如何为应用程序创建简单的本地备份和恢复？

Question

我有五个 sqlite 数据库，我希望用户能够在手机中进行本地备份，并且可以恢复备份文件。我不知道如何创建这些备份并以编程方式恢复它们。我使用了 github 存储库，但它根本不起作用，我需要你的帮助来创建这个备份和恢复过程。感谢您的关注

Answer 1

在您的活动中制作备份和恢复按钮并定义本地数据库变量，例如，

private MainDatabase localBackup = new MainDatabase(this);

然后点击即可进行备份和恢复操作

@Override

public void onClick(View v) {

    final MainDatabase db = new MainDatabase(getApplicationContext());

    switch (v.getId()) {

        case R.id.tvBackUp:

            String outFileName = Environment.getExternalStorageDirectory() + 

File.separator + getResources().getString(R.string.app_name) + File.separator;

            localBackup.performBackup(db, outFileName);

            break;

        case R.id.tvRestore:

            File folder = new File(Environment.getExternalStorageDirectory() + File.separator + getApplicationContext().getResources().getString(R.string.app_name));

            if (folder.exists()) {

                final File[] files = folder.listFiles();

                if (files.length == 0) {

                    Toast.makeText(this, "No any Backup", Toast.LENGTH_SHORT).show();

                } else {

                    localBackup.performRestore(db);

                }

            }

            break;

    }

}

在数据库文件中制定备份方法

public void performBackup(final MainDatabase db, final String outFileName) {

    File folder = new File(Environment.getExternalStorageDirectory() + File.separator 

+ mContext.getResources().getString(R.string.app_name));

    boolean success = true;

    if (!folder.exists())

        success = folder.mkdirs();

    if (success) {

        final Dialog dialog = new Dialog(mContext);

        dialog.setContentView(R.layout.backup_dialog);

        dialog.getWindow().getAttributes().windowAnimations = 

R.style.PauseDialogAnimation;

dialog.getWindow().setBackgroundDrawableResource(android.R.color.transparent);

        dialog.show();

        Button btnSave = dialog.findViewById(R.id.btnSave);

        Button btnCancel = dialog.findViewById(R.id.btnCancel);

        EditText etName = dialog.findViewById(R.id.etName);

        etName.setInputType(InputType.TYPE_CLASS_TEXT);

        btnSave.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                String m_Text = etName.getText().toString();

                String out = outFileName + m_Text + ".db";

                db.backup(out);

                dialog.dismiss();

            }

        });

        btnCancel.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                dialog.dismiss();

            }

        });

    } else

        Toast.makeText(mContext, "Unable to create directory. Retry", 

Toast.LENGTH_SHORT).show();

}

    public void backup(String outFileName) {

    //database path

    final String inFileName = mContext.getDatabasePath(DATABASE_NAME).toString();

    try {

        File dbFile = new File(inFileName);

        FileInputStream fis = new FileInputStream(dbFile);

        // Open the empty db as the output stream

        OutputStream output = new FileOutputStream(outFileName);

        // Transfer bytes from the input file to the output file

        byte[] buffer = new byte[1024];

        int length;

        while ((length = fis.read(buffer)) > 0) {

            output.write(buffer, 0, length);

        }

        // Close the streams

        output.flush();

        output.close();

        fis.close();

        Toast.makeText(mContext, "Backup Completed", Toast.LENGTH_SHORT).show();

    } catch (Exception e) {

        Toast.makeText(mContext, "Unable to backup database. Retry", 

Toast.LENGTH_SHORT).show();

        e.printStackTrace();

    }

}

以及进行恢复时，询问用户要恢复什么备份

public void performRestore(final MainDatabase db) {

    File folder = new File(Environment.getExternalStorageDirectory() + File.separator 

+ mContext.getResources().getString(R.string.app_name));

    if (folder.exists()) {

        final File[] files = folder.listFiles();

        final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<>(mContext, 

 android.R.layout.select_dialog_item);

        for (File file : files)

            arrayAdapter.add(file.getName());

        AlertDialog.Builder builderSingle = new AlertDialog.Builder(mContext);

        builderSingle.setTitle("Select & Restore ");

        builderSingle.setNegativeButton("cancle", (dialog, which) -> 

dialog.dismiss());

        builderSingle.setAdapter(arrayAdapter, (dialog, which) -> {

            try {

                db.importDB(files[which].getPath());

            } catch (Exception e) {

                Toast.makeText(mContext, "Unable to restore. Retry", 

Toast.LENGTH_SHORT).show();

            }

        });

        builderSingle.show();

    } else

        Toast.makeText(mContext, "Backup folder not present.\nDo a backup before a 

restore!", Toast.LENGTH_SHORT).show();

}

 public void importDB(String inFileName) {

    final String outFileName = mContext.getDatabasePath(DATABASE_NAME).toString();

    try {

        File dbFile = new File(inFileName);

        FileInputStream fis = new FileInputStream(dbFile);

        // Open the empty db as the output stream

        OutputStream output = new FileOutputStream(outFileName);

        // Transfer bytes from the input file to the output file

        byte[] buffer = new byte[1024];

        int length;

        while ((length = fis.read(buffer)) > 0) {

            output.write(buffer, 0, length);

        }

        // Close the streams

        output.flush();

        output.close();

        fis.close();

        Toast.makeText(mContext, "Restore Completed", Toast.LENGTH_SHORT).show();

    } catch (Exception e) {

        Toast.makeText(mContext, "Unable to import database. Retry", 

Toast.LENGTH_SHORT).show();

        e.printStackTrace();

    }

}

Answer 2

如果您的清单中有的话，Android 已经支持系统自动备份android:allowBackup="true"。如果这还不够，并且您想在应用程序重新安装之间手动管理备份，那么您必须将数据库从context.getDatabasePath("<your-database-name>")外部存储复制到某个地方，然后在需要时将其复制回来