android - 尝试使用 Canvas 在其上绘制文本时图像显示为黑色

Question

我有一个位图，我正在尝试使用 Canvas 在其上写文本。在 Canvas 中设置位图并执行必要的操作(在 Canvas 上写文本)后，我在 ImageView。最大的问题是没有图像显示...屏幕变黑。现在，我知道位图返回正常，因为我在执行 Canvas 操作之前就显示了。

所以，我是这样做的:

                     image= (ImageView) findViewById(R.id.imageview);
                    bitmap = android.provider.MediaStore.Images.Media
                       .getBitmap(cr, selectedImage);
                      int heightOfOld=bitmap.getHeight();
                      int widthOfOld=bitmap.getWidth();
                       android.graphics.Bitmap.Config hasAlpha=bitmap.getConfig();

                       Bitmap bitmapResult=bitmap.createBitmap(widthOfOld, heightOfOld, hasAlpha);
                       Canvas c=new Canvas(bitmapResult);
                       Canvas c1=drawTextImage(c);
                       image.draw(c1);

下面是在 Canvas 上绘制文本的方法:

                  private Canvas drawTextImage(Canvas c){
                       Paint paint=new Paint();
                       paint.setColor(Color.BLUE);
                       paint.setStyle(Paint.Style.FILL);
                       paint.setAntiAlias(true);
                       paint.setTextSize(20);
                       c.drawText("Golden Stag", 30, 200, paint);
                       return c;
                       }

有人能告诉我问题出在哪里吗？

Answer 1

因为 draw(Canvas) 的文档说:

"Manually render this view (and all of its children) to the given Canvas."

也许试试:

image.setImageBitmap(bitmapResult);

"Sets a Bitmap as the content of this ImageView."

更新:例子我认为这应该可行(虽然无法测试):

image = (ImageView) findViewById(R.id.imageview);
bitmap = android.provider.MediaStore.Images.Media.getBitmap(cr, selectedImage);

Canvas c = new Canvas(bitmap);
drawTextImage(bitmap);
image.setImageBitmap(bitmap);

private Canvas drawTextImage(Bitmap b){
    Canvas c = new Canvas(b);
    Paint paint = new Paint();
    paint.setColor(Color.BLUE);
    paint.setStyle(Paint.Style.FILL);
    paint.setAntiAlias(true);
    paint.setTextSize(20);
    c.drawText("Golden Stag", 30, 200, paint);
}