Android save file to external storage

在External storage下開一個app專屬資料夾並且儲存檔案:

首先建立資料夾

final String writeDir= Environment.getExternalStorageDirectory()+ "/YourAppName/log/"; File dir = new File(writeDir); dir.mkdirs();
case1. 寫入文字檔案
mFileWriter = new FileWriter(writeDir+ "/logFile.txt", true); mFileWriter.write("yayahihihello"); mFileWriter.flush(); mFileWriter.close();

case2. 使用FileOutputStream儲存圖檔


//這個路徑可以被內建的gallery app 找到 final String writePath = Environment.getExternalStorageDirectory()+"/Pictures/YourAPPName"; Bitmap bitmap = (拿到你要存的bitmap); //將Bitmap轉成bytes才能儲存 ByteArrayOutputStream bytes = new ByteArrayOutputStream(); bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bytes); //使用FileOutputStream儲存bytes FileOutputStream fo = new FileOutputStream(f); fo.write(bytes.toByteArray()); bytes.close(); fo.close();

接著最後儲存的檔案編號繼續下去


String fileName,fileNameBase = "CanvasNetPic" ; int counter =1; fileName = "CanvasNetPic0"; File f = new File(savePath+"/"+fileName+".jpg"); while(f.exists()) { fileName = fileNameBase + Integer.toString(counter); f = new File(savePath+"/"+fileName+".jpg"); counter++; }

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通知Android media scanner file system被改變過, 這樣新儲存的檔案才會馬上被gallery或其他content reader讀到


sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://"+ Environment.getExternalStorageDirectory())));

但這樣子media scanner會去重新掃描整個ExternalStroage, 或是檔案很多或是device比較慢的話要掃很久, 會導致打開gallery以後要放著一段時間新儲存的檔案才會出來

只掃描儲存檔案的資料夾可以大幅減掃掃描時間:

sendBroadcast(new Intent(Intent.ACTION_MEDIA_MOUNTED, Uri.parse("file://"+ "你的儲存路徑")));