Tinker是微信的第一个开源项目，主要用于安卓应用bug的热修复和功能的迭代。
Tinker github地址：https://github.com/Tencent/tinker
首先向微信致敬，感谢毫无保留的开源出了这么一款优秀的热更新项目。
因Tinker支持Dex，资源文件及so文件的热更新，本系列将从以下三个方面对Tinker进行源码解析：
Android热更新开源项目Tinker源码解析系列之一：Dex热更新Android热更新开源项目Tinker源码解析系列之二:资源热更新Android热更新开源项目Tinker源码解析系类之三：so热更新
Tinker中Dex的热更新也主要分为三个部分，本文也将从这三个方面进行分析：
生成补丁流程补丁包下发成功后合成全量Dex流程生成全量Dex后的加载流程
转载请标明本文来源：http://www.cnblogs.com/yyangblog/p/6249715.html 更多内容欢迎star作者的github：https://github.com/LaurenceYang/article如果发现本文有什么问题和任何建议，也随时欢迎交流~
一、生成补丁流程
当在命令行里面调用tinkerPatchRelease任务时会调用com.tencent.tinker.build.patch.Runner.tinkerPatch()进行生成补丁生成过程。
1 //gen patch 2 ApkDecoder decoder = new ApkDecoder(config); 3 decoder.onAllPatchesStart(); 4 decoder.patch(config.mOldApkFile, config.mNewApkFile); 5 decoder.onAllPatchesEnd(); 6 7 //gen meta file and version file 8 PatchInfo info = new PatchInfo(config); 9 info.gen();10 11 //build patch12 PatchBuilder builder = new PatchBuilder(config);13 builder.buildPatch();
ApkDecoder.patch(File oldFile, File newFile)函数中，
会先对manifest文件进行检测，看其是否有更改，如果发现manifest的组件有新增，则抛出异常，因为目前Tinker暂不支持四大组件的新增。
检测通过后解压apk文件，遍历新旧apk，交给ApkFilesVisitor进行处理。
1 //check manifest change first2 manifestDecoder.patch(oldFile, newFile);3 4 unzipApkFiles(oldFile, newFile);5 6 Files.walkFileTree(mNewApkDir.toPath(), new ApkFilesVisitor(config, mNewApkDir.toPath(), mOldApkDir.toPath(), dexPatchDecoder, soPatchDecoder, resPatchDecoder));
ApkFilesVisitor的visitFile函数中，对于dex类型的文件，调用dexDecoder进行patch操作；
对于so类型的文件，使用soDecoder进行patch操作；
对于Res类型文件，使用resDecoder进行操作。
本文中主要是针对dexDecoder进行分析。
1 public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException { 2 3 Path relativePath = newApkPath.relativize(file); 4 5 Path oldPath = oldApkPath.resolve(relativePath); 6 7 File oldFile = null; 8 //is a new file?! 9 if (oldPath.toFile().exists()) {10 oldFile = oldPath.toFile();11 }12 String patternKey = relativePath.toString().replace("//", "/");13 14 if (Utils.checkFileInPattern(config.mDexFilePattern, patternKey)) {15 //also treat duplicate file as unchanged16 if (Utils.checkFileInPattern(config.mResFilePattern, patternKey) && oldFile != null) {17 resDuplicateFiles.add(oldFile);18 }19 20 try {21 dexDecoder.patch(oldFile, file.toFile());22 } catch (Exception e) {23 // e.PRintStackTrace();24 throw new RuntimeException(e);25 }26 return FileVisitResult.CONTINUE;27 }28 if (Utils.checkFileInPattern(config.mSoFilePattern, patternKey)) {29 //also treat duplicate file as unchanged30 if (Utils.checkFileInPattern(config.mResFilePattern, patternKey) && oldFile != null) {31 resDuplicateFiles.add(oldFile);32 }33 try {34 soDecoder.patch(oldFile, file.toFile());35 } catch (Exception e) {36 // e.printStackTrace();37 throw new RuntimeException(e);38 }39 return FileVisitResult.CONTINUE;40 }41 if (Utils.checkFileInPattern(config.mResFilePattern, patternKey)) {42 try {43 resDecoder.patch(oldFile, file.toFile());44 } catch (Exception e) {45 // e.printStackTrace();46 throw new RuntimeException(e);47 }48 return FileVisitResult.CONTINUE;49 }50 return FileVisitResult.CONTINUE;
DexDiffDecoder.patch(final File oldFile, final File newFile)首先检测输入的dex文件中是否有不允许修改的类被修改了，如loader相关的类是不允许被修改的，这种情况下会抛出异常；
如果dex是新增的，直接将该dex拷贝到结果文件；
如果dex是修改的，收集增加和删除的class。oldAndNewDexFilePairList将新旧dex对应关系保存起来，用于后面的分析。
1 excludedClassModifiedChecker.checkIfExcludedClassWasModifiedInNewDex(oldFile, newFile); 2 ... 3 //new add file 4 if (oldFile == null || !oldFile.exists() || oldFile.length() == 0) { 5 hasDexChanged = true; 6 if (!config.mUsePreGeneratedPatchDex) { 7 copyNewDexAndLogToDexMeta(newFile, newmd5, dexDiffOut); 8 return true; 9 }10 }11 ...12 // collect current old dex file and corresponding new dex file for further processing.13 oldAndNewDexFilePairList.add(new AbstractMap.SimpleEntry<>(oldFile, newFile));
UniqueDexDiffDecoder.patch中将新的dex文件加入到addedDexFiles。
1 public boolean patch(File oldFile, File newFile) throws IOException, TinkerPatchException { 2 boolean added = super.patch(oldFile, newFile); 3 if (added) { 4 String name = newFile.getName(); 5 if (addedDexFiles.contains(name)) { 6 throw new TinkerPatchException("illegal dex name, dex name should be unique, dex:" + name); 7 } else { 8 addedDexFiles.add(name); 9 }10 }11 return added;12 }
在patch完成后，会调用generatePatchInfoFile生成补丁文件。DexFiffDecoder.generatePatchInfoFile中首先遍历oldAndNewDexFilePairList，取出新旧文件对。
判断新旧文件的MD5是否相等，不相等，说明有变化，会根据新旧文件创建DexPatchGenerator，
DexPatchGenerator构造函数中包含了15个Dex区域的比较算法：
StringDataSectionDiffAlgorithmTypeIdSectionDiffAlgorithmProtoIdSectionDiffAlgorithmFieldIdSectionDiffAlgorithmMethodIdSectionDiffAlgorithmClassDefSectionDiffAlgorithmTypeListSectionDiffAlgorithmAnnotationSetRefListSectionDiffAlgorithmAnnotationSetSectionDiffAlgorithmClassDataSectionDiffAlgorithmCodeSectionDiffAlgorithmDebugInfoItemSectionDiffAlgorithmAnnotationSectionDiffAlgorithmStaticValueSectionDiffAlgorithmAnnotationsDirectorySectionDiffAlgorithm
DexDiffDecoder.executeAndSaveTo(OutputStream out) 这个函数里面会根据上面的15个算法对dex的各个区域进行比较，最后生成dex文件的差异，
这是整个dex diff算法的核心。以StringDataSectionDiffAlgorithm为例，算法流程如下：
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获取oldDex中StringData区域的Item，并进行排序获取newDex中StringData区域的Item，并进行排序然后对ITEM依次比较<0 说明从老的dex中删除了该String，patchOperationList中添加Del操作/>0 说明添加了该String，patchOperationList添加add操作=0 说明都有该String， 记录oldIndexToNewIndexMap，oldOffsetToNewOffsetMapold item已到结尾 剩下的item说明都是新增项，patchOperationList添加add操作new item已到结尾 剩下的item说明都是删除项，patchOperationList添加del操作最后对对patchOperationList进行优化（{OP_DEL idx} followed by {OP_ADD the_same_idx newItem} will be replaced by {OP_REPLACE idx newItem}）
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Dexdiff得到的最终生成产物就是针对原dex的一个操作序列。关于DexDiff算法，更加详细的介绍可以参考https://www.zybuluo.com/dodola/note/554061，算法名曰二路归并。
对每个区域比较后会将比较的结果写入文件中，文件格式写在DexDataBuffer中
1 private void writeResultToStream(OutputStream os) throws IOException { 2 DexDataBuffer buffer = new DexDataBuffer(); 3 buffer.write(DexPatchFile.MAGIC); 4 buffer.writeShort(DexPatchFile.CURRENT_VERSION); 5 buffer.writeInt(this.patchedDexSize); 6 // we will return here to write firstChunkOffset later. 7 int posOfFirstChunkOffsetField = buffer.position(); 8 buffer.writeInt(0); 9 buffer.writeInt(this.patchedStringIdsOffset);10 buffer.writeInt(this.patchedTypeIdsOffset);11 buffer.writeInt(this.patchedProtoIdsOffset);12 buffer.writeInt(this.patchedFieldIdsOffset);13 buffer.writeInt(this.patchedMethodIdsOffset);14 buffer.writeInt(this.patchedClassDefsoffset);15 buffer.writeInt(this.patchedMapListOffset);16 buffer.writeInt(this.patchedTypeListsOffset);17 buffer.writeInt(this.patchedAnnotationSetRefListItemsOffset);18 buffer.writeInt(this.patchedAnnotationSetItemsOffset);19 buffer.writeInt(this.patchedClassDataItemsOffset);20 buffer.writeInt(this.patchedCodeItemsOffset);21 buffer.writeInt(this.patchedStringDataItemsOffset);22 buffer.writeInt(this.patchedDebugInfoItemsOffset);23 buffer.writeInt(this.patchedAnnotationItemsOffset);24 buffer.writeInt(this.patchedEncodedArrayItemsOffset);25 buffer.writeInt(this.patchedAnnotationsDirectoryItemsOffset);26 buffer.write(this.oldDex.computeSignature(false));27 int firstChunkOffset = buffer.position();28 buffer.position(posOfFirstChunkOffsetField);29 buffer.writeInt(firstChunkOffset);30 buffer.position(firstChunkOffset);31 32 writePatchOperations(buffer, this.stringDataSectionDiffAlg.getPatchOperationList());33 writePatchOperations(buffer, this.typeIdSectionDiffAlg.getPatchOperationList());34 writePatchOperations(buffer, this.typeListSectionDiffAlg.getPatchOperationList());35 writePatchOperations(buffer, this.protoIdSectionDiffAlg.getPatchOperationList());36 writePatchOperations(buffer, this.fieldIdSectionDiffAlg.getPatchOperationList());37 writePatchOperations(buffer, this.methodIdSectionDiffAlg.getPatchOperationList());38 writePatchOperations(buffer, this.annotationSectionDiffAlg.getPatchOperationList());39 writePatchOperations(buffer, this.annotationSetSectionDiffAlg.getPatchOperationList());40 writePatchOperations(buffer, this.annotationSetRefListSectionDiffAlg.getPatchOperationList());41 writePatchOperations(buffer, this.annotationsDirectorySectionDiffAlg.getPatchOperationList());42 writePatchOperations(buffer, this.debugInfoSectionDiffAlg.getPatchOperationList());43 writePatchOperations(buffer, this.codeSectionDiffAlg.getPatchOperationList());44 writePatchOperations(buffer, this.classDataSectionDiffAlg.getPatchOperationList());45 writePatchOperations(buffer, this.encodedArraySectionDiffAlg.getPatchOperationList());46 writePatchOperations(buffer, this.classDefSectionDiffAlg.getPatchOperationList());47 48 byte[] bufferData = buffer.array();49 os.write(bufferData);50 os.flush();51 }
生成的文件以dex结尾，但需要注意的是，它不是真正的dex文件，其格式可参考DexDataBuffer类。
二、补丁包下发成功后合成全量Dex流程
当app收到服务器下发的补丁后，会触发DefaultPatchListener.onPatchReceived事件，
调用TinkerPatchService.runPatchService启动patch进程进行补丁patch工作。
UpgradePatch.tryPatch()中会首先检查补丁的合法性，签名，以及是否安装过补丁，检查通过后会尝试dex，so以及res文件的patch。
本文中主要分析DexDiffPatchInternal.tryRecoverDexFiles，讨论dex的patch过程。
1 DexDiffPatchInternal.tryRecoverDexFiles2 BsDiffPatchInternal.tryRecoverLibraryFiles3 ResDiffPatchInternal.tryRecoverResourceFiles4 rewritePatchInfoFileWithLock
tryRecoverDexFiles调用DexDiffPatchInternal.patchDexFile，
最终通过DexPatchApplier.executeAndSaveTo进行执行及生产全量dex。
1 private static void patchDexFile( 2 ZipFile baseApk, ZipFile patchPkg, ZipEntry oldDexEntry, ZipEntry patchFileEntry, 3 ShareDexDiffPatchInfo patchInfo, File patchedDexFile) throws IOException { 4 InputStream oldDexStream = null; 5 InputStream patchFileStream = null; 6 try { 7 oldDexStream = baseApk.getInputStream(oldDexEntry); 8 patchFileStream = (patchFileEntry != null ? patchPkg.getInputStream(patchFileEntry) : null); 9 10 final boolean isRawDexFile = SharePatchFileUtil.isRawDexFile(patchInfo.rawName);11 if (!isRawDexFile || patchInfo.isJarMode) {12 ZipOutputStream zos = null;13 try {14 zos = new ZipOutputStream(new BufferedOutputStream(new FileOutputStream(patchedDexFile)));15 zos.putNextEntry(new ZipEntry(ShareConstants.DEX_IN_JAR));16 // Old dex is not a raw dex file.17 if (!isRawDexFile) {18 ZipInputStream zis = null;19 try {20 zis = new ZipInputStream(oldDexStream);21 ZipEntry entry;22 while ((entry = zis.getNextEntry()) != null) {23 if (ShareConstants.DEX_IN_JAR.equals(entry.getName())) break;24 }25 if (entry == null) {26 throw new TinkerRuntimeException("can't recognize zip dex format file:" + patchedDexFile.getAbsolutePath());27 }28 new DexPatchApplier(zis, (int) entry.getSize(), patchFileStream).executeAndSaveTo(zos);29 } finally {30 SharePatchFileUtil.closeQuietly(zis);31 }32 } else {33 new DexPatchApplier(oldDexStream, (int) oldDexEntry.getSize(), patchFileStream).executeAndSaveTo(zos);34 }35 zos.closeEntry();36 } finally {37 SharePatchFileUtil.closeQuietly(zos);38 }39 } else {40 new DexPatchApplier(oldDexStream, (int) oldDexEntry.getSize(), patchFileStream).executeAndSaveTo(patchedDexFile);41 }42 } finally {43 SharePatchFileUtil.closeQuietly(oldDexStream);44 SharePatchFileUtil.closeQuietly(patchFileStream);45 }46 }
DexPatchApplier.executeAndSaveTo(OutputStream out)中会对15个dex区域进行patch操作，
针对old dex和patch dex进行合并,生成全量dex文件。
1 public void executeAndSaveTo(OutputStream out) throws IOException { 2 // Before executing, we should check if this patch can be applied to 3 // old dex we passed in. 4 // 首先old apk的签名和patchfile所携带的old apk签名是否一致，不一致则抛出异常 5 byte[] oldDexSign = this.oldDex.computeSignature(false); 6 if (oldDexSign == null) { 7 throw new IOException("failed to compute old dex's signature."); 8 } 9 10 if (this.patchFile != null) { 11 byte[] oldDexSignInPatchFile = this.patchFile.getOldDexSignature(); 12 if (CompareUtils.uArrCompare(oldDexSign, oldDexSignInPatchFile) != 0) { 13 throw new IOException( 14 String.format( 15 "old dex signature mismatch! expected: %s, actual: %s", 16 Arrays.toString(oldDexSign), 17 Arrays.toString(oldDexSignInPatchFile) 18 ) 19 ); 20 } 21 } 22 23 String oldDexSignStr = Hex.toHexString(oldDexSign); 24 25 // Firstly, set sections' offset after patched, sort according to their offset so that 26 // the dex lib of aosp can calculate section size. 27 // patchedDex是最终合成的dex，首先设定各个区域的偏移量 28 TableOfContents patchedToc = this.patchedDex.getTableOfContents(); 29 30 patchedToc.header.off = 0; 31 patchedToc.header.size = 1; 32 patchedToc.mapList.size = 1; 33 34 if (extraInfoFile == null || !extraInfoFile.isAffectedOldDex(this.oldDexSignStr)) { 35 patchedToc.stringIds.off 36 = this.patchFile.getPatchedStringIdSectionOffset(); 37 patchedToc.typeIds.off 38 = this.patchFile.getPatchedTypeIdSectionOffset(); 39 patchedToc.typeLists.off 40 = this.patchFile.getPatchedTypeListSectionOffset(); 41 patchedToc.protoIds.off 42 = this.patchFile.getPatchedProtoIdSectionOffset(); 43 patchedToc.fieldIds.off 44 = this.patchFile.getPatchedFieldIdSectionOffset(); 45 patchedToc.methodIds.off 46 = this.patchFile.getPatchedMethodIdSectionOffset(); 47 patchedToc.classDefs.off 48 = this.patchFile.getPatchedClassDefSectionOffset(); 49 patchedToc.mapList.off 50 = this.patchFile.getPatchedMapListSectionOffset(); 51 patchedToc.stringDatas.off 52 = this.patchFile.getPatchedStringDataSectionOffset(); 53 patchedToc.annotations.off 54 = this.patchFile.getPatchedAnnotationSectionOffset(); 55 patchedToc.annotationSets.off 56 = this.patchFile.getPatchedAnnotationSetSectionOffset(); 57 patchedToc.annotationSetRefLists.off 58 = this.patchFile.getPatchedAnnotationSetRefListSectionOffset(); 59 patchedToc.annotationsDirectories.off 60 = this.patchFile.getPatchedAnnotationsDirectorySectionOffset(); 61 patchedToc.encodedArrays.off 62 = this.patchFile.getPatchedEncodedArraySectionOffset(); 63 patchedToc.debugInfos.off 64 = this.patchFile.getPatchedDebugInfoSectionOffset(); 65 patchedToc.codes.off 66 = this.patchFile.getPatchedCodeSectionOffset(); 67 patchedToc.classDatas.off 68 = this.patchFile.getPatchedClassDataSectionOffset(); 69 patchedToc.fileSize 70 = this.patchFile.getPatchedDexSize(); 71 } else { 72 ... 73 } 74 75 Arrays.sort(patchedToc.sections); 76 77 patchedToc.computeSizesFromOffsets(); 78 79 // Secondly, run patch algorithms according to sections' dependencies. 80 // 对每个区域进行patch操作 81 this.stringDataSectionPatchAlg = new StringDataSectionPatchAlgorithm( 82 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap, 83 patchedToSmallPatchedIndexMap, extraInfoFile 84 ); 85 this.typeIdSectionPatchAlg = new TypeIdSectionPatchAlgorithm( 86 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap, 87 patchedToSmallPatchedIndexMap, extraInfoFile 88 ); 89 this.protoIdSectionPatchAlg = new ProtoIdSectionPatchAlgorithm( 90 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap, 91 patchedToSmallPatchedIndexMap, extraInfoFile 92 ); 93 this.fieldIdSectionPatchAlg = new FieldIdSectionPatchAlgorithm( 94 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap, 95 patchedToSmallPatchedIndexMap, extraInfoFile 96 ); 97 this.methodIdSectionPatchAlg = new MethodIdSectionPatchAlgorithm( 98 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap, 99 patchedToSmallPatchedIndexMap, extraInfoFile100 );101 this.classDefSectionPatchAlg = new ClassDefSectionPatchAlgorithm(102 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,103 patchedToSmallPatchedIndexMap, extraInfoFile104 );105 this.typeListSectionPatchAlg = new TypeListSectionPatchAlgorithm(106 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,107 patchedToSmallPatchedIndexMap, extraInfoFile108 );109 this.annotationSetRefListSectionPatchAlg = new AnnotationSetRefListSectionPatchAlgorithm(110 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,111 patchedToSmallPatchedIndexMap, extraInfoFile112 );113 this.annotationSetSectionPatchAlg = new AnnotationSetSectionPatchAlgorithm(114 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,115 patchedToSmallPatchedIndexMap, extraInfoFile116 );117 this.classDataSectionPatchAlg = new ClassDataSectionPatchAlgorithm(118 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,119 patchedToSmallPatchedIndexMap, extraInfoFile120 );121 this.codeSectionPatchAlg = new CodeSectionPatchAlgorithm(122 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,123 patchedToSmallPatchedIndexMap, extraInfoFile124 );125 this.debugInfoSectionPatchAlg = new DebugInfoItemSectionPatchAlgorithm(126 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,127 patchedToSmallPatchedIndexMap, extraInfoFile128 );129 this.annotationSectionPatchAlg = new AnnotationSectionPatchAlgorithm(130 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,131 patchedToSmallPatchedIndexMap, extraInfoFile132 );133 this.encodedArraySectionPatchAlg = new StaticValueSectionPatchAlgorithm(134 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,135 patchedToSmallPatchedIndexMap, extraInfoFile136 );137 this.annotationsDirectorySectionPatchAlg = new AnnotationsDirectorySectionPatchAlgorithm(138 patchFile, oldDex, patchedDex, oldToFullPatchedIndexMap,139 patchedToSmallPatchedIndexMap, extraInfoFile140 );141 142 this.stringDataSectionPatchAlg.execute();143 this.typeIdSectionPatchAlg.execute();144 this.typeListSectionPatchAlg.execute();145 this.protoIdSectionPatchAlg.execute();146 this.fieldIdSectionPatchAlg.execute();147 this.methodIdSectionPatchAlg.execute();148 Runtime.getRuntime().gc();149 this.annotationSectionPatchAlg.execute();150 this.annotationSetSectionPatchAlg.execute();151 this.annotationSetRefListSectionPatchAlg.execute();152 this.annotationsDirectorySectionPatchAlg.execute();153 Runtime.getRuntime().gc();154 this.debugInfoSectionPatchAlg.execute();155 this.codeSectionPatchAlg.execute();156 Runtime.getRuntime().gc();157 this.classDataSectionPatchAlg.execute();158 this.encodedArraySectionPatchAlg.execute();159 this.classDefSectionPatchAlg.execute();160 Runtime.getRuntime().gc();161 162 // Thirdly, write header, mapList. Calculate and write patched dex's sign and checksum.163 Dex.Section headerOut = this.patchedDex.openSection(patchedToc.header.off);164 patchedToc.writeHeader(headerOut);165 166 Dex.Section mapListOut = this.patchedDex.openSection(patchedToc.mapList.off);167 patchedToc.writeMap(mapListOut);168 169 this.patchedDex.writeHashes();170 171 // Finally, write patched dex to file.172 this.patchedDex.writeTo(out);
每个区域的合并算法采用二路归并，在old dex的基础上对元素进行删除，增加，替换操作。
这里的算法和生成补丁的DexDiff是一个逆向的过程。
1 private void doFullPatch( 2 Dex.Section oldSection, 3 int oldItemCount, 4 int[] deletedIndices, 5 int[] addedIndices, 6 int[] replacedIndices 7 ) { 8 int deletedItemCount = deletedIndices.length; 9 int addedItemCount = addedIndices.length;10 int replacedItemCount = replacedIndices.length;11 int newItemCount = oldItemCount + addedItemCount - deletedItemCount;12 13 int deletedItemCounter = 0;14 int addActionCursor = 0;15 int replaceActionCursor = 0;16 17 int oldIndex = 0;18 int patchedIndex = 0;19 while (oldIndex < oldItemCount || patchedIndex < newItemCount) {20 if (addActionCursor < addedItemCount && addedIndices[addActionCursor] == patchedIndex) {21 T addedItem = nextItem(patchFile.getBuffer());22 int patchedOffset = writePatchedItem(addedItem);23 ++addActionCursor;24 ++patchedIndex;25 } else26 if (replaceActionCursor < replacedItemCount && replacedIndices[replaceActionCursor] == patchedIndex) {27 T replacedItem = nextItem(patchFile.getBuffer());28 int patchedOffset = writePatchedItem(replacedItem);29 ++replaceActionCursor;30 ++patchedIndex;31 } else32 if (Arrays.binarySearch(deletedIndices, oldIndex) >= 0) {33 T skippedOldItem = nextItem(oldSection); // skip old item.34 markDeletedIndexOrOffset(35 oldToFullPatchedIndexMap,36 oldIndex,37 getItemOffsetOrIndex(oldIndex, skippedOldItem)38 );39 ++oldIndex;40 ++deletedItemCounter;41 } else42 if (Arrays.binarySearch(replacedIndices, oldIndex) >= 0) {43 T skippedOldItem = nextItem(oldSection); // skip old item.44 markDeletedIndexOrOffset(45 oldToFullPatchedIndexMap,46 oldIndex,47 getItemOffsetOrIndex(oldIndex, skippedOldItem)48 );49 ++oldIndex;50 } else51 if (oldIndex < oldItemCount) {52 T oldItem = adjustItem(this.oldToFullPatchedIndexMap, nextItem(oldSection));53 54 int patchedOffset = writePatchedItem(oldItem);55 56 updateIndexOrOffset(57 this.oldToFullPatchedIndexMap,58 oldIndex,59 getItemOffsetOrIndex(oldIndex, oldItem),60 patchedIndex,61 patchedOffset62 );63 64 ++oldIndex;65 ++patchedIndex;66 }67 }68 69 if (addActionCursor != addedItemCount || deletedItemCounter != deletedItemCount70 || replaceActionCursor != replacedItemCount71 ) {72 throw new IllegalStateException(73 String.format(74 "bad patch operation sequence. addCounter: %d, addCount: %d, "75 + "delCounter: %d, delCount: %d, "76 + "replaceCounter: %d, replaceCount:%d",77 addActionCursor,78 addedItemCount,79 deletedItemCounter,80 deletedItemCount,81 replaceActionCursor,82 replacedItemCount83 )84 );85 }86 }
在extractDexDiffInternals调用完以后，
会调用TinkerParallelDexOptimizer.optimizeAll对生成的全量dex进行optimize操作，生成odex文件。
最终合成的文件会放到/data/data/${package_name}/tinker目录下。
到此，生成Dex过程完成。
三、加载全量Dex流程
Tinkerapplication通过反射的方式将实际的app业务隔离，这样可以在热更新的时候修改实际的app内容。
在TinkerApplication中的onBaseContextAttached中会通过反射调用TinkerLoader的tryLoad加载已经合成的dex。
1 private static final String TINKER_LOADER_METHOD = "tryLoad"; 2 private void loadTinker() { 3 //disable tinker, not need to install 4 if (tinkerFlags == TINKER_DISABLE) { 5 return; 6 } 7 tinkerResultIntent = new Intent(); 8 try { 9 //reflect tinker loader, because loaderClass may be define by user!10 Class<?> tinkerLoadClass = Class.forName(loaderClassName, false, getClassLoader());11 12 Method loadMethod = tinkerLoadClass.getMethod(TINKER_LOADER_METHOD, TinkerApplication.class, int.class, boolean.class);13 Constructor<?> constructor = tinkerLoadClass.getConstructor();14 tinkerResultIntent = (Intent) loadMethod.invoke(constructor.newInstance(), this, tinkerFlags, tinkerLoadVerifyFlag);15 } catch (Throwable e) {16 //has exception, put exception error code17 ShareIntentUtil.setIntentReturnCode(tinkerResultIntent, ShareConstants.ERROR_LOAD_PATCH_UNKNOWN_EXCEPTION);18 tinkerResultIntent.putExtra(INTENT_PATCH_EXCEPTION, e);19 }20 }
tryLoadPatchFilesInternal是加载Patch文件的核心函数，主要做了以下的事情：
tinkerFlag是否开启，否则不加载tinker目录是否生成，没有则表示没有生成全量的dex，不需要重新加载tinker目录是否生成，没有则表示没有生成全量的dex，不需要重新加载tinker/patch.info是否存在，否则不加载读取patch.info，读取失败则不加载比较patchInfo的新旧版本，都为空则不加载判断版本号是否为空，为空则不加载判断patch version directory（//tinker/patch.info/patch-641e634c）是否存在判断patchVersionDirectoryFile（//tinker/patch.info/patch-641e634c/patch-641e634c.apk）是否存在checkTinkerPackage,（如tinkerId和oldTinkerId不能相等，否则不加载)检测dex的完整性，包括dex是否全部生产，是否对dex做了优化，优化后的文件是否存在（//tinker/patch.info/patch-641e634c/dex）同样对so res文件进行完整性检测尝试超过3次不加载loadTinkerJars/loadTinkerResources/
TinkerDexLoader.loadTinkerJars处理加载dex文件。
1 // 获取PatchClassLoader 2 PathClassLoader classLoader = (PathClassLoader) TinkerDexLoader.class.getClassLoader(); 3 4 ... 5 // 生产合法文件列表 6 ArrayList<File> legalFiles = new ArrayList<>(); 7 8 final boolean isArtPlatForm = ShareTinkerInternals.isVmArt(); 9 for (ShareDexDiffPatchInfo info : dexList) {10 //for dalvik, ignore art support dex11 // dalvik虚拟机中，忽略掉只支持art的dex12 if (isJustArtSupportDex(info)) {13 continue;14 }15 String path = dexPath + info.realName;16 File file = new File(path);17 18 if (tinkerLoadVerifyFlag) {19 long start = System.currentTimeMillis();20 String checkMd5 = isArtPlatForm ? info.destMd5InArt : info.destMd5InDvm;21 if (!SharePatchFileUtil.verifyDexFileMd5(file, checkMd5)) {22 //it is good to delete the mismatch file23 ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_DEX_MD5_MISMATCH);24 intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_MISMATCH_DEX_PATH,25 file.getAbsolutePath());26 return false;27 }28 Log.i(TAG, "verify dex file:" + file.getPath() + " md5, use time: " + (System.currentTimeMillis() - start));29 }30 legalFiles.add(file);31 }32 33 // 如果系统OTA，对这些合法dex进行优化34 if (isSystemOTA) {35 parallelOTAResult = true;36 parallelOTAThrowable = null;37 Log.w(TAG, "systemOTA, try parallel oat dexes!!!!!");38 39 TinkerParallelDexOptimizer.optimizeAll(40 legalFiles, optimizeDir,41 new TinkerParallelDexOptimizer.ResultCallback() {42 @Override43 public void onSuccess(File dexFile, File optimizedDir) {44 // Do nothing.45 }46 @Override47 public void onFailed(File dexFile, File optimizedDir, Throwable thr) {48 parallelOTAResult = false;49 parallelOTAThrowable = thr;50 }51 }52 );53 if (!parallelOTAResult) {54 Log.e(TAG, "parallel oat dexes failed");55 intentResult.putExtra(ShareIntentUtil.INTENT_PATCH_EXCEPTION, parallelOTAThrowable);56 ShareIntentUtil.setIntentReturnCode(intentResult, ShareConstants.ERROR_LOAD_PATCH_VERSION_PARALLEL_DEX_OPT_EXCEPTION);57 return false;58 }59 }60 61 // 加载Dex62 SystemClassLoaderAdder.installDexes(application, classLoader, optimizeDir, legalFiles);
SystemClassLoaderAdder.installDexes中按照安卓的版本对dex进行install，这里应该是借鉴了MultiDex里面的install做法。
另外Tinker在生成补丁阶段会生成一个test.dex，这个test.dex的作用就是用来验证dex的加载是否成功。
test.dex中含有com.tencent.tinker.loader.TinkerTestDexLoad类，该类中包含一个字段isPatch，checkDexInstall就是通过findField该字段判断是否加载成功。
1 public static void installDexes(Application application, PathClassLoader loader, File dexOptDir, List<File> files) throws Throwable { 2 if (!files.isEmpty()) { 3 ClassLoader classLoader = loader; 4 if (Build.VERSION.SDK_INT >= 24) { 5 classLoader = AndroidNClassLoader.inject(loader, application); 6 } 7 //because in dalvik, if inner class is not the same classloader with it wrapper class. 8 //it won't fail at dex2opt 9 if (Build.VERSION.SDK_INT >= 23) {10 V23.install(classLoader, files, dexOptDir);11 } else if (Build.VERSION.SDK_INT >= 19) {12 V19.install(classLoader, files, dexOptDir);13 } else if (Build.VERSION.SDK_INT >= 14) {14 V14.install(classLoader, files, dexOptDir);15 } else {16 V4.install(classLoader, files, dexOptDir);17 }18 //install done19 sPatchDexCount = files.size();20 21 // Tinker在生成补丁阶段会生成一个test.dex，这个test.dex的作用就是用来验证dex的加载是否成功。test.dex中含有com.tencent.tinker.loader.TinkerTestDexLoad类，该类中包含一个字段isPatch，checkDexInstall就是通过findField该字段判断是否加载成功。22 if (!checkDexInstall(classLoader)) {23 //reset patch dex24 SystemClassLoaderAdder.uninstallPatchDex(classLoader);25 throw new TinkerRuntimeException(ShareConstants.CHECK_DEX_INSTALL_FAIL);26 }27 }28 }
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在讲install具体细节之前，回顾一下具体原理。关于Android的ClassLoader体系，android中加载类一般使用的是PathClassLoader和DexClassLoader
PathClassLoader，源码注释可以看出，android使用这个类作为系统类和应用类的加载器。
/** * Provides a simple {@link ClassLoader} implementation that operates on a list * of files and directories in the local file system, but does not attempt to * load classes from the network. Android uses this class for its system class * loader and for its application class loader(s). */DexClassLoader，源码注释可以看出，可以用来从.jar和.apk类型的文件内部加载classes.dex文件。
/** * A class loader that loads classes from {@code .jar} and {@code .apk} files * containing a {@code classes.dex} entry. This can be used to execute code not * installed as part of an application. * * <p>This class loader requires an application-private, writable directory to * cache optimized classes. Use {@code Context.getDir(String, int)} to create * such a directory: <pre> {@code * File dexOutputDir = context.getDir("dex", 0); * }</pre> * * <p><strong>Do not cache optimized classes on external storage.</strong> * External storage does not provide access controls necessary to protect your * application from code injection attacks. */ok，到这里，大家只需要明白，Android使用PathClassLoader作为其类加载器，DexClassLoader可以从.jar和.apk类型的文件内部加载classes.dex文件就好了。
PathClassLoader和DexClassLoader都继承自BaseDexClassLoader。在BaseDexClassLoader中有如下源码：
##BaseDexClassLoader.java##/** structured lists of path elements */private final DexPathList pathList;@Overrideprotected Class<?> findClass(String name) throws ClassNotFoundException { Class clazz = pathList.findClass(name); if (clazz == null) { throw new ClassNotFoundException(name); } return clazz;}##DexPathList.java##/** list of dex/resource (class path) elements */private final Element[] dexElements;public Class findClass(String name) { for (Element element : dexElements) { DexFile dex = element.dexFile; if (dex != null) { Class clazz = dex.loadClassBinaryName(name, definingContext); if (clazz != null) { return clazz; } } } return null;}##DexFile.java##public Class loadClassBinaryName(String name, ClassLoader loader) { return defineClass(name, loader, mCookie);}private native static Class defineClass(String name, ClassLoader loader, int cookie);通俗点讲：
一个ClassLoader可以包含多个dex文件，每个dex文件是一个Element，多个dex文件排列成一个有序的数组dexElements，当找类的时候，会按顺序遍历dex文件，然后从当前遍历的dex文件中找类，如果找类则返回，如果找不到从下一个dex文件继续查找。(来自：安卓App热补丁动态修复技术介绍)
回到分割线以前：
install的做法就是，先获取BaseDexClassLoader的dexPathList对象，
然后通过dexPathList的makeDexElements函数将我们要安装的dex转化成Element[]对象，
最后将其和dexPathList的dexElements对象进行合并，就是新的Element[]对象，
因为我们添加的dex都被放在dexElements数组的最前面，所以当通过findClass来查找这个类时，就是使用的我们最新的dex里面的类。
以V19的install为例，下面的代码非常清晰的描述了实际的加载所做的事情：
1 private static final class V19 { 2 private static void install(ClassLoader loader, List<File> additionalClassPathEntries, 3 File optimizedDirectory) 4 throws IllegalArgumentException, IllegalAccessException, 5 NoSuchFieldException, InvocationTargetException, NoSuchMethodException, IOException { 6 /* The patched class loader is expected to be a descendant of 7 * dalvik.system.BaseDexClassLoader. We modify its 8 * dalvik.system.DexPathList pathList field to append additional DEX 9 * file entries.10 */11 Field pathListField = ShareReflectUtil.findField(loader, "pathList");12 Object dexPathList = pathListField.get(loader);13 ArrayList<IOException> suppressedExceptions = new ArrayList<IOException>();14 ShareReflectUtil.expandFieldArray(dexPathList, "dexElements", makeDexElements(dexPathList,15 new ArrayList<File>(additionalClassPathEntries), optimizedDirectory,16 suppressedExceptions));17 if (suppressedExceptions.size() > 0) {18 for (IOException e : suppressedExceptions) {19 Log.w(TAG, "Exception in makeDexElement", e);20 throw e;21 }22 }23 }24 }
因为android版本更新较快，不同版本里面的DexPathList等类的函数和字段都有一些变化，这也是在install的时候需要对不同版本进行适配的原因。
到此，在当前app的classloader里面就包含了我们第二步骤里面合成的全量DEX,我们在加载类的时候就能用到新的内容了。
Congratulations！！Dex的加载流程完成。
转载请标明本文来源：http://www.cnblogs.com/yyangblog/p/6249715.html 更多内容欢迎star作者的github：https://github.com/LaurenceYang/article如果发现本文有什么问题和任何建议，也随时欢迎交流~
下一篇文章我们将对Tinker中对资源文件的热更新进行分析。
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