利用ProgressBar实现旋转loading动画

1.res\anim.loading.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layout_loading"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center">

        <ProgressBar
            android:id="@+id/progress_bar"
            android:layout_width="100dp"
            android:layout_height="100dp"
            style="@style/progressbar_style"/>
        <TextView
            android:layout_width="100dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/progress_bar"
            android:lines="1"
            android:text="等待蓝牙连接……"
            android:textSize="8sp"
            android:gravity="center"/>
    </RelativeLayout>

</LinearLayout>

2.values\Style.xml

   <!-- loading 动画-->
    <style name="progressbar_style">
        <item name="android:maxWidth">50.0dip</item>
        <item name="android:maxHeight">50.0dip</item>
        <item name="android:indeterminateDrawable">@anim/anim_loading</item>
        <item name="android:minWidth">50.0dip</item>
        <item name="android:minHeight">50.0dip</item>
    </style>

　3. anim\anim.loading.xml

<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
    android:drawable="@drawable/loading"
    android:fromDegrees="-720"
    android:duration="400"
    android:toDegrees="0"
    android:pivotX="50.0%"
    android:pivotY="50.0%"/>