android - 在android的SurfaceView上渲染字节数组

Question

您好，我有一个图像的原始转储，我将其存储为字节数组，我必须在表面 View 上显示它。我试图将此字节数组转换为可变位图并在表面支架的 Canvas 上呈现，但在调用“drawBitmap”函数时出现此空指针异常。

BlockquoteE/AndroidRuntime(28358): FATAL EXCEPTION: main E/AndroidRuntime(28358): java.lang.NullPointerException E/AndroidRuntime(28358): at android.graphics.Canvas.throwIfRecycled(Canvas.java:1025) E/AndroidRuntime(28358): at android.graphics.Canvas.drawBitmap(Canvas.java:1065) Blockquote

这就是我尝试呈现字节数组的方式

    public void surfaceCreated(SurfaceHolder holder) {
         // TODO Auto-generated method stub
              //getting byte array
              byte[] bytes;
    File f1= new File("/data/dump.txt");
    int offset = 0, n = 0;
    InputStream in;
    long length = f1.length();
    bytes = new byte[(int) length];

          try {

          in = new FileInputStream(f1);

           while (offset < bytes.length
                && (n = in.read(bytes, offset, bytes.length - offset))  >= 0) {
            offset += n;

           }
        in.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


              // getting byte array
                Bitmap bmp;
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inMutable = true;
    bmp = BitmapFactory.decodeByteArray(bytes, 0, bytes.length,options );
              Canvas  canvas = holder.lockCanvas();
            if(canvas != null){

                canvas.drawBitmap(bmp, 0, 0, null); 

              }
            holder.unlockCanvasAndPost(canvas); //finalize          

        }

Answer 1

您的字节数组 bytes 永远不会被实例化。因此，当您调用 BitmapFactory.decodeByteArray 时，它会返回 null。

来自Android Reference :

public static Bitmap decodeByteArray (byte[] data, int offset, int length, BitmapFactory.Options opts)

Since: API Level 1
Decode an immutable bitmap from the specified byte array.
...

Returns
The decoded bitmap, or null if the image data could not be decoded, or, if opts is non-null, if opts requested only the size be returned (in opts.outWidth and opts.outHeight)