本文详细介绍了Android中ContentProvider的实现方式及使用方法。包括如何创建一个ContentProvider类，重写基本方法，以及如何在AndroidManifest.xml中配置。同时，还提供了具体的代码示例，展示了如何在另一个应用程序中对ContentProvider进行增删改查操作。
当应用继承ContentProvider类，并重写该类用于提供数据和存储数据的方法，就可以向其他应用共享其数据。以前我们学习过文件的操作模式，通过指定文件的操作模式为Context.MODE_WORLD_READABLE 或Context.MODE_WORLD_WRITEABLE同样可以对外共享数据，但数据的访问方式会因数据存储的方式而不同，如：采用xml文件对外共享数据，需要进行xml解析来读写数据；采用sharedpreferences共享数据，需要使用sharedpreferences API读写数据。而使用ContentProvider共享数据的好处是统一了数据访问方式。
1.第一步需要继承ContentProvider并重写下面方法：
public class PersonContentProvider extends ContentProvider{
public boolean onCreate()
public Uri insert(Uri uri, ContentValues values)
public int delete(Uri uri, String selection, String[] selectionArgs)
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs)
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
public String getType(Uri uri)}
2. 第二步需要在AndroidManifest.xml使用<provider>对该ContentProvider进行配置，为了能让其他应用找到该ContentProvider ， ContentProvider 采用了authorities（主机名/域名）对它进行唯一标识，你可以把 ContentProvider看作是一个网站（想想，网站也是提供数据者），authorities 就是他的域名：
<manifest .... >
<application android:icon="@drawable/icon" android:label="@string/app_name">
<provider android:name=".UserProvider" android:authorities="com.example.providerdemo.userProvider"/>
</application>
</manifest>
注意：一旦应用继承了ContentProvider类，后面我们就会把这个应用称为ContentProvider（内容提供者）。
ProviderDemo 拥有DB， 提供Provider，供外围进行增删改查。 （这里可以类比通讯录）
OneApp对他进行 操作
provider定义：
/**
*
*/
package com.example.providerdemo;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
/**
*
* @author baoxing.gbx
* @version $Id: UserProvider.java, v 0.1 2015年8月21日 上午10:25:48 baoxing.gbx Exp $
*/
public class UserProvider extends ContentProvider{
private DBopenHelper dbOpenHelper;
private static final UriMatcher MATCHER = new UriMatcher(UriMatcher.NO_MATCH);
private static final int UserOne = 1;
private static final int UserList = 2;
static{
MATCHER.addURI("com.example.providerdemo.userProvider", "user", UserList);
MATCHER.addURI("com.example.providerdemo.userProvider", "user/#", UserOne);
}
@Override
public boolean onCreate() {
dbOpenHelper = new DBopenHelper(this.getContext());
return true;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
String sortOrder) {
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
switch (MATCHER.match(uri)) {
case UserOne:
long key = ContentUris.parseId(uri);
String where = "id = "+ key;
if(selection!=null && !"".equals(selection.trim())){
where += " and "+ selection;
}
Cursor cursor = db.query("user", null, where, selectionArgs, null, null, null, null);
return cursor;
case UserList:
cursor = db.query("user", null, null, selectionArgs, null, null, null, null);
return cursor;
default:
throw new IllegalArgumentException("this is Unknown Uri:"+ uri);
}
}
@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
switch (MATCHER.match(uri)) {
case UserOne:
long rowid = db.insert("user", "", values);//主键值
Uri insertUri = ContentUris.withAppendedId(uri, rowid);
this.getContext().getContentResolver().notifyChange(uri, null);//发出数据变化通知
return insertUri;
default:
throw new IllegalArgumentException("this is Unknown Uri:"+ uri);
}
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
int nnum = 0;
switch (MATCHER.match(uri)) {
case UserOne:
long key = ContentUris.parseId(uri);
String where = "id = " + key;
if (null != selection && !"".equals(selection)) {
where += "and " + selection;
}
nnum = db.delete("user", where, selectionArgs);
return nnum;
case UserList:
nnum = db.delete("user", selection, selectionArgs);
return nnum;
default:
throw new IllegalArgumentException("this is Unknown Uri:"+ uri);
}
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
int nnum = 0 ;
switch (MATCHER.match(uri)) {
case UserOne:
long key = ContentUris.parseId(uri);
String where = "id = " + key;
if (null != selection && !"".equals(selection)) {
where += "and " + selection;
}
nnum = db.update("user", values, where, selectionArgs);
return nnum;
case UserList:
nnum = db.update("user", values, selection, selectionArgs);
return nnum;
default:
throw new IllegalArgumentException("this is Unknown Uri:"+ uri);
}
}
}
DB操作：
package com.example.providerdemo;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.nfc.Tag;
import android.os.Build.VERSION;
import android.util.Log;
/**
*
* @author baoxing.gbx
* @version $Id: DBopenHelper.java, v 0.1 2015年7月11日 下午9:39:03 baoxing.gbx Exp $
*/
public class DBopenHelper extends SQLiteOpenHelper{
/** 数据库名称 */
private static final String DB_NAME = "test.db";
private static final int VERSION = 1;
private static final String Tag = "DBopenHelper";
// 初始化数据库开启装置
public DBopenHelper(Context context) {
super(context, DB_NAME, null, VERSION);
// TODO Auto-generated constructor stub
}
//
@Override
public void onCreate(SQLiteDatabase db) {
Log.i(Tag, "onCreate 被调用");
db.execSQL("create table user (id integer primary key autoincrement, name varchar(20),sex varchar(20), age integer )");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.i(Tag, "onUpgrade 被调用");
db.execSQL("DROP TABLE IF EXISTS person");
onCreate(db);
}
}
OneApp测试
/**
*
*/
package com.demo.oneapp.test;
import java.util.Date;
import android.R.integer;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.test.AndroidTestCase;
import android.util.Log;
/**
*
* @author baoxing.gbx
* @version $Id: TestProvider.java, v 0.1 2015年8月20日 下午8:50:13 baoxing.gbx Exp $
*/
public class TestProvider extends AndroidTestCase {
public void testAdd() {
Uri uri = Uri.parse("content://com.example.providerdemo.userProvider/user");
ContentResolver resolver = this.getContext().getContentResolver();
for (int i = 0; i < 10; ++i) {
ContentValues values = new ContentValues();
values.put("name", "muyou" + i);
values.put("sex", "男");
values.put("age", 18 + i);
Uri uri2 = resolver.insert(uri, values);
System.out.println("完成：" + uri2);
}
}
public void testDel() {
// 查询单个
Uri uri = Uri.parse("content://com.example.providerdemo.userProvider/user/2");
ContentResolver resolver = this.getContext().getContentResolver();
Cursor cursor = resolver.query(uri, null, null, null, null);
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
String sex = cursor.getString(cursor.getColumnIndex("sex"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Log.i("testQuery",
"id="+ id + "name=" + name + "sex=" + sex + "age=" + age);
}
uri = Uri.parse("content://com.example.providerdemo.userProvider/user/2");
resolver = this.getContext().getContentResolver();
resolver.delete(uri, null, null);
// 查询单个
uri = Uri.parse("content://com.example.providerdemo.userProvider/user/2");
resolver = this.getContext().getContentResolver();
cursor = resolver.query(uri, null, null, null, null);
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
String sex = cursor.getString(cursor.getColumnIndex("sex"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Log.i("testQuery",
"id="+ id + "name=" + name + "sex=" + sex + "age=" + age);
}
}
public void testUpdate() {
// 查询单个
Uri uri = Uri.parse("content://com.example.providerdemo.userProvider/user/3");
ContentResolver resolver = this.getContext().getContentResolver();
Cursor cursor = resolver.query(uri, null, null, null, null);
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
String sex = cursor.getString(cursor.getColumnIndex("sex"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Log.i("testQuery",
"id="+ id + "name=" + name + "sex=" + sex + "age=" + age);
}
uri = Uri.parse("content://com.example.providerdemo.userProvider/user/3");
resolver = this.getContext().getContentResolver();
ContentValues values = new ContentValues();
values.put("name", "cool");
resolver.update(uri, values, null, null);
// 查询单个
uri = Uri.parse("content://com.example.providerdemo.userProvider/user/3");
resolver = this.getContext().getContentResolver();
cursor = resolver.query(uri, null, null, null, null);
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
String sex = cursor.getString(cursor.getColumnIndex("sex"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Log.i("testQuery",
"id="+ id + "name=" + name + "sex=" + sex + "age=" + age);
}
}
public void testQuery() {
// 查询所有
Uri uri = Uri.parse("content://com.example.providerdemo.userProvider/user");
ContentResolver resolver = this.getContext().getContentResolver();
Cursor cursor = resolver.query(uri, null, null, null, null);
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
String sex = cursor.getString(cursor.getColumnIndex("sex"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Log.i("testQuery",
"id="+ id + "name=" + name + "sex=" + sex + "age=" + age);
}
// 查询单个
uri = Uri.parse("content://com.example.providerdemo.userProvider/user/5");
resolver = this.getContext().getContentResolver();
cursor = resolver.query(uri, null, null, null, null);
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
String sex = cursor.getString(cursor.getColumnIndex("sex"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
Log.i("testQuery",
"id="+ id + "name=" + name + "sex=" + sex + "age=" + age);
}
}
}
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