3

我有以下代码用于渲染带有圆角的 imageView。

public class RoundedCornerImageView extends ImageView {

private int rounded;
public RoundedCornerImageView(Context context) {
    super(context);
}

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

public RoundedCornerImageView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}


public int getRounded() {
    return rounded;
}

public void setRounded(int rounded) {
    this.rounded = rounded;

}


@Override
public void onDraw(Canvas canvas)
{


    Drawable drawable = getDrawable();

    int w = drawable.getIntrinsicHeight(),
        h = drawable.getIntrinsicWidth();

    Bitmap rounder = Bitmap.createBitmap(w,h,Bitmap.Config.ARGB_8888);
    Canvas tmpCanvas = new Canvas(rounder);

    // We're going to apply this paint eventually using a porter-duff xfer mode.
    // This will allow us to only overwrite certain pixels. RED is arbitrary. This
    // could be any color that was fully opaque (alpha = 255)
    Paint xferPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    xferPaint.setColor(Color.WHITE);

    // We're just reusing xferPaint to paint a normal looking rounded box, the 20.f
    // is the amount we're rounding by.
    tmpCanvas.drawRoundRect(new RectF(0,0,w,h), 10.0f, 10.0f, xferPaint);

    // Now we apply the 'magic sauce' to the paint
    xferPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));

    drawable.draw(canvas);
    canvas.drawBitmap(rounder, 0, 0, xferPaint);
}
}



<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:orientation="vertical"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:background='#a3deef'
    >
<com.example.scheduling_android.view.RoundedCornerImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/eventImageView"
        android:adjustViewBounds="false"/>
</LinearLayout>

它的工作原理是它确实裁剪了图像的角落。但是，当我尝试在具有背景颜色#a3deef 的线性布局中渲染它时，问题就出现了。生成的显示是#a3deef 的背景颜色，每个图像都显示为圆角，其中 4 个裁剪角全部为黑色。

我应该怎么做才能使裁剪的角落透明而不是黑色？另外，如果有人能向我解释为什么它会变黑，而不是任何其他颜色，那就太好了！

提前致谢。

4

3 回答 3

6

如果源还不是 a ，则您采用的方法实际上效果不佳Bitmap，主要是因为最好将内容绘制到Canvas绘图回调之外的 using 传输模式中（因此它只发生一次，而不是每次绘制刷新时）并且在其他任何地方调用Drawable.draw()都不会产生正确的结果，因为不会像您期望的那样设置边界。

一种更有效的方法是不修改源数据，而只是将圆形剪辑应用于绘图Canvas。对于非常大的半径，这可能会产生一点锯齿，但在 10px 时不会很明显。这种方法唯一的另一个缺点clipPath()是目前不支持硬件加速，因此您必须将此视图的图层类型设置为软件才能在 Android 3.0+ 上进行渲染

public class RoundedCornerImageView extends ImageView {

    private Path roundedPath;
    private int rounded;

    public RoundedCornerImageView(Context context) {
        super(context);
        init();
    }

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

    public RoundedCornerImageView(Context context, AttributeSet attrs,
            int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    private void init() {
        // If the application is hardware accelerated,
        // must disable it for this view.
        setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        // Set a default radius
        setRounded(10);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        if (w != oldw || h != oldh) {
            roundedPath = new Path();
            roundedPath.addRoundRect(new RectF(0, 0, w, h),
                    rounded, rounded, Path.Direction.CW);
        }
    }

    public int getRounded() {
        return rounded;
    }

    public void setRounded(int rounded) {
        this.rounded = rounded;
        roundedPath = new Path();
        roundedPath.addRoundRect(new RectF(0, 0, getWidth(), getHeight()),
                rounded, rounded, Path.Direction.CW);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        //Apply the clip
        canvas.clipPath(roundedPath);
        //Let the view draw as normal
        super.onDraw(canvas);
    }
}

在修改后的版本中，您只需在每次视图或半径大小更改时更新剪切路径，并将其Path作为剪切应用到Canvas之前的绘图。

高温高压

于 2012-09-10T21:45:37.887 回答
4

添加此行以使画布透明：

canvas.saveLayerAlpha(0, 0, canvas.getWidth(), canvas.getHeight(), 255, Canvas.HAS_ALPHA_LAYER_SAVE_FLAG);

此外，我使用反向填充的圆角矩形路径来遮罩位图，因此我不需要像您一样的中间遮罩位图。

public class RoundedImageView extends ImageView {

    private Path mMaskPath;
    private Paint mMaskPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private int mCornerRadius = 10;

    public RoundedImageView(Context context) {
        super(context);

        init();
    }

    public RoundedImageView(Context context, AttributeSet attributeSet) {
        super(context, attributeSet);

        init();
    }

    public RoundedImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        init();
    }

    private void init() {
        ViewCompat.setLayerType(this, ViewCompat.LAYER_TYPE_SOFTWARE, null);
        mMaskPaint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));
    }

    /**
     * Set the corner radius to use for the RoundedRectangle.
     * 
     * @param Primitive int - The corner radius of the rounded rectangle.
     */
    public void setCornerRadius(int cornerRadius) {
        mCornerRadius = cornerRadius;
        generateMaskPath(getWidth(), getHeight());
        invalidate();
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldW, int oldH) {
        super.onSizeChanged(w, h, oldW, oldH);

        if (w != oldW || h != oldH) {
            generateMaskPath(w, h);
        }
    }

    private void generateMaskPath(int w, int h) {
        mMaskPath = new Path();
        mMaskPath.addRoundRect(new RectF(0,0,w,h), mCornerRadius, mCornerRadius, Direction.CW);
        mMaskPath.setFillType(FillType.INVERSE_WINDING);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if(canvas.isOpaque()) { // If canvas is opaque, make it transparent
            canvas.saveLayerAlpha(0, 0, canvas.getWidth(), canvas.getHeight(), 255, Canvas.HAS_ALPHA_LAYER_SAVE_FLAG);
        }

        super.onDraw(canvas);

        if(mMaskPath != null) {
            canvas.drawPath(mMaskPath, mMaskPaint);
        }
    }
}
于 2012-11-30T06:19:04.260 回答
1

这是因为您Canvas正在使用的您不是透明的。不透明Canvas的有黑色背景。

这个答案将 a 设置SurfaceView为Canvas透明的。对你来说，它可能就像将背景设置Bitmap为透明一样简单。

Bitmap rounder = Bitmap.createBitmap(w,h,Bitmap.Config.ARGB_8888);
rounder.eraseColor(Color.TRANSPARENT);

您也可以在您的ImageView, 中尝试此操作，将其背景设置为 100% 透明：

setBackgroundColor(0);
于 2012-09-10T19:52:05.360 回答