android - 动态绘制自定义圆段

Question

我的客户想要应用程序中的以下小部件:

文本来自服务器。梯度角度取决于同样来自服务器的变量。此外，客户希望动态填充渐变(用户必须看到渐变是如何从 0 开始填充的)。
现在我执行以下操作:我使用两张图片 - 一张是彩色圆圈，第二张是灰色圆圈。我创建了一个具有特定角度的圆段并将其作为蒙版应用到灰色圆圈，然后将彩色圆圈与新的灰色圆圈(其中一个扇形被切断)结合起来。
这是我的代码。我调用 initializeVarsForCompoundImDrawing 初始化变量，然后在一秒钟内多次调用 makeCompoundImage，最后调用 nullVarsForCompoundImDrawing 以释放资源:

private static Bitmap notColoredBitmap;
private static Bitmap coloredBitmap;
private static Bitmap notColoredWithMaskBitmap;
private static Bitmap finalBitmap;
private static Canvas notColoredWithMaskCanvas;
private static Paint paintForMask;
private static Paint smoothPaint;
private static Canvas finalCanvas;
private static RectF rectForMask;

public static void initializeVarsForCompoundImDrawing()
{
    Context context = MainApplication.getContext();
    notColoredBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.not_colored);
    coloredBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.colored);
    
    paintForMask = new Paint(Paint.ANTI_ALIAS_FLAG);
    paintForMask.setStyle(Paint.Style.FILL);
    paintForMask.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
    rectForMask = new RectF(0, 0, notColoredBitmap.getWidth(), notColoredBitmap.getHeight());

    smoothPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
}

public static void nullVarsForCompoundImDrawing()
{
    notColoredBitmap = null;
    coloredBitmap = null;
    
    paintForMask = null;
    rectForMask = null;
    smoothPaint = null;
}

public static void makeCompoundImage(ImageView imageView, int angle)
{
    notColoredWithMaskBitmap = Bitmap.createBitmap(notColoredBitmap.getWidth(), notColoredBitmap.getHeight(), Bitmap.Config.ARGB_8888);
    notColoredWithMaskCanvas = new Canvas(notColoredWithMaskBitmap);
    notColoredWithMaskCanvas.drawBitmap(notColoredBitmap, 0, 0, smoothPaint);
    notColoredWithMaskCanvas.drawArc(rectForMask, 270, angle, true, paintForMask);

    finalBitmap = Bitmap.createBitmap(notColoredBitmap.getWidth(), notColoredBitmap.getHeight(), Bitmap.Config.ARGB_8888);
    finalCanvas = new Canvas(finalBitmap);
    finalCanvas.drawBitmap(coloredBitmap, 0, 0, smoothPaint);
    finalCanvas.drawBitmap(notColoredWithMaskBitmap, 0, 0, smoothPaint);

    imageView.setImageBitmap(finalBitmap);
}

第一个问题:是否可以改进这段代码以使用更少的资源？
第二个问题:如何将文本添加到 finalBitmap(现在它是一个 TextView，显示在 ImageView 的顶部，带有图片)？

Answer 1

回答你的问题:是的，它可以做得更容易，更容易:

public class Ring extends View {
    private Bitmap mBack;
    private Paint mPaint;
    private RectF mOval;
    private Paint mTextPaint;

    public Ring(Context context) {
        super(context);
        Resources res = getResources();
        mBack = BitmapFactory.decodeResource(res, R.drawable.back);
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        Bitmap ring = BitmapFactory.decodeResource(res, R.drawable.ring);
        mPaint.setShader(new BitmapShader(ring, TileMode.CLAMP, TileMode.CLAMP));
        mOval = new RectF(0, 0, mBack.getWidth(), mBack.getHeight());
        mTextPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mTextPaint.setTextSize(24);
        mTextPaint.setTextAlign(Align.CENTER);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.translate((getWidth() - mBack.getWidth()) / 2, (getHeight() - mBack.getHeight()) / 2);
        canvas.drawBitmap(mBack, 0, 0, null);
        float angle = 220;
        canvas.drawArc(mOval, -90, angle, true, mPaint);
        canvas.drawText("Text",
            mBack.getWidth() / 2,
            (mBack.getHeight() - mTextPaint.ascent()) / 2,
            mTextPaint);
    }
}

编辑:

这是另一种解决方案(没有居中，里面没有文字，只是一个概念)

class Ring extends View {
    private Bitmap back;
    private Bitmap ring;
    private RectF oval;
    private Paint arcPaint;

    public Ring(Context context) {
        super(context);
        Resources res = getResources();
        back = BitmapFactory.decodeResource(res, R.drawable.back);
        ring = BitmapFactory.decodeResource(res, R.drawable.ring);
        arcPaint = new Paint();
        arcPaint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));
        oval = new RectF(-1, -1, ring.getWidth()+1, ring.getHeight()+1);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawARGB(0xaa, 0, 255, 0);
        canvas.drawBitmap(back, 0, 0, null);
        canvas.saveLayer(oval, null, Canvas.HAS_ALPHA_LAYER_SAVE_FLAG);
        canvas.drawBitmap(ring, 0, 0, null);
        float angle = 300;
        canvas.drawArc(oval, angle-90, 360-angle, true, arcPaint);
        canvas.restore();
    }
}