在Java中序列化和反序列化android.graphics.Bitmap

Question

我已经开始在我的第一个android应用程序上进行工作，并且具有处理多层图像的应用程序。我能够将项目文件的平面版本导出为PNG，但我希望能够保存分层图像以供以后编辑（包括应用于某些层的任何选项，例如基于文本的层）。

无论如何，我已经确保需要写入文件的类是“可序列化的”，但是由于android.graphics.Bitmap不可序列化这一事实而遇到了一些障碍。以下代码实质上将位图作为PNG输出到ByteArray中，并应作为“
readObject”的一部分读回。但是，当代码运行时-我可以验证读入的’imageByteArrayLength’变量与输出的变量相同-但’Bitmap
image’始终为null。

任何帮助将不胜感激。谢谢阅读。

private String title;
private int width;
private int height;
private Bitmap sourceImage;
private Canvas sourceCanvas;        
private Bitmap currentImage;
private Canvas currentCanvas;   
private Paint currentPaint;

private void writeObject(ObjectOutputStream out) throws IOException{
    out.writeObject(title);
    out.writeInt(width);
    out.writeInt(height);

    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    currentImage.compress(Bitmap.CompressFormat.PNG, 100, stream);
    byte[] imageByteArray = stream.toByteArray();

    int length = imageByteArray.length;
    out.writeInt(length);
    out.write(imageByteArray);          
}

private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{
    this.title = (String)in.readObject();
    this.width = in.readInt();
    this.height = in.readInt();

    int imageByteArrayLength = in.readInt();
    byte[] imageByteArray = new byte[imageByteArrayLength];
    in.read(imageByteArray, 0, imageByteArrayLength);

    BitmapFactory.Options opt = new BitmapFactory.Options();
    opt.inPreferredConfig = Bitmap.Config.ARGB_8888;

    Bitmap image = BitmapFactory.decodeByteArray(imageByteArray, 0, imageByteArrayLength, opt);

    sourceImage = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
    currentImage = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

    sourceCanvas = new Canvas(sourceImage);
    currentCanvas = new Canvas(currentImage);
    currentPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

    if ( image != null ) {
        sourceCanvas.drawBitmap(image, 0, 0, currentPaint);
    }
}

Answer 1

花了一段时间，但我找到了解决此问题的干净方法。我制作了一个自定义对象（BitmapDataObject），该对象实现了Serializable，并具有byte
[]来存储原始Bitmap中的PNG数据。使用此方法，可以将数据正确存储在ObjectOutputStream / ObjectInputStream中-
通过将Pmap存储为PNG到自定义对象的byte []中，可以有效地允许序列化和反序列化Bitmap对象。下面的代码解决了我的查询。

private String title;
private int sourceWidth, currentWidth;
private int sourceHeight, currentHeight;
private Bitmap sourceImage;
private Canvas sourceCanvas;        
private Bitmap currentImage;
private Canvas currentCanvas;   
private Paint currentPaint;

protected class BitmapDataObject implements Serializable {
    private static final long serialVersionUID = 111696345129311948L;
    public byte[] imageByteArray;
}

/** Included for serialization - write this layer to the output stream. */
private void writeObject(ObjectOutputStream out) throws IOException{
    out.writeObject(title);
    out.writeInt(currentWidth);
    out.writeInt(currentHeight);

    ByteArrayOutputStream stream = new ByteArrayOutputStream();
    currentImage.compress(Bitmap.CompressFormat.PNG, 100, stream);
    BitmapDataObject bitmapDataObject = new BitmapDataObject();     
    bitmapDataObject.imageByteArray = stream.toByteArray();

    out.writeObject(bitmapDataObject);
}

/** Included for serialization - read this object from the supplied input stream. */
private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{
    title = (String)in.readObject();
    sourceWidth = currentWidth = in.readInt();
    sourceHeight = currentHeight = in.readInt();

    BitmapDataObject bitmapDataObject = (BitmapDataObject)in.readObject();
    Bitmap image = BitmapFactory.decodeByteArray(bitmapDataObject.imageByteArray, 0, bitmapDataObject.imageByteArray.length);

    sourceImage = Bitmap.createBitmap(sourceWidth, sourceHeight, Bitmap.Config.ARGB_8888);
    currentImage = Bitmap.createBitmap(sourceWidth, sourceHeight, Bitmap.Config.ARGB_8888);

    sourceCanvas = new Canvas(sourceImage);
    currentCanvas = new Canvas(currentImage);

    currentPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    thumbnailPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    thumbnailPaint.setARGB(255, 200, 200, 200);
    thumbnailPaint.setStyle(Paint.Style.FILL);
}