BlackBerry - 如何将图像设置为ButtonField的背景？

Question

如何在BlackBerry中将图像设置为ButtonField的背景？

Answer 1

另一种方法是扩展ButtonField并在paint上绘制图像:

class BitmapButtonField extends ButtonField {
    Bitmap mNormal;
    Bitmap mFocused;
    Bitmap mActive;

    int mWidth;
    int mHeight;

    public BitmapButtonField(Bitmap normal, Bitmap focused, 
        Bitmap active) {
        super(CONSUME_CLICK);
        mNormal = normal;
        mFocused = focused;
        mActive = active;
        mWidth = mNormal.getWidth();
        mHeight = mNormal.getHeight();
        setMargin(0, 0, 0, 0);
        setPadding(0, 0, 0, 0);
        setBorder(BorderFactory
                        .createSimpleBorder(new XYEdges(0, 0, 0, 0)));
        setBorder(VISUAL_STATE_ACTIVE, BorderFactory
                        .createSimpleBorder(new XYEdges(0, 0, 0, 0)));
    }

    protected void paint(Graphics graphics) {
        Bitmap bitmap = null;
        switch (getVisualState()) {
        case VISUAL_STATE_NORMAL:
                bitmap = mNormal;
                break;
        case VISUAL_STATE_FOCUS:
                bitmap = mFocused;
                break;
        case VISUAL_STATE_ACTIVE:
                bitmap = mActive;
                break;
        default:
                bitmap = mNormal;
        }
        graphics.drawBitmap(0, 0, bitmap.getWidth(), bitmap.getHeight(),
                        bitmap, 0, 0);
    }

    public int getPreferredWidth() {
        return mWidth;
    }

    public int getPreferredHeight() {
        return mHeight;
    }

    protected void layout(int width, int height) {
        setExtent(mWidth, mHeight);
    }
}

使用样本