Android中Uri的使用

1.Uri

通用资源标志符（Universal Resource Identifier, 简称"URI"）。

Uri代表要操作的数据，Android上可用的每种资源 - 图像、视频片段等都可以用Uri来表示。

URI一般由三部分组成：

访问资源的命名机制。 

存放资源的主机名。 

资源自身的名称，由路径表示。 

Android的Uri由以下三部分组成： "content://"、数据的路径、标示ID(可选)

举些例子，如： 

所有联系人的Uri： content://contacts/people

某个联系人的Uri: content://contacts/people/5

所有图片Uri: content://media/external

某个图片的Uri：content://media/external/images/media/4

我们很经常需要解析Uri，并从Uri中获取数据。

Android系统提供了两个用于操作Uri的工具类，分别为UriMatcher 和ContentUris 。

虽然这两类不是非常重要，但是掌握它们的使用，会便于我们的开发工作。

下面就一起看一下这两个类的作用。

2.UriMatcher

UriMatcher 类主要用于匹配Uri.

使用方法如下。

首先第一步，初始化：

UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);

UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);

第二步注册需要的Uri:

matcher.addURI("com.yfz.Lesson", "people", PEOPLE);
matcher.addURI("com.yfz.Lesson", "person/#", PEOPLE_ID);

matcher.addURI("com.yfz.Lesson", "people", PEOPLE);
matcher.addURI("com.yfz.Lesson", "person/#", PEOPLE_ID);

第三部，与已经注册的Uri进行匹配:

Uri uri = Uri.parse("content://" + "com.yfz.Lesson" + "/people");
int match = matcher.match(uri);
       switch (match)
       {
           case PEOPLE:
               return "vnd.Android.cursor.dir/people";
           case PEOPLE_ID:
               return "vnd.android.cursor.item/people";
           default:
               return null;
       }

Uri uri = Uri.parse("content://" + "com.yfz.Lesson" + "/people");
int match = matcher.match(uri);
       switch (match)
       {
           case PEOPLE:
               return "vnd.Android.cursor.dir/people";
           case PEOPLE_ID:
               return "vnd.Android.cursor.item/people";
           default:
               return null;
       }

match方法匹配后会返回一个匹配码Code，即在使用注册方法addURI时传入的第三个参数。 

上述方法会返回"vnd.Android.cursor.dir/person". 

总结: 

--常量 UriMatcher.NO_MATCH 表示不匹配任何路径的返回码

--# 号为通配符

--* 号为任意字符 

另外说一下，官方SDK说明中关于Uri的注册是这样写的：

private static final UriMatcher sURIMatcher = new UriMatcher();
    static
    {
        sURIMatcher.addURI("contacts", "/people", PEOPLE);
        sURIMatcher.addURI("contacts", "/people/#", PEOPLE_ID);
        sURIMatcher.addURI("contacts", "/people/#/phones", PEOPLE_PHONES);
        sURIMatcher.addURI("contacts", "/people/#/phones/#", PEOPLE_PHONES_ID);
        sURIMatcher.addURI("contacts", "/people/#/contact_methods", PEOPLE_CONTACTMETHODS);
        sURIMatcher.addURI("contacts", "/people/#/contact_methods/#", PEOPLE_CONTACTMETHODS_ID);
        sURIMatcher.addURI("contacts", "/deleted_people", DELETED_PEOPLE);
        sURIMatcher.addURI("contacts", "/phones", PHONES);
        sURIMatcher.addURI("contacts", "/phones/filter/*", PHONES_FILTER);
        sURIMatcher.addURI("contacts", "/phones/#", PHONES_ID);
        sURIMatcher.addURI("contacts", "/contact_methods", CONTACTMETHODS);
        sURIMatcher.addURI("contacts", "/contact_methods/#", CONTACTMETHODS_ID);
        sURIMatcher.addURI("call_log", "/calls", CALLS);
        sURIMatcher.addURI("call_log", "/calls/filter/*", CALLS_FILTER);
        sURIMatcher.addURI("call_log", "/calls/#", CALLS_ID);
    }

private static final UriMatcher sURIMatcher = new UriMatcher();
    static
    {
        sURIMatcher.addURI("contacts", "/people", PEOPLE);
        sURIMatcher.addURI("contacts", "/people/#", PEOPLE_ID);
        sURIMatcher.addURI("contacts", "/people/#/phones", PEOPLE_PHONES);
        sURIMatcher.addURI("contacts", "/people/#/phones/#", PEOPLE_PHONES_ID);
        sURIMatcher.addURI("contacts", "/people/#/contact_methods", PEOPLE_CONTACTMETHODS);
        sURIMatcher.addURI("contacts", "/people/#/contact_methods/#", PEOPLE_CONTACTMETHODS_ID);
        sURIMatcher.addURI("contacts", "/deleted_people", DELETED_PEOPLE);
        sURIMatcher.addURI("contacts", "/phones", PHONES);
        sURIMatcher.addURI("contacts", "/phones/filter/*", PHONES_FILTER);
        sURIMatcher.addURI("contacts", "/phones/#", PHONES_ID);
        sURIMatcher.addURI("contacts", "/contact_methods", CONTACTMETHODS);
        sURIMatcher.addURI("contacts", "/contact_methods/#", CONTACTMETHODS_ID);
        sURIMatcher.addURI("call_log", "/calls", CALLS);
        sURIMatcher.addURI("call_log", "/calls/filter/*", CALLS_FILTER);
        sURIMatcher.addURI("call_log", "/calls/#", CALLS_ID);
    }

这个说明估计已经是Google官方没有更新，首先是初始化方法，没有传参，那么现在初始化时，实际是必须传参的。 可以看一下Android2.2的源码，无参数的构造方法已经是private的了。

另外就是addURI这个方法，第二个参数开始时不需要"/"， 否则是无法匹配成功的。

3.ContentUris

ContentUris 类用于获取Uri路径后面的ID部分

1)为路径加上ID: withAppendedId(uri, id)

比如有这样一个Uri

Uri uri = Uri.parse("content://com.yfz.Lesson/people")

Uri uri = Uri.parse("content://com.yfz.Lesson/people")

通过withAppendedId方法，为该Uri加上ID

Uri resultUri = ContentUris.withAppendedId(uri, 10);

Uri resultUri = ContentUris.withAppendedId(uri, 10);

最后resultUri为: content://com.yfz.Lesson/people/10

2)从路径中获取ID: parseId(uri)

Uri uri = Uri.parse("content://com.yfz.Lesson/people/10")
long personid = ContentUris.parseId(uri);

Uri uri = Uri.parse("content://com.yfz.Lesson/people/10")
long personid = ContentUris.parseId(uri);

最后personid 为 :10 

附上实验的代码：

package com.yfz;
import com.yfz.log.Logger;
import Android.app.Activity;
import android.content.ContentUris;
import android.content.UriMatcher;
import android.net.Uri;
import android.os.Bundle;
public class Lesson_14 extends Activity {

        private static final String AUTHORITY = "com.yfz.Lesson";
        private static final int PEOPLE = 1;
        private static final int PEOPLE_ID = 2;

        //NO_MATCH表示不匹配任何路径的返回码
        private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        static
        {
            sURIMatcher.addURI(AUTHORITY, "people", PEOPLE);

            //这里的#代表匹配任意数字，另外还可以用*来匹配任意文本
            sURIMatcher.addURI(AUTHORITY, "people/#", PEOPLE_ID);
        }

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            Logger.d("------ Start Activity !!! ------");

            Uri uri1 = Uri.parse("content://" + AUTHORITY + "/people");
            Logger.e("Uri:" + uri1);
            Logger.d("Match 1" + getType(uri1));

            Uri uri2 = Uri.parse("content://" + AUTHORITY + "/people" + "/2");

            Logger.e("Uri:" + uri2);
            Logger.d("Match 2" + getType(uri2));

            //拼接Uri
            Uri cUri = ContentUris.withAppendedId(uri1, 15);
            Logger.e("Uri:" + cUri);
            //获取ID
            long id = ContentUris.parseId(cUri);
            Logger.d("Uri ID: " + id);
        }

        private String getType(Uri uri) {
            int match = sURIMatcher.match(uri);
            switch (match)
            {
                case PEOPLE:
                    return "vnd.android.cursor.dir/person";
                case PEOPLE_ID:
                    return "vnd.android.cursor.item/person";
                default:
                    return null;
            }
        }
}