Android的儲存----重新認識Android（9）

安卓的(持久化)儲存機制:

1.共享引數儲存SharedPreferences,一遍用於儲存簡單的鍵值對的配置資訊,使用者名稱....

鍵值對的值限於int,long,String,float,boolean

2.內部儲存Internal Storage,即存在手機的記憶體中.一遍用於存放一下不太大的檔案.

手機儲存:

RAM:執行時記憶體.相當於pc機的記憶體,不是持久化儲存的,裡面的資料斷點就消失.

ROM:相當於pc機的硬碟

SD CARD:擴充套件儲存卡.

核心程式碼：
public void click(View v) {
     if (v.getId() == R.id.bt_save) {// 儲存共享引數
     //要儲存,必須先獲取Editor物件
     Editor editor = sp.edit();
      // editor.putString("name", et_name.getText().toString());
       // editor.putString("phone", et_phone.getText().toString());
       editor.putString("test", "aaaaaaaaa");
       editor.clear();//清空已有的所有共享引數,再把editor裡面的資料寫出去
       editor.commit();//提交
       Toast.makeText(this, "儲存成功!", 0).show();
     } else { // 讀取共享引數
        // String name = sp.getString("name", "預設           值-無名氏");
         // String phone = sp.getString("phone", "000000");
          // tv_showData.setText("name:"+name+",phone:"+phone);
           Map<String,?> map = sp.getAll();
           Set<String> keys = map.keySet();
           StringBuilder sb = new StringBuilder();
           for(String aKey :keys){
                Object obj = map.get(aKey);
                sb.append(aKey).append("=").append(obj).append('\t');
          }
       tv_showData.setText(sb);
    }
}

public class SDCardHelper {
    private static String TAG = "SDCardHelper";

    /**
     * 判斷sdcard是否掛載
     */
    public static boolean isSDCardMounted() {
        return Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);
    }

    /**
     * 獲取sdcard絕對物理路徑 得到的格式為 /storage/sdcard 後面沒有斜線
     */
    public static String getSDCardPath() {
        if (isSDCardMounted()) {
            return Environment.getExternalStorageDirectory().getAbsolutePath();
        } else {
            return null;
        }
    }

    /**
     * 獲取sdcard的全部的空間大小。返回MB位元組
     */
    public static long getSDCardSize() {
        if (isSDCardMounted()) {
            StatFs fs = new StatFs(getSDCardPath());
// 因為帶有Long結尾的替代方法需要API 18以上的SDK才能支援,所以,暫時使用舊的
            long size = fs.getBlockSize();
            long count = fs.getBlockCount();// 獲取總塊數
            return size * count / 1024 / 1024;
        }
        return 0;
    }

    /**
     * 獲取sdcard的剩餘空間的大小。返回MB位元組
     */
    public static long getSDCardFreeSize() {
        if (isSDCardMounted()) {
            StatFs fs = new StatFs(getSDCardPath());
            long size = fs.getBlockSize();
            long count = fs.getFreeBlocks();// 獲取空閒的塊數
            return size * count / 1024 / 1024;
        }
        return 0;
    }

    /**
     * 獲取SD卡的可用空間大小，返回MB
     *
     * @return
     */
    public static long getSDCardAvailableSize() {
        if (isSDCardMounted()) {
            StatFs fs = new StatFs(getSDCardPath());
            int count = fs.getAvailableBlocks();// 獲取可用空間的大小
            int size = fs.getBlockSize();
            return count * size / 1024 / 1024;
        }
        return 0;
    }

    /**
     * 將檔案（byte[]）儲存進sdcard指定的路徑下 dir:指定的路徑
     */
    public static boolean saveFileToSDCard(byte[] data, String dir, String filename) {
        BufferedOutputStream bos = null;
        if (isSDCardMounted()) {
            Log.i(TAG, "==isSDCardMounted==TRUE");
            File file = new File(getSDCardPath() + File.separator + dir);
            Log.i(TAG, "==file:" + file.toString() + file.exists());
            if (!file.exists()) {
                boolean flags = file.mkdirs();
                Log.i(TAG, "==建立資料夾:" + flags);
            }
            try {
                bos = new BufferedOutputStream(new FileOutputStream(new File(file, filename)));
                bos.write(data, 0, data.length);
                bos.flush();
                return true;
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                try {
                    bos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return false;
    }

    /**
     * 已知檔案的絕對路徑，從sdcard中獲取到該檔案，返回byte[]
     */
    public static byte[] loadFileFromSDCard(String filepath) {
        BufferedInputStream bis = null;
        ByteArrayOutputStream baos = null;
        if (isSDCardMounted()) {
            File file = new File(filepath);
            if (file.exists()) {
                try {
                    baos = new ByteArrayOutputStream();
                    bis = new BufferedInputStream(new FileInputStream(file));
                    byte[] buffer = new byte[1024 * 8];
                    int c = 0;
                    while ((c = bis.read(buffer)) != -1) {
                        baos.write(buffer, 0, c);
                        baos.flush();
                    }
                    return baos.toByteArray();
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    try {
                        if (bis != null) {
                            bis.close();
                            baos.close();
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return null;
    }
    
}