SQLite数据库与Contentprovider（2）

概述介绍《SQLite数据库与Contentprovider（2）》开发教程，希望对您有用。

《sqlite数据库与ContentprovIDer（2）》要点：
本文介绍了sqlite数据库与ContentprovIDer（2），希望对您有用。如果有疑问，可以联系我们。

ContentProvIDer：

在创建ContentProvIDer时,必要首先使用数据库、文件系统或网络实现底层存储功能,

然后在继承ContentProvIDer的类中实现基本数据 *** 作的接口函数,包含添加、删除、查找和更新等功能.

调用者不能够直接调用ContentProvIDer的接口函数,而必要使用ContentResolver对象,

通过URI间接调用ContentProvIDer.下图是ContentProvIDer调用关系.

URI：

URI是通用资源标志符(Uniform Resource IDentifIEr),用来定位任何远程或当地的可用资源

ContentProvIDer使用的URI语法布局如下

content://<authority>/<data_path>/<ID>

content://是通用前缀,表现该URI用于ContentProvIDer定位资源,无需修改.

<authority>是授权者名称,用来确定具体由哪一个ContentProvIDer提供资源.因此,一般<authority>都由类的小写全称组成,以保证唯一性.

<data_path>是数据路径,用来确定哀求的是哪个数据集.

例如：

content://edu.hrbeu.peopleprovIDer/people/3

可以省略ID(/3)部门那么意味着整个数据.

UriMatcher:

在新构造的ContentProvIDer类中,通过构造一个UriMatcher,判断URI是单条数据还是多条数据.

public voID addURI (String authority,String path,int code)

authority表现匹配的授权者名称

path表现数据路径

#可以代表任何数字 (content://<authority>/<data_path>/#)

code表现返回代码(uriMatcher.match(uri))的返回值)

注册ContentProvIDer ：

<provIDer androID:name = ".PeopleProvIDer" androID:authoritIEs = "edu.hrbeu.peopleprovIDer"/> 

实例：

ContentProvIDer一般用于两个分歧的进程之间的数据共享.

假设我们有一个新的工程(app),在此工程中创建一个people.db数据库,然后通过自定义了一个ContentProvIDer来共享数据库中的data.我们可以通过注册provIDer时用到的authority在配合db path之类的来连接(content://<authority>/<data_path>/#)读取内容提供者(分歧进程)的数据.

首先是步骤1:

*只要在AndroIDManifast中注册provIDer就会执行对应的provIDer类.无需再MainActivity中调用或无需直接调用自定义的new provIDer.

即系统自动会加载调用PeopleProvIDer类.

继承ContentProvIDer时代码如下：

import androID.content.*;import androID.database.Cursor;import androID.net.Uri; public class PeopleProvIDer extends ContentProvIDer{    @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;    }     @OverrIDe    public Uri insert(Uri uri,ContentValues values) {        // Todo auto-generated method stub        return null;    }     @OverrIDe    public boolean onCreate {        // Todo auto-generated method stub        return false;    }         @OverrIDe    public Cursor query(Uri uri,String[] projection,String[] selectionArgs,String sortOrder) {        // Todo auto-generated method stub        return null;    }     @OverrIDe    public int update(Uri uri,ContentValues values,String[] selectionArgs) {        // Todo auto-generated method stub        return 0;    }}

类似数据库 *** 作.可以这么理解,相对来说好理解.

开始贴代码...

package edu.hrbeu.contentprovIDerdemo; import androID.content.ContentProvIDer;import androID.content.ContentUris;import androID.content.ContentValues;import androID.content.Context;import androID.content.UriMatcher;import androID.database.Cursor;import androID.database.sqlException;import androID.database.sqlite.sqliteDatabase;import androID.database.sqlite.sqliteDatabase.CursorFactory;import androID.database.sqlite.sqliteOpenHelper;import androID.database.sqlite.sqlitequeryBuilder;import androID.net.Uri;public class PeopleProvIDer extends ContentProvIDer {        private static final String DB_name = "people.db";    private static final String DB_table = "peopleinfo";    private static final int DB_VERSION = 1;        private sqliteDatabase db;    private DBOpenHelper dbOpenHelper;        private static final int MulTIPLE_PEOPLE = 1;    private static final int SINGLE_PEOPLE = 2;    private static final UriMatcher uriMatcher;    static {         uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);         uriMatcher.addURI(People.AUTHORITY,People.PATH_MulTIPLE,MulTIPLE_PEOPLE);         uriMatcher.addURI(People.AUTHORITY,People.PATH_SINGLE,SINGLE_PEOPLE);    }    @OverrIDe    public boolean onCreate {        // Todo auto-generated method stub        Context context = getContext;        dbOpenHelper = new DBOpenHelper(context,DB_name,null,DB_VERSION);        db = dbOpenHelper.getWritableDatabase;         if (db == null) return false;        else  return true;        }    @OverrIDe    public Cursor query(Uri uri,String sortOrder) {        // Todo auto-generated method stub        sqlitequeryBuilder qb = new sqlitequeryBuilder;        qb.settables(DB_table);        switch(uriMatcher.match(uri)){ case SINGLE_PEOPLE: qb.appenDWhere(People.KEY_ID + "=" + uri.getPathSegments.get(1)); break; default: break;        }        Cursor cursor = qb.query(db,projection,selection,selectionArgs,sortOrder);        cursor.setNotificationUri(getContext.getContentResolver,uri);        return cursor;    }    @OverrIDe    public String getType(Uri uri) {        // Todo auto-generated method stub        switch(uriMatcher.match(uri)){        case MulTIPLE_PEOPLE:    return People.mine_TYPE_MulTIPLE;        case SINGLE_PEOPLE:    return People.mine_TYPE_SINGLE;        default: throw new IllegalArgumentException("Unkown uri:"+uri);}    }    @OverrIDe    public Uri insert(Uri uri,ContentValues values) {        // Todo auto-generated method stub        long ID = db.insert(DB_table,values);        if ( ID > 0 ){ Uri newUri = ContentUris.withAppendedID(People.CONTENT_URI,ID); getContext.getContentResolver.notifyChange(newUri,null); return newUri;        }        throw new sqlException("Failed to insert row into " + uri);    }    @OverrIDe    public int delete(Uri uri,String[] selectionArgs) {        // Todo auto-generated method stub        int count = 0;        switch(uriMatcher.match(uri)){    case MulTIPLE_PEOPLE: count = db.delete(DB_table,selectionArgs); break; case SINGLE_PEOPLE: String segment = uri.getPathSegments.get(1); count = db.delete(DB_table,People.KEY_ID + "=" + segment,selectionArgs); break;   default: throw new IllegalArgumentException("Unsupported URI:" + uri);}        getContext.getContentResolver.notifyChange(uri,null);         return count;    }    @OverrIDe    public int update(Uri uri,String[] selectionArgs) {        // Todo auto-generated method stub        int count;        switch(uriMatcher.match(uri)){ case MulTIPLE_PEOPLE: count = db.update(DB_table,values,selectionArgs); break; case SINGLE_PEOPLE: String segment = uri.getPathSegments.get(1); count = db.update(DB_table,People.KEY_ID+"="+segment,selectionArgs); break; default: throw new IllegalArgumentException("UnkNow URI:" + uri);             }        getContext.getContentResolver.notifyChange(uri,null);        return count;    }          private static class DBOpenHelper extends sqliteOpenHelper {  public DBOpenHelper(Context context,String name,CursorFactory factory,int version) { super(context,name,factory,version); } private static final String DB_CREATE = "create table " +  DB_table + " (" + People.KEY_ID + " integer primary key autoincrement," + People.KEY_name+ " text not null," + People.KEY_AGE+ " integer," + People.KEY_HEIGHT + " float);";        @OverrIDe        public voID onCreate(sqliteDatabase _db) { // Todo auto-generated method stub _db.execsql(DB_CREATE);        }        @OverrIDe        public voID onUpgrade(sqliteDatabase _db,int oldVersion,int newVersion) { // Todo auto-generated method stub _db.execsql("DROP table IF EXISTS " + DB_table); onCreate(_db);        }      }    }

package edu.hrbeu.contentprovIDerdemo;import androID.net.Uri; public class People{        public static final String MIME_DIR_PREFIX = "vnd.androID.cursor.dir";    public static final String MIME_ITEM_PREFIX = "vnd.androID.cursor.item";    public static final String mine_ITEM = "vnd.hrbeu.people";        public static final String mine_TYPE_SINGLE = MIME_ITEM_PREFIX + "/" + mine_ITEM;    public static final String mine_TYPE_MulTIPLE = MIME_DIR_PREFIX + "/" + mine_ITEM;    public static final String AUTHORITY = "edu.hrbeu.peopleprovIDer";    public static final String PATH_SINGLE = "people/#";    public static final String PATH_MulTIPLE = "people";    public static final String CONTENT_URI_STRING = "content://" + AUTHORITY + "/" + PATH_MulTIPLE;    public static final Uri  CONTENT_URI = Uri.parse(CONTENT_URI_STRING);         public static final String KEY_ID = "_ID";    public static final String KEY_name = "name";    public static final String KEY_AGE = "age";    public static final String KEY_HEIGHT = "height";}

MainActivity是空的...不贴出来了.

运行成果没有任何内容,因为仅是添加了一个provIDer.

看一下步调2：

在另一个App中调用此ContentProvIDer.

无需再AndroIDManifast中注册provIDer.

只需对应步骤1中的People类里的静态变量是完全匹配的便是可以了.

也就是说URI需要与我们自定义的ContentProvIDer坚持一致.

package edu.hrbeu.contentresolverdemo;import androID.net.Uri; public class People{        public static final String MIME_DIR_PREFIX = "vnd.androID.cursor.dir";    public static final String MIME_ITEM_PREFIX = "vnd.androID.cursor.item";    public static final String mine_ITEM = "vnd.hrbeu.people";        public static final String mine_TYPE_SINGLE = MIME_ITEM_PREFIX + "/" + mine_ITEM;    public static final String mine_TYPE_MulTIPLE = MIME_DIR_PREFIX + "/" + mine_ITEM;    public static final String AUTHORITY = "edu.hrbeu.peopleprovIDer";    public static final String PATH_SINGLE = "people/#";    public static final String PATH_MulTIPLE = "people";    public static final String CONTENT_URI_STRING = "content://" + AUTHORITY + "/" + PATH_MulTIPLE;    public static final Uri  CONTENT_URI = Uri.parse(CONTENT_URI_STRING);         public static final String KEY_ID = "_ID";    public static final String KEY_name = "name";    public static final String KEY_AGE = "age";    public static final String KEY_HEIGHT = "height";}

*** 作Contentpriver提供的数据我们必要用到ContentResolver：

package edu.hrbeu.contentresolverdemo;import androID.app.Activity;import androID.os.Bundle;import androID.vIEw.Menu;import androID.vIEw.MenuItem;import androID.content.ContentResolver;import androID.content.ContentValues;import androID.database.Cursor;import androID.net.Uri;import androID.vIEw.VIEw;import androID.vIEw.VIEw.OnClickListener;import androID.Widget.button;import androID.Widget.EditText;import androID.Widget.TextVIEw;public class ContentResolverDemo extends Activity {    private EditText nameText;    private EditText ageText;    private EditText heightText;    private EditText IDEntry;    private TextVIEw labelVIEw;    private TextVIEw displayVIEw;    private ContentResolver resolver;    @OverrIDe    protected voID onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.activity_content_resolver_demo);        nameText = (EditText) findVIEwByID(R.ID.name);        ageText = (EditText) findVIEwByID(R.ID.age);        heightText = (EditText) findVIEwByID(R.ID.hight);        IDEntry = (EditText) findVIEwByID(R.ID.ID);        labelVIEw = (TextVIEw) findVIEwByID(R.ID.label);        displayVIEw = (TextVIEw) findVIEwByID(R.ID.display);        button addbutton = (button) findVIEwByID(R.ID.button1);        button queryAllbutton = (button) findVIEwByID(R.ID.button2);        button clearbutton = (button) findVIEwByID(R.ID.button3);        button querybutton = (button) findVIEwByID(R.ID.button6);        button deletebutton = (button) findVIEwByID(R.ID.button5);        button updatebutton = (button) findVIEwByID(R.ID.button7);        resolver = this.getContentResolver;        addbutton.setonClickListener(new OnClickListener { @OverrIDe public voID onClick(VIEw v) { // Todo auto-generated method stub ContentValues values = new ContentValues; values.put(People.KEY_name,nameText.getText.toString); values.put(People.KEY_AGE,Integer.parseInt(ageText.getText.toString)); values.put(People.KEY_HEIGHT,float.parsefloat(heightText.getText.toString)); Uri newUri = resolver.insert(People.CONTENT_URI,values); labelVIEw.setText("添加成功,URI:" + newUri); }        });        queryAllbutton.setonClickListener(new OnClickListener { @OverrIDe public voID onClick(VIEw v) { // Todo auto-generated method stub Cursor cursor = resolver.query(People.CONTENT_URI,new String[] { People.KEY_ID,People.KEY_name,People.KEY_AGE,People.KEY_HEIGHT },null); if (cursor == null) { labelVIEw.setText("数据库中没有数据"); return; } labelVIEw.setText("数据库：" + String.valueOf(cursor.getCount) + "条记录"); String msg = ""; if (cursor.movetoFirst) { do { msg += "ID：" + cursor.getInt(cursor .getColumnIndex(People.KEY_ID)) + ","; msg += "姓名：" + cursor.getString(cursor .getColumnIndex(People.KEY_name)) + ","; msg += "年龄：" + cursor.getInt(cursor .getColumnIndex(People.KEY_AGE)) + ","; msg += "身高：" + cursor.getfloat(cursor .getColumnIndex(People.KEY_HEIGHT)) + "\n"; } while (cursor.movetoNext); } displayVIEw.setText(msg); }        });        clearbutton.setonClickListener(new OnClickListener { @OverrIDe public voID onClick(VIEw v) { // Todo auto-generated method stub displayVIEw.setText(""); }        });        querybutton.setonClickListener(new OnClickListener { @OverrIDe public voID onClick(VIEw v) { // Todo auto-generated method stub Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + IDEntry.getText.toString); Cursor cursor = resolver.query(uri,null); if (cursor == null) { labelVIEw.setText("数据库中没有数据"); return; } String msg = ""; if (cursor.movetoFirst) { msg += "ID：" + cursor.getInt(cursor .getColumnIndex(People.KEY_ID)) + ","; msg += "身高：" + cursor.getfloat(cursor .getColumnIndex(People.KEY_HEIGHT)) + "\n"; } labelVIEw.setText("数据库："); displayVIEw.setText(msg); }        });        deletebutton.setonClickListener(new OnClickListener { @OverrIDe public voID onClick(VIEw v) { // Todo auto-generated method stub Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + IDEntry.getText.toString); int result = resolver.delete(uri,null); String msg = "删除ID为" + IDEntry.getText.toString + "的数据" + (result > 0 ? "成功" : "失败"); labelVIEw.setText(msg); }        });        updatebutton.setonClickListener(new OnClickListener { @OverrIDe public voID onClick(VIEw v) { // Todo auto-generated method stub ContentValues values = new ContentValues; values.put(People.KEY_name,float.parsefloat(heightText.getText.toString)); Uri uri = Uri.parse(People.CONTENT_URI_STRING + "/" + IDEntry.getText.toString); int result = resolver.update(uri,null); String msg = "更新ID为" + IDEntry.getText.toString + "的数据" + (result > 0 ? "成功" : "失败"); labelVIEw.setText(msg); }        });    }    @OverrIDe    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater.inflate(R.menu.content_resolver_demo,menu);        return true;    }    @OverrIDe    public boolean onoptionsItemSelected(MenuItem item) {        // Handle action bar item clicks here. The action bar will        // automatically handle clicks on the Home/Up button,so long        // as you specify a parent activity in AndroIDManifest.xml.        int ID = item.getItemID;        if (ID == R.ID.action_settings) { return true;        }        return super.onoptionsItemSelected(item);    }}

事成相识的结构文件也附上：

<relativeLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"    xmlns:tools="http://schemas.androID.com/tools"    androID:layout_wIDth="match_parent"    androID:layout_height="match_parent"    androID:paddingBottom="@dimen/activity_vertical_margin"    androID:paddingleft="@dimen/activity_horizontal_margin"    androID:paddingRight="@dimen/activity_horizontal_margin"    androID:paddingtop="@dimen/activity_vertical_margin"    tools:context="edu.hrbeu.contentresolverdemo.ContentResolverDemo" >    <TextVIEw androID:ID="@+ID/Username"         androID:layout_height="wrap_content"         androID:layout_wIDth="fill_parent"         androID:text="用户名：">    </TextVIEw>    <EditText        androID:ID="@+ID/name"        androID:layout_wIDth="fill_parent"        androID:layout_height="wrap_content"        androID:layout_below="@ID/Username" >    </EditText>    <TextVIEw androID:ID="@+ID/Userage"         androID:layout_height="wrap_content"         androID:layout_wIDth="fill_parent"         androID:layout_below="@ID/name"        androID:text="年龄：">    </TextVIEw>    <EditText androID:ID="@+ID/age"         androID:layout_height="wrap_content"         androID:layout_wIDth="fill_parent"         androID:layout_below="@ID/Userage">    </EditText>         <TextVIEw androID:ID="@+ID/Userhight"         androID:layout_height="wrap_content"         androID:layout_wIDth="fill_parent"         androID:layout_below="@ID/age"        androID:text="身高：">    </TextVIEw>    <EditText androID:ID="@+ID/hight"         androID:layout_height="wrap_content"         androID:layout_wIDth="fill_parent"         androID:layout_below="@ID/Userhight">    </EditText>    <button        androID:ID="@+ID/button2"        androID:layout_wIDth="wrap_content"        androID:layout_height="wrap_content"        androID:layout_alignBaseline="@+ID/button1"        androID:layout_alignBottom="@+ID/button1"        androID:layout_centerHorizontal="true"        androID:text="全部显示" />    <button        androID:ID="@+ID/button3"        androID:layout_wIDth="wrap_content"        androID:layout_height="wrap_content"        androID:layout_alignBaseline="@+ID/button2"        androID:layout_alignBottom="@+ID/button2"        androID:layout_alignRight="@+ID/hight"        androID:text="清除显示" />        <TextVIEw androID:ID="@+ID/UserID"         androID:layout_height="wrap_content"         androID:layout_wIDth="fill_parent"         androID:layout_below="@ID/button1"        androID:text="ID：">    </TextVIEw>    <EditText androID:ID="@+ID/ID"         androID:layout_height="wrap_content"         androID:layout_wIDth="fill_parent"         androID:layout_below="@ID/UserID">    </EditText>    <button        androID:ID="@+ID/button6"        androID:layout_wIDth="wrap_content"        androID:layout_height="wrap_content"        androID:layout_alignBaseline="@+ID/button5"        androID:layout_alignBottom="@+ID/button5"        androID:layout_alignleft="@+ID/button2"        androID:text="ID查询" />    <button        androID:ID="@+ID/button7"        androID:layout_wIDth="wrap_content"        androID:layout_height="wrap_content"        androID:layout_alignBaseline="@+ID/button6"        androID:layout_alignBottom="@+ID/button6"        androID:layout_alignleft="@+ID/button3"        androID:text="ID更新" />    <button        androID:ID="@+ID/button1"        androID:layout_wIDth="wrap_content"        androID:layout_height="wrap_content"        androID:layout_below="@+ID/hight"        androID:text="添加数据" />    <button        androID:ID="@+ID/button5"        androID:layout_wIDth="wrap_content"        androID:layout_height="wrap_content"        androID:layout_alignleft="@+ID/ID"        androID:layout_below="@+ID/ID"        androID:text="ID删除" />    <TextVIEw        androID:ID="@+ID/display"        androID:layout_wIDth="fill_parent"        androID:layout_height="wrap_content"        androID:layout_alignleft="@+ID/label"        androID:layout_below="@+ID/label"        androID:layout_margintop="23dp" />    <TextVIEw        androID:ID="@+ID/label"        androID:layout_wIDth="fill_parent"        androID:layout_height="wrap_content"        androID:layout_alignleft="@+ID/button5"        androID:layout_below="@+ID/button6"        androID:layout_margintop="14dp" /></relativeLayout>

运行成果：

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