6=(Button) this.findViewById(R.id.btn6);
btn6.setText("获取记录从 MyContentProvider");
btn6.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
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;
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, String name) {
Uri uri=ContentUris.withAppendedId(People.CONTENT_URI, recordNo);
Log.d("MyDebug", uri.toString());
ContentValues values=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(String name) {
ContentValues values=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 };
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">
<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>

<!--
配置一个自定义的 ContentProvider"
-->
<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>