android - 如何在圆形中显示方形图像？

Question

我正在尝试从我的应用程序的 iPhone 版本中模仿一些东西。我有一个方形图像，我想将它显示在一个带有白色边框的圆圈中。像这样

我有办法做到这一点吗？

Answer 1

您可以使用自定义 Drawable 类实现此效果或非常接近它的效果，该类包含一个带有将图像渲染为纹理的 BitmapShader 的 Paint 对象。这是我正在使用的代码(略微改编自 Romain's Guy post ，它使用相同的技术来绘制带圆角的图像)。

class CircularDrawable extends Drawable
{
    private float mCircleRadius;
    private final RectF mBackgroundRect = new RectF();
    private final Paint mBackgroundPaint;
    private final BitmapShader mBitmapShader;
    private final Paint mPaint;
    private final int mMargin;

    CircularDrawable(Bitmap bitmap, int margin, int backgroundColor)
    {
        mBitmapShader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setShader(mBitmapShader);

        mMargin = margin;
        mBackgroundPaint = new Paint();
        mBackgroundPaint.setColor(backgroundColor);
    }

    @Override
    protected void onBoundsChange(Rect bounds)
    {
        super.onBoundsChange(bounds);
        mBackgroundRect.set(bounds);
        mCircleRadius = Math.min(bounds.width() / 2 - mMargin, bounds.height() / 2 - mMargin);
    }

    @Override
    public void draw(Canvas canvas)
    {
        canvas.drawRect(mBackgroundRect, mBackgroundPaint);
        canvas.drawCircle(mBackgroundRect.width() / 2, mBackgroundRect.height() / 2, mCircleRadius, mPaint);
    }

    @Override
    public int getOpacity()
    {
        return PixelFormat.TRANSLUCENT;
    }

    @Override
    public void setAlpha(int alpha)
    {
        mPaint.setAlpha(alpha);
        mBackgroundPaint.setAlpha(alpha);
    }

    @Override
    public void setColorFilter(ColorFilter cf)
    {
        mPaint.setColorFilter(cf);
        mBackgroundPaint.setColorFilter(cf);
    }       
}

有了你想要绘制的位图，只需用它构建一个 CircularDrawable

new CircularDrawable(bitmap, margin, Color.WHITE);