android檔案快取，並SD卡建立目錄未能解決和bitmap記憶體溢出解決

標籤：

 1.相關代碼：

    加入許可權：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>      /** 擷取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();//擷取根資料夾        }        if (sdcardPath != null) {            return sdcardPath;        } else {            return "";        }    }

  解決方案：擷取根資料夾的代碼改為：
  sdcardPath = Environment.getExternalStorageDirectory().getAbsolutePath();

這樣就能夠了。

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附檔案快取類：

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;/** * 圖片檔案儲存、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;        /** 從緩衝中擷取圖片 **/    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。這樣是為了減少記憶體的消耗，防止記憶體溢出        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;    }                                                                    /** 將圖片存入檔案快取 **/    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");        }    }                                                                    /**     * 計算隱藏檔夾下的檔案大小，     * 當檔案總大小大於指定的MAX_CACHE_SIZE或者sdcard剩餘空間小於指定的LEAST_SIZE_OF_SDCARD     * 那麼刪除40%近期沒有被使用的檔案     */    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);            /* 依據檔案的最後改動時間進行升序排序 */            Arrays.sort(files, new Comparator<File>() {            @Override             public 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;        }    }                                                                    /** 改動檔案的最後改動時間 **/    public static void updateFileTime(String path) {        File file = new File(path);        long newModifiedTime = System.currentTimeMillis();        file.setLastModified(newModifiedTime);    }                                                                    /** 計算sdcard上的剩餘空間 **/    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;    }                                                                    /** 獲得快取檔案夾 **/    private static String getCacheDirectory() {        String dir = getSDPath() + "/" + CACHE_DIRECTORY;        return dir;    }                                                                    /** 擷取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();  //擷取根資料夾        }        if (sdcardPath != null) {            return sdcardPath;        } else {            return "";        }    }}

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android檔案快取，並SD卡建立目錄未能解決和bitmap記憶體溢出解決