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Fit Width of Background Image But Keep Aspect Ratio in Android

So you have an image that you want to use as a background on one of your activities.

android_01

 

You probably have something that looks like this.

android_scale_01

But the desired effect is to scale the original image into the blue outline below.

android_02

The actual effect (depending on your current layout)  is the graphic anchored to the top left (android:scaleType=”fitStart”) or center (android:scaleType=”fitCenter”) of the device’s screen with no scaling performed. Through all of your research on Google (directing you mostly to Stack Overflow threads) you’re stuck with a non-scaling graphic that’s positioned incorrectly on the screen. Or maybe you’ve got a distorted graphic that has stretched both in length and width and looks terrible. The short answer?

You can not scale the width of an ImageView to the screen’s resolution while maintaining aspect ratio in an Android layout using only XML.

That’s the information I got from one of the random Stack Overflows I found. And I ignored it for quite a while before giving in and trying to scale the image manually through code.

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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
 
    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
 
        <ImageView
            android:id="@+id/iv_background"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:scaleType="fitCenter"
            android:src="@drawable/the_background" />
    </LinearLayout>
 
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" >
 
        <Button
            android:id="@+id/b_login"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="50dp"
            android:text="@string/login_button" />
    </LinearLayout>
 
</RelativeLayout>

And the necessary code placed at the bottom of the activity’s onCreate method.

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DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);
int height = metrics.heightPixels;
int width = metrics.widthPixels;
 
BitmapDrawable bmap = (BitmapDrawable) this.getResources().getDrawable(R.drawable.the_background);
float bmapWidth = bmap.getBitmap().getWidth();
float bmapHeight = bmap.getBitmap().getHeight();
 
float wRatio = width / bmapWidth;
float hRatio = height / bmapHeight;
 
float ratioMultiplier = wRatio;
// Untested conditional though I expect this might work for landscape mode
if (hRatio < wRatio) {
	ratioMultiplier = hRatio;
}
 
int newBmapWidth = (int) (bmapWidth*ratioMultiplier);
int newBmapHeight = (int) (bmapHeight*ratioMultiplier);
 
ImageView iView = (ImageView) findViewById(R.id.iv_background);
iView.setLayoutParams(new LinearLayout.LayoutParams(newBmapWidth, newBmapHeight));

android_scale_02

This results in an ImageView that’s stretched to fit the width of the screen while maintaining the aspect ratio of the image.

  1. Chuck
    January 8th, 2014 at 00:12 | #1

    I just used this for my app. It’s as close to perfect as I could have hoped for. Thanks!!!

  2. Mehrdad
    July 20th, 2014 at 03:04 | #2

    You could’ve just used match_parent in a RelativeView. It would’ve been a lot easier!

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