无法在位图上绘制圆圈？

Question

我能够显示位图，但我绘制的圆形不显示。我不确定我错过了什么。

private void loadImage() { 
    File f = new File(imagesPath, currImageName); 

    Bitmap bitmap = BitmapFactory.decodeFile(f.getAbsolutePath()); 
    BitmapDrawable bitmapDrawable = new BitmapDrawable(bitmap); 

    Paint paint = new Paint(); 
    paint.setAntiAlias(true); 
    paint.setColor(Color.BLUE); 
    canvas = new Canvas(); 
    canvas.drawCircle(60, 50, 25, paint); 
    bitmapDrawable.draw(canvas); 

    ImageView imageView = (ImageView)findViewById(R.id.imageview); 
    imageView.setAdjustViewBounds(true); 
    imageView.setImageDrawable(bitmapDrawable); 
} 

Answer 1

您的代码不是绘制在位图上，而是将您的位图绘制到画布上，然后在该画布的位图上绘制一个圆。结果然后被丢弃。然后，将原始位图（未更改）设置到ImageView中。

您需要使用位图创建画布。然后绘制方法将绘制您的位图。

Bitmap bitmap = BitmapFactory.decodeFile(f.getAbsolutePath()); 

    Paint paint = new Paint(); 
    paint.setAntiAlias(true); 
    paint.setColor(Color.BLUE); 

     // create canvas to draw on the bitmap 
    Canvas canvas = new Canvas(bitmap); 
    canvas.drawCircle(60, 50, 25, paint); 

    ImageView imageView = (ImageView)findViewById(R.id.imageview); 
    imageView.setAdjustViewBounds(true); 
    imageView.setImageBitmap(bitmap);