DefaultExtractPolicy.java

package com.tns;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;

import com.tns.Logger;
import com.tns.ExtractPolicy;
import com.tns.FileExtractor;

public class DefaultExtractPolicy implements ExtractPolicy {
    private final Logger logger;

    private final static String ASSETS_THUMB_FILENAME = "assetsThumb";

    public DefaultExtractPolicy(Logger logger) {
        this.logger = logger;
    }

    public boolean shouldExtract(Context context) {
        String assetsThumbFilePath = context.getFilesDir().getPath() + File.separatorChar + ASSETS_THUMB_FILENAME;
        String oldAssetsThumb = getCachedAssetsThumb(assetsThumbFilePath);
        if (oldAssetsThumb == null) {
            return true;
        } else {
            String currentThumb = getAssetsThumb(context);

            if (currentThumb != null  && !currentThumb.equals(oldAssetsThumb)) {
                return true;
            }
        }

        return false;
    }

    public void setAssetsThumb(Context context) {
        String assetsThumb = generateAssetsThumb(context);
        if (assetsThumb != null) {
            String assetsThumbFilePath = context.getFilesDir().getPath() + File.separatorChar + ASSETS_THUMB_FILENAME;
            saveNewAssetsThumb(assetsThumb, assetsThumbFilePath);
        }
    }

    public boolean forceOverwrite() {
        return true;
    }

    public FileExtractor extractor() {
        return null;
    }

    public String getAssetsThumb(Context context) {
        return generateAssetsThumb(context);
    }

    private String generateAssetsThumb(Context context) {
        try {
            PackageInfo packageInfo = context.getPackageManager().getPackageInfo(context.getPackageName(), 0);
            int code = packageInfo.versionCode;
            long updateTime = packageInfo.lastUpdateTime;
            return String.valueOf(updateTime) + "-" + String.valueOf(code);
        } catch (PackageManager.NameNotFoundException e) {
            logger.write("Error while getting current assets thumb");
            e.printStackTrace();
        }

        return null;
    }

    private String getCachedAssetsThumb(String assetsThumbFilePath) {
        try {
            File cachedThumbFile = new File(assetsThumbFilePath);
            if (cachedThumbFile.exists()) {
                FileInputStream in = new FileInputStream(cachedThumbFile);
                BufferedReader reader = new BufferedReader(new InputStreamReader(in));
                String cachedThumb = reader.readLine();
                reader.close();
                in.close();
                return cachedThumb;
            }
        } catch (FileNotFoundException e) {
            logger.write("Error while getting current assets thumb");
            e.printStackTrace();
        } catch (IOException e) {
            logger.write("Error while getting current asstes thumb");
            e.printStackTrace();
        }

        return null;
    }

    private void saveNewAssetsThumb(String newThumb, String assetsThumbFile) {
        File cachedThumbFile = new File(assetsThumbFile);
        try {
            FileOutputStream out = new FileOutputStream(cachedThumbFile, false);
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out));
            try {
                writer.write(newThumb);
                writer.newLine();
                writer.flush();
            } finally {
                writer.close();
                out.close();
            }
        } catch (FileNotFoundException e) {
            logger.write("Error while writting current assets thumb");
            e.printStackTrace();
        } catch (IOException e) {
            logger.write("Error while writting current assets thumb");
            e.printStackTrace();
        }
    }

}