解析android截屏問(wèn)題
更新時(shí)間：2013年07月30日 10:35:19 作者：
筆者做過(guò)一段時(shí)間的截屏開發(fā)，稍微了解了一下這方面的知識(shí)，于是拿來(lái)分享一下，也許對(duì)你有一些幫助吧
我是基于android2.3.3系統(tǒng)之上的，想必大家應(yīng)該知道在android源碼下面有個(gè)文件叫做screencap吧，位于frameworks\base\services\surfaceflinger\tests\screencap\screencap.cpp,你直接在linux下編譯（保存在 /system/bin/test-screencap），然后push到手機(jī)上再通過(guò)電腦去敲命令test-screencap /mnt/sdcard/scapxx.png就可以實(shí)現(xiàn)截屏。
/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <utils/Log.h>
#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <binder/IServiceManager.h>
#include <binder/IMemory.h>
#include <surfaceflinger/ISurfaceComposer.h>
#include <SkImageEncoder.h>
#include <SkBitmap.h>
using namespace android;
int main(int argc, char** argv)
{
if (argc != 2) {
printf("usage: %s path\n", argv[0]);
exit(0);
}
const String16 name("SurfaceFlinger");
sp<ISurfaceComposer> composer;
getService(name, &composer);
sp<IMemoryHeap> heap;
uint32_t w, h;
PixelFormat f;
status_t err = composer->captureScreen(0, &heap, &w, &h, &f, 0, 0);
if (err != NO_ERROR) {
fprintf(stderr, "screen capture failed: %s\n", strerror(-err));
exit(0);
}
printf("screen capture success: w=%u, h=%u, pixels=%p\n",
w, h, heap->getBase());
printf("saving file as PNG in %s ...\n", argv[1]);
SkBitmap b;
b.setConfig(SkBitmap::kARGB_8888_Config, w, h);
b.setPixels(heap->getBase());
SkImageEncoder::EncodeFile(argv[1], b,
SkImageEncoder::kPNG_Type, SkImageEncoder::kDefaultQuality);
return 0;
}
其實(shí)這個(gè)程序真正用到的就是一個(gè)叫做capturescreen的函數(shù)，而capturescreen會(huì)調(diào)用captureScreenImplLocked這個(gè)函數(shù)
下面是代碼：
status_t SurfaceFlinger::captureScreenImplLocked(DisplayID dpy,
sp<IMemoryHeap>* heap,
uint32_t* w, uint32_t* h, PixelFormat* f,
uint32_t sw, uint32_t sh)
{
LOGI("captureScreenImplLocked");
status_t result = PERMISSION_DENIED;
// only one display supported for now
if (UNLIKELY(uint32_t(dpy) >= DISPLAY_COUNT))
return BAD_VALUE;
if (!GLExtensions::getInstance().haveFramebufferObject())
return INVALID_OPERATION;
// get screen geometry
const DisplayHardware& hw(graphicPlane(dpy).displayHardware());
const uint32_t hw_w = hw.getWidth();
const uint32_t hw_h = hw.getHeight();
if ((sw > hw_w) || (sh > hw_h))
return BAD_VALUE;
sw = (!sw) ? hw_w : sw;
sh = (!sh) ? hw_h : sh;
const size_t size = sw * sh * 4;
// make sure to clear all GL error flags
while ( glGetError() != GL_NO_ERROR ) ;
// create a FBO
GLuint name, tname;
glGenRenderbuffersOES(1, &tname);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, tname);
glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_RGBA8_OES, sw, sh);
glGenFramebuffersOES(1, &name);
glBindFramebufferOES(GL_FRAMEBUFFER_OES, name);
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES,
GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, tname);
GLenum status = glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES);
if (status == GL_FRAMEBUFFER_COMPLETE_OES) {
// invert everything, b/c glReadPixel() below will invert the FB
glViewport(0, 0, sw, sh);
glScissor(0, 0, sw, sh);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrthof(0, hw_w, 0, hw_h, 0, 1);
glMatrixMode(GL_MODELVIEW);
// redraw the screen entirely...
glClearColor(0,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
const Vector< sp<LayerBase> >& layers(mVisibleLayersSortedByZ);
const size_t count = layers.size();
for (size_t i=0 ; i<count ; ++i) {
const sp<LayerBase>& layer(layers[i]);
layer->drawForSreenShot();
}
// XXX: this is needed on tegra
glScissor(0, 0, sw, sh);
// check for errors and return screen capture
if (glGetError() != GL_NO_ERROR) {
// error while rendering
result = INVALID_OPERATION;
} else {
// allocate shared memory large enough to hold the
// screen capture
sp<MemoryHeapBase> base(
new MemoryHeapBase(size, 0, "screen-capture") );
void* const ptr = base->getBase();
if (ptr) {
// capture the screen with glReadPixels()
glReadPixels(0, 0, sw, sh, GL_RGBA, GL_UNSIGNED_BYTE, ptr);
if (glGetError() == GL_NO_ERROR) {
*heap = base;
*w = sw;
*h = sh;
*f = PIXEL_FORMAT_RGBA_8888;
result = NO_ERROR;
}
} else {
result = NO_MEMORY;
}
}
glEnable(GL_SCISSOR_TEST);
glViewport(0, 0, hw_w, hw_h);
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
} else {
result = BAD_VALUE;
}
// release FBO resources
glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0);
glDeleteRenderbuffersOES(1, &tname);
glDeleteFramebuffersOES(1, &name);
hw.compositionComplete();
return result;
}
status_t SurfaceFlinger::captureScreen(DisplayID dpy,
sp<IMemoryHeap>* heap,
uint32_t* width, uint32_t* height, PixelFormat* format,
uint32_t sw, uint32_t sh)
{
LOGI("into captureScreen");
// only one display supported for now
if (UNLIKELY(uint32_t(dpy) >= DISPLAY_COUNT))
return BAD_VALUE;
if (!GLExtensions::getInstance().haveFramebufferObject())
return INVALID_OPERATION;
class MessageCaptureScreen : public MessageBase {
SurfaceFlinger* flinger;
DisplayID dpy;
sp<IMemoryHeap>* heap;
uint32_t* w;
uint32_t* h;
PixelFormat* f;
uint32_t sw;
uint32_t sh;
status_t result;
public:
MessageCaptureScreen(SurfaceFlinger* flinger, DisplayID dpy,
sp<IMemoryHeap>* heap, uint32_t* w, uint32_t* h, PixelFormat* f,
uint32_t sw, uint32_t sh)
: flinger(flinger), dpy(dpy),
heap(heap), w(w), h(h), f(f), sw(sw), sh(sh), result(PERMISSION_DENIED)
{
}
status_t getResult() const {
LOGI("getResult()");
return result;
}
virtual bool handler() {
LOGI("handler()");
Mutex::Autolock _l(flinger->mStateLock);
// if we have secure windows, never allow the screen capture
if (flinger->mSecureFrameBuffer)
return true;
result = flinger->captureScreenImplLocked(dpy,
heap, w, h, f, sw, sh);
return true;
}
};
LOGI("before messagecapturescreen");
sp<MessageBase> msg = new MessageCaptureScreen(this,
dpy, heap, width, height, format, sw, sh);
status_t res = postMessageSync(msg);
if (res == NO_ERROR) {
res = static_cast<MessageCaptureScreen*>( msg.get() )->getResult();
}
return res;
}
而這個(gè)函數(shù)關(guān)鍵又使用了opengl的幾個(gè)函數(shù)去獲得圖片，然而opengl又去read framebuffer（這是我的理解）。如果你去用jni調(diào)用so的方法去截屏的話，就可以把screencap這個(gè)文件稍微修改一下然后做成so文件。
主要是補(bǔ)充一下怎么去存放文件與編譯吧，當(dāng)然我說(shuō)的方法只是我做的方法不代表是很好用的。
存放：在eclipse新建一個(gè)android工程，保存后找到這個(gè)工程（如screencap）的存放位置 然后把這個(gè)文件放到android源代碼的development文件里面，然后在你的那個(gè)工程文件里面新建一個(gè)文件夾，名字叫做jni（這個(gè)文件夾平行于src文件夾，screencap/jni），把上面博客提到的那個(gè)C++跟mk（screencap/jni/com_android_ScreenCap_ScreenCapNative.cpp和screencap/jni/Android.mk）文件放進(jìn)去，最后在把編譯的mk文件放在screencap目錄下（screencap/Android.mk）;
編譯：編譯是個(gè)很偉大的工程，需要你花大量的時(shí)間與精力。直接在終端進(jìn)入工程存放的所在位置，我的是Administrator/Android.2.3.3/development，然后mm（Builds all of the modules in the current directory），如果成功，那么你運(yùn)氣比較好，在終端回提示你APK保存的位置。push進(jìn)手機(jī)試一試。但是往往是不成功的。你可能會(huì)遇到一些問(wèn)題，比如android.permission.ACCESS_SURFACE_FLINGER ,android.permission.READ_FRAME_BUFFER（因?yàn)閏apturescrren這個(gè)函數(shù)是surfaceflinger里面的函數(shù)，然而surfaceflinger里面的opengl截屏函數(shù)會(huì)去讀取framebuffer），相關(guān)源代碼是：
status_t SurfaceFlinger::onTransact(
uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
switch (code) {
case CREATE_CONNECTION:
case OPEN_GLOBAL_TRANSACTION:
case CLOSE_GLOBAL_TRANSACTION:
case SET_ORIENTATION:
case FREEZE_DISPLAY:
case UNFREEZE_DISPLAY:
case BOOT_FINISHED:
case TURN_ELECTRON_BEAM_OFF:
case TURN_ELECTRON_BEAM_ON:
{
// codes that require permission check
IPCThreadState* ipc = IPCThreadState::self();
const int pid = ipc->getCallingPid();
const int uid = ipc->getCallingUid();
if ((uid != AID_GRAPHICS) && !mAccessSurfaceFlinger.check(pid, uid)) {
LOGE("Permission Denial: "
"can't access SurfaceFlinger pid=%d, uid=%d", pid, uid);
return PERMISSION_DENIED;
}
break;
}
case CAPTURE_SCREEN:
{
// codes that require permission check
IPCThreadState* ipc = IPCThreadState::self();
const int pid = ipc->getCallingPid();
const int uid = ipc->getCallingUid();
if ((uid != AID_GRAPHICS) && !mReadFramebuffer.check(pid, uid)) {
LOGE("Permission Denial: "
"can't read framebuffer pid=%d, uid=%d", pid, uid);
return PERMISSION_DENIED;
}
break;
}
}
status_t err = BnSurfaceComposer::onTransact(code, data, reply, flags);
if (err == UNKNOWN_TRANSACTION || err == PERMISSION_DENIED) {
CHECK_INTERFACE(ISurfaceComposer, data, reply);
if (UNLIKELY(!mHardwareTest.checkCalling())) {
IPCThreadState* ipc = IPCThreadState::self();
const int pid = ipc->getCallingPid();
const int uid = ipc->getCallingUid();
LOGI("err");
LOGE("Permission Denial: "
"can't access SurfaceFlinger pid=%d, uid=%d", pid, uid);
return PERMISSION_DENIED;
}
int n;
switch (code) {
case 1000: // SHOW_CPU, NOT SUPPORTED ANYMORE
case 1001: // SHOW_FPS, NOT SUPPORTED ANYMORE
return NO_ERROR;
case 1002: // SHOW_UPDATES
n = data.readInt32();
mDebugRegion = n ? n : (mDebugRegion ? 0 : 1);
return NO_ERROR;
case 1003: // SHOW_BACKGROUND
n = data.readInt32();
mDebugBackground = n ? 1 : 0;
return NO_ERROR;
case 1004:{ // repaint everything
Mutex::Autolock _l(mStateLock);
const DisplayHardware& hw(graphicPlane(0).displayHardware());
mDirtyRegion.set(hw.bounds()); // careful that's not thread-safe
signalEvent();
return NO_ERROR;
}
case 1005:{ // force transaction
setTransactionFlags(eTransactionNeeded|eTraversalNeeded);
return NO_ERROR;
}
case 1006:{ // enable/disable GraphicLog
int enabled = data.readInt32();
GraphicLog::getInstance().setEnabled(enabled);
return NO_ERROR;
}
case 1007: // set mFreezeCount
mFreezeCount = data.readInt32();
mFreezeDisplayTime = 0;
return NO_ERROR;
case 1010: // interrogate.
reply->writeInt32(0);
reply->writeInt32(0);
reply->writeInt32(mDebugRegion);
reply->writeInt32(mDebugBackground);
return NO_ERROR;
case 1013: {
Mutex::Autolock _l(mStateLock);
const DisplayHardware& hw(graphicPlane(0).displayHardware());
reply->writeInt32(hw.getPageFlipCount());
}
return NO_ERROR;
}
}
return err;
}
這個(gè)僅僅只是開始！ 你會(huì)發(fā)現(xiàn)你即使在xml里面添加相應(yīng)的權(quán)限仍然會(huì)有這個(gè)問(wèn)題出現(xiàn)，為什么呢？在packageManger文件里面發(fā)現(xiàn)相關(guān)代碼：
int checkSignaturesLP(Signature[] s1, Signature[] s2) {
if (s1 == null) {
return s2 == null
? PackageManager.SIGNATURE_NEITHER_SIGNED
: PackageManager.SIGNATURE_FIRST_NOT_SIGNED;
}
if (s2 == null) {
return PackageManager.SIGNATURE_SECOND_NOT_SIGNED;
}
HashSet<Signature> set1 = new HashSet<Signature>();
for (Signature sig : s1) {
set1.add(sig);
}
HashSet<Signature> set2 = new HashSet<Signature>();
for (Signature sig : s2) {
set2.add(sig);
}
// Make sure s2 contains all signatures in s1.
if (set1.equals(set2)) {
return PackageManager.SIGNATURE_MATCH;
}
return PackageManager.SIGNATURE_NO_MATCH;
}
// Check for shared user signatures
if (pkgSetting.sharedUser != null && pkgSetting.sharedUser.signatures.mSignatures != null) {
if (checkSignaturesLP(pkgSetting.sharedUser.signatures.mSignatures,
pkg.mSignatures) != PackageManager.SIGNATURE_MATCH) {
Slog.e(TAG, "Package " + pkg.packageName
+ " has no signatures that match those in shared user "
+ pkgSetting.sharedUser.name + "; ignoring!");
mLastScanError = PackageManager.INSTALL_FAILED_SHARED_USER_INCOMPATIBLE;
return false;
}
}
return true;
private boolean verifySignaturesLP(PackageSetting pkgSetting,
PackageParser.Package pkg) {
// Check for shared user signatures
if (pkgSetting.sharedUser != null && pkgSetting.sharedUser.signatures.mSignatures != null) {
if (checkSignaturesLP(pkgSetting.sharedUser.signatures.mSignatures,
pkg.mSignatures) != PackageManager.SIGNATURE_MATCH) {
Slog.e(TAG, "Package " + pkg.packageName
+ " has no signatures that match those in shared user "
+ pkgSetting.sharedUser.name + "; ignoring!");
mLastScanError = PackageManager.INSTALL_FAILED_SHARED_USER_INCOMPATIBLE;
return false;
}
}
return true;
}
你在終端輸入adb logcat | grep PackageManager 你會(huì)發(fā)現(xiàn)這兩個(gè)權(quán)限根本沒有賦予給你的apk，我的理解是，程序需要權(quán)限，然后apk仍然需要權(quán)限。那怎么樣給apk賦予權(quán)限呢，兩個(gè)方法，一個(gè)是在我上面說(shuō)的screencap/Android.mk里面添加platform一行，然后在回到mm。還有一個(gè)方法就是通過(guò)sign。這兩個(gè)方法都是給apk賦予system權(quán)限，但是我試過(guò)這兩種方法，都有問(wèn)題，就是在adb install的時(shí)候會(huì)顯示簽名不兼容，查看源代碼會(huì)發(fā)現(xiàn)uid跟gid不匹配。這些是我這段時(shí)間發(fā)現(xiàn)的問(wèn)題，大家有問(wèn)題可以交流交流。
再說(shuō)說(shuō)幾個(gè)簡(jiǎn)單的應(yīng)用層截屏吧，很簡(jiǎn)單，就是幾個(gè)函數(shù)調(diào)用而已
View view = getWindow().getDecorView();
Display display = this.getWindowManager().getDefaultDisplay();
view.layout(0, 0, display.getWidth(), display.getHeight());
view.setDrawingCacheEnabled(true);//允許當(dāng)前窗口保存緩存信息，這樣 getDrawingCache()方法才會(huì)返回一個(gè)Bitmap
Bitmap bmp = Bitmap.createBitmap(view.getDrawingCache());
我對(duì)這個(gè)程序的理解就是，它僅僅只能截取當(dāng)前的activity，也就是說(shuō)如果你運(yùn)行這個(gè)程序后它就截取你這個(gè)程序的當(dāng)前屏幕的信息。我們假設(shè)你做成一個(gè)按鈕，在點(diǎn)擊按鈕后sleep5秒再調(diào)用這個(gè)方法（假設(shè)你的activity叫做screen）。當(dāng)你點(diǎn)擊按鈕以后，然后你再點(diǎn)擊home或者返回按鈕，等到5秒后你那個(gè)程序就會(huì)截取到你當(dāng)前屏幕？不是！它只會(huì)截取那個(gè)運(yùn)行于后臺(tái)的screen這個(gè)activity。
這些只是我的一點(diǎn)小小的總結(jié)，而且肯定有不對(duì)的地方，希望大家一起來(lái)解決截屏的問(wèn)題！
復(fù)制代碼 代碼如下:
/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <utils/Log.h>
#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <binder/IServiceManager.h>
#include <binder/IMemory.h>
#include <surfaceflinger/ISurfaceComposer.h>
#include <SkImageEncoder.h>
#include <SkBitmap.h>
using namespace android;
int main(int argc, char** argv)
{
if (argc != 2) {
printf("usage: %s path\n", argv[0]);
exit(0);
}
const String16 name("SurfaceFlinger");
sp<ISurfaceComposer> composer;
getService(name, &composer);
sp<IMemoryHeap> heap;
uint32_t w, h;
PixelFormat f;
status_t err = composer->captureScreen(0, &heap, &w, &h, &f, 0, 0);
if (err != NO_ERROR) {
fprintf(stderr, "screen capture failed: %s\n", strerror(-err));
exit(0);
}
printf("screen capture success: w=%u, h=%u, pixels=%p\n",
w, h, heap->getBase());
printf("saving file as PNG in %s ...\n", argv[1]);
SkBitmap b;
b.setConfig(SkBitmap::kARGB_8888_Config, w, h);
b.setPixels(heap->getBase());
SkImageEncoder::EncodeFile(argv[1], b,
SkImageEncoder::kPNG_Type, SkImageEncoder::kDefaultQuality);
return 0;
}
其實(shí)這個(gè)程序真正用到的就是一個(gè)叫做capturescreen的函數(shù)，而capturescreen會(huì)調(diào)用captureScreenImplLocked這個(gè)函數(shù)
下面是代碼：
復(fù)制代碼 代碼如下:
status_t SurfaceFlinger::captureScreenImplLocked(DisplayID dpy,
sp<IMemoryHeap>* heap,
uint32_t* w, uint32_t* h, PixelFormat* f,
uint32_t sw, uint32_t sh)
{
LOGI("captureScreenImplLocked");
status_t result = PERMISSION_DENIED;
// only one display supported for now
if (UNLIKELY(uint32_t(dpy) >= DISPLAY_COUNT))
return BAD_VALUE;
if (!GLExtensions::getInstance().haveFramebufferObject())
return INVALID_OPERATION;
// get screen geometry
const DisplayHardware& hw(graphicPlane(dpy).displayHardware());
const uint32_t hw_w = hw.getWidth();
const uint32_t hw_h = hw.getHeight();
if ((sw > hw_w) || (sh > hw_h))
return BAD_VALUE;
sw = (!sw) ? hw_w : sw;
sh = (!sh) ? hw_h : sh;
const size_t size = sw * sh * 4;
// make sure to clear all GL error flags
while ( glGetError() != GL_NO_ERROR ) ;
// create a FBO
GLuint name, tname;
glGenRenderbuffersOES(1, &tname);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, tname);
glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_RGBA8_OES, sw, sh);
glGenFramebuffersOES(1, &name);
glBindFramebufferOES(GL_FRAMEBUFFER_OES, name);
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES,
GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, tname);
GLenum status = glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES);
if (status == GL_FRAMEBUFFER_COMPLETE_OES) {
// invert everything, b/c glReadPixel() below will invert the FB
glViewport(0, 0, sw, sh);
glScissor(0, 0, sw, sh);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrthof(0, hw_w, 0, hw_h, 0, 1);
glMatrixMode(GL_MODELVIEW);
// redraw the screen entirely...
glClearColor(0,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
const Vector< sp<LayerBase> >& layers(mVisibleLayersSortedByZ);
const size_t count = layers.size();
for (size_t i=0 ; i<count ; ++i) {
const sp<LayerBase>& layer(layers[i]);
layer->drawForSreenShot();
}
// XXX: this is needed on tegra
glScissor(0, 0, sw, sh);
// check for errors and return screen capture
if (glGetError() != GL_NO_ERROR) {
// error while rendering
result = INVALID_OPERATION;
} else {
// allocate shared memory large enough to hold the
// screen capture
sp<MemoryHeapBase> base(
new MemoryHeapBase(size, 0, "screen-capture") );
void* const ptr = base->getBase();
if (ptr) {
// capture the screen with glReadPixels()
glReadPixels(0, 0, sw, sh, GL_RGBA, GL_UNSIGNED_BYTE, ptr);
if (glGetError() == GL_NO_ERROR) {
*heap = base;
*w = sw;
*h = sh;
*f = PIXEL_FORMAT_RGBA_8888;
result = NO_ERROR;
}
} else {
result = NO_MEMORY;
}
}
glEnable(GL_SCISSOR_TEST);
glViewport(0, 0, hw_w, hw_h);
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
} else {
result = BAD_VALUE;
}
// release FBO resources
glBindFramebufferOES(GL_FRAMEBUFFER_OES, 0);
glDeleteRenderbuffersOES(1, &tname);
glDeleteFramebuffersOES(1, &name);
hw.compositionComplete();
return result;
}
status_t SurfaceFlinger::captureScreen(DisplayID dpy,
sp<IMemoryHeap>* heap,
uint32_t* width, uint32_t* height, PixelFormat* format,
uint32_t sw, uint32_t sh)
{
LOGI("into captureScreen");
// only one display supported for now
if (UNLIKELY(uint32_t(dpy) >= DISPLAY_COUNT))
return BAD_VALUE;
if (!GLExtensions::getInstance().haveFramebufferObject())
return INVALID_OPERATION;
class MessageCaptureScreen : public MessageBase {
SurfaceFlinger* flinger;
DisplayID dpy;
sp<IMemoryHeap>* heap;
uint32_t* w;
uint32_t* h;
PixelFormat* f;
uint32_t sw;
uint32_t sh;
status_t result;
public:
MessageCaptureScreen(SurfaceFlinger* flinger, DisplayID dpy,
sp<IMemoryHeap>* heap, uint32_t* w, uint32_t* h, PixelFormat* f,
uint32_t sw, uint32_t sh)
: flinger(flinger), dpy(dpy),
heap(heap), w(w), h(h), f(f), sw(sw), sh(sh), result(PERMISSION_DENIED)
{
}
status_t getResult() const {
LOGI("getResult()");
return result;
}
virtual bool handler() {
LOGI("handler()");
Mutex::Autolock _l(flinger->mStateLock);
// if we have secure windows, never allow the screen capture
if (flinger->mSecureFrameBuffer)
return true;
result = flinger->captureScreenImplLocked(dpy,
heap, w, h, f, sw, sh);
return true;
}
};
LOGI("before messagecapturescreen");
sp<MessageBase> msg = new MessageCaptureScreen(this,
dpy, heap, width, height, format, sw, sh);
status_t res = postMessageSync(msg);
if (res == NO_ERROR) {
res = static_cast<MessageCaptureScreen*>( msg.get() )->getResult();
}
return res;
}
而這個(gè)函數(shù)關(guān)鍵又使用了opengl的幾個(gè)函數(shù)去獲得圖片，然而opengl又去read framebuffer（這是我的理解）。如果你去用jni調(diào)用so的方法去截屏的話，就可以把screencap這個(gè)文件稍微修改一下然后做成so文件。
主要是補(bǔ)充一下怎么去存放文件與編譯吧，當(dāng)然我說(shuō)的方法只是我做的方法不代表是很好用的。
存放：在eclipse新建一個(gè)android工程，保存后找到這個(gè)工程（如screencap）的存放位置 然后把這個(gè)文件放到android源代碼的development文件里面，然后在你的那個(gè)工程文件里面新建一個(gè)文件夾，名字叫做jni（這個(gè)文件夾平行于src文件夾，screencap/jni），把上面博客提到的那個(gè)C++跟mk（screencap/jni/com_android_ScreenCap_ScreenCapNative.cpp和screencap/jni/Android.mk）文件放進(jìn)去，最后在把編譯的mk文件放在screencap目錄下（screencap/Android.mk）;
編譯：編譯是個(gè)很偉大的工程，需要你花大量的時(shí)間與精力。直接在終端進(jìn)入工程存放的所在位置，我的是Administrator/Android.2.3.3/development，然后mm（Builds all of the modules in the current directory），如果成功，那么你運(yùn)氣比較好，在終端回提示你APK保存的位置。push進(jìn)手機(jī)試一試。但是往往是不成功的。你可能會(huì)遇到一些問(wèn)題，比如android.permission.ACCESS_SURFACE_FLINGER ,android.permission.READ_FRAME_BUFFER（因?yàn)閏apturescrren這個(gè)函數(shù)是surfaceflinger里面的函數(shù)，然而surfaceflinger里面的opengl截屏函數(shù)會(huì)去讀取framebuffer），相關(guān)源代碼是：
復(fù)制代碼 代碼如下:
status_t SurfaceFlinger::onTransact(
uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
switch (code) {
case CREATE_CONNECTION:
case OPEN_GLOBAL_TRANSACTION:
case CLOSE_GLOBAL_TRANSACTION:
case SET_ORIENTATION:
case FREEZE_DISPLAY:
case UNFREEZE_DISPLAY:
case BOOT_FINISHED:
case TURN_ELECTRON_BEAM_OFF:
case TURN_ELECTRON_BEAM_ON:
{
// codes that require permission check
IPCThreadState* ipc = IPCThreadState::self();
const int pid = ipc->getCallingPid();
const int uid = ipc->getCallingUid();
if ((uid != AID_GRAPHICS) && !mAccessSurfaceFlinger.check(pid, uid)) {
LOGE("Permission Denial: "
"can't access SurfaceFlinger pid=%d, uid=%d", pid, uid);
return PERMISSION_DENIED;
}
break;
}
case CAPTURE_SCREEN:
{
// codes that require permission check
IPCThreadState* ipc = IPCThreadState::self();
const int pid = ipc->getCallingPid();
const int uid = ipc->getCallingUid();
if ((uid != AID_GRAPHICS) && !mReadFramebuffer.check(pid, uid)) {
LOGE("Permission Denial: "
"can't read framebuffer pid=%d, uid=%d", pid, uid);
return PERMISSION_DENIED;
}
break;
}
}
status_t err = BnSurfaceComposer::onTransact(code, data, reply, flags);
if (err == UNKNOWN_TRANSACTION || err == PERMISSION_DENIED) {
CHECK_INTERFACE(ISurfaceComposer, data, reply);
if (UNLIKELY(!mHardwareTest.checkCalling())) {
IPCThreadState* ipc = IPCThreadState::self();
const int pid = ipc->getCallingPid();
const int uid = ipc->getCallingUid();
LOGI("err");
LOGE("Permission Denial: "
"can't access SurfaceFlinger pid=%d, uid=%d", pid, uid);
return PERMISSION_DENIED;
}
int n;
switch (code) {
case 1000: // SHOW_CPU, NOT SUPPORTED ANYMORE
case 1001: // SHOW_FPS, NOT SUPPORTED ANYMORE
return NO_ERROR;
case 1002: // SHOW_UPDATES
n = data.readInt32();
mDebugRegion = n ? n : (mDebugRegion ? 0 : 1);
return NO_ERROR;
case 1003: // SHOW_BACKGROUND
n = data.readInt32();
mDebugBackground = n ? 1 : 0;
return NO_ERROR;
case 1004:{ // repaint everything
Mutex::Autolock _l(mStateLock);
const DisplayHardware& hw(graphicPlane(0).displayHardware());
mDirtyRegion.set(hw.bounds()); // careful that's not thread-safe
signalEvent();
return NO_ERROR;
}
case 1005:{ // force transaction
setTransactionFlags(eTransactionNeeded|eTraversalNeeded);
return NO_ERROR;
}
case 1006:{ // enable/disable GraphicLog
int enabled = data.readInt32();
GraphicLog::getInstance().setEnabled(enabled);
return NO_ERROR;
}
case 1007: // set mFreezeCount
mFreezeCount = data.readInt32();
mFreezeDisplayTime = 0;
return NO_ERROR;
case 1010: // interrogate.
reply->writeInt32(0);
reply->writeInt32(0);
reply->writeInt32(mDebugRegion);
reply->writeInt32(mDebugBackground);
return NO_ERROR;
case 1013: {
Mutex::Autolock _l(mStateLock);
const DisplayHardware& hw(graphicPlane(0).displayHardware());
reply->writeInt32(hw.getPageFlipCount());
}
return NO_ERROR;
}
}
return err;
}
這個(gè)僅僅只是開始！ 你會(huì)發(fā)現(xiàn)你即使在xml里面添加相應(yīng)的權(quán)限仍然會(huì)有這個(gè)問(wèn)題出現(xiàn)，為什么呢？在packageManger文件里面發(fā)現(xiàn)相關(guān)代碼：
復(fù)制代碼 代碼如下:
int checkSignaturesLP(Signature[] s1, Signature[] s2) {
if (s1 == null) {
return s2 == null
? PackageManager.SIGNATURE_NEITHER_SIGNED
: PackageManager.SIGNATURE_FIRST_NOT_SIGNED;
}
if (s2 == null) {
return PackageManager.SIGNATURE_SECOND_NOT_SIGNED;
}
HashSet<Signature> set1 = new HashSet<Signature>();
for (Signature sig : s1) {
set1.add(sig);
}
HashSet<Signature> set2 = new HashSet<Signature>();
for (Signature sig : s2) {
set2.add(sig);
}
// Make sure s2 contains all signatures in s1.
if (set1.equals(set2)) {
return PackageManager.SIGNATURE_MATCH;
}
return PackageManager.SIGNATURE_NO_MATCH;
}
// Check for shared user signatures
if (pkgSetting.sharedUser != null && pkgSetting.sharedUser.signatures.mSignatures != null) {
if (checkSignaturesLP(pkgSetting.sharedUser.signatures.mSignatures,
pkg.mSignatures) != PackageManager.SIGNATURE_MATCH) {
Slog.e(TAG, "Package " + pkg.packageName
+ " has no signatures that match those in shared user "
+ pkgSetting.sharedUser.name + "; ignoring!");
mLastScanError = PackageManager.INSTALL_FAILED_SHARED_USER_INCOMPATIBLE;
return false;
}
}
return true;
private boolean verifySignaturesLP(PackageSetting pkgSetting,
PackageParser.Package pkg) {
// Check for shared user signatures
if (pkgSetting.sharedUser != null && pkgSetting.sharedUser.signatures.mSignatures != null) {
if (checkSignaturesLP(pkgSetting.sharedUser.signatures.mSignatures,
pkg.mSignatures) != PackageManager.SIGNATURE_MATCH) {
Slog.e(TAG, "Package " + pkg.packageName
+ " has no signatures that match those in shared user "
+ pkgSetting.sharedUser.name + "; ignoring!");
mLastScanError = PackageManager.INSTALL_FAILED_SHARED_USER_INCOMPATIBLE;
return false;
}
}
return true;
}
你在終端輸入adb logcat | grep PackageManager 你會(huì)發(fā)現(xiàn)這兩個(gè)權(quán)限根本沒有賦予給你的apk，我的理解是，程序需要權(quán)限，然后apk仍然需要權(quán)限。那怎么樣給apk賦予權(quán)限呢，兩個(gè)方法，一個(gè)是在我上面說(shuō)的screencap/Android.mk里面添加platform一行，然后在回到mm。還有一個(gè)方法就是通過(guò)sign。這兩個(gè)方法都是給apk賦予system權(quán)限，但是我試過(guò)這兩種方法，都有問(wèn)題，就是在adb install的時(shí)候會(huì)顯示簽名不兼容，查看源代碼會(huì)發(fā)現(xiàn)uid跟gid不匹配。這些是我這段時(shí)間發(fā)現(xiàn)的問(wèn)題，大家有問(wèn)題可以交流交流。
再說(shuō)說(shuō)幾個(gè)簡(jiǎn)單的應(yīng)用層截屏吧，很簡(jiǎn)單，就是幾個(gè)函數(shù)調(diào)用而已
復(fù)制代碼 代碼如下:
View view = getWindow().getDecorView();
Display display = this.getWindowManager().getDefaultDisplay();
view.layout(0, 0, display.getWidth(), display.getHeight());
view.setDrawingCacheEnabled(true);//允許當(dāng)前窗口保存緩存信息，這樣 getDrawingCache()方法才會(huì)返回一個(gè)Bitmap
Bitmap bmp = Bitmap.createBitmap(view.getDrawingCache());
我對(duì)這個(gè)程序的理解就是，它僅僅只能截取當(dāng)前的activity，也就是說(shuō)如果你運(yùn)行這個(gè)程序后它就截取你這個(gè)程序的當(dāng)前屏幕的信息。我們假設(shè)你做成一個(gè)按鈕，在點(diǎn)擊按鈕后sleep5秒再調(diào)用這個(gè)方法（假設(shè)你的activity叫做screen）。當(dāng)你點(diǎn)擊按鈕以后，然后你再點(diǎn)擊home或者返回按鈕，等到5秒后你那個(gè)程序就會(huì)截取到你當(dāng)前屏幕？不是！它只會(huì)截取那個(gè)運(yùn)行于后臺(tái)的screen這個(gè)activity。
這些只是我的一點(diǎn)小小的總結(jié)，而且肯定有不對(duì)的地方，希望大家一起來(lái)解決截屏的問(wèn)題！
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