Android ContentProvider 简单学习

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);
        }
    }

}