如何在Android 12 aosp系统源码中添加三指下滑截图功能

系统中截图api非常简单：

private static ScreenshotHelper sScreenshotHelper;sScreenshotHelper = new ScreenshotHelper(mContext);//调用
sScreenshotHelper.takeScreenshot(WindowManager.TAKE_SCREENSHOT_FULLSCREEN, true, true, mScreenShotHandler, null);

如果在系统中添加三指下滑监听了：

首先找到：

我们这里基于Android12 源码

首先找到：SystemGesturesPointerEventListener类，这里面有监听系统滑动手势的地方：

找到下面代码添加手势判断：

    private int detectSwipe(int i, long time, float x, float y) {final float fromX = mDownX[i];final float fromY = mDownY[i];final long elapsed = time - mDownTime[i];if (DEBUG) Slog.d(TAG, "pointer " + mDownPointerId[i]+ " moved (" + fromX + "->" + x + "," + fromY + "->" + y + ") in " + elapsed);//添加三指下滑判断float xDistance = Math.abs(x - fromX);float yDistance = Math.abs(y - fromY);if (fromY >= mSwipeStartThreshold * 2&& yDistance > xDistance&& y > fromY + mSwipeDistanceThreshold&& elapsed < SWIPE_TIMEOUT_MS) {return SWIPE_FROM_CENTER_TO_DOWN;}if (fromY <= mSwipeStartThreshold&& y > fromY + mSwipeDistanceThreshold&& elapsed < SWIPE_TIMEOUT_MS) {return SWIPE_FROM_TOP;}if (fromY >= screenHeight - mSwipeStartThreshold&& y < fromY - mSwipeDistanceThreshold&& elapsed < SWIPE_TIMEOUT_MS) {return SWIPE_FROM_BOTTOM;}if (fromX >= screenWidth - mSwipeStartThreshold&& x < fromX - mSwipeDistanceThreshold&& elapsed < SWIPE_TIMEOUT_MS) {return SWIPE_FROM_RIGHT;}if (fromX <= mSwipeStartThreshold&& x > fromX + mSwipeDistanceThreshold&& elapsed < SWIPE_TIMEOUT_MS) {return SWIPE_FROM_LEFT;}return SWIPE_NONE;}

再找到这个方法：

public void onPointerEvent(MotionEvent event)

在里面添加代码：

            case MotionEvent.ACTION_MOVE:if (mSwipeFireable) {final int swipe = detectSwipe(event);mSwipeFireable = swipe == SWIPE_NONE;if (swipe == SWIPE_FROM_TOP) {if (DEBUG) Slog.d(TAG, "Firing onSwipeFromTop");mCallbacks.onSwipeFromTop();} else if (swipe == SWIPE_FROM_BOTTOM) {if (DEBUG) Slog.d(TAG, "Firing onSwipeFromBottom");mCallbacks.onSwipeFromBottom();} else if (swipe == SWIPE_FROM_RIGHT) {if (DEBUG) Slog.d(TAG, "Firing onSwipeFromRight");mCallbacks.onSwipeFromRight();} else if (swipe == SWIPE_FROM_LEFT) {if (DEBUG) Slog.d(TAG, "Firing onSwipeFromLeft");mCallbacks.onSwipeFromLeft();} else if (swipe == SWIPE_FROM_CENTER_TO_DOWN) {if (DEBUG) Slog.d(TAG, "Firing onSwipeFromCenterToDown:" + event.getPointerCount());//判断三指开始截图if (event.getPointerCount() == 3) {sScreenshotHelper.takeScreenshot(WindowManager.TAKE_SCREENSHOT_FULLSCREEN, true, true, mScreenShotHandler, null);}}}break;

那么三指截图就完成了！！！！

是不是很干，没有水分，有用记得点赞收藏。

补充：

private static final int SWIPE_FROM_CENTER_TO_DOWN = 5;