虽然这个控件类似的功能github上也有,但还是自己实现了下. 这个控件可以保持图片的比例去填充view,如果按图片比例计算出的大小超出view的大小,会展示图片的中心对称的中心区域.
github地址: https://github.com/X-FAN/ZoomLoadView 欢迎star
test1的原始图片
test2的原始图片
效果图
源码比较简单,主要是要算出图片的坐标的正确位置,让图片显示中间部分
public class ZoomLoadView extends View { private int mHeight; private int mWidth; private int mViewHeight;//可见的高度 private int mViewWidth;//可见的宽度 private float mScale; private EndListener mEndListener; private Drawable mZoomDrawable; private ValueAnimator mAnimator; public ZoomLoadView(Context context) { this(context, null); } public ZoomLoadView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public ZoomLoadView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(context, attrs); } private void init(Context context, AttributeSet attrs) { if (attrs == null) { throw new NullPointerException("zoomDrawable attr is needed"); } final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.ZoomLoadView); mZoomDrawable = a.getDrawable(R.styleable.ZoomLoadView_zoomDrawable); if (mZoomDrawable == null) { throw new NullPointerException("zoom drawable is null"); } int duration = a.getInt(R.styleable.ZoomLoadView_animatorDuration, 3000); float scale = a.getFloat(R.styleable.ZoomLoadView_zoomScale, 0.3f); a.recycle(); mHeight = mZoomDrawable.getIntrinsicHeight(); mWidth = mZoomDrawable.getIntrinsicWidth(); initAnimator(duration, scale); } private void initAnimator(int duration, float scale) { mAnimator = ValueAnimator.ofFloat(1.0f, 1.0f + scale); mAnimator.setDuration(duration); mAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { mScale = (float) animation.getAnimatedValue(); invalidate(); } }); mAnimator.addListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { mEndListener.onEndListener(); } }); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { int widthMode = MeasureSpec.getMode(widthMeasureSpec); int widthSize = MeasureSpec.getSize(widthMeasureSpec); int heightMode = MeasureSpec.getMode(heightMeasureSpec); int heightSize = MeasureSpec.getSize(heightMeasureSpec); int width; int height; int scaleHeight;//根据width按图片原始宽高比例所需要的高度 if (widthMode == MeasureSpec.EXACTLY) { width = widthSize; } else if (widthMode == MeasureSpec.AT_MOST) { width = Math.min(mWidth, widthSize); } else { width = mWidth; } if (heightMode == MeasureSpec.EXACTLY) { height = heightSize; } else if (heightMode == MeasureSpec.AT_MOST) { height = Math.min(mHeight, heightSize); } else { height = mHeight; } mViewWidth = width; mViewHeight = height; scaleHeight = mHeight * width / mWidth; float scale = (float) height / (float) scaleHeight; if (scale >= 1) { mWidth = (int) (width * scale); mHeight = (int) (scaleHeight * scale); } else { mWidth = width; mHeight = scaleHeight; } //将绘制的drawable的中心位置设置在view的中心位置,即展示drawable的对称中心区域 mZoomDrawable.setBounds((mViewWidth - mWidth) / 2, (mViewHeight - mHeight) / 2, (mViewWidth + mWidth) / 2, (mViewHeight + mHeight) / 2); setMeasuredDimension(width, height); } @Override protected void onDraw(Canvas canvas) { if (mEndListener != null) { super.onDraw(canvas); canvas.save(); canvas.scale(mScale, mScale, mViewWidth / 2, mViewHeight / 2); mZoomDrawable.draw(canvas); canvas.restore(); } } public void setEndListener(EndListener endListener) { mEndListener = endListener; mAnimator.start(); } public interface EndListener { void onEndListener(); } }