保存帆布为位图在Android [英] Saving canvas to bitmap on Android

问题描述

我不得不放置一个画布的内容到一个位图一些困难与问候。当我尝试这样做时，文件被写入具有约5.80KB一个文件大小，但它似乎是完全空（每一个像素是＃000）。

画布绘制一系列的由手写形成的相互连接的线。下面是我为View的onDraw。 （我知道，它的阻止UI线程/陋习/等，但是我只需要得到它的工作）

感谢您。

  @覆盖
保护无效的onDraw（帆布油画）{
    // TODO自动生成方法存根
    super.onDraw（画布）;        如果（IsTouchDown）{            //计算点
            路径currentPath =新路径（）;
            布尔IsFirst =真;
            对于（点对点：currentPoints）{
                如果（IsFirst）{
                    IsFirst = FALSE;
                        currentPath.moveTo（point.x，point.y）;
                    }其他{
                        currentPath.lineTo（point.x，point.y）;
                    }
                }            //绘制的点的路径
            canvas.drawPath（currentPath，笔）;            //企图使该位图，并将其写入文件。
            位图toDisk = NULL;
            尝试{                // TODO：获取画布的大小，更换640，480
                toDisk = Bitmap.createBitmap（640,480，Bitmap.Config.ARGB_8888）;
                canvas.setBitmap（toDisk）;
                toDisk.com preSS（Bitmap.Com pressFormat.JPEG，100，新的FileOutputStream（新文件（arun.jpg）））;            }赶上（例外前）{
            }        }其他{            //清除点
            currentPoints.clear（）;        }
    }
 

解决方案

我有类似的问题，我已经得到了解决。在这里，一个任务的全面code /不要忘记 android.permission.WRITE_EXTERNAL_STORAG​​E 在清单许可/

 公共位图saveSignature（）{      位图的位图= Bitmap.createBitmap（this.getWidth（），this.getHeight（），Bitmap.Config.ARGB_8888）;
      帆布帆布=新的Canvas（位图）;
      this.draw（画布）;      档案文件=新的文件（Environment.getExternalStorageDirectory（）+/sign.png）;      尝试{
           bitmap.com preSS（Bitmap.Com pressFormat.PNG，100，新的FileOutputStream（文件））;
      }赶上（例外五）{
           e.printStackTrace（）;
      }      返回位图;
  }
 

I'm having some difficulty with regards to placing the contents of a Canvas into a Bitmap. When I attempt to do this, the file gets written with a file size of around 5.80KB but it appears to be completely empty (every pixel is '#000').

The canvas draws a series of interconnected lines that are formed by handwriting. Below is my onDraw for the View. (I'm aware that it's blocking the UI thread / bad practices/ etc.., however I just need to get it working)

Thank you.

@Override
protected void onDraw(Canvas canvas) {
    // TODO Auto-generated method stub
    super.onDraw(canvas);

        if (IsTouchDown) {

            // Calculate the points
            Path currentPath = new Path();
            boolean IsFirst = true;
            for(Point point : currentPoints){
                if(IsFirst){
                    IsFirst = false;
                        currentPath.moveTo(point.x, point.y);
                    } else {
                        currentPath.lineTo(point.x, point.y);
                    }
                }

            // Draw the path of points
            canvas.drawPath(currentPath, pen);

            // Attempt to make the bitmap and write it to a file.
            Bitmap toDisk = null;
            try {

                // TODO: Get the size of the canvas, replace the 640, 480
                toDisk = Bitmap.createBitmap(640,480,Bitmap.Config.ARGB_8888);
                canvas.setBitmap(toDisk);
                toDisk.compress(Bitmap.CompressFormat.JPEG, 100, new FileOutputStream(new File("arun.jpg")));

            } catch (Exception ex) {


            }

        } else {

            // Clear the points
            currentPoints.clear();

        }
    }

解决方案

I had similar problem and i've got solution. Here full code of a task /don't forget about android.permission.WRITE_EXTERNAL_STORAGE permission in manifest/

  public Bitmap saveSignature(){

      Bitmap  bitmap = Bitmap.createBitmap(this.getWidth(), this.getHeight(), Bitmap.Config.ARGB_8888);
      Canvas canvas = new Canvas(bitmap);
      this.draw(canvas); 

      File file = new File(Environment.getExternalStorageDirectory() + "/sign.png");

      try {
           bitmap.compress(Bitmap.CompressFormat.PNG, 100, new FileOutputStream(file));
      } catch (Exception e) {
           e.printStackTrace();
      }

      return bitmap;
  }

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