android 熱更新(無框架)
阿新 • • 發佈:2019-02-15
一、前言
最近看了阿里的AndFix熱修復框架,但是好像不能支援所有裝置,所以,自己手動來實現一遍安卓的熱修復,究其是如何實現的。
二、原理
Java的虛擬機器JVM執行程式碼時,載入的是.class位元組碼檔案,而Android的Dalvik/ART虛擬機器載入的是Dex檔案,不過他們的工作機制是一樣的,都經過ClassLoader這個類載入器,只不過,Android重新定義了兩個類DexClassLoader和PathClassLoader去解析類,他們是繼承BaseDexClassLoader類的,關於這兩個類的介紹:
1)、PathClassLoader:官方文件解析 Android uses this class for its system class loader and for its application class loader(s),使用該類作為系統類和應用類的載入器,也即只能載入已經安裝到Android系統的apk檔案
2)、DexClassLoader:可載入jar、apk和dex檔案,可以從儲存外部載入。
三、實現步驟
1、首先寫一個測試修改效果的類Bugs ,並在activity中使用,
public class Bugs {
public static String getBugs(){
return "有bug!";
}
}
public class TestHotfixActivity extends Activity { TextView tv_result; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); tv_result=(TextView)findViewById(R.id.tv_result); } public void onPost(View view){ tv_result.setText(Bugs.getBugs()); } }
2、新建application和HotFixEngine類
public class BaseApplication extends Application { public static final String FIX_DEX_PATH = "fix_dex";//fixDex儲存的路徑 @Override public void onCreate() { super.onCreate(); copyDexFileToAppAndFix(this,"patch.dex"); loadAllDex(); } /** * 用下載的dex檔案,修復app */ public void loadAllDex() { File dexFilePath = getDir(FIX_DEX_PATH, Context.MODE_PRIVATE); for (File dexFile:dexFilePath.listFiles()){ Log.d("======>",dexFile.getAbsolutePath()); if (dexFile.getAbsolutePath().endsWith("dex") ) { new HotFixEngine().loadDex(this, dexFile); } } } /** * 複製SD卡中的補丁檔案到dex目錄,或者從伺服器下載補丁檔案程式碼 */ public static void copyDexFileToAppAndFix(Context context, String dexFileName) { File path = new File(Environment.getExternalStorageDirectory(), dexFileName); if (!path.exists()) { Toast.makeText(context, "沒有找到補丁檔案", Toast.LENGTH_SHORT).show(); return; } if (!path.getAbsolutePath().endsWith("dex")){ Toast.makeText(context, "補丁檔案格式不正確", Toast.LENGTH_SHORT).show(); return; } File dexFilePath = context.getDir(FIX_DEX_PATH, Context.MODE_PRIVATE); File dexFile = new File(dexFilePath, dexFileName); if (dexFile.exists()) { dexFile.delete(); } //copy InputStream is = null; FileOutputStream os = null; try { is = new FileInputStream(path); os = new FileOutputStream(dexFile); int len = 0; byte[] buffer = new byte[1024]; while ((len = is.read(buffer)) != -1) { os.write(buffer, 0, len); } path.delete();//刪除sdcard中的補丁檔案,或者你可以直接下載到app的路徑中 is.close(); os.close(); } catch (Exception e) { e.printStackTrace(); Log.d("======>",e.getMessage()); } finally { if (is != null) { try { is.close(); } catch (IOException e) { e.printStackTrace(); Log.d("======>",e.getMessage()); } } if (os != null) { try { os.close(); } catch (IOException e) { e.printStackTrace(); Log.d("======>",e.getMessage()); } } } } }
package com.lemon.testhotfix;
import android.content.Context;
import android.os.Environment;
import android.util.Log;
import android.widget.Toast;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import dalvik.system.DexClassLoader;
import dalvik.system.PathClassLoader;
public class HotFixEngine {
public static final String DEX_OPT_DIR = "optimize_dex";//dex的優化路徑
public static final String DEX_BASECLASSLOADER_CLASS_NAME = "dalvik.system.BaseDexClassLoader";
public static final String DEX_ELEMENTS_FIELD = "dexElements";//pathList中的dexElements欄位
public static final String DEX_PATHLIST_FIELD = "pathList";//BaseClassLoader中的pathList欄位
public static final String FIX_DEX_PATH = "fix_dex";//fixDex儲存的路徑
/**
* 獲得pathList中的dexElements
*
* @param obj
* @return
* @throws NoSuchFieldException
* @throws IllegalAccessException
*/
public Object getDexElements(Object obj) throws NoSuchFieldException, IllegalAccessException {
return getField(obj, obj.getClass(), DEX_ELEMENTS_FIELD);
}
/**
* fix
*
* @param context
*/
public void loadDex(Context context, File dexFile) {
if (context == null) {
Log.d("======>","context==null");
return;
}
File fixDir = context.getDir(FIX_DEX_PATH, Context.MODE_PRIVATE);
//mrege and fix
mergeDex(context, fixDir,dexFile);
}
/**
* 獲取指定classloader 中的pathList欄位的值(DexPathList)
*
* @param classLoader
* @return
*/
public Object getDexPathListField(Object classLoader) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
return getField(classLoader, Class.forName(DEX_BASECLASSLOADER_CLASS_NAME), DEX_PATHLIST_FIELD);
}
/**
* 獲取一個欄位的值
*
* @return
*/
public Object getField(Object obj, Class<?> clz, String fieldName) throws NoSuchFieldException, IllegalAccessException {
Field field = clz.getDeclaredField(fieldName);
field.setAccessible(true);
return field.get(obj);
}
/**
* 為指定物件中的欄位重新賦值
*
* @param obj
* @param claz
* @param filed
* @param value
*/
public void setFiledValue(Object obj, Class<?> claz, String filed, Object value) throws NoSuchFieldException, IllegalAccessException {
Field field = claz.getDeclaredField(filed);
field.setAccessible(true);
field.set(obj, value);
}
/**
* 合併dex
*
* @param context
* @param fixDexPath
*/
public void mergeDex(Context context, File fixDexPath, File dexFile) {
try {
//建立dex的optimize路徑
File optimizeDir = new File(fixDexPath.getAbsolutePath(), DEX_OPT_DIR);
if (!optimizeDir.exists()) {
optimizeDir.mkdir();
}
//載入自身Apk的dex,通過PathClassLoader
PathClassLoader pathClassLoader = (PathClassLoader) context.getClassLoader();
//找到dex並通過DexClassLoader去載入
//dex檔案路徑,優化輸出路徑,null,父載入器
DexClassLoader dexClassLoader = new DexClassLoader(dexFile.getAbsolutePath(), optimizeDir.getAbsolutePath(), null, pathClassLoader);
//獲取app自身的BaseDexClassLoader中的pathList欄位
Object appDexPathList = getDexPathListField(pathClassLoader);
//獲取補丁的BaseDexClassLoader中的pathList欄位
Object fixDexPathList = getDexPathListField(dexClassLoader);
Object appDexElements = getDexElements(appDexPathList);
Object fixDexElements = getDexElements(fixDexPathList);
//合併兩個elements的資料,將修復的dex插入到陣列最前面
Object finalElements = combineArray(fixDexElements, appDexElements);
//給app 中的dex pathList 中的dexElements 重新賦值
setFiledValue(appDexPathList, appDexPathList.getClass(), DEX_ELEMENTS_FIELD, finalElements);
Log.d("======>","修復成功!");
} catch (Exception e) {
e.printStackTrace();
Log.d("======>",e.getMessage());
}
}
/**
* 兩個數組合並
*
* @param arrayLhs
* @param arrayRhs
* @return
*/
private static Object combineArray(Object arrayLhs, Object arrayRhs) {
Class<?> localClass = arrayLhs.getClass().getComponentType();
int i = Array.getLength(arrayLhs);
int j = i + Array.getLength(arrayRhs);
Object result = Array.newInstance(localClass, j);
for (int k = 0; k < j; ++k) {
if (k < i) {
Array.set(result, k, Array.get(arrayLhs, k));
} else {
Array.set(result, k, Array.get(arrayRhs, k - i));
}
}
return result;
}
}
3、打包或者直接跑在手機或者模擬器上,然後改動Bugs的方法:Bugs.getBugs(){ return "已修復!";},重新編譯。
4、找到Bugs.class,用sdk/build-tools/dx.bat工具轉成dex檔案。
dx --dex --output=patch.dex 包名/Bugs.class
5、將patch.dex傳送到手機的根目錄。重啟應用即可。