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ImageView that respects an aspect ratio applied to a specific measurement.
// Copyright 2012 Square, Inc.
package com.squareup.widgets;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.widget.ImageView;
/** Maintains an aspect ratio based on either width or height. Disabled by default. */
public class AspectRatioImageView extends ImageView {
// NOTE: These must be kept in sync with the AspectRatioImageView attributes in attrs.xml.
public static final int MEASUREMENT_WIDTH = 0;
public static final int MEASUREMENT_HEIGHT = 1;
private static final float DEFAULT_ASPECT_RATIO = 1f;
private static final boolean DEFAULT_ASPECT_RATIO_ENABLED = false;
private static final int DEFAULT_DOMINANT_MEASUREMENT = MEASUREMENT_WIDTH;
private float aspectRatio;
private boolean aspectRatioEnabled;
private int dominantMeasurement;
public AspectRatioImageView(Context context) {
this(context, null);
}
public AspectRatioImageView(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.AspectRatioImageView);
aspectRatio = a.getFloat(R.styleable.AspectRatioImageView_aspectRatio, DEFAULT_ASPECT_RATIO);
aspectRatioEnabled = a.getBoolean(R.styleable.AspectRatioImageView_aspectRatioEnabled,
DEFAULT_ASPECT_RATIO_ENABLED);
dominantMeasurement = a.getInt(R.styleable.AspectRatioImageView_dominantMeasurement,
DEFAULT_DOMINANT_MEASUREMENT);
a.recycle();
}
@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (!aspectRatioEnabled) return;
int newWidth;
int newHeight;
switch (dominantMeasurement) {
case MEASUREMENT_WIDTH:
newWidth = getMeasuredWidth();
newHeight = (int) (newWidth * aspectRatio);
break;
case MEASUREMENT_HEIGHT:
newHeight = getMeasuredHeight();
newWidth = (int) (newHeight * aspectRatio);
break;
default:
throw new IllegalStateException("Unknown measurement with ID " + dominantMeasurement);
}
setMeasuredDimension(newWidth, newHeight);
}
/** Get the aspect ratio for this image view. */
public float getAspectRatio() {
return aspectRatio;
}
/** Set the aspect ratio for this image view. This will update the view instantly. */
public void setAspectRatio(float aspectRatio) {
this.aspectRatio = aspectRatio;
if (aspectRatioEnabled) {
requestLayout();
}
}
/** Get whether or not forcing the aspect ratio is enabled. */
public boolean getAspectRatioEnabled() {
return aspectRatioEnabled;
}
/** set whether or not forcing the aspect ratio is enabled. This will re-layout the view. */
public void setAspectRatioEnabled(boolean aspectRatioEnabled) {
this.aspectRatioEnabled = aspectRatioEnabled;
requestLayout();
}
/** Get the dominant measurement for the aspect ratio. */
public int getDominantMeasurement() {
return dominantMeasurement;
}
/**
* Set the dominant measurement for the aspect ratio.
*
* @see #MEASUREMENT_WIDTH
* @see #MEASUREMENT_HEIGHT
*/
public void setDominantMeasurement(int dominantMeasurement) {
if (dominantMeasurement != MEASUREMENT_HEIGHT && dominantMeasurement != MEASUREMENT_WIDTH) {
throw new IllegalArgumentException("Invalid measurement type.");
}
this.dominantMeasurement = dominantMeasurement;
requestLayout();
}
}
<declare-styleable name="AspectRatioImageView">
<attr name="aspectRatio" format="float" />
<attr name="aspectRatioEnabled" format="boolean" />
<attr name="dominantMeasurement">
<enum name="width" value="0"/>
<enum name="height" value="1"/>
</attr>
</declare-styleable>
@kennywyland

I think line 48 should be dividing by the aspectRatio, not multiplying. It should be:

newHeight = (int) (newWidth / aspectRatio);

The aspectRatio is (desiredWidth/desiredHeight), so:

aspectRatio = (newWidth/newHeight)

multiply both sides by newHeight...

aspectRatio * newHeight = newWidth

divide both sides by aspectRatio...

newHeight = (newWidth / aspectRatio)

@Servus7

@kennywyland your right. The following calculation for a 16:9 TV with 1920x1080 resolution makes it more understandable:

aspectRatio = 16/9 = 1.78
newWidth = getMeasuredWidth() = 1920
newHeight = (int) (newWidth * aspectRatio) = (int) (1920 * 1.78) = 3413

But newHeight should be 1080 to fit the aspect ratio.

newHeight = (int) (newWidth / aspectRatio) = (int) (1920 / 1.78) = 1080

In line 48 therefore has to be multiplied rather than divided.

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