在圆形中绘制位图并填充外部颜色画布不起作用

Question

我想用位图在圆圈内绘制图像并在外面填充颜色。

我已经扩展了AppCompatImageView并覆盖了onDraw方法，但它在画布内显示白色圆圈。

以下是我的课程：

class ImageMagnifier2 extends AppCompatImageView {
public ImageMagnifier2(final Context context) {
super(context);
init();
}
@Override
public boolean dispatchTouchEvent(MotionEvent me) {
// Call onTouchEvent of SimpleGestureFilterLongPress class
return super.dispatchTouchEvent(me);
}
private void init() {
setWillNotDraw(false);
setLayerType(LAYER_TYPE_HARDWARE, null);
zoomPos = new PointF(0, 0);
matrix = new Matrix();
paint = new Paint();
paintBackground = new Paint();
paint.setColor(getResources().getColor(android.R.color.transparent));
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_OUT));
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (!zooming) {
buildDrawingCache();
} else {
bitmap = getDrawingCache();
shader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
paint.setShader(shader);
matrix.reset();
matrix.postScale(2f, 2f, zoomPos.x, zoomPos.y);
paint.getShader().setLocalMatrix(matrix);
paintBackground.setColor(Color.parseColor("#F227aae0"));//F227aae0
paintBackground.setStyle(Paint.Style.FILL);
paintBackground.setAntiAlias(true);
Rect rectangle = new Rect( 0, 0, canvas.getWidth(), canvas.getHeight()   );
canvas.drawRect(rectangle,paintBackground);
canvas.drawCircle(zoomPos.x, zoomPos.y, sizeOfMagnifier - 5, paint);
}
}

在没有外部矩形或画布填充颜色的情况下绘制位图时，它可以正常工作。 但是我需要用位图填充外部颜色。

提前感谢您的帮助。

Answer 1

以下是我之前在遇到相同问题时编写的代码， 您可能需要使用以下类：

public class CircleImageView extends AppCompatImageView {
private RectF drawableRect = new RectF();
private Matrix shaderMatrix = new Matrix();
private Paint bmpPaint = new Paint();
private Paint backgroundPaint = new Paint();
private Bitmap bmp;
private int bmpWidth, bmpHeight;
private BitmapShader bmpShader;
private float radius;

public CircleImageView(Context context) {
super(context);
setScaleType(ScaleType.CENTER_CROP);
backgroundPaint.setStyle(Paint.Style.FILL);
backgroundPaint.setColor(Color.TRANSPARENT);
init();
}
@Override
protected void onDraw(Canvas canvas) {
if (bmp == null) return;
canvas.drawPaint(backgroundPaint);
canvas.drawCircle(drawableRect.centerX(), drawableRect.centerY(), radius, bmpPaint);
}

private Bitmap getBitmapFromDrawable(Drawable drawable) {
if (drawable == null) return null;
if (drawable instanceof BitmapDrawable) return ((BitmapDrawable) drawable).getBitmap();
try {
Bitmap bitmap;
if (drawable instanceof ColorDrawable) bitmap = Bitmap.createBitmap(5, 5, Bitmap.Config.ARGB_8888);
else bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
drawable.draw(canvas);
return bitmap;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
private void initImage() {
bmp = getBitmapFromDrawable(getDrawable());
init();
}
private void init() {
if (getWidth() == 0 && getHeight() == 0) return;
if (bmp == null) {invalidate();return;}
bmpShader = new BitmapShader(bmp, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
bmpPaint.setAntiAlias(true);
bmpPaint.setShader(bmpShader);
bmpHeight = bmp.getHeight();
bmpWidth = bmp.getWidth();
drawableRect.set(new RectF(0,0,getWidth(),getHeight()));
radius = Math.min(drawableRect.height() / 2.0f, drawableRect.width() / 2.0f);
updateMatrix();
invalidate();
}

private void updateMatrix() {
float scale;
float dx = 0;
float dy = 0;
shaderMatrix.set(null);
if (bmpWidth * drawableRect.height() > drawableRect.width() * bmpHeight) {
scale = drawableRect.height() / (float) bmpHeight;
dx = (drawableRect.width() - bmpWidth * scale) * 0.5f;
} else {
scale = drawableRect.width() / (float) bmpWidth;
dy = (drawableRect.height() - bmpHeight * scale) * 0.5f;
}
shaderMatrix.setScale(scale, scale);
shaderMatrix.postTranslate((int) (dx + 0.5f) + drawableRect.left, (int) (dy + 0.5f) + drawableRect.top);
bmpShader.setLocalMatrix(shaderMatrix);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
init();
}
public void setBackgroundColor(@ColorInt int backgroundColor) {
backgroundPaint.setColor(backgroundColor);
invalidate();
}
@Override
public void setImageBitmap(Bitmap bm) {
super.setImageBitmap(bm);
initImage();
}
@Override
public void setImageDrawable(Drawable drawable) {
super.setImageDrawable(drawable);
initImage();
}
@Override
public void setImageResource(@DrawableRes int resId) {
super.setImageResource(resId);
initImage();
}
@Override
public void setImageURI(Uri uri) {
super.setImageURI(uri);
initImage();
}
/* if this answer solved your problem please mark it as accepted by clicking the check mark next to the answer. Thank you */
}