通过类加载机制动手实现Android热修复

package xuanli.hbdx.xj.tvjoy.cn.study_hotfix.utils; import android.content.Context; import android.content.SharedPreferences; import android.util.Log; import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.JSONObject; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.lang.reflect.Array; import java.lang.reflect.Field; import java.util.Arrays; import java.util.Comparator; import dalvik.system.BaseDexClassLoader; import dalvik.system.DexClassLoader; import dalvik.system.PathClassLoader; import okhttp3.Call; import okhttp3.Callback; import okhttp3.OkHttpClient; import okhttp3.Request; import okhttp3.Response; /** * author 岳明明 * description * Created by yzm on 2017/9/5. */ public class PatchFixUtil { private static PatchFixUtil mPatchUtil ; private static final String TAG = PatchFixUtil.class.getSimpleName() ; private static final String PATCH_CODE = "patch_code" ; private static final String PATCH_CONFIG = "patch_config" ; private OkHttpClient mClient ; //检测补丁链接 private static final String CHECK_URL = "http://192.168.2.121:8080/examples/hotfix/config/config.json" ; //补丁保存地址(文件夹) private String patchPath ; //hack.dex存放地址 private String hackPath ; //补丁优化释放地址 private String optPath ; private Context context ; private String patchCode ; private String patchUrl ; private PatchFixUtil(Context context){ this.context = context.getApplicationContext() ; mClient = new OkHttpClient() ; initPatchPaths(); loadHackDex() ; } /** *初始化补丁路径 */ private void initPatchPaths(){ // /data/data/com.yam.tet/app_hack File fHackPath = context.getDir("hack", Context.MODE_PRIVATE) ; createDirs(fHackPath); hackPath = fHackPath.getAbsolutePath() ; File fPatchPath = context.getDir("patch", Context.MODE_PRIVATE) ; createDirs(fPatchPath); patchPath = fPatchPath.getAbsolutePath() ; File fOptPath = context.getDir("opt", Context.MODE_PRIVATE) ; createDirs(fOptPath); optPath = fOptPath.getAbsolutePath() ; } /** * 创建文件夹 * @param file */ private void createDirs(File file){ if(!file.exists()){ file.mkdirs() ; } } public static PatchFixUtil getInstance(Context context){ synchronized (PatchFixUtil.class){ if(mPatchUtil == null){ mPatchUtil = new PatchFixUtil(context) ; } } return mPatchUtil ; } private void loadHackDex(){ //判断hack.dex是否存在 File hack = new File(hackPath+File.separator+"hack.dex") ; if(!hack.exists()){ //从Assets文件夹中拷贝到“hackPath” copyHackDex(hack); //加载hack.dex load(hack); }else{ //加载hack.dex load(hack); } Log.d(TAG, "hack.dex加载完成...") ; } /** * 复制hack.dex到安全文件夹 * @param hack * @return */ private boolean copyHackDex(File hack){ Log.d(TAG,"copy hack.dex...") ; try { OutputStream os = new FileOutputStream(hack) ; InputStream is = context.getAssets().open("hack.dex") ; int len ; byte[] buffer = new byte[1024] ; while((len=is.read(buffer,0,buffer.length))!=-1){ os.write(buffer, 0, len); } os.close(); is.close(); Log.d(TAG,"copy hack.dex finish...") ; return true ; } catch (Exception e) { e.printStackTrace(); } return false ; } /** * 加载hack.dex和所有补丁包 */ private void load(File hack) { loadPatch(hack); fixPatch() ; } /** * 操作补丁相关 */ public void doPatchFix(){ //检测是否存在补丁包 Request request = new Request.Builder() .get() .url(CHECK_URL) .build() ; Call call = mClient.newCall(request) ; call.enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { Log.d(TAG, "check patch failed....") ; } @Override public void onResponse(Call call, Response response) throws IOException { JSONObject jsonObject = JSON.parseObject(response.body().string()); patchCode = jsonObject.getString("patchCode") ; Log.d(TAG, "pathCode:"+patchCode) ; //判断是否存在补丁 if(!"-1".equals(patchCode)){ //判断当前补丁是否已经下载过 if(isFixed()){ Log.d(TAG, "this version pathCode is fixed...") ; fixPatch(); }else{ //获取补丁链接 patchUrl = jsonObject.getString("patchUrl") ; //开启补丁下载 downLoadPatch() ; } } } }); } /** * 下载补丁 */ private void downLoadPatch() { Request request = new Request.Builder() .get() .url(patchUrl) .build() ; Call call = mClient.newCall(request) ; call.enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { Log.d(TAG, "the patch download failed...") ; Log.d(TAG, e.getMessage()) ; } @Override public void onResponse(Call call, Response response) throws IOException { byte[] buffer = new byte[2048] ; int len = 0 ; OutputStream os = new FileOutputStream(patchPath+File.separator+patchCode+".dex") ; InputStream is = response.body().byteStream() ; Log.d(TAG, "start download patch...") ; while((len=is.read(buffer,0,buffer.length))!=-1){ os.write(buffer,0, len); } os.close(); is.close(); Log.d(TAG, "download patch finish...") ; Log.d(TAG, "start fixed patch...") ; } }); } /** * 修复补丁(热修复的核心代码) * 几个知识点： * * 1. Android类加载机制中2个重要类加载器：”PathClassLoader“和”DexClassLoader“均继承自BaseDexClassLoader * PathClassLoader：用于加载系统类(类均在dex文件中)，PS：app运行时，会一并将本app所有类加载 * DexClassLoader：用于加载应用类，我们自己的动态加载的类 * * 2. 系统运行APP的时候，会用“PathClassLoader”装载运行该app所有需的dex，从java层面，这个过程我们是无法干预的 * * 3. 当app运行中，用到某个类A的时候，PathClassLoader会去查找自己的PathList中的Element[]数组中查找类A， * 一旦找到，立马返回，不去管Element[]数组中是否还有一个类A * * 4. 通过源码，可知道Element类，是PathList的一个内部类，其中存储的是dex文件、dex路径等等，找类A的真正实现， * 是通过本地方法从dex文件中查找的。结论：用到某个类时，PathClassLoad