Identifies the latest backup file on the SD card an loads it into the app directory. - Android App

Android examples for App:Backup

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Description

Identifies the latest backup file on the SD card an loads it into the app directory.

Demo Code

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.util.Date;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Environment;
import android.util.Log;
import android.widget.Toast;

public class Main {
  /**//from  ww  w .  ja va  2 s  .  c  o m
   * Identifies the latest backup file on the SD card an loads it into the app
   * directory.
   */
  public static void loadBackup(final Context context) {
    String sdState = Environment.getExternalStorageState();
    if (!Environment.MEDIA_MOUNTED.equals(sdState)) {
      Toast.makeText(context, "SD card not accessible.", Toast.LENGTH_SHORT)
          .show();
      return;
    }

    File sd = Environment.getExternalStorageDirectory();
    Pattern backupFilePattern = Pattern.compile("diary-backup-(\\d+)");
    long latestBackupTimestamp = 0l;
    File latestBackupFile = null;
    for (File potentialBackupFile : sd.listFiles()) {
      Matcher matcher = backupFilePattern
          .matcher(potentialBackupFile.getName());
      if (matcher.matches()) {
        long timestamp = Long.parseLong(matcher.group(1));
        if (latestBackupTimestamp < timestamp) {
          latestBackupTimestamp = timestamp;
          latestBackupFile = potentialBackupFile;
        }
      }
    }

    if (latestBackupFile == null) {
      Toast.makeText(context, "Could not find a backup file.",
          Toast.LENGTH_SHORT);
      return;
    }

    final File finalBackupFile = latestBackupFile;

    DialogInterface.OnClickListener onClickListener = new DialogInterface.OnClickListener() {

      @Override
      public void onClick(DialogInterface dialog, int which) {
        if (which == DialogInterface.BUTTON_POSITIVE) {
          try {
            copy(finalBackupFile, context.getDatabasePath("DB_NAME"));
          } catch (IOException e) {
            Toast.makeText(context, "Backup failed:\n" + e.getMessage(),
                Toast.LENGTH_SHORT).show();
            return;
          }
          Toast.makeText(context, "Backup successful.", Toast.LENGTH_SHORT)
              .show();
        }

      }
    };
    String dialogMsg = String.format("Latest backup from %s, use that?",
        new Date(latestBackupTimestamp));
    new AlertDialog.Builder(context).setMessage(dialogMsg)
        .setPositiveButton("Yes", onClickListener)
        .setNegativeButton("No", onClickListener).show();

  }

  private static void copy(File srcFile, File targetFile) throws IOException {
    FileChannel src = null, dst = null;
    try {
      if (srcFile.exists() && (!targetFile.exists() || targetFile.delete())) {
        src = new FileInputStream(srcFile).getChannel();
        dst = new FileOutputStream(targetFile).getChannel();
        dst.transferFrom(src, 0, src.size());
        src.close();
        dst.close();
      }
    } finally {
      try {
        if (src != null)
          src.close();
      } catch (IOException e) {
        Log.e("DIARY", "Failed to close resource.", e);
      }
      try {
        if (dst != null)
          src.close();
      } catch (IOException e) {
        Log.e("DIARY", "Failed to close resource.", e);
      }
    }
  }
}

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