框架动画有透明背景

Question

I want to use animation like progress bar.

I have the xml file prog_drawable.xml

<?xml version="1.0" encoding="utf-8"?>
<animation-list xmlns:android="http://schemas.android.com/apk/res/android"
android:oneshot="false" >
<item
    android:drawable="@drawable/progress01"
    android:duration="100"/>
<item
    android:drawable="@drawable/progress02"
    android:duration="100"/>
<item
    android:drawable="@drawable/progress03"
    android:duration="100"/>
<item
    android:drawable="@drawable/progress04"
    android:duration="100"/>
<item
    android:drawable="@drawable/progress05"
    android:duration="100"/>
</animation-list>

File progress0x.png looks like this (for example)

Background in this file is transparent.

In activity's layout xml I have imageview

<RelativeLayout
    android:id="@+id/loadingPanel"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <TextView
        android:id="@+id/tv_logo2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/app_name"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <ImageView
        android:id="@+id/iv_pb"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/tv_logo2"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:background="@android:color/transparent"
        android:contentDescription="@string/app_name" />
</RelativeLayout>

Then in java file

AnimationDrawable ad;
ImageView iv_pb;
...
iv_pb = (ImageView)findViewById(R.id.iv_pb);
iv_pb.setBackgroundResource(R.drawable.prog_drawable);

ad = (AnimationDrawable)iv_pb.getBackground();
ad.start();

When I launch my application I see this animation, but with black background. How can I get transparent background?

Answer 1

Even though you are setting android:background="@android:color/transparent" to your ImageView for transparent background, but calling iv_pb.setBackgroundResource(R.drawable.prog_drawable); overrides this, causing your animation-drawable to be set as new background.

So, eventually you need to implement transparency in your image files. Make sure all the files are in .png with their background set as transparent.