Android Image View's setImageMatrix not working - Stack Overflow

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I'm trying to apply transformation to an image view using Matrix class. My idea is to be able to mirror the image, but actually any transformation I apply (e.g. scale or translate) doesn't work. I tried creating a custom view and add the code in onPreDraw event placed in the constructor, also tried on click event - non of them worked. My code is as follows:

Image drawable I use

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android=";
    android:shape="oval">
    <solid android:color="@color/bright_sun" />
</shape>

Setting the matrix (either in onPreDraw or on click)

val m = Matrix()
m.setScale(0.5f, 0.5f)
//m.setTranslate(30f, 30f) // doesn't work either
setImageMatrix(m)
binding.sun.invalidate()

XML code for ImageView

It's nested in a FrameLayout which is part of vertical LinearLayout. The frame layout has android:layout_weight applied. Other than that, nothing special.

<ImageView
    android:id="@+id/sun"
    android:layout_width="100dp"
    android:layout_height="100dp"
    android:layout_gravity="center"
    android:scaleType="matrix"
    android:src="@drawable/sun" />

Tried all sorts of combinations (specifying scaleType and drawable in both code and XML), but with no success. Code is based on this article I encountered.

I'm trying to apply transformation to an image view using Matrix class. My idea is to be able to mirror the image, but actually any transformation I apply (e.g. scale or translate) doesn't work. I tried creating a custom view and add the code in onPreDraw event placed in the constructor, also tried on click event - non of them worked. My code is as follows:

Image drawable I use

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android/apk/res/android"
    android:shape="oval">
    <solid android:color="@color/bright_sun" />
</shape>

Setting the matrix (either in onPreDraw or on click)

val m = Matrix()
m.setScale(0.5f, 0.5f)
//m.setTranslate(30f, 30f) // doesn't work either
setImageMatrix(m)
binding.sun.invalidate()

XML code for ImageView

It's nested in a FrameLayout which is part of vertical LinearLayout. The frame layout has android:layout_weight applied. Other than that, nothing special.

<ImageView
    android:id="@+id/sun"
    android:layout_width="100dp"
    android:layout_height="100dp"
    android:layout_gravity="center"
    android:scaleType="matrix"
    android:src="@drawable/sun" />

Tried all sorts of combinations (specifying scaleType and drawable in both code and XML), but with no success. Code is based on this article I encountered.

• android

Share Improve this question Follow asked Feb 23 at 9:27 RokataRokata 1,2571515 silver badges3434 bronze badges 4

• Your drawable doesn't have a set size, so there's not really anything to do matrix calculations against, and it's just measured to fit the ImageView. If you add <size android:width="100dp" android:height="100dp" />, for example, your matrix stuff should start working. – Mike M. Commented Feb 23 at 10:32
• Wow, I though about it, but didn't try it out. Thanks! Can you post it as an answer so I can accept it? – Rokata Commented Feb 23 at 11:05
• 1 No problem! I don't really post answers here anymore, though. Please feel free to finish this up however you like. Thank you, I appreciate the offer. Glad you got it working. Cheers! – Mike M. Commented Feb 23 at 11:11
• 1 I posted it as an answer and will accept it in 2 days so others can see the official solution. Thanks again and cheers! :) – Rokata Commented Feb 23 at 11:56

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1 Answer 1

Sorted by: Reset to default 1

As suggested by @Mike M's comment, I had to just add

<size android:width="100dp" android:height="100dp" />

to the drawable to get it working.

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