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SDCard中文件存取的實(shí)現(xiàn)-創(chuàng)新互聯(lián)

注意:

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第一步要先添加權(quán)限:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

步驟:

        文件流

        1、寫(xiě):

                  a)創(chuàng)建文件輸出流(PATH)

                  b)將內(nèi)容寫(xiě)入文件輸出流(str.getBytes())

                  bb)關(guān)閉流

        2、讀:

                  a)創(chuàng)建文件輸入流

                  b)創(chuàng)建字節(jié)數(shù)組緩存(ByteArrayBufferarrayBuffer = new ByteArrayBuffer(1000);)——>為了后面分段讀取時(shí)拼接數(shù)據(jù)

                  c)創(chuàng)建字節(jié)數(shù)組buffer(1024)(建立變量len=0)

                  d)循環(huán)讀入——while(-1!=(len=fis.read(buffer)){arrayBuffer.append(buffer, 0, len) }

                  e)通過(guò)創(chuàng)建String的形式將字節(jié)數(shù)組轉(zhuǎn)換成字符串(new String(arrayBuffer.toByteArray()))

                  f)將內(nèi)容顯示在文本框中

                  ff)關(guān)閉流

        對(duì)象流

        1、寫(xiě):

                  a)創(chuàng)建對(duì)象

                  b)創(chuàng)建文件輸出流(PATH)

                  c)創(chuàng)建對(duì)象輸出流(ObjectOutputStream,將文件輸出流嵌套在里面)

                  d)將對(duì)象寫(xiě)入對(duì)象輸出流(oos.writeObject(person);)

                  dd)關(guān)閉最外層流(對(duì)象流)

        2、讀:

                  a)創(chuàng)建文件輸入流

                  b)創(chuàng)建對(duì)象輸入流

                  c)將讀到的Object對(duì)象強(qiáng)轉(zhuǎn)成所需對(duì)象(Personperson = (Person)ois.readObject();)

                  d)在文本框中顯示對(duì)象的各項(xiàng)內(nèi)容

                  dd)關(guān)閉最外層流(對(duì)象流)

代碼實(shí)現(xiàn)(文件流):

1、往sdcard中寫(xiě)入數(shù)據(jù)

        FileOutputStreamfos = null;

                  try{

                           fos= new FileOutputStream(PATH);

                           Stringstr = writeToSdcard.getText().toString();

                           //將字符串打散寫(xiě)入流中

                           fos.write(str.getBytes());

                  }catch (FileNotFoundException e) {

                           //TODO Auto-generated catch block

                           e.printStackTrace();

                  }catch (IOException e) {

                           //TODO Auto-generated catch block

                           e.printStackTrace();

                  }finally{

                           if(fos!=null){

                                    try{

//如果path有問(wèn)題,會(huì)跳到finally中,而fos此時(shí)為null,會(huì)發(fā)生空指針異常

                                              fos.close();

                                    }catch (IOException e) {

                                              //TODO Auto-generated catch block

                                              e.printStackTrace();

                                    }

                           }

                  }

2、從sdcard中讀取數(shù)據(jù)

        FileInputStreamfis = null;

                  //1000表示的是預(yù)留空間

                  ByteArrayBufferarrayBuffer = new ByteArrayBuffer(1000);

                  try{

                           fis= new FileInputStream(PATH);

                           byte[]buffer = new byte[1024];

                           intlen = 0;

                           while(-1!=(len=fis.read(buffer))){

                                    //拼接

                                    arrayBuffer.append(buffer,0, len);

                           }

                           //通過(guò)新建字符串的形式將arrayBuffer轉(zhuǎn)換成字節(jié)數(shù)組

                           StringreadBuffer = new String(arrayBuffer.toByteArray());

                           writeToSdcard.setText(readBuffer);

                  }catch (FileNotFoundException e) {

                           //TODO Auto-generated catch block

                           e.printStackTrace();

                  }catch (IOException e) {

                           //TODO Auto-generated catch block

                           e.printStackTrace();

                  }finally{

                           if(fis!=null){

                                    try{

                                              fis.close();

                                    }catch (IOException e) {

                                              //TODO Auto-generated catch block

                                              e.printStackTrace();

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