百分比布局的出现主要是因为LinearLayout中可以通过android:layout_weight="1"这种方法来支持按比例指定控件大小

但是FrameLayout和RelativeLayout中并没有这种实现比例分配的功能，因此引入了PercentFrameLayout和PercentRelativeLayout这两个全新的布局

接下来是PercentFrameLayout的具体应用，需要导入support库

在app的build.gradle中添加如下的包

dependencies {
    compile fileTree(dir: ‘libs‘, include: [‘*.jar‘])
    androidTestCompile(‘com.android.support.test.espresso:espresso-core:2.2.2‘, {
        exclude group: ‘com.android.support‘, module: ‘support-annotations‘
    })
    compile ‘com.android.support:appcompat-v7:25.3.1‘
compile ‘com.android.support:percent:25.3.1‘
    testCompile ‘junit:junit:4.12‘
}
接下来对布局的安排代码为：

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
    android:id="@+id/activity_main"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.itheima.album.uilayouttest.MainActivity">
 <android.support.percent.PercentFrameLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        >
        <Button
            android:id="@+id/button1"
            android:text="Button 1"
            android:layout_gravity="left|top"
            app:layout_widthPercent="50%"
            app:layout_heightPercent="50%"
            />
        <Button
            android:id="@+id/button2"
            android:text="Button 2"
            android:layout_gravity="right|top"
            app:layout_widthPercent="50%"
            app:layout_heightPercent="50%"
            />
        <Button
            android:id="@+id/button3"
            android:text="Button 3"
            android:layout_gravity="left|bottom"
            app:layout_widthPercent="50%"
            app:layout_heightPercent="50%"
            />
        <Button
            android:id="@+id/button4"
            android:text="Button 4"
            android:layout_gravity="right|bottom"
            app:layout_widthPercent="50%"
            app:layout_heightPercent="50%"
            />
    </android.support.percent.PercentFrameLayout>
</FrameLayout>
程序运行截图如下：

 PercentRelativeLayout实现上图所示：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:id="@+id/activity_main"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.itheima.album.uilayouttest.MainActivity">
 <android.support.percent.PercentRelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        >
        <Button
            android:id="@+id/button1"
            android:text="Button1"
            app:layout_widthPercent="50%"
            app:layout_heightPercent="50%"
            />
        <Button
            android:id="@+id/button2"
            android:text="Button2"
            android:layout_toRightOf="@id/button1"
            app:layout_widthPercent="50%"
            app:layout_heightPercent="50%"
            />
        <Button
            android:id="@+id/button3"
            android:text="Button3"
            android:layout_below="@id/button1"
            app:layout_widthPercent="50%"
            app:layout_heightPercent="50%"
            />
        <Button
            android:id="@+id/button4"
            android:text="Button4"
            android:layout_below="@id/button1"
            android:layout_toRightOf="@id/button3"
            app:layout_widthPercent="50%"
            app:layout_heightPercent="50%"
            />
    </android.support.percent.PercentRelativeLayout>
</RelativeLayout>
执行如下图所示：

Android中百分比布局