如何以程序的方式居中裁剪布局背景

Question

我正在以编程方式设置布局的背景。如何居中裁剪背景？

Bitmap bm = BitmapFactory.decodeFile(myUri);
BitmapDrawable dw = new BitmapDrawable(bm);
layout.setBackgroundDrawable(dw); 

编辑

我正在寻找android:scaleType="centerCrop" 的Java等价物

Answer 1

在此处找到答案

public Bitmap scaleCenterCrop(Bitmap source, int newHeight, int newWidth) {
    int sourceWidth = source.getWidth();
    int sourceHeight = source.getHeight();
    // Compute the scaling factors to fit the new height and width, respectively.
    // To cover the final image, the final scaling will be the bigger 
    // of these two.
    float xScale = (float) newWidth / sourceWidth;
    float yScale = (float) newHeight / sourceHeight;
    float scale = Math.max(xScale, yScale);
    // Now get the size of the source bitmap when scaled
    float scaledWidth = scale * sourceWidth;
    float scaledHeight = scale * sourceHeight;
    // Let's find out the upper left coordinates if the scaled bitmap
    // should be centered in the new size give by the parameters
    float left = (newWidth - scaledWidth) / 2;
    float top = (newHeight - scaledHeight) / 2;
    // The target rectangle for the new, scaled version of the source bitmap will now
    // be
    RectF targetRect = new RectF(left, top, left + scaledWidth, top + scaledHeight);
    // Finally, we create a new bitmap of the specified size and draw our new,
    // scaled bitmap onto it.
    Bitmap dest = Bitmap.createBitmap(newWidth, newHeight, source.getConfig());
    Canvas canvas = new Canvas(dest);
    canvas.drawBitmap(source, null, targetRect, null);
    return dest;
}

Answer 2

使用View背景无法直接实现这一点。

但您可以选择使用ImageView，并使用FrameLayout将其放置在实际视图后面，以"模拟"背景。然后您可以使用centerCrop选项：

<FrameLayout  
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ImageView 
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerCrop" />
    <!-- your actual View here -->
</FrameLayout>