blocks|key|41363|text|它是这样的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|41364|<activity+android:name=".usual.activity.Declaration"+android:theme="@android:style/Theme.Translucent.NoTitleBar"+/>|code-block|syntax|javascript|41365|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|$]]

It goes like this:

<pre><code>&lt;activity android:name=".usual.activity.Declaration" android:theme="@android:style/Theme.Translucent.NoTitleBar" /&gt;
</code></pre>

blocks|key|1044724|text|在您的res/values/styles.xml文件中添加以下样式(如果没有，请创建它)。下面是一个完整的文件：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1044725|<?xml+version="1.0"+encoding="utf-8"?>
<resources>
++<style+name="Theme.Transparent"+parent="android:Theme">
++++<item+name="android:windowIsTranslucent">true</item>
++++<item+name="android:windowBackground">@android:color/transparent</item>
++++<item+name="android:windowContentOverlay">@null</item>
++++<item+name="android:windowNoTitle">true</item>
++++<item+name="android:windowIsFloating">true</item>
++++<item+name="android:backgroundDimEnabled">false</item>
++</style>
</resources>|code-block|syntax|javascript|1044726|(值@color/transparent是我放在res/values/color.xml文件中的颜色值#00000000。你也可以在更高的安卓版本中使用@android:color/transparent。)|1044727|然后将样式应用于您的活动，例如：|1044728|<activity+android:name=".SampleActivity"+android:theme="@style/Theme.Transparent">
...
</activity>|1044729|entityMap^0|3|L|0|0|2|I|O|K|1F|9|24|Q|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|15|8|@]|D|@]|E|$]]|$1|O|3|P|5|H|7|16|8|@]|D|@]|E|$I|J]]|$1|Q|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|R|$]]

Add the following style in your <code>res/values/styles.xml</code> file (if you don’t have one, create it.) Here’s a complete file:

<pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;resources&gt;
 &lt;style name="Theme.Transparent" parent="android:Theme"&gt;
 &lt;item name="android:windowIsTranslucent"&gt;true&lt;/item&gt;
 &lt;item name="android:windowBackground"&gt;@android:color/transparent&lt;/item&gt;
 &lt;item name="android:windowContentOverlay"&gt;@null&lt;/item&gt;
 &lt;item name="android:windowNoTitle"&gt;true&lt;/item&gt;
 &lt;item name="android:windowIsFloating"&gt;true&lt;/item&gt;
 &lt;item name="android:backgroundDimEnabled"&gt;false&lt;/item&gt;
 &lt;/style&gt;
&lt;/resources&gt;
</code></pre>

(The value <code>@color/transparent</code> is the color value <code>#00000000</code> which I put in the <code>res/values/color.xml</code> file. You can also use <code>@android:color/transparent</code> in later Android versions.)

Then apply the style to your activity, for example:

<pre><code>&lt;activity android:name=".SampleActivity" android:theme="@style/Theme.Transparent"&gt;
...
&lt;/activity&gt;
</code></pre>

blocks|key|2454569|text|我想补充一点，因为我也是一个新的Android开发人员。公认的答案很好，但我确实遇到了一些麻烦。我不确定如何在colors.xml文件中添加颜色。下面是应该怎么做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2454570|colors.xml|2454571|<?xml+version="1.0"+encoding="utf-8"?>
<resources>
+++++<color+name="class_zero_background">#7f040000</color>
+++++<color+name="transparent">#00000000</color>
</resources>|code-block|syntax|javascript|2454572|在我的原始colors.xml文件中，我有“drawable”标签：|2454573|<drawable+name="class_zero_background">#7f040000</drawable>|2454574|所以我对颜色也这样做了，但我不理解"@+color+/“引用是指在XML中查找标记"color”。我想我也应该提到这一点，以帮助其他人。|2454575|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|T|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

I wanted to add to this a little bit as I am a new Android developer as well. The accepted answer is great, but I did run into some trouble. I wasn't sure how to add in the color to the colors.xml file. Here is how it should be done:
<h3>colors.xml</h3>
<pre><code>&lt;?xml version=&quot;1.0&quot; encoding=&quot;utf-8&quot;?&gt;
&lt;resources&gt;
 &lt;color name=&quot;class_zero_background&quot;&gt;#7f040000&lt;/color&gt;
 &lt;color name=&quot;transparent&quot;&gt;#00000000&lt;/color&gt;
&lt;/resources&gt;
</code></pre>
In my original colors.xml file I had the tag &quot;drawable&quot;:
<pre><code>&lt;drawable name=&quot;class_zero_background&quot;&gt;#7f040000&lt;/drawable&gt;
</code></pre>
And so I did that for the color as well, but I didn't understand that the &quot;@color/&quot; reference meant look for the tag &quot;color&quot; in the XML. I thought that I should mention this as well to help anyone else out.

blocks|key|1044821|text|我在2.3.3中通过在清单的activity标签中添加android:theme="@android:style/Theme.Translucent"实现了这一点。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1044822|我不知道更低的版本...|1044823|entityMap^0|R|1C|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

I achieved it on 2.3.3 by just adding <code>android:theme="@android:style/Theme.Translucent"</code> in the activity tag in the manifest.

I don't know about lower versions...

blocks|key|1044864|text|只要让活动背景图像透明即可。或者在XML文件中添加主题：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1044865|<activity+android:name=".usual.activity.Declaration"+android:theme="@android:style/Theme.Translucent.NoTitleBar"+/>|code-block|syntax|javascript|1044866|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|$]]

Just let the activity background image be transparent. Or add the theme in the XML file:

<pre><code>&lt;activity android:name=".usual.activity.Declaration" android:theme="@android:style/Theme.Translucent.NoTitleBar" /&gt;
</code></pre>

blocks|key|789329|text|在清单中声明您的活动，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|789330|+<activity+++
+++++android:name=".yourActivity"++++
+++++android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen"/>|code-block|syntax|javascript|789331|并为您的布局添加透明背景。|789332|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Declare your activity in the manifest like this:

<pre><code> &lt;activity 
 android:name=".yourActivity" 
 android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen"/&gt;
</code></pre>

And add a transparent background to your layout.

blocks|key|1044922|text|我找到的最简单的方法是在AndroidManifest中将活动的主题设置为android:theme="@android:style/Theme.Holo.Dialog"。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1044923|然后在活动的onCreate方法中，调用getWindow().setBackgroundDrawable(new+ColorDrawable(0));。|1044924|entityMap^0|11|1C|0|K|1K|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

The easiest way that I have found is to set the activity's theme in the AndroidManifest to <code>android:theme="@android:style/Theme.Holo.Dialog"</code>. 

Then in the activity's onCreate method, call <code>getWindow().setBackgroundDrawable(new ColorDrawable(0));</code>.

blocks|key|788815|text|为其指定半透明主题|type|unstyled|depth|inlineStyleRanges|entityRanges|data|788816|android:theme="@android:style/Theme.Translucent.NoTitleBar"|code-block|syntax|javascript|788817|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|$]]

Assign it the Translucent theme

<pre><code>android:theme="@android:style/Theme.Translucent.NoTitleBar"
</code></pre>

blocks|key|1044970|text|我只做了两件事，它让我的活动变得透明。它们在下面。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1044971|1044972|在清单文件中，我刚刚在activity标记中添加了以下代码。|ordered-list-item|offset|length|style|BOLD|1044973|1044974|android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen"|1044975|And我刚刚将该活动的主布局的背景设置为"#80000000“。喜欢|unordered-list-item|1044976|1044977|android:background="#80000000"|1044978|它非常适合我。|1044979|entityMap^0|0|0|B|8|0|0|0|L|9|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|X|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|Y|8|@$F|Z|G|10|H|I]]|9|@]|A|$]]|$1|J|3|-4|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|12|8|@]|9|@]|A|$]]|$1|M|3|N|5|O|7|13|8|@$F|14|G|15|H|I]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|16|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|18|8|@]|9|@]|A|$]]|$1|U|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|V|$]]

I just did two things, and it made my activity transparent. They are below.

<ol>
<li>In the manifest file I just added the below code in the activity tag.

<pre><code>android:theme="@android:style/Theme.Translucent.NoTitleBar.Fullscreen"
</code></pre></li>
<li>And I just set the background of the main layout for that activity as "#80000000". Like

<pre><code>android:background="#80000000"
</code></pre></li>
</ol>

It perfectly works for me.

blocks|key|2454788|text|在项目的Android清单文件中，将半透明主题分配给要使其透明的活动：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2454789|<activity
++++android:name="YOUR+COMPLETE+ACTIVITY+NAME+WITH+PACKAGE"
++++android:theme="@android:style/Theme.Translucent.NoTitleBar"+/>|code-block|syntax|javascript|2454790|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|$]]

Assign the translucent theme to the activity that you want to make transparent in the Android manifest file of your project:

<pre><code>&lt;activity
 android:name="YOUR COMPLETE ACTIVITY NAME WITH PACKAGE"
 android:theme="@android:style/Theme.Translucent.NoTitleBar" /&gt;
</code></pre>

blocks|key|2454831|text|在setContentView，下面的onCreate函数中，添加以下行：|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2454832|getWindow().setBackgroundDrawable(new+ColorDrawable(Color.TRANSPARENT));|code-block|syntax|javascript|2454833|entityMap^0|1|E|J|8|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|L|$]]

In the onCreate function, below the setContentView, add this line:

<pre><code>getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
</code></pre>

blocks|key|1045086|text|在styles.xml中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1045087|<style+name="Theme.AppCompat.Translucent"+parent="Theme.AppCompat.NoActionBar">
++++<item+name="android:background">#33000000</item>+
++++<item+name="android:windowNoTitle">true</item>
++++<item+name="android:windowBackground">@android:color/transparent</item>
++++<item+name="android:colorBackgroundCacheHint">@null</item>
++++<item+name="android:windowIsTranslucent">true</item>
++++<item+name="android:windowAnimationStyle">@android:style/Animation</item>
</style>|code-block|syntax|javascript|1045088|在AndroidManifest.xml中：|1045089|<activity
++++android:name=".WhateverNameOfTheActivityIs"
++++android:theme="@style/Theme.AppCompat.Translucent">
++++...
</activity>|1045090|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

In the styles.xml:

<pre><code>&lt;style name="Theme.AppCompat.Translucent" parent="Theme.AppCompat.NoActionBar"&gt;
 &lt;item name="android:background"&gt;#33000000&lt;/item&gt; &lt;!-- Or any transparency or color you need --&gt;
 &lt;item name="android:windowNoTitle"&gt;true&lt;/item&gt;
 &lt;item name="android:windowBackground"&gt;@android:color/transparent&lt;/item&gt;
 &lt;item name="android:colorBackgroundCacheHint"&gt;@null&lt;/item&gt;
 &lt;item name="android:windowIsTranslucent"&gt;true&lt;/item&gt;
 &lt;item name="android:windowAnimationStyle"&gt;@android:style/Animation&lt;/item&gt;
&lt;/style&gt;
</code></pre>

In the AndroidManifest.xml:

<pre><code>&lt;activity
 android:name=".WhateverNameOfTheActivityIs"
 android:theme="@style/Theme.AppCompat.Translucent"&gt;
 ...
&lt;/activity&gt;
</code></pre>

blocks|key|41194|text|在我的例子中，我必须根据一些条件在java中设置运行时的主题。所以我在风格上创建了一个主题(类似于其他答案)：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|41195|<?xml+version="1.0"+encoding="utf-8"?>
<resources>
++<style+name="Theme.Transparent"+parent="android:Theme">
++++<item+name="android:windowIsTranslucent">true</item>
++++<item+name="android:windowBackground">@android:color/transparent</item>
++++<item+name="android:windowContentOverlay">@null</item>
++++<item+name="android:windowNoTitle">true</item>
++++<item+name="android:windowIsFloating">true</item>
++++<item+name="android:backgroundDimEnabled">false</item>
++</style>
</resources>|code-block|syntax|javascript|41196|然后在Java中，我将其应用到我的活动中：|41197|@Override
protected+void+onCreate(Bundle+savedInstanceState)+{

++++String+email+=+getIntent().getStringExtra(AppConstants.REGISTER_EMAIL_INTENT_KEY);
++++if+(email+!=+null+&&+!email.isEmpty())+{
++++++++//+We+have+the+valid+email+ID,+no+need+to+take+it+from+user,
++++++++//+prepare+transparent+activity+just+to+perform+bg+tasks+required+for+login
++++++++setTheme(R.style.Theme_Transparent);
++++++++super.onCreate(savedInstanceState);
++++++++setContentView(R.layout.activity_login);

++++}+else
++++++++super.onCreate(savedInstanceState);

++++++++setContentView(R.layout.activity_dummy);
}|41198|记住这里的要点：您必须在调用super.onCreate(savedInstanceState);之前调用setTheme()函数。我错过了这一点，并停留了2个小时，思考为什么我的主题在运行时没有反映出来。|offset|length|style|BOLD|CODE|41199|entityMap^0|0|0|0|0|5|2|E|Z|1H|A|0^^$0|@$1|2|3|4|5|6|7|T|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|U|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|V|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|W|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|X|8|@$M|Y|N|Z|O|P]|$M|10|N|11|O|Q]|$M|12|N|13|O|Q]]|9|@]|A|$]]|$1|R|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|S|$]]

In my case, i have to set the theme on the runtime in java based on some conditions. So I created one theme in style (similar to other answers):

<pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;resources&gt;
 &lt;style name="Theme.Transparent" parent="android:Theme"&gt;
 &lt;item name="android:windowIsTranslucent"&gt;true&lt;/item&gt;
 &lt;item name="android:windowBackground"&gt;@android:color/transparent&lt;/item&gt;
 &lt;item name="android:windowContentOverlay"&gt;@null&lt;/item&gt;
 &lt;item name="android:windowNoTitle"&gt;true&lt;/item&gt;
 &lt;item name="android:windowIsFloating"&gt;true&lt;/item&gt;
 &lt;item name="android:backgroundDimEnabled"&gt;false&lt;/item&gt;
 &lt;/style&gt;
&lt;/resources&gt;
</code></pre>

Then in Java I applied it to my activity:

<pre><code>@Override
protected void onCreate(Bundle savedInstanceState) {

 String email = getIntent().getStringExtra(AppConstants.REGISTER_EMAIL_INTENT_KEY);
 if (email != null &amp;&amp; !email.isEmpty()) {
 // We have the valid email ID, no need to take it from user,
 // prepare transparent activity just to perform bg tasks required for login
 setTheme(R.style.Theme_Transparent);
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_login);

 } else
 super.onCreate(savedInstanceState);

 setContentView(R.layout.activity_dummy);
}
</code></pre>

Remember one Important point here: You must call the <code>setTheme()</code> function before <code>super.onCreate(savedInstanceState);</code>. I missed this point and stucked for 2 hours, thinking why my theme is not reflected at run time.

blocks|key|789436|text|注意1:在Drawable文件夹中创建test.xml并复制以下代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|789437|+++<?xml+version="1.0"+encoding="UTF-8"?>
<shape+xmlns:android="http://schemas.android.com/apk/res/android"
++++android:shape="rectangle"+>

++++<stroke+android:width="2dp"+/>

++++<gradient
++++++++android:angle="90"
++++++++android:endColor="#29000000"
++++++++android:startColor="#29000000"+/>

++++<corners
++++++++android:bottomLeftRadius="7dp"
++++++++android:bottomRightRadius="7dp"
++++++++android:topLeftRadius="7dp"
++++++++android:topRightRadius="7dp"+/>

</shape>|code-block|syntax|javascript|789438|//注意:角点和形状根据您的要求而定。|789439|//注意2:创建xml：|789440|++++<?xml+version="1.0"+encoding="utf-8"?>
++++<LinearLayout+xmlns:android="http://schemas.android.com/apk/res/android"
++++++++android:layout_width="match_parent"
++++++++android:layout_height="match_parent"
++++++++android:background="@drawable/test"
++++++++android:orientation="vertical"+>

++++++++<LinearLayout
++++++++++++android:layout_width="fill_parent"
++++++++++++android:layout_height="wrap_content"
++++++++++++android:layout_weight="1.09"
++++++++++++android:gravity="center"
+++++++++android:background="@drawable/transperent_shape"
++++++++++++android:orientation="vertical"+>
+++++</LinearLayout>
++++</LinearLayout>|789441|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Note 1:In Drawable folder create test.xml and copy the following code

<pre><code> &lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;shape xmlns:android="http://schemas.android.com/apk/res/android"
 android:shape="rectangle" &gt;

 &lt;stroke android:width="2dp" /&gt;

 &lt;gradient
 android:angle="90"
 android:endColor="#29000000"
 android:startColor="#29000000" /&gt;

 &lt;corners
 android:bottomLeftRadius="7dp"
 android:bottomRightRadius="7dp"
 android:topLeftRadius="7dp"
 android:topRightRadius="7dp" /&gt;

&lt;/shape&gt;
</code></pre>

// Note: Corners and shape is as per your requirement.

// Note 2:Create xml:

<pre><code> &lt;?xml version="1.0" encoding="utf-8"?&gt;
 &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:background="@drawable/test"
 android:orientation="vertical" &gt;

 &lt;LinearLayout
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 android:layout_weight="1.09"
 android:gravity="center"
 android:background="@drawable/transperent_shape"
 android:orientation="vertical" &gt;
 &lt;/LinearLayout&gt;
 &lt;/LinearLayout&gt;
</code></pre>

blocks|key|41646|text|只需将以下行添加到清单文件中需要看起来透明的活动标记中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|41647|android:theme="@android:style/Theme.Translucent"|code-block|syntax|javascript|41648|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|$]]

Just add the following line to the activity tag in your manifest file that needs to look transparent.

<pre><code>android:theme="@android:style/Theme.Translucent"
</code></pre>

blocks|key|1045243|text|对于对话活动，我使用以下代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1045244|getWindow().getDecorView().setBackgroundResource(android.R.color.transparent);|code-block|syntax|javascript|1045245|但您还需要将活动中的主视图设置为不可见。否则，背景将不可见，而其中的所有视图都将可见。|1045246|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

For dialog activity I use this:

<pre><code>getWindow().getDecorView().setBackgroundResource(android.R.color.transparent);
</code></pre>

But you also need to set your main View in the activity to invisible. Otherwise the background will be invisible while all views in it will be visible.

blocks|key|1045289|text|有两种方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1045290|使用Theme.NoDisplay|1045291|Using+Theme.Translucent.NoTitleBar|unordered-list-item|1045292|
的|1045293|ordered-list-item|1045294|1045295|使用Theme.NoDisplay仍然可以在…上工作但仅限于较旧的Android设备。在安卓6.0和更高版本上，使用Theme.NoDisplay而不在onCreate()+(or,+technically,+before+onResume())中调用finish()将导致应用程序崩溃。这就是为什么recommendation要使用不受此limitation.”影响的Theme.Translucent.NoTitleBar|offset|length|style|CODE|BOLD|1045296|entityMap^0|0|0|0|0|0|0|2|F|24|1B|3I|8|55|S|3X|20|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|X|8|@]|9|@]|A|$]]|$1|I|3|-4|5|J|7|Y|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|10|8|@$N|11|O|12|P|Q]|$N|13|O|14|P|Q]|$N|15|O|16|P|Q]|$N|17|O|18|P|Q]|$N|19|O|1A|P|R]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|T|$]]

<h2>There're two ways:</h2>

<ol>
<li>Using Theme.NoDisplay</li>
<li>Using Theme.Translucent.NoTitleBar</li>
</ol>

Using <code>Theme.NoDisplay</code> will still work… but only on older Android devices. On Android 6.0 and higher, using Theme.NoDisplay without calling <code>finish()</code> in <code>onCreate() (or, technically, before onResume())</code> will crash your app. This is why the recommendation is to use <code>Theme.Translucent.NoTitleBar</code>, which does not suffer from this limitation.”

blocks|key|789009|text|除了上面的答案之外：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|789010|为了避免与android+Oreo相关的活动崩溃|789011|<style+name="AppTheme.Transparent"+parent="@style/Theme.AppCompat.Dialog">
++++<item+name="windowNoTitle">true</item>
++++<item+name="android:windowCloseOnTouchOutside">false</item>
</style>

<activity
+++++android:name="xActivity"
+++++android:theme="@style/AppTheme.Transparent"+/>|code-block|syntax|javascript|789012|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

in addition to the above answers:

to avoid android Oreo related crash on activity

<pre><code>&lt;style name="AppTheme.Transparent" parent="@style/Theme.AppCompat.Dialog"&gt;
 &lt;item name="windowNoTitle"&gt;true&lt;/item&gt;
 &lt;item name="android:windowCloseOnTouchOutside"&gt;false&lt;/item&gt;
&lt;/style&gt;

&lt;activity
 android:name="xActivity"
 android:theme="@style/AppTheme.Transparent" /&gt;
</code></pre>

blocks|key|2455063|text|如果您使用的是AppCompatActivity，则在styles.xml中添加以下内容|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|2455064|<style+name="TransparentCompat"+parent="@style/Theme.AppCompat.Light.DarkActionBar">
++++<item+name="android:windowNoTitle">true</item>
++++<item+name="android:windowBackground">@android:color/transparent</item>
++++<item+name="android:colorBackgroundCacheHint">@null</item>
++++<item+name="android:windowIsTranslucent">true</item>
++++<item+name="android:windowAnimationStyle">@android:style/Animation</item>
</style>|code-block|syntax|javascript|2455065|在manifest文件中，您可以将此主题添加到活动标签中，如下所示|2455066|android:theme="@style/TransparentCompat"|2455067|有关更多详细信息，请阅读此article|2455068|entityMap|0|LINK|mutability|MUTABLE|url|http://nullpointerbay.com/android-appcompat-design-lib-activity-transparency^0|7|H|7|H|R|A|0|0|1|8|0|0|D|7|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|D]|$9|14|A|15|B|D]]|E|@]|F|$]]|$1|G|3|H|5|I|7|16|8|@]|E|@]|F|$J|K]]|$1|L|3|M|5|6|7|17|8|@$9|18|A|19|B|D]]|E|@]|F|$]]|$1|N|3|O|5|I|7|1A|8|@]|E|@]|F|$J|K]]|$1|P|3|Q|5|6|7|1B|8|@]|E|@$9|1C|A|1D|1|1E]]|F|$]]|$1|R|3|-4|5|6|7|1F|8|@]|E|@]|F|$]]]|S|$T|$5|U|V|W|F|$X|Y]]]]

If you are using <code>AppCompatActivity</code> then add this in <code>styles.xml</code>

<pre><code>&lt;style name="TransparentCompat" parent="@style/Theme.AppCompat.Light.DarkActionBar"&gt;
 &lt;item name="android:windowNoTitle"&gt;true&lt;/item&gt;
 &lt;item name="android:windowBackground"&gt;@android:color/transparent&lt;/item&gt;
 &lt;item name="android:colorBackgroundCacheHint"&gt;@null&lt;/item&gt;
 &lt;item name="android:windowIsTranslucent"&gt;true&lt;/item&gt;
 &lt;item name="android:windowAnimationStyle"&gt;@android:style/Animation&lt;/item&gt;
&lt;/style&gt;
</code></pre>

In <code>manifest</code> file you can add this theme to activity tag like this

<pre><code>android:theme="@style/TransparentCompat"
</code></pre>

for more details read this <a href="http://nullpointerbay.com/android-appcompat-design-lib-activity-transparency" rel="nofollow noreferrer">article</a>

blocks|key|789040|text|所有这些答案可能会令人困惑，透明活动和无UI活动之间是有区别的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|789041|使用以下命令：|789042|android:theme="@android:style/Theme.Translucent.NoTitleBar"|offset|length|style|CODE|789043|将使活动透明，但会阻止UI。|789044|如果您想要一个None+UI活动，请使用以下代码：|789045|android:theme="@android:style/Theme.NoDisplay"|789046|entityMap^0|0|0|0|1N|0|0|0|0|1A|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|T|8|@$F|U|G|V|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|W|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|X|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|Y|8|@$F|Z|G|10|H|I]]|9|@]|A|$]]|$1|P|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|Q|$]]

All those answers might be confusing, there is a difference between Transparent activity and None UI activity.

Using this:

<code>android:theme="@android:style/Theme.Translucent.NoTitleBar"</code>

Will make the activity transparent but will block the UI.

If you want a None UI activity than use this:

<code>android:theme="@android:style/Theme.NoDisplay"</code>

blocks|key|1045424|text|您可以从您的活动中删除主题，并将setContentView(R.layout.mLayout)设置为android:theme="@style/AppTheme.Transparent"。有关更多详细信息，请查看此link。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1045425|entityMap|0|LINK|mutability|MUTABLE|url|https://medium.com/mindorks/android-developers-needs-to-be-creative-da032e53a478^0|G|W|1F|17|30|4|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@$9|S|A|T|1|U]]|E|$]]|$1|F|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

You can remove <code>setContentView(R.layout.mLayout)</code> from your activity and set theme as <code>android:theme="@style/AppTheme.Transparent"</code>. Check this <a href="https://medium.com/mindorks/android-developers-needs-to-be-creative-da032e53a478" rel="nofollow noreferrer">link</a> for more details.

blocks|key|789570|text|2021年事实|type|unstyled|depth|inlineStyleRanges|entityRanges|data|789571|只需添加|789572|<item+name="android:windowBackground">@android:color/transparent</item>|code-block|syntax|javascript|789573|你的任务完成了。|789574|windowIsFloating错误，这会产生一个嵌入的浮动窗口。|offset|length|style|CODE|789575|windowContentOverlay仅与阴影相关。|789576|windowIsTranslucent是错的，它没有成功，所以你可以看到后面的活动。仅当设置变换动画时，windowIsTranslucent才相关。|789577|backgroundDimEnabled降低了下面的活动，但是，它在不同的设备上是完全错误的。(在某些情况下，除非您使用windowIsFloating，否则它什么也不做；通常情况下，这种行为完全是错误的/不确定的。)|789578|除非在非常旧的设备上，否则colorBackgroundCacheHint是无关紧要的，无论如何，缺省值是null。|789579|entityMap^0|0|0|0|0|0|G|0|0|K|0|0|J|0|0|K|0|D|O|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|14|8|@$M|15|N|16|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|17|8|@$M|18|N|19|O|P]]|9|@]|A|$]]|$1|S|3|T|5|6|7|1A|8|@$M|1B|N|1C|O|P]]|9|@]|A|$]]|$1|U|3|V|5|6|7|1D|8|@$M|1E|N|1F|O|P]]|9|@]|A|$]]|$1|W|3|X|5|6|7|1G|8|@$M|1H|N|1I|O|P]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]]|Z|$]]

<h2>2021 facts</h2>
Just add
<pre><code>&lt;item name=&quot;android:windowBackground&quot;&gt;@android:color/transparent&lt;/item&gt;
</code></pre>
You're done.
<code>windowIsFloating</code> wrong, this makes an INSET floating window.
<code>windowContentOverlay</code> only relates to shadows.
<code>windowIsTranslucent</code> is WRONG, it DOES NOT make it so you can see the activity behind. windowIsTranslucent is only relevant if animating transitions.
<code>backgroundDimEnabled</code> dims the activity below, BUT, it is completely buggy on different devices. (In some cases, it does nothing unless you are using windowIsFloating; in general the behavior is totally buggy/indeterminate.)
<code>colorBackgroundCacheHint</code> is irrelevant except on extremely old devices, the default is null anyway.

blocks|key|1045527|text|只需将此代码放入style.xml|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1045528|<item+name="android:windowBackground">@android:color/transparent</item>|code-block|syntax|javascript|1045529|oR加载项清单|1045530|<activity+android:name=".usual.activity.Declaration"+
+android:theme="@android:style/Theme.Translucent.NoTitleBar"+/>|1045531|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

just put this in style.xml
<pre><code>&lt;item name=&quot;android:windowBackground&quot;&gt;@android:color/transparent&lt;/item&gt;
</code></pre>
oR Add in Manifest
<pre><code>&lt;activity android:name=&quot;.usual.activity.Declaration&quot; 
 android:theme=&quot;@android:style/Theme.Translucent.NoTitleBar&quot; /&gt;
</code></pre>

I want to create a transparent Activity on top of another activity.

How can I achieve this?

How do I create a transparent Activity on Android?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想在另一个活动之上创建一个透明的活动。我如何才能做到这一点？

问如何在Android上创建透明的Activity？
EN

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问如何在Android上创建透明的Activity？EN