将 int 数组（图像数据）写入文件的最佳方法是什么

Question

I have a large int array containing image data in the format ARGB (alpha, R, G and B channels, 1 byte each). I want to save it to file in onPause() to be able to reload it when the app is restarted. What do you think is the best way to do that?

I found the following methods:

• Convert the int array to a byte array manually (see here ) and then use a FileOutputStream to output the byte array.

• Wrap the array into a java.nio.IntBuffer and then write the object to file using java.io.ObjectOutputStream.writeObject() .

• Write each element one at a time using java.io.ObjectOutputStream.writeInt() .

All these methods seem quite wasteful so there is probably another, better way. Possibly even a way to use image compression to reduce the size of the file?

Answer 1

From my point of view you can also use android specific storages

1. Use database/content provider for storing image data
2. Use out Bundle in onSaveInstance method

If your still want to write to a file you can use following NIO based code:

static void writeIntArray(int[] array) throws IOException {
    FileOutputStream fos = new FileOutputStream("out.file");
    try {
        ByteBuffer byteBuff = ByteBuffer.allocate((Integer.SIZE / Byte.SIZE) * array.length);
        IntBuffer intBuff = byteBuff.asIntBuffer();
        intBuff.put(array);
        intBuff.flip();
        FileChannel fc = fos.getChannel();
        fc.write(byteBuff);
    } finally {
        fos.close();
    }
}

Answer 2

None of those. Some of them don't even make sense.

DataOutputStream dos = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(file)));

then call dos.writeInt() as many times as necessary, then close dos . The buffer will take away most of the pain.

Or else create an IntBuffer and use FileChannel.write() , but I've never been able to figure out how that works in the absence of an IntBuffer.asByteBuffer() method. Or else create a ByteBuffer , take it as an IntBuffer via asIntBuffer() , put the data in, then adjust the ByteBuffer 's length, which is another missing piece of the API, and again use FileChannel.write(ByteBuffer) .