android HOME点击事件的获取

浏览数：32 / 时间：2015年06月11日

首先声明我是做系统开发的(高通平台)，所以下面介绍的方法并不适合应用开发者。

最经有个需求要屏蔽HOME按键返回桌面并且实现自己的功能，发现以前的方式报错用不了，上网搜索了一下，发现都是抄来抄去基本是无用的。网上的方法不外乎这几种：

第一，大家最常用的重写onAttachedToWindow()方法，然后在HOME点击事件KeyEvent.KEYCODE_HOME中做自己想做的事情，但是这个方法google处于安全考虑在android2.3.3之后就不支持了。

第二，抓取系统log日志，判断有没有打印“android.intent.category.HOME”信息来获得是否按下了HOME按键，这样做就算代码知道是按下HOME键，那怎么阻止返回桌面呢？这只能是截获HOME按键，并不能屏蔽它返回桌面的功能。

第三，修改framework源码，在PhoneWindowManager中处理HOME按键的地方发送一个消息，然后在上层应用中捕获这个消息，这和上面是一样的，只能截获HOME按键，并不能阻止返回桌面的动作。

第四，在setContentView之前getWindow().setFlags(FLAG_HOMEKEY_DISPATCHED, FLAG_HOMEKEY_DISPATCHED); 这个FLAG_HOMEKEY_DISPATCHED其实是个标志位，是个常量，值为0x80000000，这个方法确实可以，但仅限于MTK(联发科)平台的系统，因为MTK自己实现了一套机制来规避HOME按键，而其它的平台，如高通、博通、展迅的代码中是没有加这个属性的，所以也不行。

还有极少数思路很极端的方式，看上去都觉得很繁琐，根本没耐心细看。

现在介绍我的思路，首先还是复写onAttachedToWindow()方法，具体代码是在activity中加入这一段：

@Override
public void onAttachedToWindow() {
this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);
super.onAttachedToWindow();

}

结果当然是一进入这个activity就报错，logcat查看错误信息，报的错误是"Window type can not be changed after the window is added."，发现是WindowManagerService.java中报的错，源码位置frameworks/base/services/java/com/android/server/wm/WindowManagerService.java，具体代码段是relayoutWindow方法中判断窗口类型的时候报错：

if (attrs != null) {
if (win.mAttrs.type != attrs.type) {
throw new IllegalArgumentException(
"Window type can not be changed after the window is added.");
}
flagChanges = win.mAttrs.flags ^= attrs.flags;
attrChanges = win.mAttrs.copyFrom(attrs);
if ((attrChanges & (WindowManager.LayoutParams.LAYOUT_CHANGED
| WindowManager.LayoutParams.SYSTEM_UI_VISIBILITY_CHANGED)) != 0) {
win.mLayoutNeeded = true;
}
}

刚才说了，google可能是出于安全原因不能让你把窗口类型设为WindowManager.LayoutParams.TYPE_KEYGUARD了，设置了就报错，要屏蔽这个错误只需要把if (win.mAttrs.type != attrs.type) {
throw new IllegalArgumentException(
"Window type can not be changed after the window is added.");
}

注释掉就行了，再次运行就不会报错了，但是按HOME键还是返回桌面。继续看分发HOME按键事件的代码，源码位置frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java中的if (keyCode == KeyEvent.KEYCODE_HOME) {...}中，这里就是处理上层用户按下HOME键的代码，在里面会看到// If a system window has focus, then it doesn‘t make sense
// right now to interact with applications.
WindowManager.LayoutParams attrs = win != null ? win.getAttrs() : null;
if (attrs != null) {
final int type = attrs.type;
if (type == WindowManager.LayoutParams.TYPE_KEYGUARD
|| type == WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG) {
// the "app" is keyguard, so give it the key
return 0;
}
final int typeCount = WINDOW_TYPES_WHERE_HOME_DOESNT_WORK.length;
for (int i=0; i<typeCount; i++) {
if (type == WINDOW_TYPES_WHERE_HOME_DOESNT_WORK[i]) {
// don‘t do anything, but also don‘t pass it to the app
return -1;
}
}
}

这一段代码，意思就是如果设置了窗口类型为 WindowManager.LayoutParams.TYPE_KEYGUARD(值为2004) 或者WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG，那就return 0，交给用户自己处理，不返回桌面，否则返回－1，返回桌面。通过打log发现代码确实是return 0，但还是返回桌面，后来才发现还有方法在返回桌面：/**
* A home key -> launch home action was detected. Take the appropriate action
* given the situation with the keyguard.
*/
void launchHomeFromHotKey() {
if (mKeyguardMediator != null && mKeyguardMediator.isShowingAndNotHidden()) {
// don‘t launch home if keyguard showing
} else if (!mHideLockScreen && mKeyguardMediator.isInputRestricted()) {
// when in keyguard restricted mode, must first verify unlock
// before launching home
mKeyguardMediator.verifyUnlock(new OnKeyguardExitResult() {
public void onKeyguardExitResult(boolean success) {
if (success) {
try {
ActivityManagerNative.getDefault().stopAppSwitches();
} catch (RemoteException e) {
}
sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);
startDockOrHome();
}
}
});
} else {
// no keyguard stuff to worry about, just launch home!
try {
ActivityManagerNative.getDefault().stopAppSwitches();
} catch (RemoteException e) {
}
sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);
startDockOrHome();
}
}

不知道高通怎么改的，就算return 0也会执行这个方法，也会返回桌面，因为这个方法在判断窗口类型前面调用，现在要做的就简单了，只需要加个判断，就可以屏蔽返回HOME了：

boolean isGoHome = true;
WindowManager.LayoutParams attrs = win != null ? win.getAttrs() : null;
if (attrs != null) {
final int type = attrs.type;
if (type == WindowManager.LayoutParams.TYPE_KEYGUARD) {
isGoHome = false;
}
}
// Go home!
if (isGoHome) {
launchHomeFromHotKey();
}

整个HOME按键的代码段：

// First we always handle the home key here, so applications
// can never break it, although if keyguard is on, we do let
// it handle it, because that gives us the correct 5 second
// timeout.
if (keyCode == KeyEvent.KEYCODE_HOME) {

// If we have released the home key, and didn‘t do anything else
// while it was pressed, then it is time to go home!
if (!down) {
cancelPreloadRecentApps();
mHomePressed = false;
if (mHomeConsumed) {
mHomeConsumed = false;
return -1;
}

if (canceled) {
Log.i(TAG, "Ignoring HOME; event canceled.");
return -1;
}

// If an incoming call is ringing, HOME is totally disabled.
// (The user is already on the InCallScreen at this point,
// and his ONLY options are to answer or reject the call.)
try {
ITelephony telephonyService = getTelephonyService();
if (telephonyService != null && telephonyService.isRinging()) {
Log.i(TAG, "Ignoring HOME; there‘s a ringing incoming call.");
return -1;
}
} catch (RemoteException ex) {
Log.w(TAG, "RemoteException from getPhoneInterface()", ex);
}

// Delay handling home if a double-tap is possible.
if (mDoubleTapOnHomeBehavior != DOUBLE_TAP_HOME_NOTHING) {
mHandler.removeCallbacks(mHomeDoubleTapTimeoutRunnable); // just in case
mHomeDoubleTapPending = true;
mHandler.postDelayed(mHomeDoubleTapTimeoutRunnable,
ViewConfiguration.getDoubleTapTimeout());
return -1;
}

boolean isGoHome = true;
WindowManager.LayoutParams attrs = win != null ? win.getAttrs() : null;
if (attrs != null) {
final int type = attrs.type;
if (type == WindowManager.LayoutParams.TYPE_KEYGUARD) {
isGoHome = false;
}
}
// Go home!
if (isGoHome) {
launchHomeFromHotKey();
}
return -1;
}

// If a system window has focus, then it doesn‘t make sense
// right now to interact with applications.
WindowManager.LayoutParams attrs = win != null ? win.getAttrs() : null;
if (attrs != null) {
final int type = attrs.type;
if (type == WindowManager.LayoutParams.TYPE_KEYGUARD
|| type == WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG) {
// the "app" is keyguard, so give it the key
return 0;
}
final int typeCount = WINDOW_TYPES_WHERE_HOME_DOESNT_WORK.length;
for (int i=0; i<typeCount; i++) {
if (type == WINDOW_TYPES_WHERE_HOME_DOESNT_WORK[i]) {
// don‘t do anything, but also don‘t pass it to the app
return -1;
}
}
}

// Remember that home is pressed and handle special actions.
if (repeatCount == 0) {
mHomePressed = true;
if (mHomeDoubleTapPending) {
mHomeDoubleTapPending = false;
mHandler.removeCallbacks(mHomeDoubleTapTimeoutRunnable);
handleDoubleTapOnHome();
} else if (mLongPressOnHomeBehavior == LONG_PRESS_HOME_RECENT_SYSTEM_UI
|| mDoubleTapOnHomeBehavior == DOUBLE_TAP_HOME_RECENT_SYSTEM_UI) {
preloadRecentApps();
}
} else if ((event.getFlags() & KeyEvent.FLAG_LONG_PRESS) != 0) {
if (!keyguardOn) {
handleLongPressOnHome();
}
}
return -1;
}