自定义宽高比例的ImageView

public class ScaleImageView extends android.support.v7.widget.AppCompatImageView {

    private float scaleValue;

    public ScaleImageView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        TypedArray typedArray = context.obtainStyledAttributes(attrs,R.styleable.ScaleImageView);
        this.scaleValue=typedArray.getFloat(R.styleable.ScaleImageView_scaleValue,0.0f);
        typedArray.recycle();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        //获取宽度的模式和尺寸
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        //获取高度的模式和尺寸
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);

        if(widthMode == MeasureSpec.EXACTLY&&heightMode!=MeasureSpec.EXACTLY&&scaleValue!=0){
            heightSize = (int) (widthSize*scaleValue+0.5f);//根据宽度和比例计算高度
            heightMeasureSpec = MeasureSpec.makeMeasureSpec(heightSize, MeasureSpec.EXACTLY);
        }
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
}