我从事Android设备的自动化工作，并且SDK或Android OS通常没有必要的功能，或者它的工作速度很慢/非常慢。
使用本机开发工具包（NDK）的功能，我们可以编写比Java中相同功能执行得更快的功能。 由于有了这个工具包，我们可以将用C / C ++编写的代码添加到我们的应用程序中，或者为Android移动设备创建我们自己的二进制文件。
在本文中，我将告诉您如何为Android OS配置二进制文件的编译，并说明如何补充此OS中现有二进制文件的功能的过程。
例如，我将“屏蔽”一个屏幕截图，它不仅可以获取整个屏幕的屏幕截图或显示“原始数据”，还可以返回指定点的像素颜色或仅获得所需区域的图像。 所以走吧！
安装NDK
下载
Android NDK并解压缩归档文件，或通过
SDK Manager安装。
如果还没有，那么您可以添加其他内容。 工具：
sudo apt-get install android-tools-adb android-tools-fastboot
并为您的移动设备的体系结构创建一个“项目”：
./android-ndk-r12b/build/tools/make_standalone_toolchain.py --arch <arm or arm64 or other> --install-dir ~/arm
由于我的HOMTOM HT16具有armeabi-v7a架构，因此我将使用以下命令：
./android-ndk-r12b/build/tools/make_standalone_toolchain.py --arch arm --install-dir ~/arm
然后，我们等待脚本创建所有必需的文件（大约需要5分钟）。
性能检查
使用简单的代码创建一个hello_world.c文件：
#include <stdio.h> int main () { puts("hello world"); }
并尝试编译它：
~/arm/bin/clang -pie hello_world.c -o hello_world
使用
-o属性，指定文件名，并使用
-pie开关，我们指示每次执行应用程序时，PIE二进制文件及其所有依赖项都加载到虚拟内存中的随机位置。
如果编译成功，则将文件上传到手机：
adb push ./hello_world /data/local/tmp
并尝试二进制文件：
adb shell /data/local/tmp/hello_world
如果您看到短语“ hello world”的输出，那么您所做的一切都对！
如果仍然有错误，可能是您选择了错误的体系结构，则只需删除此目录并使用正确的目录重新创建即可。
要确定体系结构，可以运行以下命令
adb shell cat /proc/cpuinfo
来源和图书馆
由于对编译后的二进制文件的分析非常耗时，并且Android是开放系统，所以为什么不利用这种质量！
我们在
这里寻找合适的Android版本。 好了，已经-下载档案并寻找所需的二进制文件源。 尽管当然有一个选项-Google和“正确的请求”。
就我而言，我需要的文件位于
此链接 。
screencap.cpp #include <errno.h> #include <unistd.h> #include <stdio.h> #include <fcntl.h> #include <stdlib.h> #include <string.h> #include <linux/fb.h> #include <sys/ioctl.h> #include <sys/mman.h> #include <binder/ProcessState.h> #include <gui/SurfaceComposerClient.h> #include <gui/ISurfaceComposer.h> #include <ui/DisplayInfo.h> #include <ui/PixelFormat.h> // TODO: Fix Skia. #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-parameter" #include <SkImageEncoder.h> #include <SkData.h> #pragma GCC diagnostic pop using namespace android; static uint32_t DEFAULT_DISPLAY_ID = ISurfaceComposer::eDisplayIdMain; static void usage(const char* pname) { fprintf(stderr, "usage: %s [-hp] [-d display-id] [FILENAME]\n" " -h: this message\n" " -p: save the file as a png.\n" " -d: specify the display id to capture, default %d.\n" "If FILENAME ends with .png it will be saved as a png.\n" "If FILENAME is not given, the results will be printed to stdout.\n", pname, DEFAULT_DISPLAY_ID ); } static SkColorType flinger2skia(PixelFormat f) { switch (f) { case PIXEL_FORMAT_RGB_565: return kRGB_565_SkColorType; default: return kN32_SkColorType; } } static status_t vinfoToPixelFormat(const fb_var_screeninfo& vinfo, uint32_t* bytespp, uint32_t* f) { switch (vinfo.bits_per_pixel) { case 16: *f = PIXEL_FORMAT_RGB_565; *bytespp = 2; break; case 24: *f = PIXEL_FORMAT_RGB_888; *bytespp = 3; break; case 32: // TODO: do better decoding of vinfo here *f = PIXEL_FORMAT_RGBX_8888; *bytespp = 4; break; default: return BAD_VALUE; } return NO_ERROR; } static status_t notifyMediaScanner(const char* fileName) { String8 cmd("am broadcast -a android.intent.action.MEDIA_SCANNER_SCAN_FILE -d file://"); String8 fileUrl("\""); fileUrl.append(fileName); fileUrl.append("\""); cmd.append(fileName); cmd.append(" > /dev/null"); int result = system(cmd.string()); if (result < 0) { fprintf(stderr, "Unable to broadcast intent for media scanner.\n"); return UNKNOWN_ERROR; } return NO_ERROR; } int main(int argc, char** argv) { ProcessState::self()->startThreadPool(); const char* pname = argv[0]; bool png = false; int32_t displayId = DEFAULT_DISPLAY_ID; int c; while ((c = getopt(argc, argv, "phd:")) != -1) { switch (c) { case 'p': png = true; break; case 'd': displayId = atoi(optarg); break; case '?': case 'h': usage(pname); return 1; } } argc -= optind; argv += optind; int fd = -1; const char* fn = NULL; if (argc == 0) { fd = dup(STDOUT_FILENO); } else if (argc == 1) { fn = argv[0]; fd = open(fn, O_WRONLY | O_CREAT | O_TRUNC, 0664); if (fd == -1) { fprintf(stderr, "Error opening file: %s (%s)\n", fn, strerror(errno)); return 1; } const int len = strlen(fn); if (len >= 4 && 0 == strcmp(fn+len-4, ".png")) { png = true; } } if (fd == -1) { usage(pname); return 1; } void const* mapbase = MAP_FAILED; ssize_t mapsize = -1; void const* base = NULL; uint32_t w, s, h, f; size_t size = 0; // Maps orientations from DisplayInfo to ISurfaceComposer static const uint32_t ORIENTATION_MAP[] = { ISurfaceComposer::eRotateNone, // 0 == DISPLAY_ORIENTATION_0 ISurfaceComposer::eRotate270, // 1 == DISPLAY_ORIENTATION_90 ISurfaceComposer::eRotate180, // 2 == DISPLAY_ORIENTATION_180 ISurfaceComposer::eRotate90, // 3 == DISPLAY_ORIENTATION_270 }; ScreenshotClient screenshot; sp<IBinder> display = SurfaceComposerClient::getBuiltInDisplay(displayId); if (display == NULL) { fprintf(stderr, "Unable to get handle for display %d\n", displayId); return 1; } Vector<DisplayInfo> configs; SurfaceComposerClient::getDisplayConfigs(display, &configs); int activeConfig = SurfaceComposerClient::getActiveConfig(display); if (static_cast<size_t>(activeConfig) >= configs.size()) { fprintf(stderr, "Active config %d not inside configs (size %zu)\n", activeConfig, configs.size()); return 1; } uint8_t displayOrientation = configs[activeConfig].orientation; uint32_t captureOrientation = ORIENTATION_MAP[displayOrientation]; status_t result = screenshot.update(display, Rect(), 0, 0, 0, -1U, false, captureOrientation); if (result == NO_ERROR) { base = screenshot.getPixels(); w = screenshot.getWidth(); h = screenshot.getHeight(); s = screenshot.getStride(); f = screenshot.getFormat(); size = screenshot.getSize(); } else { const char* fbpath = "/dev/graphics/fb0"; int fb = open(fbpath, O_RDONLY); if (fb >= 0) { struct fb_var_screeninfo vinfo; if (ioctl(fb, FBIOGET_VSCREENINFO, &vinfo) == 0) { uint32_t bytespp; if (vinfoToPixelFormat(vinfo, &bytespp, &f) == NO_ERROR) { size_t offset = (vinfo.xoffset + vinfo.yoffset*vinfo.xres) * bytespp; w = vinfo.xres; h = vinfo.yres; s = vinfo.xres; size = w*h*bytespp; mapsize = offset + size; mapbase = mmap(0, mapsize, PROT_READ, MAP_PRIVATE, fb, 0); if (mapbase != MAP_FAILED) { base = (void const *)((char const *)mapbase + offset); } } } close(fb); } } if (base != NULL) { if (png) { const SkImageInfo info = SkImageInfo::Make(w, h, flinger2skia(f), kPremul_SkAlphaType); SkAutoTUnref<SkData> data(SkImageEncoder::EncodeData(info, base, s*bytesPerPixel(f), SkImageEncoder::kPNG_Type, SkImageEncoder::kDefaultQuality)); if (data.get()) { write(fd, data->data(), data->size()); } if (fn != NULL) { notifyMediaScanner(fn); } } else { write(fd, &w, 4); write(fd, &h, 4); write(fd, &f, 4); size_t Bpp = bytesPerPixel(f); for (size_t y=0 ; y<h ; y++) { write(fd, base, w*Bpp); base = (void *)((char *)base + s*Bpp); } } } close(fd); if (mapbase != MAP_FAILED) { munmap((void *)mapbase, mapsize); } return 0; }
我们将部分分析此代码。
DEFAULT_DISPLAY_ID-要从中获取屏幕截图的显示器的标识符。 在我们的情况下为0。
flinger2skia和
vinfoToPixelFormat-负责确定图像应采用的格式。
notifyMediaScanner-在文件系统中创建图像后，您需要发送广播，以便可以正确显示文件。 如果您不拨打此广播，则并非所有应用程序都可以看到创建的文件。
主要功能并不难“阅读”，因此我们将仅分析直接负责获取图像数据的重要点。
/ dev / graphics / fb0是所谓的帧缓冲区。 帧缓冲区是一种视频存储区域，用于短期存储一个或多个视频帧。 根据主代码，很明显，有一些版本的Android设备将屏幕图像存储在此文件中。 因此，如果您很幸运，那么可以识别vinfo.xoffset和vinfo.yoffset（在大多数情况下为0），并使用控制台可以轻松获取颜色信息：
dd if=/dev/graphics/fb0 bs=<bytes per pixel> count=1 skip=<pixel offset> 2>/dev/null | hd
就我而言，事实并非如此简单，该文件不包含有关图像的任何信息。
screenshot.update是获取图像的第二种方法。 此函数有几种重载方法，可以在
这里找到。
考虑使用最多参数的函数描述：
ScreenshotClient::update(const sp<IBinder>& display, Rect sourceCrop, uint32_t reqWidth, uint32_t reqHeight, uint32_t minLayerZ, uint32_t maxLayerZ, bool useIdentityTransform, uint32_t rotation)
显示 -链接到所需的显示。
sourceCrop-选定图像区域的裁剪。 它可以包含左上点和右下角的坐标（总共4个参数xLeft，yTop，xRight和yBottom）。 原点是左上角。
reqWidth-返回图像的宽度
reqHeight-返回图像的高度
minLayerZ和
maxLayerZ-无法理解这些参数的工作方式。 枚举值有时会产生黑点
useIdentityTransform-如果为true，则禁用应用程序顶部的覆盖层，即 使用
ACTION_MANAGE_OVERLAY_PERMISSION的那些
活动旋转 -图片的旋转。
因此，为了获得像素颜色，我们需要设置xLeft和yTop，将它们移位1，因为 计数将从0开始，并将指定的坐标设置为xRight，yBottom。 在reqWidth和reqHeight中，将值设置为1。通过更改此函数的参数，我们可以确定所需区域的边界。
编译基本的screencap.cpp
这实际上是最困难的部分，可能需要几天或整个一周的时间。 不幸的是，我找不到任何快速的解决方案来在网络上构建新版本的屏幕截图，因此我不得不专门用clang及其参数来折磨自己。
如果您立即尝试编译此代码，则编译器会不断发誓没有文件，有时它可能会报告该文件存在，但不需要构造函数。
因此，最初我添加了NDK库中没有的所有文件。 错误使您知道该文件或该文件应位于的位置。 为此，您需要添加丢失的文件，并找出sysroot所在的位置（clang所在的目录），可以使用以下“功能”：
echo "#include <bogus.h> int main(){}" > tc; ~/arm/bin/clang -v tc; rm tc
错误将显示此目录的路径。 如果您的c位于其他位置，请更改其路径。
记录 Android (4751641 based on r328903) clang version 7.0.2 (https://android.googlesource.com/toolchain/clang 003100370607242ddd5815e4a043907ea9004281) (https://android.googlesource.com/toolchain/llvm 1d739ffb0366421d383e04ff80ec2ee591315116) (based on LLVM 7.0.2svn) Target: armv7a-none-linux-android16 Thread model: posix InstalledDir: /Users/macbookair/arm/bin Found candidate GCC installation: /Users/macbookair/arm/bin/../lib/gcc/arm-linux-androideabi/4.9.x Selected GCC installation: /Users/macbookair/arm/bin/../lib/gcc/arm-linux-androideabi/4.9.x Candidate multilib: thumb;@mthumb Candidate multilib: armv7-a;@march=armv7-a Candidate multilib: armv7-a/thumb;@march=armv7-a@mthumb Candidate multilib: .; Selected multilib: armv7-a;@march=armv7-a "/Users/macbookair/arm/bin/clang70" -cc1 -triple armv7-none-linux-android16 -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name tc -mrelocation-model pic -pic-level 2 -pic-is-pie -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -fuse-init-array -target-cpu generic -target-feature +soft-float-abi -target-abi aapcs-linux -mfloat-abi soft -fallow-half-arguments-and-returns -dwarf-column-info -debugger-tuning=gdb -target-linker-version 241.9 -v -resource-dir /Users/macbookair/arm/lib64/clang/7.0.2 -isysroot /Users/macbookair/arm/bin/../sysroot -internal-isystem /Users/macbookair/arm/bin/../sysroot/usr/local/include -internal-isystem /Users/macbookair/arm/lib64/clang/7.0.2/include -internal-externc-isystem /Users/macbookair/arm/bin/../sysroot/include -internal-externc-isystem /Users/macbookair/arm/bin/../sysroot/usr/include -fdebug-compilation-dir /Users/macbookair/Downloads/sji-android-screen-capture-master/src/android/capture -ferror-limit 19 -fmessage-length 80 -fno-signed-char -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/t-9f5ef7.o -xc tc clang -cc1 version 7.0.2 based upon LLVM 7.0.2svn default target x86_64-apple-darwin18.0.0 ignoring nonexistent directory "/Users/macbookair/arm/bin/../sysroot/include" https://android.googlesource.com/toolchain/clang 003100370607242ddd5815e4a043907ea9004281）（https://android.googlesource.com/toolchain/llvm 1d739ffb0366421d383e04ff80ec2ee591315116）（基于LLVM 7.0。 Android (4751641 based on r328903) clang version 7.0.2 (https://android.googlesource.com/toolchain/clang 003100370607242ddd5815e4a043907ea9004281) (https://android.googlesource.com/toolchain/llvm 1d739ffb0366421d383e04ff80ec2ee591315116) (based on LLVM 7.0.2svn) Target: armv7a-none-linux-android16 Thread model: posix InstalledDir: /Users/macbookair/arm/bin Found candidate GCC installation: /Users/macbookair/arm/bin/../lib/gcc/arm-linux-androideabi/4.9.x Selected GCC installation: /Users/macbookair/arm/bin/../lib/gcc/arm-linux-androideabi/4.9.x Candidate multilib: thumb;@mthumb Candidate multilib: armv7-a;@march=armv7-a Candidate multilib: armv7-a/thumb;@march=armv7-a@mthumb Candidate multilib: .; Selected multilib: armv7-a;@march=armv7-a "/Users/macbookair/arm/bin/clang70" -cc1 -triple armv7-none-linux-android16 -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name tc -mrelocation-model pic -pic-level 2 -pic-is-pie -mthread-model posix -mdisable-fp-elim -fmath-errno -masm-verbose -mconstructor-aliases -fuse-init-array -target-cpu generic -target-feature +soft-float-abi -target-abi aapcs-linux -mfloat-abi soft -fallow-half-arguments-and-returns -dwarf-column-info -debugger-tuning=gdb -target-linker-version 241.9 -v -resource-dir /Users/macbookair/arm/lib64/clang/7.0.2 -isysroot /Users/macbookair/arm/bin/../sysroot -internal-isystem /Users/macbookair/arm/bin/../sysroot/usr/local/include -internal-isystem /Users/macbookair/arm/lib64/clang/7.0.2/include -internal-externc-isystem /Users/macbookair/arm/bin/../sysroot/include -internal-externc-isystem /Users/macbookair/arm/bin/../sysroot/usr/include -fdebug-compilation-dir /Users/macbookair/Downloads/sji-android-screen-capture-master/src/android/capture -ferror-limit 19 -fmessage-length 80 -fno-signed-char -fobjc-runtime=gcc -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/t-9f5ef7.o -xc tc clang -cc1 version 7.0.2 based upon LLVM 7.0.2svn default target x86_64-apple-darwin18.0.0 ignoring nonexistent directory "/Users/macbookair/arm/bin/../sysroot/include"
我们求助于Google，查找所有必要的文件。 就我而言，我必须添加以下目录和文件：
目录和文件 // ~/arm/sysroot/usr/include/binder ~/arm/sysroot/usr/include/utils ~/arm/sysroot/usr/include/cutils ~/arm/sysroot/usr/include/log ~/arm/sysroot/usr/include/system ~/arm/sysroot/usr/include/gui ~/arm/sysroot/usr/include/ui ~/arm/sysroot/usr/include/hardware ~/arm/sysroot/usr/ports // ~/arm/sysroot/usr/include/SkAnnotation.h ~/arm/sysroot/usr/include/SkAtomics.h ~/arm/sysroot/usr/include/SkBBHFactory.h ~/arm/sysroot/usr/include/SkBitmap.h ~/arm/sysroot/usr/include/SkBitmapDevice.h ~/arm/sysroot/usr/include/SkBlitRow.h ~/arm/sysroot/usr/include/SkBlurTypes.h ~/arm/sysroot/usr/include/SkCanvas.h ~/arm/sysroot/usr/include/SkChunkAlloc.h ~/arm/sysroot/usr/include/SkClipStack.h ~/arm/sysroot/usr/include/SkColor.h ~/arm/sysroot/usr/include/SkColorFilter.h ~/arm/sysroot/usr/include/SkColorPriv.h ~/arm/sysroot/usr/include/SkColorTable.h ~/arm/sysroot/usr/include/SkComposeShader.h ~/arm/sysroot/usr/include/SkData.h ~/arm/sysroot/usr/include/SkDataTable.h ~/arm/sysroot/usr/include/SkDeque.h ~/arm/sysroot/usr/include/SkDevice.h ~/arm/sysroot/usr/include/SkDither.h ~/arm/sysroot/usr/include/SkDocument.h ~/arm/sysroot/usr/include/SkDraw.h ~/arm/sysroot/usr/include/SkDrawable.h ~/arm/sysroot/usr/include/SkDrawFilter.h ~/arm/sysroot/usr/include/SkDrawLooper.h ~/arm/sysroot/usr/include/SkDrawPictureCallback.h ~/arm/sysroot/usr/include/SkEndian.h ~/arm/sysroot/usr/include/SkError.h ~/arm/sysroot/usr/include/SkFilterQuality.h ~/arm/sysroot/usr/include/SkFixed.h ~/arm/sysroot/usr/include/SkFlattenable.h ~/arm/sysroot/usr/include/SkFlattenableSerialization.h ~/arm/sysroot/usr/include/SkFloatBits.h ~/arm/sysroot/usr/include/SkFloatingPoint.h ~/arm/sysroot/usr/include/SkFont.h ~/arm/sysroot/usr/include/SkFontHost.h ~/arm/sysroot/usr/include/SkFontLCDConfig.h ~/arm/sysroot/usr/include/SkFontStyle.h ~/arm/sysroot/usr/include/SkGraphics.h ~/arm/sysroot/usr/include/SkImage.h ~/arm/sysroot/usr/include/SkImageDecoder.h ~/arm/sysroot/usr/include/SkImageEncoder.h ~/arm/sysroot/usr/include/SkImageFilter.h ~/arm/sysroot/usr/include/SkImageGenerator.h ~/arm/sysroot/usr/include/SkImageInfo.h ~/arm/sysroot/usr/include/SkInstCnt.h ~/arm/sysroot/usr/include/SkLazyPtr.h ~/arm/sysroot/usr/include/SkMallocPixelRef.h ~/arm/sysroot/usr/include/SkMask.h ~/arm/sysroot/usr/include/SkMaskFilter.h ~/arm/sysroot/usr/include/SkMath.h ~/arm/sysroot/usr/include/SkMatrix.h ~/arm/sysroot/usr/include/SkMetaData.h ~/arm/sysroot/usr/include/SkMultiPictureDraw.h ~/arm/sysroot/usr/include/SkMutex.h ~/arm/sysroot/usr/include/SkOnce.h ~/arm/sysroot/usr/include/SkOSFile.h ~/arm/sysroot/usr/include/SkPackBits.h ~/arm/sysroot/usr/include/SkPaint.h ~/arm/sysroot/usr/include/SkPath.h ~/arm/sysroot/usr/include/SkPathEffect.h ~/arm/sysroot/usr/include/SkPathMeasure.h ~/arm/sysroot/usr/include/SkPathRef.h ~/arm/sysroot/usr/include/SkPicture.h ~/arm/sysroot/usr/include/SkPictureRecorder.h ~/arm/sysroot/usr/include/SkPixelRef.h ~/arm/sysroot/usr/include/SkPixelSerializer.h ~/arm/sysroot/usr/include/SkPoint.h ~/arm/sysroot/usr/include/SkPostConfig.h ~/arm/sysroot/usr/include/SkPreConfig.h ~/arm/sysroot/usr/include/SkRasterizer.h ~/arm/sysroot/usr/include/SkRect.h ~/arm/sysroot/usr/include/SkRefCnt.h ~/arm/sysroot/usr/include/SkRegion.h ~/arm/sysroot/usr/include/SkRRect.h ~/arm/sysroot/usr/include/SkScalar.h ~/arm/sysroot/usr/include/SkShader.h ~/arm/sysroot/usr/include/SkSize.h ~/arm/sysroot/usr/include/SkSpinlock.h ~/arm/sysroot/usr/include/SkStream.h ~/arm/sysroot/usr/include/SkString.h ~/arm/sysroot/usr/include/SkStrokeRec.h ~/arm/sysroot/usr/include/SkSurface.h ~/arm/sysroot/usr/include/SkSurfaceProps.h ~/arm/sysroot/usr/include/SkTArray.h ~/arm/sysroot/usr/include/SkTDArray.h ~/arm/sysroot/usr/include/SkTDict.h ~/arm/sysroot/usr/include/SkTDStack.h ~/arm/sysroot/usr/include/SkTemplates.h ~/arm/sysroot/usr/include/SkTextBlob.h ~/arm/sysroot/usr/include/SkThread.h ~/arm/sysroot/usr/include/SkTime.h ~/arm/sysroot/usr/include/SkTInternalLList.h ~/arm/sysroot/usr/include/SkTLazy.h ~/arm/sysroot/usr/include/SkTRegistry.h ~/arm/sysroot/usr/include/SkTSearch.h ~/arm/sysroot/usr/include/SkTypeface.h ~/arm/sysroot/usr/include/SkTypes.h ~/arm/sysroot/usr/include/SkUnPreMultiply.h ~/arm/sysroot/usr/include/SkUserConfig.h ~/arm/sysroot/usr/include/SkUtils.h ~/arm/sysroot/usr/include/SkWeakRefCnt.h ~/arm/sysroot/usr/include/SkWriteBuffer.h ~/arm/sysroot/usr/include/SkWriter32.h ~/arm/sysroot/usr/include/SkXfermode.h // ~/arm/sysroot/usr/include/android/log.h
看来他在这里是成功的，所有这些都需要补充。 编译中
~/arm/bin/clang -pie screencap.cpp -o ./screencap
我们得到了一个可怕的结果：
别紧张 /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ProcessState::self()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ProcessState::startThreadPool()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::ScreenshotClient()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::SurfaceComposerClient::getBuiltInDisplay(int)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::SurfaceComposerClient::getDisplayConfigs(android::sp<android::IBinder> const&, android::Vector<android::DisplayInfo>*)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::SurfaceComposerClient::getActiveConfig(android::sp<android::IBinder> const&)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::update(android::sp<android::IBinder> const&, android::Rect, unsigned int, unsigned int, unsigned int, unsigned int, bool, unsigned int)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::getPixels() const' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::getWidth() const' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::getHeight() const' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::getStride() const' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::getFormat() const' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::getSize() const' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::bytesPerPixel(int)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'SkImageEncoder::EncodeData(SkImageInfo const&, void const*, unsigned int, SkImageEncoder::Type, int)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::bytesPerPixel(int)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::~ScreenshotClient()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'android::ScreenshotClient::~ScreenshotClient()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'stderr' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'stderr' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function main: error: undefined reference to 'stderr' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function usage(char const*): error: undefined reference to 'stderr' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::String8(char const*)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::String8(char const*)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::append(char const*)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::append(char const*)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::append(char const*)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::append(char const*)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::~String8()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::~String8()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::~String8()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function notifyMediaScanner(char const*): error: undefined reference to 'android::String8::~String8()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o(.ARM.extab+0x0): error: undefined reference to '__gxx_personality_v0' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o(.ARM.extab+0x48): error: undefined reference to '__gxx_personality_v0' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function android::sp<android::ProcessState>::~sp(): error: undefined reference to 'android::RefBase::decStrong(void const*) const' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o(.ARM.extab.text._ZN7android2spINS_12ProcessStateEED2Ev+0x0): error: undefined reference to '__gxx_personality_v0' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function android::Vector<android::DisplayInfo>::Vector(): error: undefined reference to 'android::VectorImpl::VectorImpl(unsigned int, unsigned int)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function android::Vector<android::DisplayInfo>::operator[](unsigned int) const: error: undefined reference to '__android_log_assert' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o(.ARM.extab.text._ZN12SkAutoTUnrefI6SkDataED2Ev+0x0): error: undefined reference to '__gxx_personality_v0' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function android::Vector<android::DisplayInfo>::~Vector(): error: undefined reference to 'android::VectorImpl::finish_vector()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function android::Vector<android::DisplayInfo>::~Vector(): error: undefined reference to 'android::VectorImpl::~VectorImpl()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function android::Vector<android::DisplayInfo>::~Vector(): error: undefined reference to 'android::VectorImpl::~VectorImpl()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function android::sp<android::IBinder>::~sp(): error: undefined reference to 'android::RefBase::decStrong(void const*) const' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function __clang_call_terminate: error: undefined reference to '__cxa_begin_catch' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function __clang_call_terminate: error: undefined reference to 'std::terminate()' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function android::Vector<android::DisplayInfo>::~Vector(): error: undefined reference to 'operator delete(void*)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:function SkRefCntBase::unref() const: error: undefined reference to 'SkDebugf(char const*, ...)' /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:typeinfo for android::Vector<android::DisplayInfo>: error: undefined reference to 'vtable for __cxxabiv1::__vmi_class_type_info' /Users/macbookair/Documents/test/bin/../lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/bin/ld: the vtable symbol may be undefined because the class is missing its key function /var/folders/_4/7d51802j1hz2rnmql8kngx5w0000gn/T/screencap-175810.o:screencap.cpp:typeinfo for android::Vector<android::DisplayInfo>: error: undefined reference to 'typeinfo for android::VectorImpl' clang70: error: linker command failed with exit code 1 (use -v to see invocation)
对我来说，那真是个地狱，因为 许多文件都有错误，从理论上讲是不应该的，因为这些文件的内容没有更改。 在这个阶段，我坐了很长时间，开始积极地用Google搜索错误，但没有找到我需要的答案。 我如何决定学习我不记得的clang教程，但是这种解决方案救了我！
事实证明，clang有一个参数（或更确切地说是
ld ）--unresolved-symbols，它负责处理未解析的字符。 , . :
~/arm/bin/clang -pie screencap.cpp -o ./screencap -Wl,--unresolved-symbols=ignore-all -s
- ! , , , . , :
CANNOT LINK EXECUTABLE: cannot locate symbol "_ZN7android12ProcessState4selfEv"
, , Android .so . , . screencap, Android- (/system/bin/screencap) .so , . :
...libdl.so__libc_initlibc.so__cxa_atexit__register_atfork__gnu_Unwind_Find_exidxLIBC_PRIVATE_ZNK7android6VectorINS_11DisplayInfoEE12do_constructEPvj__snprintf_chk__aeabi_memset__aeabi_memcpy_ZNK7android6VectorINS_11DisplayInfoEE10do_destroyEPvj_ZNK7android6VectorINS_11DisplayInfoEE7do_copyEPvPKvj_ZNK7android6VectorINS_11DisplayInfoEE8do_splatEPvPKvj_ZNK7android6VectorINS_11DisplayInfoEE15do_move_forwardEPvPKvj_ZNK7android6VectorINS_11DisplayInfoEE16do_move_backwardEPvPKvj_ZN7android10VectorImpl13finish_vectorEv_ZN7android10VectorImplD2Ev_ZTVN7android6VectorINS_11DisplayInfoEEE_ZdlPvsignal__android_log_print_ZN7android12ProcessState4selfEv_ZN7android12ProcessState15startThreadPoolEv_ZNK7android7RefBase9decStrongEPKvgetoptatoidupopen__errnostrerrorfprintfstrlenstrcmp_ZN7android16ScreenshotClientC1Ev_ZN7android21SurfaceComposerClient17getBuiltInDisplayEi_ZN7android10VectorImplC2Ejj_ZN7android21SurfaceComposerClient17getDisplayConfigsERKNS_2spINS_7IBinderEEEPNS_6VectorINS_11DisplayInfoEEE_ZN7android21SurfaceComposerClient15getActiveConfigERKNS_2spINS_7IBinderEEE_ZN7android16ScreenshotClient6updateERKNS_2spINS_7IBinderEEENS_4RectEjjjjbj_ZNK7android16ScreenshotClient9getPixelsEv_ZNK7android16ScreenshotClient8getWidthEv_ZNK7android16ScreenshotClient9getHeightEv_ZNK7android16ScreenshotClient9getStrideEv_ZNK7android16ScreenshotClient9getFormatEv_ZNK7android16ScreenshotClient7getSizeEvioctlclose_ZN7android13bytesPerPixelEi_ZN14SkImageEncoder10EncodeDataERK11SkImageInfoPKvjNS_4TypeEiwrite_ZN7android7String8C1EPKc_ZN7android7String86appendEPKcsystemfputs_ZN7android7String8D1Evmunmap_ZN7android16ScreenshotClientD1Evmmapoptargstderroptindabort_edata__bss_start_endlibcutils.solibutils.solibbinder.solibskia.solibui.solibgui.solibc++.solibm.so...
, . : libgui.so, libui.so, libcutils.so, libutils.so, libbinder.so, libskia.so. ( , ):
find -name 'libskia.so' 2>/dev/null /system/lib/libskia.so
sdcard/libs ( libskia.so):
./system/lib/libskia.so /sdcard/
adb pull . :
adb pull /sdcard/libs ~/arm
, *.so, , .so , — .
~/arm/bin/clang -pie screencap.cpp *.so -o ./screencap -Wl,--unresolved-symbols=ignore-all -s
. .
您可能已经注意到，将功能“添加到其他人的代码中”并不是一件容易的事。修改后的屏幕截图文件代码如下所示。它的组装与原始组装相同。我认为，大多数读者可以理解这些新增的更改，因此我决定不对此发表评论。改进了screencap.cpp #include <errno.h> #include <unistd.h> #include <stdio.h> #include <fcntl.h> #include <stdlib.h> #include <string.h> #include <linux/fb.h> #include <sys/ioctl.h> #include <sys/mman.h> #include <binder/ProcessState.h> #include <gui/SurfaceComposerClient.h> #include <gui/ISurfaceComposer.h> #include <ui/DisplayInfo.h> #include <ui/PixelFormat.h> // TODO: Fix Skia. #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-parameter" #include <SkImageEncoder.h> #include <SkData.h> #pragma GCC diagnostic pop using namespace android; static uint32_t DEFAULT_DISPLAY_ID = ISurfaceComposer::eDisplayIdMain; static void usage(const char* pname) { fprintf(stderr, "usage: %s [-hpcr] [-d display-id] [FILENAME] [x1 y1] [x2 y2]\n" " -h: this message\n" " -p: save the file as a png.\n" " -d: specify the display id to capture, default %d.\n" " -c: print pixel color [xy].\n" " -r: get rectangle area [x1 - left y1 - top x2 - right y2 - bottom].\n" "If FILENAME ends with .png it will be saved as a png.\n" "If FILENAME is not given, the results will be printed to stdout.\n", pname, DEFAULT_DISPLAY_ID ); } static SkColorType flinger2skia(PixelFormat f) { switch (f) { case PIXEL_FORMAT_RGB_565: return kRGB_565_SkColorType; default: return kN32_SkColorType; } } static status_t vinfoToPixelFormat(const fb_var_screeninfo& vinfo, uint32_t* bytespp, uint32_t* f) { switch (vinfo.bits_per_pixel) { case 16: *f = PIXEL_FORMAT_RGB_565; *bytespp = 2; break; case 24: *f = PIXEL_FORMAT_RGB_888; *bytespp = 3; break; case 32: // TODO: do better decoding of vinfo here *f = PIXEL_FORMAT_RGBX_8888; *bytespp = 4; break; default: return BAD_VALUE; } return NO_ERROR; } static status_t notifyMediaScanner(const char* fileName) { String8 cmd("am broadcast -a android.intent.action.MEDIA_SCANNER_SCAN_FILE -d file://"); String8 fileUrl("\""); fileUrl.append(fileName); fileUrl.append("\""); cmd.append(fileName); cmd.append(" > /dev/null"); int result = system(cmd.string()); if (result < 0) { fprintf(stderr, "Unable to broadcast intent for media scanner.\n"); return UNKNOWN_ERROR; } return NO_ERROR; } int main(int argc, char** argv) { ProcessState::self()->startThreadPool(); const char* pname = argv[0]; int x1,x2,y1,y2; bool png = false; bool color = false; bool rectangle = false; int32_t displayId = DEFAULT_DISPLAY_ID; int c; while ((c = getopt(argc, argv, "phdcr:")) != -1) { switch (c) { case 'p': png = true; break; case 'd': displayId = atoi(optarg); break; case 'c': color = true; break; case 'r': rectangle = true; break; case '?': case 'h': usage(pname); return 1; } } argc -= optind; if (color) { x1 = atoi(argv[2])-1; y1 = atoi(argv[3])-1; x2 = atoi(argv[2]); y2 = atoi(argv[3]); } else if (rectangle) { x1 = atoi(argv[3]); y1 = atoi(argv[4]); x2 = atoi(argv[5]); y2 = atoi(argv[6]); optind--; } argv += optind; int fd = -1; const char* fn = NULL; if (argc == 0) { fd = dup(STDOUT_FILENO); } else if (argc == 1 || argc == 4) { fn = argv[0]; fd = open(fn, O_WRONLY | O_CREAT | O_TRUNC, 0664); if (fd == -1) { fprintf(stderr, "Error opening file: %s (%s)\n", fn, strerror(errno)); return 1; } const int len = strlen(fn); if (len >= 4 && 0 == strcmp(fn+len-4, ".png")) { png = true; } } if (fd == -1 && !color && !rectangle) { usage(pname); return 1; } void const* mapbase = MAP_FAILED; ssize_t mapsize = -1; void const* base = NULL; uint32_t w, s, h, f; size_t size = 0; // Maps orientations from DisplayInfo to ISurfaceComposer static const uint32_t ORIENTATION_MAP[] = { ISurfaceComposer::eRotateNone, // 0 == DISPLAY_ORIENTATION_0 ISurfaceComposer::eRotate270, // 1 == DISPLAY_ORIENTATION_90 ISurfaceComposer::eRotate180, // 2 == DISPLAY_ORIENTATION_180 ISurfaceComposer::eRotate90, // 3 == DISPLAY_ORIENTATION_270 }; ScreenshotClient screenshot; sp<IBinder> display = SurfaceComposerClient::getBuiltInDisplay(displayId); if (display == NULL) { fprintf(stderr, "Unable to get handle for display %d\n", displayId); return 1; } Vector<DisplayInfo> configs; SurfaceComposerClient::getDisplayConfigs(display, &configs); int activeConfig = SurfaceComposerClient::getActiveConfig(display); if (static_cast<size_t>(activeConfig) >= configs.size()) { fprintf(stderr, "Active config %d not inside configs (size %zu)\n", activeConfig, configs.size()); return 1; } uint8_t displayOrientation = configs[activeConfig].orientation; uint32_t captureOrientation = ORIENTATION_MAP[displayOrientation]; status_t result; if (color || rectangle) { result = screenshot.update(display, Rect(x1,y1,x2,y2), x2-x1, y2-y1, 0, -1U, false, captureOrientation); } else { result = screenshot.update(display, Rect(), 0, 0, 0, -1U, false, captureOrientation); } if (result == NO_ERROR) { base = screenshot.getPixels(); w = screenshot.getWidth(); h = screenshot.getHeight(); s = screenshot.getStride(); f = screenshot.getFormat(); size = screenshot.getSize(); if (color) { size_t Bpp = 4; //bytesPerPixel char* rawImageData; rawImageData = (char *)base; base = (void *)((char *)base + Bpp); for (int i=0; i<sizeof(rawImageData); i++) { printf( "%02X", rawImageData[i]); } return 1; } } else { const char* fbpath = "/dev/graphics/fb0"; int fb = open(fbpath, O_RDONLY); if (fb >= 0) { struct fb_var_screeninfo vinfo; if (ioctl(fb, FBIOGET_VSCREENINFO, &vinfo) == 0) { uint32_t bytespp; if (vinfoToPixelFormat(vinfo, &bytespp, &f) == NO_ERROR) { size_t offset = (vinfo.xoffset + vinfo.yoffset*vinfo.xres) * bytespp; w = vinfo.xres; h = vinfo.yres; s = vinfo.xres; size = w*h*bytespp; mapsize = offset + size; mapbase = mmap(0, mapsize, PROT_READ, MAP_PRIVATE, fb, 0); if (mapbase != MAP_FAILED) { base = (void const *)((char const *)mapbase + offset); } } } close(fb); } } if (base != NULL) { if (png) { const SkImageInfo info = SkImageInfo::Make(w, h, flinger2skia(f), kPremul_SkAlphaType); SkAutoTUnref<SkData> data(SkImageEncoder::EncodeData(info, base, s*bytesPerPixel(f), SkImageEncoder::kPNG_Type, SkImageEncoder::kDefaultQuality)); if (data.get()) { write(fd, data->data(), data->size()); } if (fn != NULL) { notifyMediaScanner(fn); } } else { write(fd, &w, 4); write(fd, &h, 4); write(fd, &f, 4); size_t Bpp = bytesPerPixel(f); for (size_t y=0 ; y<h ; y++) { write(fd, base, w*Bpp); base = (void *)((char *)base + s*Bpp); } } } close(fd); if (mapbase != MAP_FAILED) { munmap((void *)mapbase, mapsize); } return 0; }
获取像素颜色的示例： ./screencap -c 100 100
在给定区域中获取图像的示例： ./screencap -r /sdcard/test.png 0 0 720 640
该项目已上传到GitHub，因此欢迎任何有兴趣的人。PS：如果您知道如何找到可执行文件的必要源代码或编译所需的库的最佳方法，请添加注释，我将在本文中添加此建议。