ImageViewWithoutIntrinsicSizes.java
/*
* Copyright 2021 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.wear.tiles.renderer.internal;
import android.annotation.SuppressLint;
import android.content.Context;
import android.util.AttributeSet;
import android.widget.ImageView;
import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
/**
* Fixed version of ImageView which doesn't ever use the intrinsic size of its drawables.
*
* <p>Tiles has a rule that the size of the layout should be statically resolvable. Because it can
* asynchronously load the resources though, this is not possible if we ever use the intrinsic sizes
* of images, as the layout may resize itself after an image is loaded. Take the following example:
*
* <p>Box (size = wrap()) { Text("Hello World") Image(size = expand()) }
*
* <p>The Box will size itself to wrap the contents, which it does by asking each child how large it
* wishes to be. For Text, this is the size of the text run (ish, it gets a little more complex with
* multiple lines), and for images, this is the intrinsic size of the drawable (even in the case
* where the image is MATCH_PARENT; that gets applied later). This means that the layout can "jump"
* after the image is loaded, if the image's intrinsic size is larger than the text.
*
* <p>This wrapper prevents that; if the image ever gets a MeasureSpec which allows it to pick its
* own size, we clamp the max size to 0 to prevent it from ever doing that. This is safe within
* Tiles; images only support absolute sizes (in which case, it has an exact measurespec), ratio
* sizes (which is handled in RatioViewWrapper), and expand sizes, in which case this image gets
* ignored for the first measure pass, and will receive an exact measurespec on the second measure
* pass.
*
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY)
@SuppressLint("AppCompatCustomView")
class ImageViewWithoutIntrinsicSizes extends ImageView {
ImageViewWithoutIntrinsicSizes(Context context) {
super(context);
}
ImageViewWithoutIntrinsicSizes(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
}
ImageViewWithoutIntrinsicSizes(
Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
ImageViewWithoutIntrinsicSizes(
Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// Helpfully, half of ImageView that is needed in Measure (resolveUri) is private. We can
// still hack this though. If we ever get an AT_MOST measurespec, then we _don't_ want to
// use our intrinsic dimensions. Just measure that as AT_MOST = 0.
if (MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.EXACTLY) {
widthMeasureSpec = MeasureSpec.makeMeasureSpec(1, MeasureSpec.AT_MOST);
}
if (MeasureSpec.getMode(heightMeasureSpec) != MeasureSpec.EXACTLY) {
heightMeasureSpec = MeasureSpec.makeMeasureSpec(1, MeasureSpec.AT_MOST);
}
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}