java - NullpointerException 在 Canvas 上绘制位图

Question

为什么我会收到 NullpointerException？

谢谢!

PS:我是 Java 新手。

    try {
        URL uri = new URL("http://static.panoramio.com/photos/original/41455707.jpg");
            URLConnection connection = uri.openConnection();
            Log.i(TAG, "connecting...");
            connection.connect();
            InputStream is = connection.getInputStream();
            BufferedInputStream bis = new BufferedInputStream(is, 8 * 1024);
            Bitmap bmp = BitmapFactory.decodeStream(bis);
            bis.close();
            is.close();

            Log.i(TAG, "setting bitmap");
            //Log.d(TAG, canvas.toString());
            //Log.d(TAG, bmp.toString());
            canvas.setBitmap(bmp);
    } catch (Exception exc){
        Log.e(TAG, exc.toString());
        return;
    }

输出:

06-28 17:29:04.857   391   397 I MyWallpaperPainting: connecting...
06-28 17:29:07.248   391   397 I MyWallpaperPainting: setting bitmap
06-28 17:29:07.248   391   397 E MyWallpaperPainting: java.lang.NullPointerException

Answer 1

这可能很愚蠢，但是您之前是否在某处初始化了 Canvas ？