Android and setting alpha for (image) view alpha

Is there really no XML attribute counterpart to setAlpha(int)?

If not, what alternatives are there?

No, there is not, see how the "Related XML Attributes" section is missing in the ImageView.setAlpha(int) documentation. The alternative is to use View.setAlpha(float) whose XML counterpart is android:alpha. It takes a range of 0.0 to 1.0 instead of 0 to 255. Use it e.g. like

<ImageView android:alpha="0.4">

However, the latter in available only since API level 11.

jfcogato

It's easier than the other response. There is an xml value alpha that takes double values.

android:alpha="0.0" thats invisible

android:alpha="0.5" see-through

android:alpha="1.0" full visible

That's how it works.

Umesh

I am not sure about the XML but you can do it by code in the following way.

ImageView myImageView = new ImageView(this);
myImageView.setAlpha(xxx);

In pre-API 11:

range is from 0 to 255 (inclusive), 0 being transparent and 255 being opaque.

In API 11+:

range is from 0f to 1f (inclusive), 0f being transparent and 1f being opaque.

marnaish

Maybe a helpful alternative for a plain-colored background:

Put a LinearLayout over the ImageView and use the LinearLayout as a opacity filter. In the following a small example with a black background:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FF000000" >

<RelativeLayout
    android:id="@+id/relativeLayout2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/icon_stop_big" />

    <LinearLayout
        android:id="@+id/opacityFilter"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="#CC000000"
        android:orientation="vertical" >
    </LinearLayout>
</RelativeLayout>

Vary the android:background attribute of the LinearLayout between #00000000 (fully transparent) and #FF000000 (fully opaque).

There is now an XML alternative:

        <ImageView
        android:id="@+id/example"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/example"
        android:alpha="0.7" />

It is: android:alpha="0.7"

With a value from 0 (transparent) to 1 (opaque).

use android:alpha=0.5 to achieve the opacity of 50% and to turn Android Material icons from Black to Grey.

Use this form to ancient version of android.

ImageView myImageView;
myImageView = (ImageView) findViewById(R.id.img);

AlphaAnimation alpha = new AlphaAnimation(0.5F, 0.5F);
alpha.setDuration(0); 
alpha.setFillAfter(true); 
myImageView.startAnimation(alpha);

setAlpha(int) is deprecated as of API 16: Android 4.1

Please use setImageAlpha(int) instead

The alpha can be set along with the color using the following hex format #ARGB or #AARRGGBB. See http://developer.android.com/guide/topics/resources/color-list-resource.html

来源：https://stackoverflow.com/questions/4931071/android-and-setting-alpha-for-image-view-alpha

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