如何使三个点出现在Android工具栏中 [英] How to make the three dots appear in the Android toolbar

问题描述

我是Android应用程序开发的新手，我试图在UI中开发应用程序，我添加了一个工具栏，但是在不知道为什么工具栏右侧的三个点对我来说是必要的，因为我想要在其中添加注销按钮.

I am new in Android applications development, and I am trying to develop an application in UI I added a toolbar but In don't know why the three dots in the right side of the toolbar, it is necessary for me because I want to add a logout button there.

这是工具栏布局:

 <?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="wrap_content"
    android:background="#000">

</android.support.v7.widget.Toolbar>

这是我在活动类中添加工具栏的地方:

And here is where i add the toolbar inside the activity class:

 toolbar= (Toolbar) findViewById(R.id.app_bar);
    setSupportActionBar(toolbar);
    toolbar.setTitle(R.string.app_name);
    toolbar.setTitleTextColor(getResources().getColor(R.color.com_facebook_button_background_color_focused));

这是我的menu.xml:

and this is my menu.xml:

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools" tools:context=".HomeActivity">


    <item android:id="@+id/action_settings"

        android:title="Settings"
        android:orderInCategory="100"
        app:showAsAction="always"
        android:icon="@drawable/icon"
        />

    <item
        android:id="@+id/action_search"
        android:title="Search">
        </item>
</menu>

奇怪的是，在android studio预览中显示了三个点:

And what is weird is that in the android studio preview the three dots are shown:

我做错了什么?

推荐答案

三个点被隐藏了，因为它们是黑色的，并且工具栏背景是黑色的，所以我不得不添加这个白色主题

The three dots were hidden because they were black, and the toolbar background is black, so I had to add this white theme

  android:theme="@style/ThemeOverlay.AppCompat.Dark"

进入我的工具栏布局.

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