1.相關代碼：

??? 加入權限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/><uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/> /** 獲取SD卡路徑 **/private static String getSDPath() {String sdcardPath = null;boolean sdCardExist = Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED); //推斷sd卡是否存在if (sdCardExist) {sdcardPath = Environment.getExternalStorageDirectory();//獲取根文件夾}if (sdcardPath != null) {return sdcardPath;} else {return "";}}

? 解決方法：獲取根文件夾的代碼改為：
? sdcardPath = Environment.getExternalStorageDirectory().getAbsolutePath();

這樣就能夠了。

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附文件緩存類：

package com.etnet.utilities;import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.OutputStream; import java.util.Arrays; import java.util.Comparator;import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.Environment; import android.os.StatFs; import android.util.Log;/*** 圖片文件保存、讀寫類* @author Barry*/ public class FileOperationUtil {private static final String TAG = "FileOperationUtil";private static final String CACHE_DIRECTORY = "TqProCache";private static final int MB = 1024*1024;private static final int MAX_CACHE_SIZE = 10 * MB;private static final int LEAST_SIZE_OF_SDCARD = 10 * MB;/** 從緩存中獲取圖片 **/public static Bitmap getImage(final String imageUrl) { final String path = getCacheDirectory() + "/" + convertUrlToFileName(imageUrl);// Log.i(TAG, "getImage filepath:" + path);// Log.i(TAG, "getImage url:" + url);File file = new File(path);if (file.exists()) { // Log.i(TAG, "getImage file exists");Bitmap bmp = null;try {//寬變為原圖的1/3。高也變為原圖的1/3。這樣是為了減少內存的消耗，防止內存溢出BitmapFactory.Options options=new BitmapFactory.Options(); options.inSampleSize = 3; bmp = BitmapFactory.decodeFile(path,options);LogUtil.d(TAG, "bmp size="+bmp.getByteCount());} catch (Exception e) {e.printStackTrace();}if (bmp == null) {file.delete();} else {updateFileTime(path);return bmp;}}return null;}/** 將圖片存入文件緩存 **/public static void saveBitmap(String imageUrl, Bitmap bm ) {if (bm == null) {return;}//推斷sdcard上的空間if (getFreeSpaceOfSdcard() < LEAST_SIZE_OF_SDCARD) {//SD空間不足return;}String filename = convertUrlToFileName(imageUrl);String dir = getCacheDirectory();File dirFile = new File(dir);if (!dirFile.exists()){if(!dirFile.mkdirs()){Log.w(TAG, "create cache file directorys failed");}}File file = new File(dir +"/" + filename);try {file.createNewFile();OutputStream outStream = new FileOutputStream(file);bm.compress(Bitmap.CompressFormat.JPEG, 100, outStream);outStream.flush();outStream.close();} catch (FileNotFoundException e) {Log.w(TAG, "FileNotFoundException");} catch (IOException e) {Log.w(TAG, "IOException");}}/*** 計算存儲文件夾下的文件大小，* 當文件總大小大于指定的MAX_CACHE_SIZE或者sdcard剩余空間小于指定的LEAST_SIZE_OF_SDCARD* 那么刪除40%近期沒有被使用的文件*/public static boolean removeExtraCache() {File dir = new File(getCacheDirectory());File[] files = dir.listFiles();if (files == null) {return true;}if (!android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED)) {return false;}int dirSize = 0;for (int i = 0; i < files.length; i++) {dirSize += files[i].length();} // LogUtil.d("Barry", "dirSize="+dirSize);if (dirSize > MAX_CACHE_SIZE || getFreeSpaceOfSdcard() < LEAST_SIZE_OF_SDCARD) {int removeNum = (int) ((0.4 * files.length) + 1);/* 依據文件的最后改動時間進行升序排序 */Arrays.sort(files, new Comparator<File>() {@Overridepublic int compare(File file1, File file2) {if (file1.lastModified() > file2.lastModified()) {return 1;} else if (file1.lastModified() == file2.lastModified()) {return 0;} else {return -1;}}});/* for (int i = 0; i < files.length; i++) {LogUtil.d("Barry", "file.modifiedTime="+files[i].lastModified());}*/for (int i = 0; i < removeNum; i++) {files[i].delete();}return true;}else{return false;}}/** 改動文件的最后改動時間 **/public static void updateFileTime(String path) {File file = new File(path);long newModifiedTime = System.currentTimeMillis();file.setLastModified(newModifiedTime);}/** 計算sdcard上的剩余空間 **/private static int getFreeSpaceOfSdcard() {StatFs stat = new StatFs(Environment.getExternalStorageDirectory().getPath());double sdFreeSize = ((double)stat.getAvailableBlocks() * (double) stat.getBlockSize());return (int) sdFreeSize;}private static String convertUrlToFileName(String url) {String[] strs = url.split("/");String savedImageName = strs[strs.length - 1];return savedImageName;}/** 獲得緩存文件夾 **/private static String getCacheDirectory() {String dir = getSDPath() + "/" + CACHE_DIRECTORY;return dir;}/** 獲取SD卡路徑 **/private static String getSDPath() {String sdcardPath = null;boolean sdCardExist = Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED); //推斷sd卡是否存在if (sdCardExist) {sdcardPath = Environment.getExternalStorageDirectory().getAbsolutePath(); //獲取根文件夾}if (sdcardPath != null) {return sdcardPath;} else {return "";}} }

版權聲明：本文博客原創文章，博客，未經同意，不得轉載。

轉載于:https://www.cnblogs.com/mengfanrong/p/4642169.html

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