blocks|key|281684|text|接受两个String的ComponentName构造函数可以用来引用另一个应用程序中的组件。但是，第一个参数不是类的包名；而是应用程序的包名-应用程序的AndroidManifest.xml中manifest元素的package属性。所以你的第一个例子应该是|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|281685|ComponentName+cn+=+new+ComponentName("de.zordid.sampleapp",
++++"de.zordid.sampleapp.widget.WidgetProvider");|code-block|syntax|javascript|281686|该构造函数当然可以用来引用您自己的应用程序中的组件，但是既然您已经从自己的应用程序中获得了一个Context，那么您最好使用它并使用其他构造函数之一。在我看来，只要可用，参加Class考试的人应该是首选的。如果出于某种原因只动态地知道类，那么可以使用接受String的方法；在这种情况下，它应该采用上面的完全限定类名。|281687|entityMap^0|4|6|B|D|24|J|2O|8|2Z|7|0|0|1B|7|2F|5|3J|6|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|N|$]]

The <code>ComponentName</code> constructor taking two <code>String</code>s can be used to refer to a component in another application. But, the first argument is not the package name of the class; it is the package name of the application---the <code>package</code> attribute of the <code>manifest</code> element in that application's <code>AndroidManifest.xml</code>. So your first example should be

<pre><code>ComponentName cn = new ComponentName("de.zordid.sampleapp",
 "de.zordid.sampleapp.widget.WidgetProvider");
</code></pre>

That constructor could certainly be used to refer to components in your own application, but since you already have hold of a <code>Context</code> from your own application you might as well use it and use one of the other constructors. In my opinion, the one taking a <code>Class</code> should be preferred whenever usable. You could use the one taking a <code>String</code> if you only know the class dynamically for some reason; in that case, it should take the fully-qualified class name as above.

blocks|key|281689|text|或者您可以像这样在BroadcastReceiver中使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|281690|ComponentName+smsReceiver+=+new+ComponentName(this,+SMSReceiver.class);|code-block|syntax|javascript|281691|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Or you can use like this inside BroadcastReceiver :

<pre><code>ComponentName smsReceiver = new ComponentName(this, SMSReceiver.class);
</code></pre>

blocks|key|281698|text|关于优先选择对象而不是字符串，Robert+Tupelo-Schneck的回答是正确的，下面是我的看法。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|281699|281700|要引用您自己的组件，请使用：|unordered-list-item|281701|281702|WidgetProvider.class);|281703|To+(getApplicationContext()，new+ComponentName指的是您自己的应用程序中一些动态引用的组件，请使用：|281704|281705|//取值/字符串.xml:+de.zordid.sampleapp.widget.WidgetProvider+String+fqcn+=+getResources().getString(R.string.provider)；new+ComponentName(getApplicationContext()，fqcn)；|281706|当你想使用Android的资源限定符来决定使用哪个组件时，这是很有用的，你可以覆盖values-*/strings.xml.|style|CODE|281707|To中的默认字符串引用另一个应用程序的组件，使用：|281708|281709|context.getPackageManager().getPackageInfo("com.other.app"，componentFlags+=+GET_ACTIVITIES+%7C+GET_PROVIDERS+%7C+GET_RECEIVERS+%7C+GET_SERVICES；PackageInfo+otherApp+=+int+componentFlags)；ComponentInfo+info+=+otherApp.activitiesi；//或者提供者/接收者/...新建ComponentName(info.packageName，info.name);|281710|关于.Names和<manifest+package="|281711|这里可能有一些混淆，因为我认为从历史上看，罗伯特的说法是正确的：|281712|281713|它是应用程序的包名-该应用程序的AndroidManifest.xml中清单元素的包属性|blockquote|281714|281715|281716|但现在不是了。自从引入了新的Gradle构建系统后，这里就出现了some+changes。|281717|如果您在build.gradle中指定了一个android.defaultConfig.applicationId，它将是应用程序包的名称，那么在构建应用程序时，清单中的package属性是另一回事。现在，ComponentName的第一个参数引用了applicationId+%2B+applicationIdSuffix。棘手的是，在最终的清单合并和打包之后，APK将拥有<manifest+package=applicationId+%2B+applicationIdSuffix，所有的.Names都将扩展为FQCN。|281718|学习名称解析的示例应用程序|281719|这是一个基于我的一个应用程序结构的示例结构。考虑一下名为“app”的假想应用程序中的以下类：|281720|281721|net.twisterrob.app.android.App|281722|net.twisterrob.app.android.GlideSetup|281723|net.twisterrob.app.android.subpackage.SearchResultsActivity|281724|net.twisterrob.app.android.subpackage.Activity|281725|net.twisterrob.app.android.content.AppProvider|281726|281727|在应用程序的服务器端后端和/或一些共享模型类上：|281728|281729|net.twisterrob.app.data.*|281730|net.twisterrob.app.backend.*|281731|net.twisterrob.app.web.*|281732|281733|在我的Android助手库中：|281734|281735|net.twisterrob.android.activity.AboutActivity|281736|281737|其他库：|281738|281739|android.support.v4.content.FileProvider|281740|281741|这样，所有内容都在net.twisterrob.app中命名空间。android应用程序只是它自己的子包中整体的一部分。|281742|AndroidManifest.xml+(省略不相关的部分)|281743|<?xml+version="1.0"+encoding="utf-8"?>
<manifest+xmlns:android="http://schemas.android.com/apk/res/android"
++++++++++package="net.twisterrob.app.android">
++++

++++
++++<application+android:name=".App">
++++++++
++++++++<meta-data+android:name="net.twisterrob.app.android.GlideSetup"+android:value="GlideModule"+/>
++++++++<meta-data+android:name="android.app.default_searchable"+android:value="net.twisterrob.app.android.subpackage.SearchResultsActivity"+/>
++++++++
++++++++<activity+android:name=".subpackage.Activity"+/>
++++++++
++++++++<activity+android:name="net.twisterrob.android.activity.AboutActivity"+/>
++++++++
++++++++<provider+android:name=".content.AppProvider"+android:authorities="${applicationId}"+/>
++++++++
++++++++<provider+android:name="android.support.v4.content.FileProvider"+android:authorities="${applicationId}.share"+/>
++++</application>
++++
</manifest>|code-block|syntax|javascript|281744|build.gradle|281745|android+{
++++defaultConfig+{
++++++++//+this+is+what+will+be+used+when+you+upload+it+to+the+Play+Store
++++++++applicationId+'net.twisterrob.app'
++++}
++++buildTypes+{
++++++++debug+{
++++++++++++//+The+neatest+trick+ever!
++++++++++++//+Released+application:+net.twisterrob.app
++++++++++++//+IDE+built+debug+application:+net.twisterrob.app.debug
++++++++++++//+This+will+allow+you+to+have+your+installed+released+version
++++++++++++//+and+sideloaded+debug+application+at+the+same+time+working+independently.
++++++++++++//+All+the+ContentProvider+authorities+within+a+system+must+have+a+unique+name+
++++++++++++//+so+using+${applicationId}+as+authority+will+result+in+having+two+different+content+providers.
++++++++++++applicationIdSuffix+'.debug'
++++++++}
++++}
}|281746|要查看所有合并后的最终清单会是什么样子，请打开build\intermediates\manifests\full\debug\AndroidManifest.xml。|281747|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/4986081/253468|1|http://tools.android.com/tech-docs/new-build-system/applicationid-vs-packagename^0|F|L|0|0|0|0|0|0|0|0|0|15|K|0|0|0|0|9|J|0|0|0|0|0|0|W|C|1|0|4|C|M|Z|2D|7|2V|D|3H|Z|56|1H|0|0|0|0|0|U|0|0|11|0|0|1N|0|0|1A|0|0|1A|0|0|0|0|0|P|0|0|S|0|0|O|0|0|0|0|0|19|0|0|0|0|0|13|0|0|9|I|0|0|J|0|0|0|C|0|0|N|1O|0^^$0|@$1|2|3|4|5|6|7|33|8|@]|9|@$A|34|B|35|1|36]]|C|$]]|$1|D|3|-4|5|6|7|37|8|@]|9|@]|C|$]]|$1|E|3|F|5|G|7|38|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|39|8|@]|9|@]|C|$]]|$1|I|3|J|5|6|7|3A|8|@]|9|@]|C|$]]|$1|K|3|L|5|G|7|3B|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|3C|8|@]|9|@]|C|$]]|$1|N|3|O|5|6|7|3D|8|@]|9|@]|C|$]]|$1|P|3|Q|5|6|7|3E|8|@$A|3F|B|3G|R|S]]|9|@]|C|$]]|$1|T|3|U|5|G|7|3H|8|@]|9|@]|C|$]]|$1|V|3|-4|5|6|7|3I|8|@]|9|@]|C|$]]|$1|W|3|X|5|6|7|3J|8|@]|9|@]|C|$]]|$1|Y|3|Z|5|6|7|3K|8|@$A|3L|B|3M|R|S]]|9|@]|C|$]]|$1|10|3|11|5|6|7|3N|8|@]|9|@]|C|$]]|$1|12|3|-4|5|6|7|3O|8|@]|9|@]|C|$]]|$1|13|3|14|5|15|7|3P|8|@]|9|@]|C|$]]|$1|16|3|-4|5|6|7|3Q|8|@]|9|@]|C|$]]|$1|17|3|-4|5|6|7|3R|8|@]|9|@]|C|$]]|$1|18|3|19|5|6|7|3S|8|@]|9|@$A|3T|B|3U|1|3V]]|C|$]]|$1|1A|3|1B|5|6|7|3W|8|@$A|3X|B|3Y|R|S]|$A|3Z|B|40|R|S]|$A|41|B|42|R|S]|$A|43|B|44|R|S]|$A|45|B|46|R|S]|$A|47|B|48|R|S]]|9|@]|C|$]]|$1|1C|3|1D|5|6|7|49|8|@]|9|@]|C|$]]|$1|1E|3|1F|5|6|7|4A|8|@]|9|@]|C|$]]|$1|1G|3|-4|5|6|7|4B|8|@]|9|@]|C|$]]|$1|1H|3|1I|5|G|7|4C|8|@$A|4D|B|4E|R|S]]|9|@]|C|$]]|$1|1J|3|1K|5|G|7|4F|8|@$A|4G|B|4H|R|S]]|9|@]|C|$]]|$1|1L|3|1M|5|G|7|4I|8|@$A|4J|B|4K|R|S]]|9|@]|C|$]]|$1|1N|3|1O|5|G|7|4L|8|@$A|4M|B|4N|R|S]]|9|@]|C|$]]|$1|1P|3|1Q|5|G|7|4O|8|@$A|4P|B|4Q|R|S]]|9|@]|C|$]]|$1|1R|3|-4|5|6|7|4R|8|@]|9|@]|C|$]]|$1|1S|3|1T|5|6|7|4S|8|@]|9|@]|C|$]]|$1|1U|3|-4|5|6|7|4T|8|@]|9|@]|C|$]]|$1|1V|3|1W|5|G|7|4U|8|@$A|4V|B|4W|R|S]]|9|@]|C|$]]|$1|1X|3|1Y|5|G|7|4X|8|@$A|4Y|B|4Z|R|S]]|9|@]|C|$]]|$1|1Z|3|20|5|G|7|50|8|@$A|51|B|52|R|S]]|9|@]|C|$]]|$1|21|3|-4|5|6|7|53|8|@]|9|@]|C|$]]|$1|22|3|23|5|6|7|54|8|@]|9|@]|C|$]]|$1|24|3|-4|5|6|7|55|8|@]|9|@]|C|$]]|$1|25|3|26|5|G|7|56|8|@$A|57|B|58|R|S]]|9|@]|C|$]]|$1|27|3|-4|5|6|7|59|8|@]|9|@]|C|$]]|$1|28|3|29|5|6|7|5A|8|@]|9|@]|C|$]]|$1|2A|3|-4|5|6|7|5B|8|@]|9|@]|C|$]]|$1|2B|3|2C|5|G|7|5C|8|@$A|5D|B|5E|R|S]]|9|@]|C|$]]|$1|2D|3|-4|5|6|7|5F|8|@]|9|@]|C|$]]|$1|2E|3|2F|5|6|7|5G|8|@$A|5H|B|5I|R|S]]|9|@]|C|$]]|$1|2G|3|2H|5|6|7|5J|8|@$A|5K|B|5L|R|S]]|9|@]|C|$]]|$1|2I|3|2J|5|2K|7|5M|8|@]|9|@]|C|$2L|2M]]|$1|2N|3|2O|5|6|7|5N|8|@$A|5O|B|5P|R|S]]|9|@]|C|$]]|$1|2P|3|2Q|5|2K|7|5Q|8|@]|9|@]|C|$2L|2M]]|$1|2R|3|2S|5|6|7|5R|8|@$A|5S|B|5T|R|S]]|9|@]|C|$]]|$1|2T|3|-4|5|6|7|5U|8|@]|9|@]|C|$]]]|2U|$2V|$5|2W|2X|2Y|C|$2Z|30]]|31|$5|2W|2X|2Y|C|$2Z|32]]]]

<a href="https://stackoverflow.com/a/4986081/253468">Robert Tupelo-Schneck</a>'s answer is right about preferring objects against Strings. Here's how I see it.

<ul>
<li>To refer to your own components, use:

<pre><code>new ComponentName(getApplicationContext(), WidgetProvider.class);
</code></pre></li>
<li>To refer to some dynamically referenced component in your own app, use:

<pre><code>// values/strings.xml: &lt;string name="provider"&gt;de.zordid.sampleapp.widget.WidgetProvider&lt;/string&gt;
String fqcn = getResources().getString(R.string.provider);
new ComponentName(getApplicationContext(), fqcn);
</code></pre>

This is useful when you want to use Android's resource qualifiers to decide which component to use, you can override the default string in <code>values-*/strings.xml</code>.</li>
<li>To refer to another application's component, use:

<pre><code>int componentFlags = GET_ACTIVITIES | GET_PROVIDERS | GET_RECEIVERS | GET_SERVICES;
PackageInfo otherApp = context.getPackageManager().getPackageInfo("com.other.app", componentFlags);
ComponentInfo info = otherApp.activities[i]; // or providers/receivers/...
new ComponentName(info.packageName, info.name);
</code></pre></li>
</ul>

<h1>About .Names and <code>&lt;manifest package="</code></h1>

There may be some confusion here because I think historically Robert's statement was true:

<blockquote>
 it is the package name of the application---the package attribute of the manifest element in that application's AndroidManifest.xml
</blockquote>

but not any more. Since the new Gradle build system was introduced there has been <a href="http://tools.android.com/tech-docs/new-build-system/applicationid-vs-packagename" rel="noreferrer">some changes</a> around here.

If you have an <code>android.defaultConfig.applicationId</code> specified in your <code>build.gradle</code> that'll be the app package name, and then <code>package</code> attribute in manifest is a separate thing when building your app. The first argument of <code>ComponentName</code> now refers to <code>applicationId + applicationIdSuffix</code>. The tricky thing is that after the final manifest merge and packaging the APK will have <code>&lt;manifest package=applicationId + applicationIdSuffix</code> and all the .Names will be expanded to FQCNs.

<h2>Example app for learning name resolution</h2>

Here's an example structure based on the structure of one of my apps. Consider the following classes in a hypothetical app called "app":

<ul>
<li><code>net.twisterrob.app.android.App</code></li>
<li><code>net.twisterrob.app.android.GlideSetup</code></li>
<li><code>net.twisterrob.app.android.subpackage.SearchResultsActivity</code></li>
<li><code>net.twisterrob.app.android.subpackage.Activity</code></li>
<li><code>net.twisterrob.app.android.content.AppProvider</code></li>
</ul>

on the server side backend of the app and/or some shared model classes:

<ul>
<li><code>net.twisterrob.app.data.*</code></li>
<li><code>net.twisterrob.app.backend.*</code></li>
<li><code>net.twisterrob.app.web.*</code></li>
</ul>

in my Android helper library:

<ul>
<li><code>net.twisterrob.android.activity.AboutActivity</code></li>
</ul>

other libraries:

<ul>
<li><code>android.support.v4.content.FileProvider</code></li>
</ul>

This way everything is namespaced in <code>net.twisterrob.app</code>. The android app being just a single part of the whole inside it's own subpackage.

<h3><code>AndroidManifest.xml</code> (irrelevant parts omitted)</h3>

<pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
 package="net.twisterrob.app.android"&gt;
 &lt;!--
 `package` above defines the base package for .Names
 to simplify reading/writing the manifest.
 Notice that it's different than the `applicationId` in build.gradle
 and can be independently changed in case you want to refactor your packages.
 This way you can still publish the same app with the same name.
 --&gt;

 &lt;!-- Will be expanded to net.twisterrob.app.android.App in the manifest merging phase. --&gt;
 &lt;application android:name=".App"&gt;
 &lt;!-- meta-data needs FQCNs because the merger can't know if you want to expand them or not.
 Also notice that name and value both can contain class names, depending on what you use. --&gt;
 &lt;meta-data android:name="net.twisterrob.app.android.GlideSetup" android:value="GlideModule" /&gt;
 &lt;meta-data android:name="android.app.default_searchable" android:value="net.twisterrob.app.android.subpackage.SearchResultsActivity" /&gt;
 &lt;!-- Will be expanded to net.twisterrob.app.android.subpackage.Activity in the manifest merging phase. --&gt;
 &lt;activity android:name=".subpackage.Activity" /&gt;
 &lt;!-- Needs full qualification because it's not under the package defined on manifest element. --&gt;
 &lt;activity android:name="net.twisterrob.android.activity.AboutActivity" /&gt;
 &lt;!-- Will be expanded to net.twisterrob.app.android.content.AppProvider in the manifest merging phase. --&gt;
 &lt;provider android:name=".content.AppProvider" android:authorities="${applicationId}" /&gt;
 &lt;!-- Needs full qualification because it's not under the package defined on manifest element. --&gt;
 &lt;provider android:name="android.support.v4.content.FileProvider" android:authorities="${applicationId}.share" /&gt;
 &lt;/application&gt;
 &lt;!-- ${applicationId} will be replaced with what's defined in `build.gradle` --&gt;
&lt;/manifest&gt;
</code></pre>

<h3><code>build.gradle</code></h3>

<pre><code>android {
 defaultConfig {
 // this is what will be used when you upload it to the Play Store
 applicationId 'net.twisterrob.app'
 }
 buildTypes {
 debug {
 // The neatest trick ever!
 // Released application: net.twisterrob.app
 // IDE built debug application: net.twisterrob.app.debug
 // This will allow you to have your installed released version
 // and sideloaded debug application at the same time working independently.
 // All the ContentProvider authorities within a system must have a unique name 
 // so using ${applicationId} as authority will result in having two different content providers.
 applicationIdSuffix '.debug'
 }
 }
}
</code></pre>

To check out what your final manifest will look like after all the merging open <code>build\intermediates\manifests\full\debug\AndroidManifest.xml</code>.

I am a little bit confused about the ComponentName class in Android.

There are different ways to get to a component name object, but I don't know when to use which... and why!

Example:

<ul>
<li>Application package is <code>de.zordid.sampleapp</code></li>
<li>but widget provider class is <code>de.zordid.sampleapp.widget.WidgetProvider</code></li>
</ul>

Using 

<pre><code>ComponentName cn = new ComponentName("de.zordid.sampleapp.widget",
 "WidgetProvider");
</code></pre>

I got this component info: <code>ComponentInfo{de.zordid.sampleapp.widget/WidgetProvider}</code>, but I could not use this - the component is unknown!
But the JavaDoc says I should give the package and the class within that package - and that is what I did, didn't I??

Using

<pre><code>ComponentName cn = new ComponentName(context, WidgetProvider.class);
</code></pre>

yields <code>ComponentInfo{de.zordid.sampleapp/de.zordid.sampleapp.widget.WidgetProvider}</code> - and that works fine!!

There is even another way to get a ComponentName - by context and a string.
Which one should be used where and when??

Thanks!

When to use which constructor for ComponentName in Android?

服务器

Android

我对安卓中的ComponentName类有点困惑。有不同的方法可以获取组件名称对象，但我不知道何时使用哪种方法……为什么！示例：de.zordid.sampleappbut微件提供程序类为de.zordid.sampleapp.widget.WidgetProvider的应用程序包使用ComponentName cn ...

问什么时候在Android中使用ComponentName的构造函数？
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