如何用半透明视图覆盖ImageView？

Question

I have an ImageView in an activity that takes up the whole screen. What I want to do is have a few translucent buttons in the corner of this ImageView overlayed on top (like 30% transparency). Is this possible with an ImageView in android? If it is can someone point me in the right direction to get started?

Answer 1

Use a layout, and make your ImageView and two Buttons children within the layout.

Example using RelativeLayout:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <ImageView
            android:src="@drawable/image"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

    <Button
            android:id="@+id/button1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:alpha="0.5"
            android:text="Button 1"/>

    <Button
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toRightOf="@id/button1"
            android:alpha="0.5"
            android:text="Button 2"/>

</RelativeLayout>

You can position your buttons better by using android:layout_marginTop and android:layout_marginLeft attributes.

The key parts to understand here are:

1/ The ImageView is set to match_parent , therefore it'll stretch to fill the RelativeLayout.

2/ By default, sub Views are positioned at the top left of RelativeLayouts, this is why button1 appears there.

3/ Button2 is positioned to the right of button1 using the RelativeLayout attribute layout_toRightOf . Its vertical position is still set to the default - top.