问题
Below is the notepad sample code, why the android:authorities = com.google.provider.NotePad instead of using the project package name? and what exactly is android:authorities asking for?
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<!-- Declare the contents of this Android application. The namespace
attribute brings in the Android platform namespace, and the package
supplies a unique name for the application. When writing your
own application, the package name must be changed from "com.example.*"
to come from a domain that you own or have control over. -->
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android.notepad" >
<uses-sdk android:minSdkVersion="11" />
<application android:icon="@drawable/app_notes"
android:label="@string/app_name"
>
<provider android:name="NotePadProvider"
android:authorities="com.google.provider.NotePad"
android:exported="false">
<grant-uri-permission android:pathPattern=".*" />
</provider>
<activity android:name="NotesList" android:label="@string/title_notes_list">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.EDIT" />
<action android:name="android.intent.action.PICK" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.dir/vnd.google.note" />
</intent-filter>
<intent-filter>
<action android:name="android.intent.action.GET_CONTENT" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
</intent-filter>
</activity>
<activity android:name="NoteEditor"
android:theme="@android:style/Theme.Holo.Light"
android:screenOrientation="sensor"
android:configChanges="keyboardHidden|orientation"
>
<!-- This filter says that we can view or edit the data of
a single note -->
<intent-filter android:label="@string/resolve_edit">
<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.EDIT" />
<action android:name="com.android.notepad.action.EDIT_NOTE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
</intent-filter>
<!-- This filter says that we can create a new note inside
of a directory of notes. The INSERT action creates an
empty note; the PASTE action initializes a new note from
the current contents of the clipboard. -->
<intent-filter>
<action android:name="android.intent.action.INSERT" />
<action android:name="android.intent.action.PASTE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:mimeType="vnd.android.cursor.dir/vnd.google.note" />
</intent-filter>
</activity>
<activity android:name="TitleEditor"
android:label="@string/title_edit_title"
android:icon="@drawable/ic_menu_edit"
android:theme="@android:style/Theme.Holo.Dialog"
android:windowSoftInputMode="stateVisible">
<!-- This activity implements an alternative action that can be
performed on notes: editing their title. It can be used as
a default operation if the user invokes this action, and is
available as an alternative action for any note data. -->
<intent-filter android:label="@string/resolve_title">
<!-- This is the action we perform. It is a custom action we
define for our application, not a generic VIEW or EDIT
action since we are not a general note viewer/editor. -->
<action android:name="com.android.notepad.action.EDIT_TITLE" />
<!-- DEFAULT: execute if being directly invoked. -->
<category android:name="android.intent.category.DEFAULT" />
<!-- ALTERNATIVE: show as an alternative action when the user is
working with this type of data. -->
<category android:name="android.intent.category.ALTERNATIVE" />
<!-- SELECTED_ALTERNATIVE: show as an alternative action the user
can perform when selecting this type of data. -->
<category android:name="android.intent.category.SELECTED_ALTERNATIVE" />
<!-- This is the data type we operate on. -->
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
</intent-filter>
</activity>
<activity android:name="NotesLiveFolder" android:label="@string/live_folder_name"
android:icon="@drawable/live_folder_notes">
<intent-filter>
<action android:name="android.intent.action.CREATE_LIVE_FOLDER" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
回答1:
Why the android:authorities = com.google.provider.NotePad instead of using the project package name?
I guess because google liked it that way. It's a provider and it's from com.google. You can also have multiple providers in your app so just the package name may not be enough.
and what exactly is android:authorities asking for?
A system wide unique identifier for your provider. Or better worldwide unique. All providers are registered with the system and they need to be unique or the second app that wants to use the same name can't be installed.
You use that string in the end to communicate with your provider via an Uri like
Uri uri = Uri.parse("content://" + "your.authoritiy.string")
回答2:
why the android:authorities = com.google.provider.NotePad instead of using the project package name?
Because that is what the author of the code decided to type in. So long as it is likely to be unique, it does not matter.
That being said, using your app's package name as part of the authority is a good idea, simply to help make it likely to be unique.
and what exactly is android:authorities asking for?
It is asking for the authority value(s) supported by the ContentProvider. In a Uri like:
content://please.read.the.documentation/for/content/provider/1
the authority is please.read.the.documentation. Android will find the ContentProvider associated with this Uri by looking up please.read.the.documentation in the roster of all authorities registered by android:authorities attributes in <provider> elements on the device. You can think of it as serving a similar role as the host does in an HTTP URL.
Here is the point in the documentation on ContentProvider that starts discussing authorities.
来源：https://stackoverflow.com/questions/13536478/why-in-the-android-developer-guide-the-androidauthorities-is-defined-like-this