java - 不同的 View 取决于 android 版本

Question

我尝试绘制一些饼图，但得到了不同的结果:
这是在 Android 4.3 上(正确的变体)

在 Android 4.1 上获取下一个(不正确的变体):

我的代码如下:

@Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
//        int saveFlag = Canvas.MATRIX_SAVE_FLAG | Canvas.CLIP_SAVE_FLAG | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG
//                | Canvas.FULL_COLOR_LAYER_SAVE_FLAG | Canvas.CLIP_TO_LAYER_SAVE_FLAG;

//        int sc = canvas.saveLayer(0, 0, getWidth(), getHeight(), null, saveFlag);
//        canvas.translate(0, 0);
        float temp = 0;
        float values[] = {700, 500, 300, 444, 222};
        values = calculateData(values);
        float[] value_degree;
        value_degree = new float[values.length];
        for (int i = 0; i < values.length; i++) {
            value_degree[i] = values[i];
        }
        int height = getHeight();
        int width = getWidth();
        Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setStrokeWidth(20f);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(getResources().getColor(R.color.circle_background));
        int radius = (int) ((height / 2) + (Math.pow((double) width, 2) / (8 * height))) / 2;
        float left = width / 2 - radius;
        float top = height / 2 - radius;
        float right = width / 2 + radius;
        float bottom = height / 2 + radius;
        RectF rectF = new RectF(left, top, right, bottom);
        canvas.drawOval(rectF, mPaint);
        rectF.set(left + 11f, top + 11f, right - 11f, bottom - 11f);
        mPaint.setColor(Color.GRAY);
        mPaint.setStyle(Paint.Style.FILL);
        Random r;
        for (int i = 0; i < value_degree.length; i++) {
            if (i == 0) {
                r = new Random();
                int color = Color.argb(100, r.nextInt(256), r.nextInt(256),
                        r.nextInt(256));
                mPaint.setColor(color);
                canvas.drawArc(rectF, 270, value_degree[i], true, mPaint);
            } else {
                if (i == 1) {
                    temp += value_degree[i - 1] + 270 - 360;
                } else {
                    temp += value_degree[i - 1];
                }
                r = new Random();
                int color = Color.argb(255, r.nextInt(256), r.nextInt(256),
                        r.nextInt(256));
                mPaint.setColor(color);
                canvas.drawArc(rectF, temp, value_degree[i], true, mPaint);
            }
        }
        mPaint.setColor(getResources().getColor(R.color.circle_background_small));
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(20f);
        canvas.drawCircle(rectF.centerX(), rectF.centerY(), radius / 1.8f, mPaint);
//        mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        mPaint.setColor(getResources().getColor(android.R.color.transparent));
        mPaint.setAlpha(1);
        mPaint.setStyle(Paint.Style.FILL);
        canvas.drawCircle(rectF.centerX(), rectF.centerY(), radius / 1.9f, mPaint);
}

我做错了什么？
此致
附言中心应该是带有 Activity 背景的透明圆圈，为此我使用 PorterDuffXfermode 和恢复层。但现在是评论。

Answer 1

在 Canvas 上绘图时，指定的大小以像素为单位，而不是与密度无关的像素(dp 或 dip)。为了缩放值，您应该指定所需的大小并将其乘以屏幕的密度。

mPaint.setStrokeWidth(20f * getResources().getDisplayMetrics().density);

(尽管您可能希望先将密度缓存在某处)。

这将根据屏幕的密度缩放笔划宽度，因此宽度应该全部匹配。