linux网站服务器搭建,电子商务网站建设怎么做,门户网站广告的类型,网上装修平台哪个最好今天这篇文章我们主要讲一下Android系统中的截屏事件处理流程。用过android系统手机的同学应该都知道#xff0c;一般的android手机按下音量减少键和电源按键就会触发截屏事件#xff08;国内定制机做个修改的这里就不做考虑了#xff09;。那么这里的截屏事件是如何触发的呢…今天这篇文章我们主要讲一下Android系统中的截屏事件处理流程。用过android系统手机的同学应该都知道一般的android手机按下音量减少键和电源按键就会触发截屏事件国内定制机做个修改的这里就不做考虑了。那么这里的截屏事件是如何触发的呢触发之后android系统是如何实现截屏操作的呢带着这两个问题开始我们的源码阅读流程。 我们知道这里的截屏事件是通过我们的按键操作触发的所以这里就需要我们从android系统的按键触发模块开始看起由于我们在不同的App页面操作音量减少键和电源键都会触发系统的截屏处理所以这里的按键触发逻辑应该是Android系统的全局按键处理逻辑。 在android系统中由于我们的每一个Android界面都是一个Activity而界面的显示都是通过Window对象实现的每个Window对象实际上都是PhoneWindow的实例而每个PhoneWindow对象都一个PhoneWindowManager对象当我们在Activity界面执行按键操作的时候在将按键的处理操作分发到App之前首先会回调PhoneWindowManager中的dispatchUnhandledKey方法该方法主要用于执行当前App处理按键之前的操作我们具体看一下该方法的实现。 /** {inheritDoc} */Overridepublic KeyEvent dispatchUnhandledKey(WindowState win, KeyEvent event, int policyFlags) {...KeyEvent fallbackEvent null;if ((event.getFlags() KeyEvent.FLAG_FALLBACK) 0) {final KeyCharacterMap kcm event.getKeyCharacterMap();final int keyCode event.getKeyCode();final int metaState event.getMetaState();final boolean initialDown event.getAction() KeyEvent.ACTION_DOWN event.getRepeatCount() 0;// Check for fallback actions specified by the key character map.final FallbackAction fallbackAction;if (initialDown) {fallbackAction kcm.getFallbackAction(keyCode, metaState);} else {fallbackAction mFallbackActions.get(keyCode);}if (fallbackAction ! null) {...final int flags event.getFlags() | KeyEvent.FLAG_FALLBACK;fallbackEvent KeyEvent.obtain(event.getDownTime(), event.getEventTime(),event.getAction(), fallbackAction.keyCode,event.getRepeatCount(), fallbackAction.metaState,event.getDeviceId(), event.getScanCode(),flags, event.getSource(), null);if (!interceptFallback(win, fallbackEvent, policyFlags)) {fallbackEvent.recycle();fallbackEvent null;}if (initialDown) {mFallbackActions.put(keyCode, fallbackAction);} else if (event.getAction() KeyEvent.ACTION_UP) {mFallbackActions.remove(keyCode);fallbackAction.recycle();}}}...return fallbackEvent;}这里我们关注一下方法体中调用的interceptFallback方法通过调用该方法将处理按键的操作下发到该方法中我们继续看一下该方法的实现逻辑。 private boolean interceptFallback(WindowState win, KeyEvent fallbackEvent, int policyFlags) {int actions interceptKeyBeforeQueueing(fallbackEvent, policyFlags);if ((actions ACTION_PASS_TO_USER) ! 0) {long delayMillis interceptKeyBeforeDispatching(win, fallbackEvent, policyFlags);if (delayMillis 0) {return true;}}return false;}然后我们看到在interceptFallback方法中我们调用了interceptKeyBeforeQueueing方法通过阅读我们我们知道该方法主要实现了对截屏按键的处理流程这样我们继续看一下interceptKeyBeforeWueueing方法的处理 Overridepublic int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {if (!mSystemBooted) {// If we have not yet booted, dont let key events do anything.return 0;}...// Handle special keys.switch (keyCode) {case KeyEvent.KEYCODE_VOLUME_DOWN:case KeyEvent.KEYCODE_VOLUME_UP:case KeyEvent.KEYCODE_VOLUME_MUTE: {if (mUseTvRouting) {// On TVs volume keys never go to the foreground appresult ~ACTION_PASS_TO_USER;}if (keyCode KeyEvent.KEYCODE_VOLUME_DOWN) {if (down) {if (interactive !mScreenshotChordVolumeDownKeyTriggered (event.getFlags() KeyEvent.FLAG_FALLBACK) 0) {mScreenshotChordVolumeDownKeyTriggered true;mScreenshotChordVolumeDownKeyTime event.getDownTime();mScreenshotChordVolumeDownKeyConsumed false;cancelPendingPowerKeyAction();interceptScreenshotChord();}} else {mScreenshotChordVolumeDownKeyTriggered false;cancelPendingScreenshotChordAction();}}...return result;}可以发现这里首先判断当前系统是否已经boot完毕若尚未启动完毕则所有的按键操作都将失效若启动完成则执行后续的操作这里我们只是关注音量减少按键和电源按键组合的处理事件。另外这里多说一句想安卓系统的HOME按键事件MENU按键事件进程列表按键事件等等都是在这里实现的后续中我们会陆续介绍这方面的内容。 回到我们的interceptKeyBeforeQueueing方法当我用按下音量减少按键的时候回进入到case KeyEvent.KEYCODE_VOLUME_MUTE分支并执行相应的逻辑然后同时判断用户是否按下了电源键若同时按下了电源键则执行 if (interactive !mScreenshotChordVolumeDownKeyTriggered (event.getFlags() KeyEvent.FLAG_FALLBACK) 0) {mScreenshotChordVolumeDownKeyTriggered true;mScreenshotChordVolumeDownKeyTime event.getDownTime();mScreenshotChordVolumeDownKeyConsumed false;cancelPendingPowerKeyAction();interceptScreenshotChord();}可以发现这里的interceptScreenshotChrod方法就是系统准备开始执行截屏操作的开始我们继续看一下interceptcreenshotChord方法的实现。 private void interceptScreenshotChord() {if (mScreenshotChordEnabled mScreenshotChordVolumeDownKeyTriggered mScreenshotChordPowerKeyTriggered !mScreenshotChordVolumeUpKeyTriggered) {final long now SystemClock.uptimeMillis();if (now mScreenshotChordVolumeDownKeyTime SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS now mScreenshotChordPowerKeyTime SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS) {mScreenshotChordVolumeDownKeyConsumed true;cancelPendingPowerKeyAction();mHandler.postDelayed(mScreenshotRunnable, getScreenshotChordLongPressDelay());}}}在方法体中我们最终会执行发送一个延迟的异步消息请求执行截屏的操作而这里的延时时间若当前输入框是打开状态则延时时间为输入框关闭时间加上系统配置的按键超时时间若当前输入框没有打开则直接是系统配置的按键超时处理时间可看一下getScreenshotChordLongPressDelay方法的具体实现。 private long getScreenshotChordLongPressDelay() {if (mKeyguardDelegate.isShowing()) {// Double the time it takes to take a screenshot from the keyguardreturn (long) (KEYGUARD_SCREENSHOT_CHORD_DELAY_MULTIPLIER *ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout());}return ViewConfiguration.get(mContext).getDeviceGlobalActionKeyTimeout();}回到我们的interceptScreenshotChord方法发送了异步消息之后系统最终会被我们发送的Runnable对象的run方法执行这里关于异步消息的逻辑可参考android源码解析之二– 异步消息机制 这样我们看一下Runnable类型的mScreenshotRunnable的run方法的实现: private final Runnable mScreenshotRunnable new Runnable() {Overridepublic void run() {takeScreenshot();}};好吧方法体中并未执行其他操作直接就是调用了takeScreenshot方法这样我们继续看一下takeScreenshot方法的实现。 private void takeScreenshot() {synchronized (mScreenshotLock) {if (mScreenshotConnection ! null) {return;}ComponentName cn new ComponentName(com.android.systemui,com.android.systemui.screenshot.TakeScreenshotService);Intent intent new Intent();intent.setComponent(cn);ServiceConnection conn new ServiceConnection() {Overridepublic 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()) {Overridepublic 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) {}}}Overridepublic void onServiceDisconnected(ComponentName name) {}};if (mContext.bindServiceAsUser(intent, conn, Context.BIND_AUTO_CREATE, UserHandle.CURRENT)) {mScreenshotConnection conn;mHandler.postDelayed(mScreenshotTimeout, 10000);}}}可以发现这里通过反射机制创建了一个TakeScreenshotService对象然后调用了bindServiceAsUser这样就创建了TakeScreenshotService服务并在服务创建之后发送了一个异步消息。好了我们看一下TakeScreenshotService的实现逻辑。 public class TakeScreenshotService extends Service {private static final String TAG TakeScreenshotService;private static GlobalScreenshot mScreenshot;private Handler mHandler new Handler() {Overridepublic 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);}}};Overridepublic IBinder onBind(Intent intent) {return new Messenger(mHandler).getBinder();} }可以发现在在TakeScreenshotService类的定义中有一个Handler成员变量而我们在启动TakeScreentshowService的时候回发送一个异步消息这样就会执行mHandler的handleMessage方法然后在handleMessage方法中我们创建了一个GlobalScreenshow对象然后执行了takeScreenshot方法好吧继续看一下takeScreentshot方法的执行逻辑。 /*** 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 orientationmDisplayMatrix.reset();mDisplayMatrix.preRotate(-degrees);mDisplayMatrix.mapPoints(dims);dims[0] Math.abs(dims[0]);dims[1] Math.abs(dims[1]);}// Take the screenshotmScreenBitmap SurfaceControl.screenshot((int) dims[0], (int) dims[1]);if (mScreenBitmap null) {notifyScreenshotError(mContext, mNotificationManager);finisher.run();return;}if (requiresRotation) {// Rotate the screenshot to the current orientationBitmap 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);// Recycle the previous bitmapmScreenBitmap.recycle();mScreenBitmap ss;}// OptimizationsmScreenBitmap.setHasAlpha(false);mScreenBitmap.prepareToDraw();// Start the post-screenshot animationstartAnimation(finisher, mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels,statusBarVisible, navBarVisible);}可以看到这里后两个参数statusBarVisiblenavBarVisible是否可见而这两个参数在我们PhoneWindowManager.takeScreenshot方法传递的 if (mStatusBar ! null mStatusBar.isVisibleLw())msg.arg1 1;if (mNavigationBar ! null mNavigationBar.isVisibleLw())msg.arg2 1;可见若果mStatusBar可见则传递的statusBarVisible为true若mNavigationBar可见则传递的navBarVisible为true。然后我们在截屏的时候判断nStatusBar是否可见mNavigationBar是否可见若可见的时候则截屏同样将其截屏出来。继续回到我们的takeScreenshot方法然后调用了 // Take the screenshot mScreenBitmap SurfaceControl.screenshot((int) dims[0], (int) dims[1]);方法看注释这里就是执行截屏事件的具体操作了然后我看一下SurfaceControl.screenshot方法的具体实现另外这里需要注意的是截屏之后返回的是一个Bitmap对象其实熟悉android绘制机制的童鞋应该知道android中所有显示能够显示的东西在内存中表现都是Bitmap对象。 public static Bitmap screenshot(int width, int height) {// TODO: should take the display as a parameterIBinder displayToken SurfaceControl.getBuiltInDisplay(SurfaceControl.BUILT_IN_DISPLAY_ID_MAIN);return nativeScreenshot(displayToken, new Rect(), width, height, 0, 0, true,false, Surface.ROTATION_0);}好吧这里调用的是nativeScreenshot方法它是一个native方法具体的实现在JNI层这里就不做过多的介绍了。继续回到我们的takeScreenshot方法在调用了截屏方法screentshot之后判断是否截屏成功 if (mScreenBitmap null) {notifyScreenshotError(mContext, mNotificationManager);finisher.run();return;}若截屏之后截屏的bitmap对象为空这里判断截屏失败调用了notifyScreenshotError方法发送截屏失败的notification通知。 static void notifyScreenshotError(Context context, NotificationManager nManager) {Resources r context.getResources();// Clear all existing notification, compose the new notification and show itNotification.Builder b new Notification.Builder(context).setTicker(r.getString(R.string.screenshot_failed_title)).setContentTitle(r.getString(R.string.screenshot_failed_title)).setContentText(r.getString(R.string.screenshot_failed_text)).setSmallIcon(R.drawable.stat_notify_image_error).setWhen(System.currentTimeMillis()).setVisibility(Notification.VISIBILITY_PUBLIC) // ok to show outside lockscreen.setCategory(Notification.CATEGORY_ERROR).setAutoCancel(true).setColor(context.getColor(com.android.internal.R.color.system_notification_accent_color));Notification n new Notification.BigTextStyle(b).bigText(r.getString(R.string.screenshot_failed_text)).build();nManager.notify(R.id.notification_screenshot, n);}然后继续看takeScreenshot方法判断截屏的图像是否需要旋转若需要的话则旋转图像 if (requiresRotation) {// Rotate the screenshot to the current orientationBitmap 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);// Recycle the previous bitmapmScreenBitmap.recycle();mScreenBitmap ss;}在takeScreenshot方法的最后若截屏成功我们调用了 // Start the post-screenshot animationstartAnimation(finisher, mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels,statusBarVisible, navBarVisible);开始截屏的动画好吧看一下动画效果的实现 /*** Starts the animation after taking the screenshot*/private void startAnimation(final Runnable finisher, int w, int h, boolean statusBarVisible,boolean navBarVisible) {// Add the view for the animationmScreenshotView.setImageBitmap(mScreenBitmap);mScreenshotLayout.requestFocus();// Setup the animation with the screenshot just takenif (mScreenshotAnimation ! null) {mScreenshotAnimation.end();mScreenshotAnimation.removeAllListeners();}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() {Overridepublic void onAnimationEnd(Animator animation) {// Save the screenshot once we have a bit of time nowsaveScreenshotInWorkerThread(finisher);mWindowManager.removeView(mScreenshotLayout);// Clear any references to the bitmapmScreenBitmap null;mScreenshotView.setImageBitmap(null);}});mScreenshotLayout.post(new Runnable() {Overridepublic void run() {// Play the shutter sound to notify that weve taken a screenshotmCameraSound.play(MediaActionSound.SHUTTER_CLICK);mScreenshotView.setLayerType(View.LAYER_TYPE_HARDWARE, null);mScreenshotView.buildLayer();mScreenshotAnimation.start();}});}好吧经过着一些列的操作之后我们实现了截屏之后的动画效果了这里暂时不分析动画效果我们看一下动画效果之后做了哪些还记不记的一般情况下我们截屏之后都会收到一个截屏的notification通知这里应该也是在其AnimatorListenerAdapter的onAnimationEnd方法中实现的也就是动画执行完成之后我们看一下其saveScreenshotInWorkerThread方法的实现 /*** 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;data.previewWidth mPreviewWidth;data.previewheight mPreviewHeight;if (mSaveInBgTask ! null) {mSaveInBgTask.cancel(false);}mSaveInBgTask new SaveImageInBackgroundTask(mContext, data, mNotificationManager,R.id.notification_screenshot).execute(data);}好吧这里主要逻辑就是构造了一个SaveImageInBackgroundTask对象看样子发送截屏成功的通知应该是在这里实现的我们看一下SaveImageInBackgroundTask构造方法的实现逻辑 SaveImageInBackgroundTask(Context context, SaveImageInBackgroundData data,NotificationManager nManager, int nId) {...// Show the intermediate notificationmTickerAddSpace !mTickerAddSpace;mNotificationId nId;mNotificationManager nManager;final long now System.currentTimeMillis();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(now).setColor(r.getColor(com.android.internal.R.color.system_notification_accent_color));mNotificationStyle new Notification.BigPictureStyle().bigPicture(picture.createAshmemBitmap());mNotificationBuilder.setStyle(mNotificationStyle);// For public situations we want to show all the same info but// omit the actual screenshot image.mPublicNotificationBuilder new Notification.Builder(context).setContentTitle(r.getString(R.string.screenshot_saving_title)).setContentText(r.getString(R.string.screenshot_saving_text)).setSmallIcon(R.drawable.stat_notify_image).setCategory(Notification.CATEGORY_PROGRESS).setWhen(now).setColor(r.getColor(com.android.internal.R.color.system_notification_accent_color));mNotificationBuilder.setPublicVersion(mPublicNotificationBuilder.build());Notification n mNotificationBuilder.build();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(icon.createAshmemBitmap());// But we still dont set it for the expanded view, allowing the smallIcon to show here.mNotificationStyle.bigLargeIcon((Bitmap) null);}可以发现在构造方法的后面狗仔了一个NotificationBuilder对象然后发送了一个截屏成功的Notification 这样我们在截屏动画之后就收到了Notification的通知了。 总结 在PhoneWindowManager的dispatchUnhandledKey方法中处理App无法处理的按键事件当然也包括音量减少键和电源按键的组合按键 通过一系列的调用启动TakeScreenshotService服务并通过其执行截屏的操作。 具体的截屏代码是在native层实现的。 截屏操作时候若截屏失败则直接发送截屏失败的notification通知。 截屏之后若截屏成功则先执行截屏的动画并在动画效果执行完毕之后发送截屏成功的notification的通知 以上就是本文的全部内容希望对大家的学习有所帮助。 更多Android进阶指南 可以扫码 解锁 《Android十大板块文档》 1.Android车载应用开发系统学习指南附项目实战 2.Android Framework学习指南助力成为系统级开发高手 3.2023最新Android中高级面试题汇总解析告别零offer 4.企业级Android音视频开发学习路线项目实战附源码 5.Android Jetpack从入门到精通构建高质量UI界面 6.Flutter技术解析与实战跨平台首要之选 7.Kotlin从入门到实战全方面提升架构基础 8.高级Android插件化与组件化含实战教程和源码 9.Android 性能优化实战360°全方面性能调优 10.Android零基础入门到精通高手进阶之路 敲代码不易关注一下吧。ღ( ´ᴗ )