Android 錯誤：沒有那個文件或目錄？

Question

我正在嘗試通過我的 android 應用程序創建一個數據庫，該應用程序正在模擬器上工作。

但是，由於我無法直接在我的三星設備上查看數據庫（它沒有扎根），我正在嘗試將數據庫文件傳輸到 SD 卡。

該文件沒有成功傳輸到 SD 卡，當我嘗試在 eclipse 中打開它時它不存在。

我在 Logcat 中收到以下錯誤：

07-15 14:31:07.035: E/mypck(17369): /data/com.example.multapply/databases/MultapplyDatabase.db: open failed: ENOENT (No such file or directory)
07-15 14:31:07.035: E/mypck(17369): java.io.FileNotFoundException: /data/com.example.multapply/databases/MultapplyDatabase.db: open failed: ENOENT (No such file or directory)
07-15 14:31:07.035: E/mypck(17369):     at libcore.io.IoBridge.open(IoBridge.java:409)
07-15 14:31:07.035: E/mypck(17369):     at java.io.FileInputStream.<init>(FileInputStream.java:78)
07-15 14:31:07.035: E/mypck(17369):     at com.example.multapply.ExportDatabaseFileTask.copyFile(ExportDatabaseFileTask.java:71)
07-15 14:31:07.035: E/mypck(17369):     at com.example.multapply.ExportDatabaseFileTask.doInBackground(ExportDatabaseFileTask.java:49)
07-15 14:31:07.035: E/mypck(17369):     at com.example.multapply.ExportDatabaseFileTask.doInBackground(ExportDatabaseFileTask.java:1)
07-15 14:31:07.035: E/mypck(17369):     at android.os.AsyncTask$2.call(AsyncTask.java:288)
07-15 14:31:07.035: E/mypck(17369):     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
07-15 14:31:07.035: E/mypck(17369):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
07-15 14:31:07.035: E/mypck(17369):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
07-15 14:31:07.035: E/mypck(17369):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
07-15 14:31:07.035: E/mypck(17369):     at java.lang.Thread.run(Thread.java:841)
07-15 14:31:07.035: E/mypck(17369): Caused by: libcore.io.ErrnoException: open failed: ENOENT (No such file or directory)
07-15 14:31:07.035: E/mypck(17369):     at libcore.io.Posix.open(Native Method)
07-15 14:31:07.035: E/mypck(17369):     at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110)
07-15 14:31:07.035: E/mypck(17369):     at libcore.io.IoBridge.open(IoBridge.java:393)
07-15 14:31:07.035: E/mypck(17369):     ... 10 more

相關代碼：

Class relating to exporting the file:

public class ExportDatabaseFileTask extends AsyncTask<String, Void, Boolean> {

    //Default constructor
    public ExportDatabaseFileTask() {

    }

    //delete if necessary
    //private final ProgressDialog dialog = new ProgressDialog(null);


    // can use UI thread here
    protected void onPreExecute() {
//      this.dialog.setMessage("Exporting database...");
//      this.dialog.show();
    }

    // automatically done on worker thread (separate from UI thread)
    protected Boolean doInBackground(final String... args) {

        //original database file location
        File dbFile = new File(Environment.getDataDirectory()
                + "/com.example.multapply/databases/MultapplyDatabase.db");

        //the destination file location
        File exportDir = new File(Environment.getExternalStorageDirectory(), "");
        if (!exportDir.exists()) {
            exportDir.mkdirs();
        }


        File file = new File(exportDir, dbFile.getName());
        try {
            file.createNewFile();
            this.copyFile(dbFile, file);
            return true;
        } catch (IOException e) {
            Log.e("mypck", e.getMessage(), e);
            return false;
        }
    }

    // can use UI thread here
    protected void onPostExecute(final Boolean success) {
//      if (this.dialog.isShowing()) {
//          this.dialog.dismiss();
//      }
//      if (success) {
//          Toast.makeText( null, "Export successful!", Toast.LENGTH_SHORT)
//                  .show();
//      } else {
//          Toast.makeText(null, "Export failed", Toast.LENGTH_SHORT).show();
//      }
    }

    void copyFile(File src, File 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();
        }
    }

}

此類被實例化和調用的代碼：

/**
             * CRUD Operations
             * */
            // Inserting Contacts
            Log.d("Insert: ", "Inserting ..");

            db.addScore(new Score(UserName.getUserName(), score, System.currentTimeMillis() ));

            //attempting to export the file to the sd card
            ExportDatabaseFileTask task = new ExportDatabaseFileTask();
            task.execute();

注意：我之前遇到過與我在這里詢問的“Writing exception to parcel”相關的錯誤，但是現在我刪除了這個錯誤：

<uses-permission android:name="android.permission.INTERACT_ACROSS_USERS_FULL"/>

從清單中。

Answer 1

不要使用Environment.getDataDirectory()來獲取您的數據位置。 使用您的Context對象來獲取您的數據庫和/或數據位置。 請參閱方法getDir() 、 getDatabasePath()和getExternalFilesDir() 。

Answer 2

如果將 DB 文件復制到 SD 卡，例如復制到：/sdcard/MyApp/Databases/MultapplyDatabase.db，則需要從該位置打開該文件。

File dbFile = new File("/sdcard/MyApp/Databases/MultapplyDatabase.db");

Answer 3

在您的清單應用程序中添加以下內容。

android:requestLegacyExternalStorage="true"