I. principle

After decompressing an Android application package as a zip file package, it is found that adding an empty file to the META-INF directory does not require re-signing. Using this mechanism, the file name of the file is the channel name. This method does not require re-signature and other steps, it is very efficient.

Two. Method

Metro's packaging tools have been placed in the test01 file under tools:
1. Place the packaged apk in Python Tool
2. Write the required channel in Python Tool/info/channel.txt, one channel occupies one line
3. Double-click to execute the Python Tool/MultiChannelBuildTool.py file (requiring a Python environment) to generate the channel package
4. Get Channel Information: Copy ChannelUtil.java from JavaUtil file to project and call ChannelUtil.getChannel to get channel information.

package com.czt.util;

import java.io.IOException;
import java.util.Enumeration;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.preference.PreferenceManager;
import android.text.TextUtils;

public class ChannelUtil {
	
	private static final String CHANNEL_KEY = "cztchannel";
	private static final String CHANNEL_VERSION_KEY = "cztchannel_version";
	private static String mChannel;
	/**
	 * Return to the market. If the acquisition fails, return ""
	 * @param context
	 * @return
	 */
	public static String getChannel(Context context){
		return getChannel(context, "");
	}
	/**
	 * Return to the market. Return defaultChannel if acquisition fails
	 * @param context
	 * @param defaultChannel
	 * @return
	 */
	public static String getChannel(Context context, String defaultChannel) {
		//In-memory acquisition
		if(!TextUtils.isEmpty(mChannel)){
			return mChannel;
		}
		//Get in sp
		mChannel = getChannelBySharedPreferences(context);
		if(!TextUtils.isEmpty(mChannel)){
			return mChannel;
		}
		//Get from apk
		mChannel = getChannelFromApk(context, CHANNEL_KEY);
		if(!TextUtils.isEmpty(mChannel)){
			//Save spare in sp
			saveChannelBySharedPreferences(context, mChannel);
			return mChannel;
		}
		//All acquisition failures
		return defaultChannel;
    }
	/**
	 * Get version information from apk
	 * @param context
	 * @param channelKey
	 * @return
	 */
	private static String getChannelFromApk(Context context, String channelKey) {
		//Get from the apk package
        ApplicationInfo appinfo = context.getApplicationInfo();
        String sourceDir = appinfo.sourceDir;
        //The default is in meta-inf/, so you need to stitch it up again.
        String key = "META-INF/" + channelKey;
        String ret = "";
        ZipFile zipfile = null;
        try {
            zipfile = new ZipFile(sourceDir);
            Enumeration<?> entries = zipfile.entries();
            while (entries.hasMoreElements()) {
                ZipEntry entry = ((ZipEntry) entries.nextElement());
                String entryName = entry.getName();
                if (entryName.startsWith(key)) {
                    ret = entryName;
                    break;
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (zipfile != null) {
                try {
                    zipfile.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        String[] split = ret.split("_");
        String channel = "";
        if (split != null && split.length >= 2) {
        	channel = ret.substring(split[0].length() + 1);
        }
        return channel;
	}
	/**
	 * Locally saved Channel & corresponding version number
	 * @param context
	 * @param channel
	 */
	private static void saveChannelBySharedPreferences(Context context, String channel){
		SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(context);
		Editor editor = sp.edit();
		editor.putString(CHANNEL_KEY, channel);
		editor.putInt(CHANNEL_VERSION_KEY, getVersionCode(context));
		editor.commit();
	}
	/**
	 * Getting channel from sp
	 * @param context
	 * @return Get an exception for null, the value in sp is invalid, and there is no value in sp
	 */
	private static String getChannelBySharedPreferences(Context context){
		SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(context);
		int currentVersionCode = getVersionCode(context);
		if(currentVersionCode == -1){
			//Get errors
			return "";
		}
		int versionCodeSaved = sp.getInt(CHANNEL_VERSION_KEY, -1);
		if(versionCodeSaved == -1){
			//Version number corresponding to channel that is not stored locally
			//Exceptions to the first use or original storage version number
			return "";
		}
		if(currentVersionCode != versionCodeSaved){
			return "";
		}
		return sp.getString(CHANNEL_KEY, "");
	}
	/**
	 * Get version number from package information
	 * @param context
	 * @return
	 */
	private static int getVersionCode(Context context){
		try{
			return context.getPackageManager().getPackageInfo(context.getPackageName(), 0).versionCode;
		}catch(NameNotFoundException e) {
			e.printStackTrace();
		}
		return -1;
	}
}

Tool download address: http://pan.baidu.com/share/link?shareid=1485267923&uk=4218015263#list/path=%2F

Advantages and disadvantages

Advantage:
This packaging method is very fast, more than 900 channels can be completed in less than a minute.

Disadvantages:
1. google will not be available if it changes the packing rules one day, making it necessary to repackage empty files in META-INF.

2. Some illegal channel merchants can easily modify channels through tools. If a channel merchant gains windfall profits through the combination of network hijacking and tampering channels, there may be huge economic losses for programmers.