【Android】自定义ImageView高度自适应，宽度成比例缩放

约定不等于承诺〃 2022-06-13 12:38 192阅读 0赞

/**
     * 高度自适应ImageView，高度始终充满显示区域，宽度成比例缩放
     */
    public class AutoHeightImageView extends ImageView {
        
    
        public AutoHeightImageView(Context context) {
            super(context);
        }
    
        public AutoHeightImageView(Context context, AttributeSet attrs) {
            super(context, attrs);
        }
    
        public AutoHeightImageView(Context context, AttributeSet attrs, int defStyleAttr) {
            super(context, attrs, defStyleAttr);
        }
    
        @Override
        protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
            Drawable drawable = getDrawable();
                if(drawable != null){
                    int width = drawable.getMinimumWidth();
                    int height = drawable.getMinimumHeight();
                    float scale = (float)width/height;
    
                    //强制根据图片原有比例，重新计算ImageView显示区域宽度
                    int heightMeasure = MeasureSpec.getSize(heightMeasureSpec);
                    int widthMeasure = (int)(heightMeasure * scale);
    
                    //并设置为MeasureSpec.EXACTLY精确模式保证之后的super.onMeasure()不再调整
                    widthMeasureSpec = MeasureSpec.makeMeasureSpec(widthMeasure, MeasureSpec.EXACTLY);
                }
                super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        }
    
    }

相反地，如果是宽度自适应，高度成比例缩放的话，使用以下代码：

/**
     * 宽度自适应ImageView，宽度始终充满显示区域，高度成比例缩放
     */
    public class AutoScaleWidthImageView extends ImageView {
        
    
        public AutoScaleWidthImageView (Context context, AttributeSet attrs) {
            super(context, attrs);
        }
        @Override
        protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
             Drawable drawable = getDrawable();
             if(drawable != null){
                 int width = drawable.getMinimumWidth();
                 int height = drawable.getMinimumHeight();
                 float scale = (float)height/width;
    
                 int widthMeasure = MeasureSpec.getSize(widthMeasureSpec);
                 int heightMeasure = (int)(widthMeasure*scale);
    
                 heightMeasureSpec =  MeasureSpec.makeMeasureSpec(heightMeasure, MeasureSpec.EXACTLY);
             }
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        }
    }