Android 创建一个私有的数据库（内容提供者）

public class MyOpenHelper extends SQLiteOpenHelper {

/**
*
* @param context
* @param name  数据库的名字
* @param factory   游标工厂
* @param version   版本
*/
public MyOpenHelper(Context context) {
super(context, "Account.db", null, 1);
}
// 表结构的初始化
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table info(_id integer primary key autoincrement, name varchar(20), money varchar(20))");
db.execSQL("insert into info(name, money) values(?, ?)", new String[] {"张三", "5000"});
db.execSQL("insert into info(name, money) values(?, ?)", new String[] {"李四", "3000"});
}

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

}
}

public class AccountProvider extends ContentProvider {

//1 定义一个urimacher 定义路径匹配器
private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);
private static final int QUERYSUCCESS = 0; // 大小写转换 ctrl + shift + u
private static final int INSERTSUCCESS = 1;
private static final int UPDATESUCCESS = 2;
private static final int DELETESUCCESS = 3;
private MyOpenHelper myOpenHelper;

//2 定义静态代码块 添加匹配规则
static {
/**
* authority 注意 这个参数和你在清单文件里面定义的要一样
* URL http://baidu.com * uri content://com.itheima.provider/query
*     content://com.itheima.provider/insert
*     content://com.itheima.provider/update
*     content://com.itheima.provider/delete
*/
sURIMatcher.addURI("com.itheima.provider", "query", QUERYSUCCESS);
sURIMatcher.addURI("com.itheima.provider", "insert", INSERTSUCCESS);
sURIMatcher.addURI("com.itheima.provider", "update", UPDATESUCCESS );
sURIMatcher.addURI("com.itheima.provider", "delete", DELETESUCCESS);
}

public AccountProvider() {
}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// Implement this to handle requests to delete one or more rows.
int match = sURIMatcher.match(uri);
if (match == DELETESUCCESS) {
// 说明路径匹配成功 对数据库进行删除的操作
SQLiteDatabase db = myOpenHelper.getReadableDatabase();
// 代表影响的函数 clause：子句
int delete = db.delete("info", selection, selectionArgs);
db.close(); // 关闭数据库
if (delete > 0) {
// 发送一条消息 说明数据库发生了改变
getContext().getContentResolver().notifyChange(uri, null);
}
return delete;
} else {
// 路径不匹配
throw new IllegalArgumentException("您的路径不匹配，请检查路径");
}
}

@Override
public String getType(Uri uri) {
// TODO: Implement this to handle requests for the MIME type of the data
// at the given URI.
throw new UnsupportedOperationException("Not yet implemented");
}

@Override
public Uri insert(Uri uri, ContentValues values) {
// TODO: Implement this to handle requests to insert a new row.
int code = sURIMatcher.match(uri);
if (code == INSERTSUCCESS) {
// 操作数据库 说明路径匹配成功
SQLiteDatabase db = myOpenHelper.getReadableDatabase();
// 返回值代表新插入行数的id
long insert = db.insert("info", null, values);
db.close(); // 关闭数据库
if (insert > 0) {
// 发送一条消息 说明数据库发生了改变
getContext().getContentResolver().notifyChange(uri, null);
}

Uri uri2 = uri.parse("com.itheima.insert/" + insert);
return uri2;
} else {
// 路径不匹配
throw new IllegalArgumentException("您的路径不匹配，请检查路径");
}
}

@Override
public boolean onCreate() {
// TODO: Implement this to initialize your content provider on startup.
myOpenHelper = new MyOpenHelper(getContext());
return false;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// TODO: Implement this to handle query requests from clients.
int code = sURIMatcher.match(uri);
if (code == QUERYSUCCESS) {
// 说明路径匹配成功 把query方法给实现 数据库的查询方法，对数据库进行查询的操作，想操作数据库必须得获得sqlitedatabase对象
SQLiteDatabase db = myOpenHelper.getReadableDatabase();
Cursor cursor = db.query("info", projection, selection, selectionArgs, null, null, sortOrder);
// cursor 不能关闭 注意
// 数据库被人操作了 自己发送一条消息
getContext().getContentResolver().notifyChange(uri, null);
return cursor;
} else {
// 路径不匹配
throw new IllegalArgumentException("路径不匹配，请检查路径");
}
}

@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO: Implement this to handle requests to update one or more rows.
int code = sURIMatcher.match(uri);
if (code == UPDATESUCCESS) {
SQLiteDatabase db = myOpenHelper.getReadableDatabase();
// 影响的行数
int update = db.update("info", values, selection, selectionArgs);
db.close(); // 关闭数据库
if (update > 0) {
// 发送一条消息 说明数据库发生了改变
getContext().getContentResolver().notifyChange(uri, null);
}
return update;
} else {
// 路径不匹配
throw new  IllegalArgumentException("你的路径不匹配，请检查路径");
}
}
}

<provider
android:name=".AccountProvider"
android:authorities="com.itheima.provider" <!--在AndroidStudio中 创建内容提供者文件直接在创建时声明authorities-->
android:enabled="true"
android:exported="true"></provider>