内容提供者(ContentReslove)

ContentReslove

可以通过getContentResolver( )方法获取到该类的实例，ContentReslover中提供了一系列的方法用于对数据进行CRUD操作，其中insert( )方法用于添加数据，update（）方法用于更新数据，delete()方法用于删除数据，query（）方法用于查询数据。

Uri主要由两部分组成，权限和路径。一般权限写为com.example.app.provider,路径为要查的表名所以标准写法为：

content://com.example.app.provider/table1Cursor cursor = getContentResolver().query(uri,projection,selection,selectionArgs,sortOrder);

query()方法 对应SQL部分 描述 uri from table_name 指定查询某个应用下的某一张表 projection select column,column2 指定查询的列名 selection where column=value 指定where的约束条件 selectionArgs - 为where中的占位符提供具体的值 orderBy order by column1,column2 指定查询结果的排序方式

    if(cursor!=null){        while(cursor.moveToNext()){            String column1 = cur.getString(cursor.getColumnIndex("column1"));            int column2 = cursor.getInt(cursor.getColumnIndex("column2"));        }        //关闭索引        cursor.close();    }

添加数据

    ContentValues values = new ContentValues();    values.put("column1","text");    values.put("column2",1);    getContentResolver().insert(uri,values);

修改数据

    ContentValues values = new ContentValues();    vallues.put("column1","");    getContentResolver().update(uri,values,"column1 = ? and column2 = ?",new String[]{"text","1"});

删除数据

    getContentResolver().delete(uri,"column2 = ?",new String[]{"1"});

读取联系人

添加权限
<uses-permission android:name="android.permission.READ_CONTACTS"/>

"*********************主布局文件为Listview************************"<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    >    <ListView    //ListView的id，便于在java文件下寻找        android:id="@+id/contacts_view"        android:layout_width="match_parent"        android:layout_height="match_parent"         /></LinearLayout>"*********************主方法*********************"import android.support.v7.app.ActionBarActivity;import java.util.ArrayList;import java.util.List;import android.app.Activity;import android.database.Cursor;import android.os.Bundle;import android.provider.ContactsContract;import android.view.Menu;import android.view.MenuItem;import android.widget.ArrayAdapter;import android.widget.ListView;public class MainActivity extends Activity {    ListView contactsView;    // 添加适配器    ArrayAdapter<String> adapter;    // 定义一个联系人的集合    List<String> contactsList = new ArrayList<String>();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        contactsView = (ListView) findViewById(R.id.contacts_view);        //适配器的设置        adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, contactsList);        //安装好适配器        contactsView.setAdapter(adapter);        readContacts();    }    private void readContacts() {        Cursor cursor = null;        try {        //ContactsContract.CommonDataKinds.Phone.CONTENT_URI是一个常量，这个常量就是Uri.parse()方法解析出来的，下面的那两个也是同样的意思            cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, null, null,                    null);            //遍历要查找的联系人表            while (cursor.moveToNext()) {                String displayName = cursor                        .getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));                String number = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));                //将对象加入到集合中                contactsList.add(displayName + "\n" + number);            }        } catch (Exception e) {            e.printStackTrace();        } finally {            if (cursor != null) {            //千万记得把Cursor对象关闭                cursor.close();            }        }    }}

创建自己的内容提供者

uri的写法

    content://com.example.app.provider/table1                "包名"    "内容提供者标志"   "表名"    *：表示匹配任意长度的字符,因此匹配任意表内容的URI为    content://com.example.app.provider/*    #:表示匹配任意长度的数字，一次匹配一个表中任意一行数据内容的uri可以写为    content://com.example.app.provider/table1/#

MIME在android中的规定

    1.必须以vnd开头    2.如果内容以URI以路径结尾，则后面跟android.cursor.dir/,如果内容URI以id结尾，则后面接android.cursor.item/    3.最后接上vnd.<authority>.<path>    例如1：对于content://com.example.app.provider/table1    对应MIME:vnd.android.cursor.dir/vnd.com.example.app.provider.table1    例如2：对于content://com.example.app.provider/table1MIME:vnd.android.cursor.item/vnd.com.example.app.provider.table1

下面要用到的辅助类

    package com.example.databaseandroid;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;import android.widget.Toast;    public class MyDatabaseeHelper extends SQLiteOpenHelper{        public static final String CREATE_BOOK = "create table book ("+"id integer primary key autoincrement,"                +"author text,"                 +"price real,"                +"pages integer,"                +"name text,"                //新添加的语句                +"category_id integer)";        public static final String CREATE_CATEGORY = "create table category("+                "id integer primary key autoincrement,"                +"category_name text,"                +"category_code integer)";        public MyDatabaseeHelper(Context context, String name, CursorFactory factory, int version) {            super(context, name, factory, version);        }        @Override        public void onCreate(SQLiteDatabase db) {            db.execSQL(CREATE_BOOK);            db.execSQL(CREATE_CATEGORY);        }        @Override        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {            switch(oldVersion){            case 1:                db.execSQL(CREATE_CATEGORY);            //添加语句            case 2:                db.execSQL("alter table Book add column category_id integer");            default:            }        }    }

1.创建自己的ContentProvider

总体思路,只需要获取到该应用程序的内容URI，然后借助ContentResolver进行增删改查操作。

"********************主要的布局文件**************************"package com.example.databaseandroid;import android.content.ContentProvider;import android.content.ContentValues;import android.content.UriMatcher;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.net.Uri;/**  * 继承ContentProvider来创建自己的内容提供器  */public class MyProvider extends ContentProvider{    public static final int BOOK_DIR = 0;    public static final int BOOK_ITEM = 1;    public static final int CATEGORY_DIR = 2;    public static final int CATEGORY_ITEM = 3;    public static final String AUTHORITY = "com.example.databaseandroid.provider";    private MyDatabaseeHelper dbHelper;    private static UriMatcher uriMatcher;    /**     *在静态代码块里对UriMatcher进行了初始化操作，将期望匹配的几种Uri格式添加进去了。     */    static{        //uriMatcher可以轻松的实现匹配内容URI功能        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);        //addURI()方法接收三个参数，可以分别把权限、路径和一个自定义的代码传进去。        uriMatcher.addURI(AUTHORITY,"book",BOOK_DIR);        uriMatcher.addURI(AUTHORITY,"book/#",BOOK_ITEM);        uriMatcher.addURI(AUTHORITY,"category",CATEGORY_DIR);        uriMatcher.addURI(AUTHORITY,"category/#",CATEGORY_ITEM);    }    /**    *初始化内容提供其时使用，只有当ContentResolver尝试访问我们程序中的数据时，内容提供者才会被初始化，初始化成功返回true    */    @Override    public boolean onCreate() {        //创建数据库，获得数据库的实例        dbHelper = new MyDatabaseeHelper(getContext(), "BookStore.db", null, 2);        return true;    }    /**    *从内容提供器查询数据，使用URI参数来确定是哪一张表，projection参数用于指定查询的列，selection和selectionArgs参数用来约束查询的条件，sortOrder指定排序方式，查询结果放在Cursor中。    */    @Override    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {        //查询数据        SQLiteDatabase db= dbHelper.getReadableDatabase();        Cursor cursor = null;        //当调用match（）方法时，可以传入uri，返回自定义的代码        switch(uriMatcher.match(uri)){        case BOOK_DIR:            cursor = db.query("book", projection, selection, selectionArgs, null, null, sortOrder);            break;        case BOOK_ITEM:            String bookId = uri.getPathSegments().get(1);            cursor = db.query("book", projection, "id = ?", new String[]{bookId}, null, null, sortOrder);            break;        case CATEGORY_DIR:            cursor = db.query("category", projection, selection, selectionArgs, null, null, sortOrder);            break;        case CATEGORY_ITEM:            String categoryId = uri.getPathSegments().get(1);            cursor = db.query("category", projection, "id = ?", new String[]{categoryId}, null, null, sortOrder);            break;        default:            break;        }        return cursor;    }    /**    *根据传入内容的uri来返回相应的MIME类型，这个参数正是调用ContentResolver的增删改查时传递过来的    */    @Override    public String getType(Uri uri) {        switch (uriMatcher.match(uri)){        case BOOK_DIR:            return "vnd.android.cursor.dir/vnd.com.example.databaseandroid.provider.book";        case BOOK_ITEM:            return "vnd.android.currsor.item/vnd.com.example.databaseandroid.provider.book";        case CATEGORY_DIR:            return "vnd.android.cursor.dir/vnd.com.example.databaseandroid.provider.category";        case CATEGORY_ITEM:            return "vnd.android.cursor.item/vnd.com.example.databaseandroid.provider.category";        }        return null;    }    /**    *向内容提供器添加一条数据，使用uri找到要添加的表，待添加的数据保存在values中，添加完成后，返回一个用于表示这条新纪录的uri    */    @Override    public Uri insert(Uri uri, ContentValues values) {        //添加数据        SQLiteDatabase db = dbHelper.getWritableDatabase();        Uri uriReturn = null;        switch(uriMatcher.match(uri)){        case BOOK_DIR:        case BOOK_ITEM:            long newBookId = db.insert("book", null, values);            uriReturn = Uri.parse("content://"+AUTHORITY+"/book/"+newBookId);            break;        case CATEGORY_DIR:        case CATEGORY_ITEM:            long newCategoryId = db.insert("category", null, values);            uriReturn = Uri.parse("content://"+AUTHORITY+"/category/"+newCategoryId);            break;        default:            break;        }        return uriReturn;    }    /**     * 删除数据，被删除的哪一行将作为返回值返回。     */    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        SQLiteDatabase db = dbHelper.getWritableDatabase();        int deletedRows = 0;        switch(uriMatcher.match(uri)){        case BOOK_DIR:            deletedRows = db.delete("book", selection, selectionArgs);            break;        case BOOK_ITEM:            String bookId = uri.getPathSegments().get(1);            deletedRows = db.delete("book", "id = ?", new String[]{bookId});            break;        case CATEGORY_DIR:            deletedRows = db.delete("category", selection, selectionArgs);            break;        case CATEGORY_ITEM:            String categoryId = uri.getPathSegments().get(1);            deletedRows = db.delete("category", "id = ?", new String[]{categoryId});            break;        default:            break;        }        return deletedRows;    }    /**     * 使用uri参数来确定更新哪一张表中的数据，新数据保存在values参数中，selection和selectionArgs参数用于约束更新哪一行，受影响的行数将作为返回值返回。     */    @Override    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {        SQLiteDatabase db = dbHelper.getWritableDatabase();        int updatedRows =0;        switch(uriMatcher.match(uri)){        case BOOK_DIR:            updatedRows = db.update("book", values, selection, selectionArgs);            break;        case BOOK_ITEM:            String bookId = uri.getPathSegments().get(1);            updatedRows = db.update("book", values, "id = ?", new String[]{bookId});            break;        case CATEGORY_DIR:            updatedRows = db.update("category", values, selection, selectionArgs);            break;        case CATEGORY_ITEM:            String categoryId = uri.getPathSegments().get(1);            updatedRows = db.update("category", values, "id = ?", new String[]{categoryId});            break;        default:            break;        }        return updatedRows;    }}"***************必须要在内容提供者的应用中添加权限***************"//MyProvider为上面所写的类名，前面为包名。 <provider            android:name="com.example.databaseandroid.MyProvider"            android:authorities="com.example.databaseandroid.provider" >        </provider>

在其他应用中访问上一个应用的数据

"************************布局文件************************"    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"   >    <Button        android:id="@+id/add_data"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Add to book" />    <Button        android:id="@+id/query_data"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Query From Book" />    <Button        android:id="@+id/update_data"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Updata Book" />    <Button        android:id="@+id/delete_data"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Delete From book" />    <TextView         android:id="@+id/textView"        android:layout_width="wrap_content"        android:layout_height="wrap_content"/></LinearLayout>"*********************主要的活动文件***********************"package com.test.dukang;import android.support.v7.app.ActionBarActivity;import android.util.Log;import android.app.Activity;import android.content.ContentValues;import android.database.Cursor;import android.net.Uri;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.TextView;public class MainActivity extends Activity implements OnClickListener {    private String newId;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button addData = (Button) findViewById(R.id.add_data);        addData.setOnClickListener(this);        Button queryData = (Button) findViewById(R.id.query_data);        queryData.setOnClickListener(this);        Button updateData = (Button) findViewById(R.id.update_data);        updateData.setOnClickListener(this);        Button deleteData = (Button) findViewById(R.id.delete_data);        deleteData.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()) {        case R.id.add_data:            Uri uri = Uri.parse("content://com.example.databaseandroid.provider/book");            ContentValues values = new ContentValues();            values.put("name", "A Clash of Kings");            values.put("author", "Gerge Martin");            values.put("pages", 1040);            values.put("price", 22.85);            Uri newUri = getContentResolver().insert(uri, values);            newId = newUri.getPathSegments().get(1);            break;        case R.id.query_data:            Uri quri = Uri.parse("content://com.example.databaseandroid.provider/book");            Cursor cursor = getContentResolver().query(quri, null, null, null, null);            if (cursor != null) {                while (cursor.moveToNext()) {                    String name = cursor.getString(cursor.getColumnIndex("name"));                    String author = cursor.getString(cursor.getColumnIndex("author"));                    int pages = cursor.getInt(cursor.getColumnIndex("pages"));                    double price = cursor.getDouble(cursor.getColumnIndex("price"));                    System.out.println("你好");                    Log.d("MainAcivity", name);                    Log.d("MainAcivity", author);                    Log.d("MainAcivity", ""+pages);                    Log.d("MainAcivity", ""+price);                }                cursor.close();            }            break;        case R.id.update_data:            Uri uuri = Uri.parse("content://com.example.databaseandroid.provider/book/" + newId);            ContentValues valuesUpdate = new ContentValues();            valuesUpdate.put("name", "A Storm of Swords");            valuesUpdate.put("pages", 1216);            valuesUpdate.put("price", 24.05);            getContentResolver().update(uuri, valuesUpdate, null, null);            break;        case R.id.delete_data:            Uri uriDelete=Uri.parse("content://com.example.databaseandroid.provider/book/"+newId);            getContentResolver().delete(uriDelete, null, null);            break;        }    }}