通经常使用Base64这样的编解码方式将二进制数据转换成可见的字符串格式，就是我们常说的大串。10块钱一串的那种，^_^。

Android的android.util包下直接提供了一个功能十分完备的Base64类供我们使用，以下就演示一下怎样将一张图片进行Base64的编解码。

1.找到那张图片

public void onEncodeClicked(View view) {

        //select picture

        Intent intent = new Intent();

        intent.setType("image/*");

        intent.setAction(Intent.ACTION_GET_CONTENT);

        startActivityForResult(intent, OPEN_PHOTO_FOLDER_REQUEST_CODE);

    }

    @Override

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {

        super.onActivityResult(requestCode, resultCode, data);

        if(OPEN_PHOTO_FOLDER_REQUEST_CODE == requestCode && RESULT_OK == resultCode) {

            //encode the image

            Uri uri = data.getData();

            try {

                //get the image path

                String[] projection = {MediaStore.Images.Media.DATA};

                CursorLoader cursorLoader = new CursorLoader(this,uri,projection,null,null,null);

                Cursor cursor = cursorLoader.loadInBackground();

                int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);

                cursor.moveToFirst();

                String path = cursor.getString(column_index);

                Log.d(TAG,"real path: "+path);

                encode(path);

            } catch (Exception ex) {

                Log.e(TAG, "failed." + ex.getMessage());

            }

        }

    }

2.将图片转换成bitmap并编码

private void encode(String path) {

                //decode to bitmap

                Bitmap bitmap = BitmapFactory.decodeFile(path);

                Log.d(TAG, "bitmap width: " + bitmap.getWidth() + " height: " + bitmap.getHeight());

                //convert to byte array

                ByteArrayOutputStream baos = new ByteArrayOutputStream();

                bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);

                byte[] bytes = baos.toByteArray();

                //base64 encode

                byte[] encode = Base64.encode(bytes,Base64.DEFAULT);

                String encodeString = new String(encode);

                mTvShow.setText(encodeString);

}

3.将大串还原成图片

    public void onDecodeClicked(View view) {

        byte[] decode = Base64.decode(mTvShow.getText().toString(),Base64.DEFAULT);

        Bitmap bitmap = BitmapFactory.decodeByteArray(decode, 0, decode.length);

        //save to image on sdcard

        saveBitmap(bitmap);

    }

    private void saveBitmap(Bitmap bitmap) {

        try {

            String path = Environment.getExternalStorageDirectory().getPath()

                    +"/decodeImage.jpg";

            Log.d("linc","path is "+path);

            OutputStream stream = new FileOutputStream(path);

            bitmap.compress(Bitmap.CompressFormat.JPEG, 90, stream);

            stream.close();

            Log.e("linc","jpg okay!");

        } catch (IOException e) {

            e.printStackTrace();

            Log.e("linc","failed: "+e.getMessage());

        }

    }

须要注意的是，一张图片的编码速度会非常慢，假设图片非常大就更慢了。毕竟手机的处理能力有限。只是decode的速度确实相当的快，超出你的想象。好了，就是这样简单，今天就到这里了，晚安！