android - ImageView的比例类型意外行为

我有一个带有scaleType="fitCenter"和layout_width="match_parent"的ImageView，因此我希望其中的图像能够缩放和填充所有视图。

布局文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="20dp"
    android:layout_marginTop="20dp"
    android:gravity="center"
    android:orientation="vertical">

<FrameLayout
    android:layout_width="250dp"
    android:layout_height="wrap_content">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="fitXY"
        android:src="@drawable/border" />

    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:padding="6dp">

        <ImageView
            android:id="@+id/myImageView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:adjustViewBounds="true"
            android:scaleType="fitCenter"
            android:src="@drawable/aaa"
            android:transitionName="image" />

        <!-- Some other views... -->
    </RelativeLayout>
</FrameLayout>

当图像太小（例如50x50像素）时，问题就开始出现，并且无法在所有设备上正常工作。

下图显示了API 16和22之间的区别。



任何想法如何解决这个问题？

最佳答案

问题不在于您的代码，而在于android:adjustViewBounds的工作方式。这在ImageView的setAdjustViewBounds方法中记录。


  注意：如果应用程序的目标是API级别17或更低，
  AdjustViewBounds将允许drawable缩小视图范围，
  但并非在所有情况下都会增长以填充可用的测量空间。


根据nuuneoi发布的Correct the ImageView's adjustViewBounds behaviour on API Level 17 and below with AdjustableImageView，此问题的可能解决方案是使用自定义AdjustableImageView。

码：

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.widget.ImageView;

/**
 * Created by nuuneoi on 2/17/15 AD.
 */
public class AdjustableImageView extends ImageView {

    boolean mAdjustViewBounds;

    public AdjustableImageView(Context context) {
        super(context);
    }

    public AdjustableImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public AdjustableImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    public void setAdjustViewBounds(boolean adjustViewBounds) {
        mAdjustViewBounds = adjustViewBounds;
        super.setAdjustViewBounds(adjustViewBounds);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        Drawable mDrawable = getDrawable();
        if (mDrawable == null) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            return;
        }

        if (mAdjustViewBounds) {
            int mDrawableWidth = mDrawable.getIntrinsicWidth();
            int mDrawableHeight = mDrawable.getIntrinsicHeight();
            int heightSize = MeasureSpec.getSize(heightMeasureSpec);
            int widthSize = MeasureSpec.getSize(widthMeasureSpec);
            int heightMode = MeasureSpec.getMode(heightMeasureSpec);
            int widthMode = MeasureSpec.getMode(widthMeasureSpec);

            if (heightMode == MeasureSpec.EXACTLY && widthMode != MeasureSpec.EXACTLY) {
                // Fixed Height & Adjustable Width
                int height = heightSize;
                int width = height * mDrawableWidth / mDrawableHeight;
                if (isInScrollingContainer())
                    setMeasuredDimension(width, height);
                else
                    setMeasuredDimension(Math.min(width, widthSize), Math.min(height, heightSize));
            } else if (widthMode == MeasureSpec.EXACTLY && heightMode != MeasureSpec.EXACTLY) {
                // Fixed Width & Adjustable Height
                int width = widthSize;
                int height = width * mDrawableHeight / mDrawableWidth;
                if (isInScrollingContainer())
                    setMeasuredDimension(width, height);
                else
                    setMeasuredDimension(Math.min(width, widthSize), Math.min(height, heightSize));
            } else {
                super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            }
        } else {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        }
    }

    private boolean isInScrollingContainer() {
        ViewParent p = getParent();
        while (p != null && p instanceof ViewGroup) {
            if (((ViewGroup) p).shouldDelayChildPressedState()) {
                return true;
            }
            p = p.getParent();
        }
        return false;
    }
}