如何从外部文件替换（覆盖）数据库

Question

我想从特定路径将旧基础替换为新基础。我应该删除旧版本只复制新文件吗？它可以工作，但在我清除现金或重新启动设备后，应用程序会应用新的基础。为什么这样？或者我应该使用dbHelper.onUpgrade()？可能会更好。但我无法将参数设置为onUpgrade()，因为它需要SQLiteDatabase 作为参数，我有数据库的文件路径，所以我如何设置必要的参数？它应该看起来像这样：

    downloadDbPath = file.getPath();
    sql = new SQLiteDatabase().getPath(downloadDbPath);
    dbHelper.onUpgrade(sql, 1, 2);

第二行出现错误Error: SQLiteDatabase() is not public in SQLiteDatabase; cannot be accessed from outside package 所以我无法创建新对象

Answer 1

好的，如果有人感兴趣，我接下来要做： 主要方法：

  public void downloadDb() {
        new FileChooser(this).setFileListener(new FileChooser.FileSelectedListener() {
            @Override public void fileSelected(final File file) {
                downloadDbPath = file.getPath();
                try {
                    InputStream in = new FileInputStream(downloadDbPath);
                    OutputStream out = new FileOutputStream(uploadDbPath);

                    // Transfer bytes from in to out
                    byte[] buf = new byte[1024];
                    int len;
                    while ((len = in.read(buf)) > 0) {
                        out.write(buf, 0, len);
                    }
                    deleteCache(context);
                    restartApp();
                    in.close();
                    out.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).showDialog();
    }

配件：

清理缓存： https://stackoverflow.com/a/23908638/4540861

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

public static void deleteCache(Context context) {
    try {
        File dir = context.getCacheDir();
        deleteDir(dir);
    } catch (Exception e) {}
}

public static boolean deleteDir(File dir) {
    if (dir != null && dir.isDirectory()) {
        String[] children = dir.list();
        for (int i = 0; i < children.length; i++) {
            boolean success = deleteDir(new File(dir, children[i]));
            if (!success) {
                return false;
            }
        }
        return dir.delete();
    } else if(dir!= null && dir.isFile()) {
        return dir.delete();
    } else {
        return false;
    }
}

重启应用： https://stackoverflow.com/a/17166729/4540861

public void restartApp(){
    Intent mStartActivity = new Intent(context, MainActivity.class);
    int mPendingIntentId = 123456;
    PendingIntent mPendingIntent = PendingIntent.getActivity(context, mPendingIntentId,    mStartActivity, PendingIntent.FLAG_CANCEL_CURRENT);
    AlarmManager mgr = (AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
    mgr.set(AlarmManager.RTC, System.currentTimeMillis() + 100, mPendingIntent);
    System.exit(0);
}

文件选择器： https://rogerkeays.com/simple-android-file-chooser

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

class FileChooser {
    private static final String PARENT_DIR = "..";

    private final Activity activity;
    private ListView list;
    private Dialog dialog;
    private File currentPath;

    // filter on file extension
    private String extension = null;
    public void setExtension(String extension) {
        this.extension = (extension == null) ? null :
                extension.toLowerCase();
    }

    // file selection event handling
    public interface FileSelectedListener {
        void fileSelected(File file);
    }

    public FileChooser setFileListener(FileSelectedListener fileListener) {
        this.fileListener = fileListener;
        return this;
    }

    private FileSelectedListener fileListener;

    public FileChooser(Activity activity) {
        this.activity = activity;
        dialog = new Dialog(activity);
        list = new ListView(activity);
        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override public void onItemClick(AdapterView<?> parent, View view, int which, long id) {
                String fileChosen = (String) list.getItemAtPosition(which);
                File chosenFile = getChosenFile(fileChosen);
                if (chosenFile.isDirectory()) {
                    refresh(chosenFile);
                } else {
                    if (fileListener != null) {
                        fileListener.fileSelected(chosenFile);
                    }
                    dialog.dismiss();
                }
            }
        });
        dialog.setContentView(list);
        dialog.getWindow().setLayout(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);
        refresh(Environment.getExternalStorageDirectory());
    }

    public void showDialog() {
        dialog.show();
    }


    /**
     * Sort, filter and display the files for the given path.
     */
    private void refresh(File path) {
        this.currentPath = path;
        if (path.exists()) {
            File[] dirs = path.listFiles(new FileFilter() {
                @Override public boolean accept(File file) {
                    return (file.isDirectory() && file.canRead());
                }
            });
            File[] files = path.listFiles(new FileFilter() {
                @Override public boolean accept(File file) {
                    if (!file.isDirectory()) {
                        if (!file.canRead()) {
                            return false;
                        } else if (extension == null) {
                            return true;
                        } else {
                            return file.getName().toLowerCase().endsWith(extension);
                        }
                    } else {
                        return false;
                    }
                }
            });

            // convert to an array
            int i = 0;
            String[] fileList;
            if (path.getParentFile() == null) {
                fileList = new String[dirs.length + files.length];
            } else {
                fileList = new String[dirs.length + files.length + 1];
                fileList[i++] = PARENT_DIR;
            }
            Arrays.sort(dirs);
            Arrays.sort(files);
            for (File dir : dirs) { fileList[i++] = dir.getName(); }
            for (File file : files ) { fileList[i++] = file.getName(); }

            // refresh the user interface
            dialog.setTitle(currentPath.getPath());
            list.setAdapter(new ArrayAdapter(activity,
                    android.R.layout.simple_list_item_1, fileList) {
                @Override public View getView(int pos, View view, ViewGroup parent) {
                    view = super.getView(pos, view, parent);
                    ((TextView) view).setSingleLine(true);
                    return view;
                }
            });
        }
    }


    /**
     * Convert a relative filename into an actual File object.
     */
    private File getChosenFile(String fileChosen) {
        if (fileChosen.equals(PARENT_DIR)) {
            return currentPath.getParentFile();
        } else {
            return new File(currentPath, fileChosen);
        }
    }
}