如何为应用程序创建简单的本地备份和还原?

Question

我有五个sqlite数据库，我希望用户能够在他的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还原它们。 我使用了 github 存储库，但它根本不起作用， 我需要您的帮助来创建此备份和还原过程。 感谢您的关注

Answer 1

在您的活动中制作备份和还原按钮并定义本地数据库变量，例如，

private MainDatabase localBackup = new MainDatabase(this);

然后只需单击即可执行备份和还原操作

@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;
}
}

在数据库文件中创建备份方法

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();
}
}

以及为了恢复做这件事， 询问用户要还原的备份

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android:allowBackup="true"，Android 已经支持系统自动备份。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，则必须将数据库从context.getDatabasePath("<your-database-name>")复制到某个位置的外部存储，然后在需要时将其复制回来