Android Path内部存储

Question

I'm having a problem with the internal path to export the database. The Log says it is the wrong path.

File sd = Environment.getExternalStorageDirectory();
            File data = Environment.getDataDirectory();
           FileChannel source=null;
           FileChannel destination=null;
           String cartella = (getString(R.string.app_name));
           String currentDBPath = "/data/"+getPackageName()+"/cartella/"+"Backup.db";
           String backupDBPath = "/cartella/Backup.db";

           File currentDB = new File(data, currentDBPath);
           File backupDB = new File(sd, backupDBPath);
           try {
                source = new FileInputStream(currentDB).getChannel();
                destination = new FileOutputStream(backupDB).getChannel();
                destination.transferFrom(source, 0, source.size());
                source.close();
                destination.close();
                Toast.makeText(this, "DB Exported!", Toast.LENGTH_LONG).show();
            } catch(IOException e) {
                e.printStackTrace();
                  Toast toast = Toast.makeText(getApplicationContext(),(R.string.Toast_export_errore), Toast.LENGTH_SHORT);
                     toast.show();

Log

01-20 08:55:14.757: W/System.err(1383): java.io.FileNotFoundException: /data/data/info.androidhive.slidingmenu/cartella/Backup.db: open failed: ENOENT (No such file or directory)

01-20 08:55:14.787: W/System.err(1383): at libcore.io.IoBridge.open(IoBridge.java:409) 01-20 08:55:14.787: W/System.err(1383): at java.io.FileInputStream.(FileInputStream.java:78) 01-20 08:55:14.827: W/System.err(1383): at main.Impostazioni.Esporta(Impostazioni.java:334) 01-20 08:55:14.827: W/System.err(1383): at java.lang.reflect.Method.invokeNative(Native Method) 01-20 08:55:14.827: W/System.err(1383): at java.lang.reflect.Method.invoke(Method.java:525) 01-20 08:55:14.827: W/System.err(1383): at android.view.View$1.onClick(View.java:3628) 01-20 08:55:14.857: W/System.err(1383): at android.view.View.performClick(View.java:4240) 01-20 08:55:14.857: W/System.err(1383): at android.view.View$PerformClick.run(View.java:17721) 01-20 08:55:14.877: W/System.err(1383): at android.os.Handler.handleCallback(Handler.java:730) 01-20 08:55:14.877: W/System.err(1383): at android.os.Handler.dispatchMessage(Handler.java:92) 01-20 08:55:14.887: W/System.err(1383): at android.os.Looper.loop(Looper.java: 137) 01-20 08:55:14.898: W/System.err(1383): at android.app.ActivityThread.main(ActivityThread.java:5103) 01-20 08:55:14.927: W/System.err(1383): at java.lang.reflect.Method.invokeNative(Native Method) 01-20 08:55:14.927: W/System.err(1383): at java.lang.reflect.Method.invoke(Method.java:525) 01-20 08:55:14.957: W/System.err(1383): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 01-20 08:55:14.957: W/System.err(1383): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 01-20 08:55:14.987: W/System.err(1383): at dalvik.system.NativeStart.main(Native Method) 01-20 08:55:14.987: W/System.err(1383): Caused by: libcore.io.ErrnoException: open failed: ENOENT (No such file or directory)

Answer 1

Try replacing:

File currentDB = new File(data, currentDBPath);

with:

File currentDB = getDatabasePath("Backup.db");

Hardcoding the database path is not a good idea since it is not guaranteed to be the same on all devices. Using getDatabasePath() will return the path on which the database was created. So if the database does exist, the correct path to it will be returned.

EDIT:

To restore a database you have previously exported, do exactly as you did for the export. The only difference is that you need to switch the source and destination around so that the source is now your backup file path and the destination is now the database file path. The database will then be overwritten with the backup:

source = new FileInputStream(backupDB).getChannel();
destination = new FileOutputStream(currentDB).getChannel();

Answer 2

Is

/data/data/info.androidhive.slidingmenu/cartella/Backup.db

a valid path? You can use DDMS to check in your app data that Backup.db exist