從內部到外部存儲的Android複製數據庫

我試圖將我現有的數據庫從我的內部存儲複製到外部存儲，但我遇到了一些問題。它說the file does not exist。下面是我使用的究竟是什麼：從內部到外部存儲的Android複製數據庫

從內部的文件複製到外部存儲：

private void copyFile(String src, String dst) throws IOException{ 
    FileChannel inChannel = new FileInputStream(src).getChannel(); 
    FileChannel outChannel = new FileOutputStream(dst).getChannel(); 
    try 
    { 
     inChannel.transferTo(0, inChannel.size(), outChannel); 
    } 
    finally 
    { 
     if (inChannel != null) 
      inChannel.close(); 
     if (outChannel != null) 
      outChannel.close(); 
    } 
}

，我使用它是這樣的：

copyFile("/data/data/com.example.test/databases/database.sqlite","/sdcard/.Example/Data/database.sqlite");

，但它沒有工作，我很確定內部存儲中的數據庫在那裏。

如果我在copyFile"/sdcard/.Example/Data/"中設置了目標文件夾，它將在.Example中創建文件Data。

任何建議我失蹤了？

來源

2012-01-30 Android-Droid

您是否添加了WRITE_EXTERNAL_STORAGE權限？

<?xml version="1.0" encoding="utf-8"?> 
<manifest ... 
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> 
</manifest>

來源

2012-01-30 16:20:14 jacknad

是的，我已經這樣做。其實我注意到文件被複制，但是它是空的。 – 2012-01-30 16:27:51

使用此選項將數據庫複製到SD卡。

public void copyFile() 
    { 
     try 
     { 
      File sd = Environment.getExternalStorageDirectory(); 
      File data = Environment.getDataDirectory(); 

      if (sd.canWrite()) 
      { 
       String currentDBPath = "\\data\\your.package.name\\databases\\dabase_name"; 
       String backupDBPath = "database_name"; 
       File currentDB = new File(data, currentDBPath); 
       File backupDB = new File(sd, backupDBPath); 

       if (currentDB.exists()) { 
        FileChannel src = new FileInputStream(currentDB).getChannel(); 
        FileChannel dst = new FileOutputStream(backupDB).getChannel(); 
        dst.transferFrom(src, 0, src.size()); 
        src.close(); 
        dst.close(); 
       } 
       if(bool == true) 
       { 
        Toast.makeText(Settings.this, "Backup Complete", Toast.LENGTH_SHORT).show(); 
        bool = false; 
       } 
      }    
     } 
     catch (Exception e) { 
      Log.w("Settings Backup", e); 
     } 
    }

來源

2012-01-30 16:31:24 Deepak

你當前的數據庫路徑不適用於我。這工作：「/data/my.package.name/databases/mydbName.db」 – Mike6679 2013-10-31 02:28:34

「if（bool == true）」？我認爲有一個初始化丟失的地方。最好的猜測是你想檢查「transferFrom」長反應對原始數據庫的大小，或檢查，看它是否大於1見：https://developer.android.com/reference/java/nio/channels/FileChannel .html＃transferFrom（java.nio.channels.ReadableByteChannel，long，long） – 2017-07-19 17:35:13

如果你不知道你的應用程序的路徑，那麼你可以使用這個：

或者，如果你需要複製數據庫公開「下載」文件夾中，那麼你可以使用這個：

public void copyAppDbToDownloadFolder() throws IOException { 
    try { 
     File backupDB = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), "toDatabaseName"); // for example "my_data_backup.db" 
     File currentDB = getApplicationContext().getDatabasePath("databaseName"); //databaseName=your current application database name, for example "my_data.db" 
     if (currentDB.exists()) { 
      FileInputStream fis = new FileInputStream(currentDB); 
      FileOutputStream fos = new FileOutputStream(backupDB); 
      fos.getChannel().transferFrom(fis.getChannel(), 0, fis.getChannel().size()); 
      // or fis.getChannel().transferTo(0, fis.getChannel().size(), fos.getChannel()); 
      fis.close(); 
      fos.close(); 
      Log.i("Database successfully", " copied to download folder"); 
      return true; 
     } else Log.i("Copying Database", " fail, database not found"); 
    } catch (IOException e) { 
     Log.d("Copying Database", "fail, reason:", e); 
    } 
}

這是在我的Nexus 4設備上完美運行。

來源

2013-12-27 04:42:06

該程序可以複製指定的數據庫「數據庫名稱」從Android應用程序與外部storage.It的內部存儲創建一個名爲「文件夾名稱」，然後將數據庫複製到一個名爲「備份數據庫名稱」文件夾該文件夾內

1.本程序與Android兼容棉花糖
2.As MediaScannerConnection使用，可以立即從電腦windows操作系統的複製備份文件而無需重新啓動您的系統
3.如果「文件夾名稱「不存在它將自動創建它
4.如果您指定的備份文件名稱爲a lready存在，它會顯示一個警告對話框

if(ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE)== PackageManager.PERMISSION_DENIED){ 
    if(ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE)){ 
     ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 5); 
    } 
    else{ 
     ActivityCompat.requestPermissions(MainActivity.this,new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},5); 
    } 
} 
else{ 
    final File backupDb=new File(Environment.getExternalStorageDirectory().getPath()+File.separator+"<Folder Name>"+File.separator+"<Backup Database Name>"); 
    final File currentDB = new File(String.valueOf(getApplicationContext().getDatabasePath("<Your Database Name>"))); 
    if(backupDb.exists()){ 
     AlertDialog.Builder builder=new AlertDialog.Builder(MainActivity.this) 
       .setTitle("Alert") 
       .setMessage("File already exists.Do you want to replace it") 
       .setCancelable(false) 
       .setPositiveButton(android.R.string.yes, new DialogInterface.OnClickListener() { 
        @Override 
        public void onClick(DialogInterface dialog, int which) { 
         if(!new File(Environment.getExternalStorageDirectory().getPath()+File.separator+"<Folder Name>").canWrite()) { 
          Toast.makeText(MainActivity.this, "Unable to write into external storage", Toast.LENGTH_SHORT).show(); 
         } 
         else{ 
          if(!currentDB.exists()){ 
           Toast.makeText(MainActivity.this, "Database doesn't exists", Toast.LENGTH_SHORT).show(); 
          } 
          else{ 
           try { 
            FileChannel src = new FileInputStream(currentDB).getChannel(); 
            FileChannel dst = new FileOutputStream(backupDb).getChannel(); 
            dst.transferFrom(src, 0, src.size()); 
            src.close(); 
            dst.close(); 
            MediaScannerConnection.scanFile(getApplicationContext(), new String[]{backupDb.toString()}, null, null); 
            Toast.makeText(MainActivity.this, "Database successfully copied to external storage", Toast.LENGTH_SHORT).show(); 
            editText.setText(null); 
           }catch(Exception e){ 
            Toast.makeText(MainActivity.this, "Got exception" + e, Toast.LENGTH_SHORT).show(); 
           } 
          } 
         } 
        } 
       }) 
       .setNegativeButton(android.R.string.no, new DialogInterface.OnClickListener() { 
        @Override 
        public void onClick(DialogInterface dialog, int which) { 
         Toast.makeText(MainActivity.this, "Please enter another name", Toast.LENGTH_SHORT).show(); 
        } 
       }) 
       .setIcon(R.drawable.alert); 
     AlertDialog dialog = builder.create(); 
     dialog.show(); 
    } 
    else{ 
     new File(Environment.getExternalStorageDirectory().getPath()+File.separator+"<Folder Name>").mkdir(); 
     if(!new File(Environment.getExternalStorageDirectory().getPath()+File.separator+"<Folder Name>").canWrite()) { 
      Toast.makeText(MainActivity.this, "Unable to write into external storage", Toast.LENGTH_SHORT).show(); 
     } 
     else{ 
      if(!currentDB.exists()){ 
       Toast.makeText(MainActivity.this, "Database doesn't exists", Toast.LENGTH_SHORT).show(); 
      } 
      else{ 
       try { 
        FileChannel src = new FileInputStream(currentDB).getChannel(); 
        FileChannel dst = new FileOutputStream(backupDb).getChannel(); 
        dst.transferFrom(src, 0, src.size()); 
        src.close(); 
        dst.close(); 
        MediaScannerConnection.scanFile(getApplicationContext(), new String[]{backupDb.toString()}, null, null); 
        editText.setText(null); 
        Toast.makeText(MainActivity.this, "Database successfully copied to external storage", Toast.LENGTH_SHORT).show(); 
       }catch(Exception e){ 
        Toast.makeText(MainActivity.this, "Got exception" + e, Toast.LENGTH_SHORT).show(); 
       } 
      } 
     } 
    } 
}

「數據庫名稱」 - >數據庫內部應用程序
「備份數據庫名稱」 - >文件中，你要複製的數據庫
「文件夾名稱」 - >將備份數據庫文件夾存儲

來源

2016-10-28 14:00:08

從內部到外部存儲的Android複製數據庫

回答

相關問題