SD卡的讀寫是我們在開發Android 應用程序過程中最常見的操作。下面介紹SD卡的讀寫操作方式：
1. 獲取SD卡的根目錄
2. 在SD卡上創建文件夾目錄
/** * 在SD卡上創建目錄 */ public File createDirOnSDCard(String dir) { File dirFile = new File(sdCardRoot + File.separator + dir +File.separator); Log.v("createDirOnSDCard", sdCardRoot + File.separator + dir +File.separator); dirFile.mkdirs(); return dirFile; } 3. 在SD卡上創建文件
/** * 在SD卡上創建文件 */ public File createFileOnSDCard(String fileName, String dir) throws IOException { File file = new File(sdCardRoot + File.separator + dir + File.separator + fileName); Log.v("createFileOnSDCard", sdCardRoot + File.separator + dir + File.separator + fileName); file.createNewFile(); return file; } 4.判斷文件是否存在于SD卡的某個目錄
/** * 判斷SD卡上文件是否存在 */ public boolean isFileExist(String fileName, String path) { File file = new File(sdCardRoot + path + File.separator + fileName); return file.exists(); } 5.將數據寫入到SD卡指定目錄文件
/* 寫入數據到SD卡中 */ public File writeData2SDCard(String path, String fileName, InputStream data) { File file = null; OutputStream output = null; try { createDirOnSDCard(path); //創建目錄 file = createFileOnSDCard(fileName, path); //創建文件 output = new FileOutputStream(file); byte buffer[] = new byte[2*1024]; //每次寫2K數據 int temp; while((temp = data.read(buffer)) != -1 ) { output.write(buffer,0,temp); } output.flush(); } catch (Exception e) { e.printStackTrace(); } finally{ try { output.close(); //關閉數據流操作 } catch (Exception e2) { e2.printStackTrace(); } } return file; } 注意事項
對SD卡的操作，必須要申請權限：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
詳情看這里 //m.survivalescaperooms.com/article/34296.htm
注意：不直接進行讀出是為了防止打文件操作對內存的消耗，所以用輸入流讀到硬盤上。
public String readFile(String fileName) throws Exception{ FileInputStream fis = context.openFileInput(fileName); byte[] bytes = new byte[fis.available()]; fis.read(bytes); fis.close(); return new String(bytes,"utf-8"); }當文件很大的時候，byte[]會占用很大的內存。
package cn.itcast.fileio.service; import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream; import android.content.Context;import android.os.Environment; public class SdCardService { private Context ctx; public SdCardService(Context ctx) { this.ctx = ctx; } /** * 寫文件入skcard */ public void writeToSdCard(String fileName, String cont) { try { // 判斷是否有掛載sdcard if (Environment.getExternalStorageState().equals( Environment.MEDIA_MOUNTED)) { // 得到sdcar文件目錄 File dir = Environment.getExternalStorageDirectory(); File file = new File(dir, "itcast.txt"); FileOutputStream fos = new FileOutputStream(file); fos.write(cont.getBytes()); fos.close(); } } catch (Exception e) { e.printStackTrace(); } } /** * 讀SdCard中的文件 */ public String readSdCard(String fileName) { try { // 判斷是否有掛載sdcard if (Environment.getExternalStorageState().equals( Environment.MEDIA_MOUNTED)) { // 得到sdcar文件目錄 File dir = Environment.getExternalStorageDirectory(); File file = new File(dir, "itcast.txt"); FileInputStream fis = new FileInputStream(file); return readIs2String(fis); } } catch (Exception e) { e.printStackTrace(); } return null; } /** * 將輸入流數據讀取到輸出流當中 */ private OutputStream readIs2Os(InputStream is ,OutputStream os){ try { byte[] bytes = new byte[1024]; int length = 0 ; while((length = is.read(bytes)) != -1){ os.write(bytes, 0, length); } is.close(); os.close(); } catch (IOException e) { e.printStackTrace(); } return os ; } /** * 將輸入流數據讀取到輸出流當中 */ public byte[] readIs2Bytes(InputStream is){ ByteArrayOutputStream baos = new ByteArrayOutputStream(); readIs2Os(is,baos); return baos.toByteArray() ; } public String readIs2String(InputStream is){ try { return new String(readIs2Bytes(is),"utf-8"); } catch (Exception e) { e.printStackTrace(); } return null ; } public String readIs2String(String fileName){ try { if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){ File dir = Environment.getExternalStorageDirectory(); File file = new File(dir,fileName); FileInputStream is = new FileInputStream(file); return readIs2String(is); } } catch (Exception e) { e.printStackTrace(); } return null ; }}新聞熱點
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