您好我有我正在使用，以填补我的网页布局，我必须设置在我的绘制文件夹在布局召开的背景图像。

Hi I have a layout which I'm using to fill my page and I have to set a background image held in my drawable folder in that layout.

我要接盘 alpha值形象的东西相当低，几乎让像水标志的图像。

I want to then set the alpha value of the image to something quite low almost make the image like a water mark.

我的XML看起来像

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/background"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:background="@drawable/main_background" >

正如你可以看到我分配了id的布局

As you can see I have assigned an id to the layout

我想在我的OnCreate我可以做这样的事情？

I thought in my oncreate I could do something like this?

View backgroundimage = (View) findViewById(R.id.background);
backgroundimage.setAlpha(80);

这是不工作但我怀疑它，因为我想投背景为查看我要抛弃它？

This is not working however I suspect its because I'm trying to cast the background as a View what should I cast it as?

推荐答案

尝试使用 Drawable.setAlpha（）;

Try to use Drawable.setAlpha();

你应该做的是这样的：

View backgroundimage = findViewById(R.id.background);
Drawable background = backgroundimage.getBackground();
background.setAlpha(80);