概述

敲android代碼也快半年了，大神都說(shuō)好記性不如爛筆頭，把自己看的一些東西也記錄下來(lái)，本次學(xué)習(xí)android File操作這一塊。

File

打開(kāi)文件夾

public File openFileDirectory(final String path) {
        Log.i(TAG, "openFileDirectory: string = " + path);
        if (path == null)
            return null;
        File file = new File(path);
        if (!file.exists()) {
            if (file.mkdir())
                Log.e(TAG, "openFileDirectory: Dir create success"  );
        }
        Log.i(TAG, "openFileDirectory: dir absolutepath = " + file.getAbsolutePath());
        openFile(file.getAbsolutePath(),"qian.txt");
        return file;
    }

保存字符串到txt 文檔中

 public File openFile(final String path,final String name) {
        if (path == null || name == null) {
            Log.e(TAG, "openFile path or name is null" );
        }

        File mfile = new File(path,name); // 打開(kāi)文件，打開(kāi)后并不會(huì)保存，調(diào)用Filewrite才會(huì)保存
        Log.e(TAG, "openFile: ");

        writeStrWithStream(mfile,"facai zheng daqian");
        return mfile;
    }

public void writeStrWithStream(final File file,final String str) {
        FileWriter fw = null;
        try {
             fw = new FileWriter(file);
             fw.write(str);
             fw.write("\r\n");  //換行
        }catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                if (fw != null) {
                    fw.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

保存圖片NV21

private void SaveNV21Bitmap(ByteBuffer fram) {
        byte[] data = new byte[fram.capacity()];
        fram.get(data);

        File pictureFile = new File(Environment.getExternalStorageDirectory().toString() + File.separator + "UsbCamera" + ".jpg");
            try {
                FileOutputStream filecon = new FileOutputStream(pictureFile);
                YuvImage image = new YuvImage(data, ImageFormat.NV21, 640, 480, null);   //將NV21 data保存成YuvImage
                //圖像壓縮
                image.compressToJpeg(
                        new Rect(0, 0, image.getWidth(), image.getHeight()),
                        70, filecon);   // 將NV21格式圖片，以質(zhì)量70壓縮成Jpeg，并得到JPEG數(shù)據(jù)流

            }catch (IOException e)
            {
                e.printStackTrace();
            }

    }

Bitmap保存圖片

 public void saveByteToImage(final byte[] data,File file) {
        if (data == null || file == null)
            return;
        Bitmap bitmap = BitmapFactory.decodeByteArray(data,0,data.length);
        try {
            FileOutputStream fos = new FileOutputStream(file);
            bitmap.compress(Bitmap.CompressFormat.PNG,85,fos);
        }catch (FileNotFoundException e){s
            Log.e(TAG, "saveByteToImage: " + e.getMessage() );
        }
}