Android的全局键（home键/长按耳机键）详解【android源码解析八】

来源：互联网发布：禁止网络医疗平台编辑：程序博客网时间：2024/04/30 03:49

如果想在Android手机要想扩展一个实体键，就我知道而言有两种方法，基于Android4.0的源码来分析的和2.3的源码有点区别，区别不大，下面分享给大家：

转载请标明出处：

（一）可以在frameworks层的KeyEvent.java这个类中定义一个值，在PhoneWindowManager.java这个类中做处理就可以了。（Home键就是这么实现的）。效果图如下：

（二）可以利用广播的形式，frameworks层PhoneWindow.java这个类的onKeyDown( )对这个实体键发广播，上层接受这个广播来处理也可以达到这个效果。耳机键就是利用广播来接受的。无论在哪个界面长按耳机键，都会进入到音乐的界面。（长按耳机键的）效果图如下：

下面我详细展开来说明一下：

一、先说Home键的实现的大致流程，即---->为什么点击Home键，都进入到launcher的待机界面；

（1）Home键的定义在

step1: frameworks/base/core/java/android/view/KeyEvent.java这个类中,在KeyEvent.java这个类中有个static的静态块：

[java] view plaincopyprint?
static {
populateKeycodeSymbolicNames();
}


step2: 这个populateKeycodeSymbolicNames（）方法其实就是加载了许多键的定义，把这些键对应的值都放到Array数组中。

[java] view plaincopyprint?
private static void populateKeycodeSymbolicNames() {
SparseArray<String> names = KEYCODE_SYMBOLIC_NAMES;
names.append(KEYCODE_UNKNOWN, "KEYCODE_UNKNOWN");
names.append(KEYCODE_SOFT_LEFT, "KEYCODE_SOFT_LEFT");
names.append(KEYCODE_SOFT_RIGHT, "KEYCODE_SOFT_RIGHT");
names.append(KEYCODE_HOME, "KEYCODE_HOME");
names.append(KEYCODE_BACK, "KEYCODE_BACK");
names.append(KEYCODE_CALL, "KEYCODE_CALL");
names.append(KEYCODE_ENDCALL, "KEYCODE_ENDCALL");
names.append(KEYCODE_0, "KEYCODE_0");
names.append(KEYCODE_1, "KEYCODE_1");
names.append(KEYCODE_2, "KEYCODE_2");
names.append(KEYCODE_3, "KEYCODE_3");
names.append(KEYCODE_4, "KEYCODE_4");
names.append(KEYCODE_5, "KEYCODE_5");
names.append(KEYCODE_6, "KEYCODE_6");
names.append(KEYCODE_7, "KEYCODE_7");
names.append(KEYCODE_8, "KEYCODE_8");
names.append(KEYCODE_9, "KEYCODE_9");

step3: 而Home键对应的值如下：

[java] view plaincopyprint?
/** Key code constant: Home key.
* This key is handled by the framework and is never delivered to applications. */
public static final int KEYCODE_HOME = 3;

（2）Home键的处理如下：在
step1: frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java这个类中：

在这个方法interceptKeyBeforeDispatching（... ... ...）中处理有对Home，Search，menu，音量大小键等等：

[java] view plaincopyprint?
 /** {@inheritDoc} */
@Override
public long interceptKeyBeforeDispatching(WindowState win, KeyEvent event, int policyFlags) {
final boolean keyguardOn = keyguardOn();
final int keyCode = event.getKeyCode();
final int repeatCount = event.getRepeatCount();
final int metaState = event.getMetaState();
final int flags = event.getFlags();
final boolean down = event.getAction() == KeyEvent.ACTION_DOWN;
final boolean canceled = event.isCanceled();

if (false) {
Log.d(TAG, "interceptKeyTi keyCode=" + keyCode + " down=" + down + " repeatCount="
+ repeatCount + " keyguardOn=" + keyguardOn + " mHomePressed=" + mHomePressed);
}

// If we think we might have a volume down & power key chord on the way
// but we're not sure, then tell the dispatcher to wait a little while and
// try again later before dispatching.
if ((flags & KeyEvent.FLAG_FALLBACK) == 0) {
if (mVolumeDownKeyTriggered && !mPowerKeyTriggered) {
final long now = SystemClock.uptimeMillis();
final long timeoutTime = mVolumeDownKeyTime + SCREENSHOT_CHORD_DEBOUNCE_DELAY_MILLIS;
if (now < timeoutTime) {
return timeoutTime - now;
}
}
if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN
&& mVolumeDownKeyConsumedByScreenshotChord) {
if (!down) {
mVolumeDownKeyConsumedByScreenshotChord = false;
}
return -1;
}
}

// 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 (mHomePressed && !down) {
mHomePressed = false;
if (!canceled) {
// 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.)
boolean incomingRinging = false;
try {
ITelephony telephonyService = getTelephonyService();
if (telephonyService != null) {
incomingRinging = telephonyService.isRinging();
}
} catch (RemoteException ex) {
Log.w(TAG, "RemoteException from getPhoneInterface()", ex);
}

if (incomingRinging) {
Log.i(TAG, "Ignoring HOME; there's a ringing incoming call.");
} else {
launchHomeFromHotKey();
}
} else {
Log.i(TAG, "Ignoring HOME; event canceled.");
}
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;
}
}
}

if (down) {
if (repeatCount == 0) {
mHomePressed = true;
} else if ((event.getFlags() & KeyEvent.FLAG_LONG_PRESS) != 0) {
if (!keyguardOn) {
handleLongPressOnHome();
}
}
}
return -1;
} else if (keyCode == KeyEvent.KEYCODE_MENU) {
........
[java] view plaincopyprint?


 Step2: 插曲《网上有例子说怎么在自己的应用中屏蔽Home键》--->原理：是在你的应用的Activity中加入了锁屏的type，因为系统对锁屏界面，点击Home键失效！网摘代码如下：
[java] view plaincopyprint?
public class DMActivity extends Activity {

private boolean flag = true;//true位屏蔽，false位不屏蔽

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
@Override
public void onAttachedToWindow() {
if(flag) {
this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);
}
super.onAttachedToWindow();
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(keyCode == KeyEvent.KEYCODE_HOME){
return true;
}
return super.onKeyDown(keyCode, event);
}
}


Step3: 真正的原因如下，对锁屏模式的处理：

[java] view plaincopyprint?
 // 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;
}
}
}

Step4: 我们来看点击home键，为什么进入到launcher的待机界面：

[java] view plaincopyprint?
// 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 (mHomePressed && !down) {
mHomePressed = false;
if (!canceled) {
// 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.)
boolean incomingRinging = false;
try {
ITelephony telephonyService = getTelephonyService();
if (telephonyService != null) {
incomingRinging = telephonyService.isRinging();
}
} catch (RemoteException ex) {
Log.w(TAG, "RemoteException from getPhoneInterface()", ex);
}

if (incomingRinging) {
Log.i(TAG, "Ignoring HOME; there's a ringing incoming call.");
} else {
launchHomeFromHotKey();
}
} else {
Log.i(TAG, "Ignoring HOME; event canceled.");
}
return -1;
}

Step5: 系统会判断，当前点击Home键并且没有电话打入的情况，才对Home键进行处理---->launchHomeFromHotKey();进入到----->launchHomeFromHotKey()方法中：

[java] view plaincopyprint?
/**
* A home key -> launch home action was detected. Take the appropriate action
* given the situation with the keyguard.
*/
void launchHomeFromHotKey() {
if (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();
}
}


Step6: 也是对锁屏模式有个判断，如果不在锁屏模式，就launch Home---->startDockOrHome(),进入——>

[java] view plaincopyprint?
 void startDockOrHome() {
Intent dock = createHomeDockIntent();
if (dock != null) {
try {
mContext.startActivity(dock);
return;
} catch (ActivityNotFoundException e) {
}
}
mContext.startActivity(mHomeIntent);
}

Step 7: 其实这个createHomeDockIntent（）方法就是对android手机的几种模式进行判断，

The device is not in either car mode or desk mode
The device is in car mode but ENABLE_CAR_DOCK_HOME_CAPTURE is false
The device is in desk mode but ENABLE_DESK_DOCK_HOME_CAPTURE is false
The device is in car mode but there's no CAR_DOCK app with METADATA_DOCK_HOME
The device is in desk mode but there's no DESK_DOCK app with METADATA_DOCK_HOME

如果是以上模式，车载模式或者桌面模式，就返回dock不为空，否则为空。启动这个mHomeIntent。----->mHomeIntent定义如下：

[java] view plaincopyprint?
 mHomeIntent = new Intent(Intent.ACTION_MAIN, null);
mHomeIntent.addCategory(Intent.CATEGORY_HOME);
mHomeIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK
| Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);
Step 8: 这个mHomeIntent就是启动activity中配置Category属性的值为CATEGORY_HOME，启动的时候新启动一个任务，不是在当前的这个任务中启动launcherHome，而是新建一个task。

FLAG_ACTIVITY_RESET_TASK_IF_NEEDED标记进入前台时（典型的操作是用户在主画面重启它），这个Activity和它之上的都将关闭，以至于用户不能再返回到它们，但是可以回到之前的Activity。

到这为止，Home键的流程已经分析完了。

二、下面看看长按耳机键接受的广播的处理方式：


（1）这个长按耳机键捕获是在PhoneWindow.java类的onKeyDown()中，然后发送有序的广播---->如下：

[java] view plaincopyprint?
 case KeyEvent.KEYCODE_HEADSETHOOK:
case KeyEvent.KEYCODE_MEDIA_STOP:
case KeyEvent.KEYCODE_MEDIA_NEXT:
case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
case KeyEvent.KEYCODE_MEDIA_REWIND:
case KeyEvent.KEYCODE_MEDIA_FAST_FORWARD: {
Intent intent = new Intent(Intent.ACTION_MEDIA_BUTTON, null);
intent.putExtra(Intent.EXTRA_KEY_EVENT, event);
getContext().sendOrderedBroadcast(intent, null);
return true;
}

接受这个长按耳机键的广播是在Music的app中的----->

public class MediaButtonIntentReceiver extends BroadcastReceiver{ ... ... }

，需要在Manifest.xml中注册这个广播<intent-filter>

<action android:name="android.intent.action.MEDIA_BUTTON" />

</intent-filter>。---->注册MediaButtonReceiver这个广播，

这个类中onReceive（）方法定义的：代码如下--->

[java] view plaincopyprint?
 @Override
public void onReceive(Context context, Intent intent) {
String intentAction = intent.getAction();
if (AudioManager.ACTION_AUDIO_BECOMING_NOISY.equals(intentAction)) {
Intent i = new Intent(MediaPlaybackService.SERVICECMD);
i.putExtra(MediaPlaybackService.CMDNAME, MediaPlaybackService.CMDPAUSE);
context.sendBroadcast(i);
} else if (Intent.ACTION_MEDIA_BUTTON.equals(intentAction)) {
KeyEvent event = (KeyEvent)
intent.getParcelableExtra(Intent.EXTRA_KEY_EVENT);

if (event == null) {
return;
}

int keycode = event.getKeyCode();
int action = event.getAction();
long eventtime = event.getEventTime();

// single quick press: pause/resume.
// double press: next track
// long press: start auto-shuffle mode.

String command = null;
switch (keycode) {
case KeyEvent.KEYCODE_MEDIA_STOP:
command = MediaPlaybackService.CMDSTOP;
break;
case KeyEvent.KEYCODE_HEADSETHOOK:
case KeyEvent.KEYCODE_MEDIA_PLAY_PAUSE:
command = MediaPlaybackService.CMDTOGGLEPAUSE;
break;
case KeyEvent.KEYCODE_MEDIA_NEXT:
command = MediaPlaybackService.CMDNEXT;
break;
case KeyEvent.KEYCODE_MEDIA_PREVIOUS:
command = MediaPlaybackService.CMDPREVIOUS;
break;
case KeyEvent.KEYCODE_MEDIA_PAUSE:
command = MediaPlaybackService.CMDPAUSE;
break;
case KeyEvent.KEYCODE_MEDIA_PLAY:
command = MediaPlaybackService.CMDPLAY;
break;
}

if (command != null) {
if (action == KeyEvent.ACTION_DOWN) {
if (mDown) {
if ((MediaPlaybackService.CMDTOGGLEPAUSE.equals(command) ||
MediaPlaybackService.CMDPLAY.equals(command))
&& mLastClickTime != 0
&& eventtime - mLastClickTime > LONG_PRESS_DELAY) {
mHandler.sendMessage(
mHandler.obtainMessage(MSG_LONGPRESS_TIMEOUT, context));
}
} else if (event.getRepeatCount() == 0) {
// only consider the first event in a sequence, not the repeat events,
// so that we don't trigger in cases where the first event went to
// a different app (e.g. when the user ends a phone call by
// long pressing the headset button)

// The service may or may not be running, but we need to send it
// a command.
Intent i = new Intent(context, MediaPlaybackService.class);
i.setAction(MediaPlaybackService.SERVICECMD);
if (keycode == KeyEvent.KEYCODE_HEADSETHOOK &&
eventtime - mLastClickTime < 300) {
i.putExtra(MediaPlaybackService.CMDNAME, MediaPlaybackService.CMDNEXT);
context.startService(i);
mLastClickTime = 0;
} else {
i.putExtra(MediaPlaybackService.CMDNAME, command);
context.startService(i);
mLastClickTime = eventtime;
}

mLaunched = false;
mDown = true;
}
} else {
mHandler.removeMessages(MSG_LONGPRESS_TIMEOUT);
mDown = false;
}
if (isOrderedBroadcast()) {
abortBroadcast();
}
}
}
}


step1: 在方法if (action == KeyEvent.ACTION_DOWN) { ... ... }做的处理，event.getRepeatCount() == 0这个判断的意思是“是否长按耳机键？”，如果长按耳机键event.getRepeatCount() 的值就一直增加。

step 2:短按耳机键：播放/暂停 --->音乐；短按启动MediaPlaybackService.java这个类，并且传入参数---->在这个服务类中有个接受广播的内部类：如下-->

[java] view plaincopyprint?
private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
String cmd = intent.getStringExtra("command");
MusicUtils.debugLog("mIntentReceiver.onReceive " + action + " / " + cmd);
if (CMDNEXT.equals(cmd) || NEXT_ACTION.equals(action)) {
next(true);
} else if (CMDPREVIOUS.equals(cmd) || PREVIOUS_ACTION.equals(action)) {
prev();
} else if (CMDTOGGLEPAUSE.equals(cmd) || TOGGLEPAUSE_ACTION.equals(action)) {
if (isPlaying()) {
pause();
mInternalPause = false;
} else {
play();
}
} else if (CMDPAUSE.equals(cmd) || PAUSE_ACTION.equals(action)) {
pause();
mInternalPause = false;
} else if (CMDPLAY.equals(cmd)) {
play();
} else if (CMDSTOP.equals(cmd)) {
pause();
mInternalPause = false;
seek(0);
} else if (MediaAppWidgetProvider.CMDAPPWIDGETUPDATE.equals(cmd)) {
// Someone asked us to refresh a set of specific widgets, probably
// because they were just added.
int[] appWidgetIds = intent.getIntArrayExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS);
mAppWidgetProvider.performUpdate(MediaPlaybackService.this, appWidgetIds);
}
}
span>
通过：如下方法来控制点击播放音乐，再次点击暂停，如此循环。

else if (CMDTOGGLEPAUSE.equals(cmd) || TOGGLEPAUSE_ACTION.equals(action)) {

if (isPlaying()) {

pause();

mInternalPause = false;

} else {

play();

}

}

内部类的广播是在启动MediaPlaybackService.java中注册的，解除注册在onDestroy（）的方法中。

[java] view plaincopyprint?
 IntentFilter commandFilter = new IntentFilter();
commandFilter.addAction(SERVICECMD);
commandFilter.addAction(TOGGLEPAUSE_ACTION);
commandFilter.addAction(PAUSE_ACTION);
commandFilter.addAction(NEXT_ACTION);
commandFilter.addAction(PREVIOUS_ACTION);
commandFilter.addAction(PLAYSTATUS_REQUEST);
registerReceiver(mIntentReceiver, commandFilter);

Step 3: 长按耳机键--->发消息给mHandler,

[java] view plaincopyprint?
 mHandler.removeMessages(MSG_LONGPRESS_TIMEOUT);
在MediaButtonIntentReceiver.java中有个内部类Handler（）如下——>

[java] view plaincopyprint?
 private static Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_LONGPRESS_TIMEOUT:
if (!mLaunched) {
Context context = (Context)msg.obj;
Intent i = new Intent();
i.putExtra("autoshuffle", "true");
i.setClass(context, MusicBrowserActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP);
context.startActivity(i);
mLaunched = true;
}
break;
}
}
};
长按耳机后就启动MusicBrowserActivity.java这个音乐播放类。并且传入参数“autoshuffle==true”，这个启动和launcher的启动相似，也是启动一个新的任务task，但是这个后面的标志有不同的地方Intent.FLAG_ACTIVITY_CLEAR_TOP。

到这为止就是实现了在任何界面长按耳机键都能进入到music的主界面。

总结如下：

其实启动的时候，要注意当前activity的launcherMode是什么，如果是SingleTask，就要小心一下。比如说：想要长按耳机键，进入到launcher的Mainmenu界面，这时候如果单纯的用以上方法套，返回键点击的时候不会回到上个activity中，会有问题。因为launcher是一直启动的运行于每个task之中的，你再次启动Launcher的时候，无论是否设置属性“i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK)”，都会把前一个activity给finish掉，launcher会在栈顶也是栈底。因为launcher的launcherMode=singleTask。我们可以做个实验；

三、例子写两个app，一个属性为singletask，一个为standard。应singletask的启动standard的activity，然后在再次基础上启动singletask的activity，看standard的activity是否会destory掉。

step1：先看截图：

launchMode="singleTask" launchMode="standard"

Step 2：先启动launchMode="singleTask"的activity---->点击调用第二个App2的launchMode="standard"---->

点击按钮调用第一个App1的launchMode="singleTask"---->点击返回键。看log分析：

（1）点击启动launchMode="singleTask"的activity的log如下：

（2）点击调用第二个App2的launchMode="standard"的activity的log如下图：

（3）点击调用第一个App1launchMode="singleTask"的activity的log如下：
分析如下：看到这时候App2Activity--22已经执行了onStop()和onDestroy（）方法了。验证了我以上的说法。

（4）点击返回键---->直接回到了launcher界面。log如下：

备注：要想解决以上问题也是可以的。就是在以上第（2）步：点击调用第二个App2的launchMode="standard"的activity的时候设置flag。Intent.FLAG_ACTIVITY_NEW_TASK。就可以解决以上问题了，每次启动一个新的任务，这样就能返回到App2Activity了。



（1）点击启动launchMode="singleTask"的activity的log如下：

（2）点击调用第二个App2的launchMode="standard"的activity的log如下图：

（3）点击调用第一个App1launchMode="singleTask"的activity的log如下：

看到如上图:App2Activity--22--->只是onStop（）了，没有onDestroy掉。

（4）点击返回键---->直接回到了launcher界面---->log如下：

（5）通过log，我们可以看出返回到App2Activity了，我们再次点击返回键，--->返回到Launcher界面的log如下：

通过以上验证说明我的结论是正确的。launcherMode一直是android的核心技术，通过这次我会更加注意到activity的LauncherMode的。

欢迎各界人士留言，讨论，拍砖！转载请标明出处！