接收到的包含 bitmap 的字節數組返回 null

Question

我一直在嘗試使用 Google 的 BluetoothChat 示例將圖像從一台設備發送到另一台設備。 我可以從一個設備向另一個設備發送字符串值，但我在發送圖像時遇到了問題。 我有兩個類處理數據的接收和發送。

為了發送圖像，我將圖像路徑轉換為 bitmap，然后將其轉換為 byte[]，並將其傳遞給實用程序 class，與 BluetoothChat 示例相同，但緩沖區大小增加（默認為 1024，將其更改為 8192）。 我的 BluetoothSend class 將數據發送到實用程序 class 的代碼是這樣的，

send.setOnClickListener(view -> {
            Bitmap bitmap = BitmapFactory.decodeFile(filePath);

            int width = bitmap.getRowBytes();
            int height = bitmap.getHeight();
            int bmpSize = width * height;

            ByteBuffer byteBuffer = ByteBuffer.allocate(bmpSize);
            bitmap.copyPixelsToBuffer(byteBuffer);

            byte[] byteArray = byteBuffer.array();
            sendUtils.write(byteArray);

            bitmap.recycle();
    });

這是處理數據發送和接收的實用程序 class，

/**
 * This thread runs during a connection with a remote device.
 * It handles all incoming and outgoing transmissions.
 */
private class ConnectedThread extends Thread {
    private final BluetoothSocket bluetoothsocket;
    private final InputStream inputStream;
    private final OutputStream outputStream;

    public ConnectedThread(BluetoothSocket socket) {
        bluetoothsocket = socket;
        InputStream tmpIn = null;
        OutputStream tmpOut = null;

        try {
            tmpIn = bluetoothsocket.getInputStream();
            tmpOut = bluetoothsocket.getOutputStream();
        } catch (IOException e) {
            Log.e("ConnectedThrd->Cons", "Socket not created.");
            e.printStackTrace();
        }
        inputStream = tmpIn;
        outputStream = tmpOut;
    }

    public void run() {
        byte[] buffer = new byte[8192]; //1024 original
        int bytes;

        // Keep listening to the InputStream while connected
        while (true) {
            try {
                // Read from the InputStream
                try {
                    bytes = inputStream.read(buffer);
                    // Send the obtained bytes to the UI Activity
                    handler.obtainMessage(BluetoothSend.MESSAGE_READ, bytes, -1, buffer).sendToTarget();
                    handler.obtainMessage(BluetoothReceive.MESSAGE_READ, bytes, -1, buffer).sendToTarget();
                } catch (NullPointerException n) {
                    Log.e("ConnectedThrd->Run", n.getMessage());
                }
            } catch (IOException e) {
                Log.e("ConnectedThrd->Run", "Connection Lost.", e);
                e.printStackTrace();
                connectionLost();
                break;
            }
        }
    }

    public void write(byte[] buffer) {
        try {
            try {
                outputStream.write(buffer);
                handler.obtainMessage(BluetoothSend.MESSAGE_WRITE, -1, -1, buffer)
                        .sendToTarget();
                handler.obtainMessage(BluetoothReceive.MESSAGE_WRITE, -1, -1, buffer)
                        .sendToTarget();
            } catch (NullPointerException n) {
                Log.e("ConnectedThrd->Write", "Bluetooth Socket is null: " + n.getMessage());
            }
        } catch (IOException e) {
            Log.e("ConnectedThread->Write", "Empty write stream.");
        }
    }

    public void cancel() {
        try {
            bluetoothsocket.close();
        } catch (IOException e) {
            Log.e("ConnectedThread->Cancel", "Failed to close socket.");
        }
    }
}

最后，在 BluetoothReceive class 上，我使用處理程序接收數據。 處理程序 object 的代碼如下，

            case MESSAGE_READ:
                //Read message from sender
                byte[] bufferRead = (byte[]) message.obj;
                //bitmap decodedByte is null
                Bitmap decodedByte = BitmapFactory.decodeByteArray(bufferRead, 0, bufferRead.length);
                int height = decodedByte.getHeight();
                int width = decodedByte.getWidth();

                Bitmap.Config config = Bitmap.Config.valueOf(decodedByte.getConfig().name());
                Bitmap bitmap_tmp = Bitmap.createBitmap(width, height, config);
                ByteBuffer buffer = ByteBuffer.wrap(bufferRead);
                bitmap_tmp.copyPixelsFromBuffer(buffer);
                fileView.setImageBitmap(bitmap_tmp);
                break;

當我嘗試轉換從其他設備接收的字節數組時，我似乎總是得到一個 null 值，當我將它轉換為 bitmap 時，我可以用它在 ImageView 中顯示它。

我究竟做錯了什么？

Answer 1

如您所說，您可以傳遞字符串。 您可以將 bitmap 轉換為Base64字符串格式並發送。

Bitmap bitmap = BitmapFactory.decodeFile("filePath");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos); 
byte[] bytes = baos.toByteArray();
String encodedImage = Base64.encodeToString(bytes, Base64.DEFAULT);

在接收端，反轉它（字符串Base64到圖像）

byte[] decodedString = Base64.decode(encodedImage, Base64.DEFAULT);
Bitmap decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length);