android - 如何在删除 Realm 文件之前在 Android 中备份 Realm DB。有没有办法恢复备份文件？

Question

我正在开发一个应用程序，在将新数据复制到 Realm 之前Android我将删除该应用程序。Realm有什么方法可以在删除数据之前备份数据，如果使用时出现问题，可以将其恢复realm.copyToRealm()？

Answer 1

Realm.writeCopyTo可能对这种情况有所帮助。你可以在这里找到文档。

//Backup
Realm orgRealm = Realm.getInstance(orgConfig);
orgRealm.writeCopyTo(pathToBackup);
orgRealm.close();
//Restore
Realm.deleteRealm(orgConfig);
Realm backupRealm = Realm.getInstance(backupConfig);
backupRealm.writeCopyTo(pathToRestore);
backupRealm.close();
orgRealm = Realm.getInstance(orgConfig);

但是在您的情况下，将您的 Realm 文件移动到要备份的地方，并在您想要恢复它时将其移回，会更加简单和快捷。要获取 Realm 文件路径，请尝试：

realm.getPath();

Answer 2

这是领域数据库备份和恢复的示例代码。

public class RealmMigration  {

private final static String TAG = RealmMigration.class.getName();

private Context context;
private Realm realm;

public RealmMigration(Context context) {
    this.realm = Realm.getInstance(BaseApplication.realmConfiguration);
    this.context = context;
}

public void backup() {

    File exportRealmFile = null;

    File exportRealmPATH = context.getExternalFilesDir(null);
    String exportRealmFileName = "default.realm";

    Log.d(TAG, "Realm DB Path = "+realm.getPath());

    try {
        // create a backup file
        exportRealmFile = new File(exportRealmPATH, exportRealmFileName);

        // if backup file already exists, delete it
        exportRealmFile.delete();

        // copy current realm to backup file
        realm.writeCopyTo(exportRealmFile);

    } catch (IOException e) {
        e.printStackTrace();
    }

    String msg =  "File exported to Path: "+ context.getExternalFilesDir(null);
        Toast.makeText(context, msg, Toast.LENGTH_LONG).show();
        Log.d(TAG, msg);


    realm.close();

}

public void restore() {

    //Restore
    File exportRealmPATH = context.getExternalFilesDir(null);
    String FileName = "default.realm";

    String restoreFilePath = context.getExternalFilesDir(null) + "/"+FileName;

    Log.d(TAG, "oldFilePath = " + restoreFilePath);

    copyBundledRealmFile(restoreFilePath, FileName);
        Log.d(TAG, "Data restore is done");

}

private String copyBundledRealmFile(String oldFilePath, String outFileName) {
    try {
        File file = new File(context.getFilesDir(), outFileName);

        Log.d(TAG, "context.getFilesDir() = " + context.getFilesDir().toString());
        FileOutputStream outputStream = new FileOutputStream(file);

        FileInputStream inputStream = new FileInputStream(new File(oldFilePath));

        byte[] buf = new byte[1024];
        int bytesRead;
        while ((bytesRead = inputStream.read(buf)) > 0) {
            outputStream.write(buf, 0, bytesRead);
        }
        outputStream.close();
        return file.getAbsolutePath();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

private String dbPath(){

    return realm.getPath();
}

}