Android4.0 源码-Screenshot 截屏流程分析

LOG： I/ActivityManager(  195): Start proc com.android.systemui:screenshot for service com.android.systemui/.screenshot.TakeScreenshotServ}

1)  按下组合键，进如PhoneWindowManager.java (/framework/base/policy/src/com/android/internal/policy/impl )

 public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags, boolean isScreenOn) {
        final boolean down = event.getAction() == KeyEvent.ACTION_DOWN;
        final boolean canceled = event.isCanceled();
        final int keyCode = event.getKeyCode();
        ....

       switch (keyCode) {
           ....
                if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) {
                    if (down) {
                        if (isScreenOn && !mVolumeDownKeyTriggered
                                && (event.getFlags() & KeyEvent.FLAG_FALLBACK) == 0) {
                            mVolumeDownKeyTriggered = true;
                            mVolumeDownKeyTime = event.getDownTime();
                            mVolumeDownKeyConsumedByScreenshotChord = false;
                            cancelPendingPowerKeyAction();
                            interceptScreenshotChord();
                      Slog.d(TAG,"[Paul]interceptKeyBeforeQueueing.........Call  interceptScreenshotChord().... 1 "); //按组合键之后先到这 
                        }
                    } else {
                        mVolumeDownKeyTriggered = false;
                        cancelPendingScreenshotChordAction();
                     Slog.d(TAG,"[Paul]interceptKeyBeforeQueueing.........Call cancelPendingScreenshotChordAction().... 2 "); //按键放手到这
            
                    }
                } else if (keyCode == KeyEvent.KEYCODE_VOLUME_UP) {
                       .... 

 }

2)Call interceptScreenshotChord() 方法；

 private void cancelPendingPowerKeyAction() {
        if (!mPowerKeyHandled) {
            mHandler.removeCallbacks(mPowerLongPress);
        }
        if (mPowerKeyTriggered) {
            mPendingPowerKeyUpCanceled = true;
                      Slog.d(TAG,"[Paul]cancelPendingPowerKeyAction...........5 "); //paul
        }
    }

    private void interceptScreenshotChord() {
        if (mVolumeDownKeyTriggered && mPowerKeyTriggered && !mVolumeUpKeyTriggered) {
            final long now = SystemClock.uptimeMillis();
            if (now <= mVolumeDownKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS
                    && now <= mPowerKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS) {
                mVolumeDownKeyConsumedByScreenshotChord = true;
                cancelPendingPowerKeyAction();
                      Slog.d(TAG,"[Paul]interceptScreenshotChord...........6 "); //paul
                mHandler.postDelayed(mScreenshotChordLongPress,
                        ViewConfiguration.getGlobalActionKeyTimeout());
            }
        }
    }

3）运行takeScreenshot() 方法：

 private final Runnable mScreenshotChordLongPress = new Runnable() {
        public void run() {
                      Slog.d(TAG,"[Paul]mScreenshotChordLongPress...........7 "); //paul
            takeScreenshot();
        }
    };

4）哈哈  跑到TakeScreenshotService里去了

  private void takeScreenshot() {
        synchronized (mScreenshotLock) {
            if (mScreenshotConnection != null) {
                return;
            }
            ComponentName cn = new ComponentName("com.android.systemui",
                    "com.android.systemui.screenshot.TakeScreenshotService");
                      Slog.d(TAG,"[Paul]takeScreenshot()...................8 "); //paul
            Intent intent = new Intent();
            intent.setComponent(cn);
            ServiceConnection conn = new ServiceConnection() {
                @Override
                public void onServiceConnected(ComponentName name, IBinder service) {
                    synchronized (mScreenshotLock) {
                        if (mScreenshotConnection != this) {
                            return;
                        }
                        Messenger messenger = new Messenger(service);
                        Message msg = Message.obtain(null, 1);
                        final ServiceConnection myConn = this;
                        Handler h = new Handler(mHandler.getLooper()) {
                            @Override
                            public void handleMessage(Message msg) {
                                synchronized (mScreenshotLock) {
                                    if (mScreenshotConnection == myConn) {
                                        mContext.unbindService(mScreenshotConnection);
                                        mScreenshotConnection = null;
                                        mHandler.removeCallbacks(mScreenshotTimeout);
                                    }
                                }
                            }
                        };
                        msg.replyTo = new Messenger(h);
                        msg.arg1 = msg.arg2 = 0;
                        if (mStatusBar != null && mStatusBar.isVisibleLw())
                            msg.arg1 = 1;
                        if (mNavigationBar != null && mNavigationBar.isVisibleLw())
                            msg.arg2 = 1;
                        try {
                            messenger.send(msg);
                        } catch (RemoteException e) {
                        }
                    }
                }
                @Override
                public void onServiceDisconnected(ComponentName name) {}
            };
            if (mContext.bindService(intent, conn, Context.BIND_AUTO_CREATE)) {
                mScreenshotConnection = conn;
                mHandler.postDelayed(mScreenshotTimeout, 10000);
            }
        }
    }

5）TakeScreenshotService.java  (/frameworks/base/packages/SystemUI/src/com/android/systemui/screenshot )

     

public class TakeScreenshotService extends Service {
    private static final String TAG = "TakeScreenshotService";

    private static GlobalScreenshot mScreenshot;

    private Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case 1:
                    final Messenger callback = msg.replyTo;
                    if (mScreenshot == null) {
                        mScreenshot = new GlobalScreenshot(TakeScreenshotService.this);
                    }
                    mScreenshot.takeScreenshot(new Runnable() {
                        @Override public void run() {
                            Message reply = Message.obtain(null, 1);
                            try {
                                callback.send(reply);
                            } catch (RemoteException e) {
                            }
                        }
                    }, msg.arg1 > 0, msg.arg2 > 0);
            }
        }
    };

6) GlobalScreenshot.java (/frameworks/base/packages/SystemUI/src/com/android/systemui/screenshot )  终于找到真相了，隐藏在这里！这个方法会完成截图动作，以及显示动画。

 /**
     * Takes a screenshot of the current display and shows an animation.
     */
    void takeScreenshot(Runnable finisher, boolean statusBarVisible, boolean navBarVisible) {
        // We need to orient the screenshot correctly (and the Surface api seems to take screenshots
        // only in the natural orientation of the device :!)
        mDisplay.getRealMetrics(mDisplayMetrics);
        float[] dims = {mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels};
        float degrees = getDegreesForRotation(mDisplay.getRotation());
        boolean requiresRotation = (degrees > 0);
        if (requiresRotation) {
            // Get the dimensions of the device in its native orientation
            mDisplayMatrix.reset();
            mDisplayMatrix.preRotate(-degrees);
            mDisplayMatrix.mapPoints(dims);
            dims[0] = Math.abs(dims[0]);
            dims[1] = Math.abs(dims[1]);
        }

        // Take the screenshot
        mScreenBitmap = Surface.screenshot((int) dims[0], (int) dims[1]);
        if (mScreenBitmap == null) {
            notifyScreenshotError(mContext, mNotificationManager);
            finisher.run();
            return;
        }

        if (requiresRotation) {
            // Rotate the screenshot to the current orientation
            Bitmap ss = Bitmap.createBitmap(mDisplayMetrics.widthPixels,
                    mDisplayMetrics.heightPixels, Bitmap.Config.ARGB_8888);
            Canvas c = new Canvas(ss);
            c.translate(ss.getWidth() / 2, ss.getHeight() / 2);
            c.rotate(degrees);
            c.translate(-dims[0] / 2, -dims[1] / 2);
            c.drawBitmap(mScreenBitmap, 0, 0, null);
            c.setBitmap(null);
            mScreenBitmap = ss;
        }

        // Optimizations
        mScreenBitmap.setHasAlpha(false);
        mScreenBitmap.prepareToDraw();

        // Start the post-screenshot animation
        startAnimation(finisher, mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels,
                statusBarVisible, navBarVisible);
    }


private void startAnimation(final Runnable finisher, int w, int h, boolean statusBarVisible,
            boolean navBarVisible) {
        // Add the view for the animation
        mScreenshotView.setImageBitmap(mScreenBitmap);
        mScreenshotLayout.requestFocus();

        // Setup the animation with the screenshot just taken
        if (mScreenshotAnimation != null) {
            mScreenshotAnimation.end();
        }

        mWindowManager.addView(mScreenshotLayout, mWindowLayoutParams);
        ValueAnimator screenshotDropInAnim = createScreenshotDropInAnimation();
        ValueAnimator screenshotFadeOutAnim = createScreenshotDropOutAnimation(w, h,
                statusBarVisible, navBarVisible);
        mScreenshotAnimation = new AnimatorSet();
        mScreenshotAnimation.playSequentially(screenshotDropInAnim, screenshotFadeOutAnim);
        mScreenshotAnimation.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                // Save the screenshot once we have a bit of time now
                saveScreenshotInWorkerThread(finisher);
                mWindowManager.removeView(mScreenshotLayout);
            }
        });
        mScreenshotLayout.post(new Runnable() {
            @Override
            public void run() {
                // Play the shutter sound to notify that we've taken a screenshot
                mCameraSound.playSound(CameraSound.SHUTTER_CLICK);  //截图会播放快门音啊

                mScreenshotView.setLayerType(View.LAYER_TYPE_HARDWARE, null);
                mScreenshotView.buildLayer();
                mScreenshotAnimation.start();
            }
        });

接下来关键看把截图的图片存放在何处？！

7）还是刚刚上面的那个类里。

/**
     * Creates a new worker thread and saves the screenshot to the media store.
     */
    private void saveScreenshotInWorkerThread(Runnable finisher) {
        SaveImageInBackgroundData data = new SaveImageInBackgroundData();
        data.context = mContext;
        data.image = mScreenBitmap;
        data.iconSize = mNotificationIconSize;
        data.finisher = finisher;
        new SaveImageInBackgroundTask(mContext, data, mNotificationManager,
                SCREENSHOT_NOTIFICATION_ID).execute(data);
    }

8）这回是到类外个类里面，发现在这里有environment里面的成员。

SaveImageInBackgroundTask(Context context, SaveImageInBackgroundData data,
            NotificationManager nManager, int nId) {
        Resources r = context.getResources();

        // Prepare all the output metadata
        mImageTime = System.currentTimeMillis();
        String imageDate = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date(mImageTime));
        String imageDir = Environment.getExternalStoragePublicDirectory(
                Environment.DIRECTORY_PICTURES).getAbsolutePath();
        mImageFileName = String.format(SCREENSHOT_FILE_NAME_TEMPLATE, imageDate);
        mImageFilePath = String.format(SCREENSHOT_FILE_PATH_TEMPLATE, imageDir,
                SCREENSHOTS_DIR_NAME, mImageFileName);

        // Create the large notification icon
        int imageWidth = data.image.getWidth();
        int imageHeight = data.image.getHeight();
        int iconWidth = data.iconSize;
        int iconHeight = data.iconSize;
        if (imageWidth > imageHeight) {
            iconWidth = (int) (((float) iconHeight / imageHeight) * imageWidth);
        } else {
            iconHeight = (int) (((float) iconWidth / imageWidth) * imageHeight);
        }
        Bitmap rawIcon = Bitmap.createScaledBitmap(data.image, iconWidth, iconHeight, true);
        Bitmap croppedIcon = Bitmap.createBitmap(rawIcon, (iconWidth - data.iconSize) / 2,
                (iconHeight - data.iconSize) / 2, data.iconSize, data.iconSize);

        // Show the intermediate notification
        mTickerAddSpace = !mTickerAddSpace;
        mNotificationId = nId;
        mNotificationManager = nManager;
        mNotificationBuilder = new Notification.Builder(context)
            .setTicker(r.getString(R.string.screenshot_saving_ticker)
                    + (mTickerAddSpace ? " " : ""))
            .setContentTitle(r.getString(R.string.screenshot_saving_title))
            .setContentText(r.getString(R.string.screenshot_saving_text))
            .setSmallIcon(R.drawable.stat_notify_image)
            .setWhen(System.currentTimeMillis());
        Notification n = mNotificationBuilder.getNotification();
        n.flags |= Notification.FLAG_NO_CLEAR;
        mNotificationManager.notify(nId, n);

        // On the tablet, the large icon makes the notification appear as if it is clickable (and
        // on small devices, the large icon is not shown) so defer showing the large icon until
        // we compose the final post-save notification below.
        mNotificationBuilder.setLargeIcon(croppedIcon);
    }

9）Environment.java (framework/base/core/java/android/os )

public static File getExternalStoragePublicDirectory(String type) {
        return new File(getExternalStorageDirectory(), type);
    }

   public static File getExternalStorageDirectory() {
        return EXTERNAL_STORAGE_DIRECTORY;
    }

 private static final File EXTERNAL_STORAGE_DIRECTORY
            = getDirectory("EXTERNAL_STORAGE", "/mnt/sdcard");

终于截图功能基本上分析完成，存放路径也找到，很简单，一路下来~~ENVIRONMENT.JAVA 里面好多资源啊：

参考如下：http://blog.youkuaiyun.com/djpraul/article/details/8727534