Android复制数据库从内部到外部存储 [英] Android copy database from internal to external storage

问题描述

我试图将我现有的数据库从我的内部到外部存储，但我有一个问题。它表示文件不存在。这里是我实际使用：

将文件从内部复制到外部存储：

  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（）; 
} 
} 
  

p>

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

但它不工作，我很确定内部存储中的数据库。 p>

如果我在 copyFile / sdcard / .Example / Data / 它正在 .Example 中创建文件数据。

任何建议我缺少什么？

解决方案

如果你不知道你的应用程序路径，您可以使用：

  //没有资源泄漏：<未分配关闭值> ，这样的东西
 public void copyAppDbToDownloadFolder（）throws IOException {
 try {
 String currDate = Constants.APP_DATE_SHORT_FORMAT.format（new Date（））; 
文件backupDB =新文件（Environment.getExternalStoragePublicDirectory（Environment.DIRECTORY_DOWNLOADS），DbContract.DATABASE_BUCKUP_NAME + currDate +.db）; 
文件currentDB = appCon.getDatabasePath（DbContract.DATABASE_NAME）; 
 if（currentDB.exists（））{
 FileInputStream fis = new FileInputStream（currentDB）; 
 FileOutputStream fos = new FileOutputStream（backupDB）; 
 fos.getChannel（）。transferFrom（fis.getChannel（），0，fis.getChannel（）。size（））; 
 //或fis.getChannel（）。transferTo（0，fis.getChannel（）。size（），fos.getChannel（））; 
 fis.close（）; 
 fos.close（）; 
 Log.i（数据库成功，复制到下载文件夹）; 
 return true; 
} 
} catch（IOException e）{
 Log.d（复制数据库，失败，原因：，e）; 
} 
} 
  

然后你可以使用这个：

  public void copyAppDbToDownloadFolder（）throws IOException {
 try {
 File backupDB = new File（Environment.getExternalStoragePublicDirectory（Environment.DIRECTORY_DOWNLOADS），toDatabaseName）; //例如my_data_backup.db
文件currentDB = getApplicationContext（）。getDatabasePath（databaseName）; // databaseName =您当前的应用程序数据库名称，例如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（））; 
 //或fis.getChannel（）。transferTo（0，fis.getChannel（）。size（），fos.getChannel（））; 
 fis.close（）; 
 fos.close（）; 
 Log.i（数据库成功，复制到下载文件夹）; 
 return true; 
} else Log.i（复制数据库，失败，数据库未找到）; 
} catch（IOException e）{
 Log.d（复制数据库，失败，原因：，e）; 
} 
} 
  

这在我的Nexus 4设备上可以正常工作。 / p>

I'm trying to copy my existing databases from my Internal to External Storage,but I have a little problem. It says that the file does not exist. Here is what I'm using actually :

to copy files from internal to external storage :

    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();
    }
}

and I'm using it like this :

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

but it's not working and I'm pretty sure that the database in internal storage is there.

If I set as a destination folder in copyFile "/sdcard/.Example/Data/" it's creating file Data in .Example.

Any suggestions what I'm missing?

解决方案

If you don't know your application path then you can use this:

//for without "Resource leak: '<unassigned Closeable value>' is never closed" warning, something like this
public void copyAppDbToDownloadFolder() throws IOException {
    try {
        String currDate = Constants.APP_DATE_SHORT_FORMAT.format(new Date());
        File backupDB = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), DbContract.DATABASE_BUCKUP_NAME + currDate + ".db");
        File currentDB = appCon.getDatabasePath(DbContract.DATABASE_NAME);
        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;
        }
    } catch (IOException e) {
        Log.d("Copying Database", "fail, reason:", e);
    }
}

Or if you need copy database to public "Download" folder then you can use this:

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);
    }
}

This is working perfectly on my Nexus 4 device.

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