Android中Home键的监听和拦截

首先大家应该先了解一种情况，就是Android在应用中是无法拦截Home键的，今天我们带大家看一下Home键的三种情况。

1、在应用中按下Home键的逻辑处理

当我们在应用中按下Home键时界面会启动到桌面，我们在frameworks\base\policy\src\com\android\internal\policy\impl\PhoneWindowManager.java类中可以看到其实现原理，其不外乎就是调用了以下代码。

    Intent mHomeIntent;    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);    startActivity(mHomeIntent);

创建一个启动到桌面的Intent。

2、在应用中监听Home键

在Android应用中如果想监听Home键可以使用广播机制，这个在源码中也有体现。

static public final String SYSTEM_DIALOG_REASON_KEY = "reason";    static public final String SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS = "globalactions";    static public final String SYSTEM_DIALOG_REASON_RECENT_APPS = "recentapps";    static public final String SYSTEM_DIALOG_REASON_HOME_KEY = "homekey";    static public final String SYSTEM_DIALOG_REASON_ASSIST = "assist";    @Override    public void onReceive(Context arg0, Intent arg1) {        String action = arg1.getAction();        //按下Home键会发送ACTION_CLOSE_SYSTEM_DIALOGS的广播        if (action.equals(Intent.ACTION_CLOSE_SYSTEM_DIALOGS)) {            String reason = arg1.getStringExtra(SYSTEM_DIALOG_REASON_KEY);            if (reason != null) {                if (reason.equals(SYSTEM_DIALOG_REASON_HOME_KEY)) {                    // 短按home键                    Toast.makeText(arg0, "短按Home键", Toast.LENGTH_SHORT).show();                } else if (reason.equals(SYSTEM_DIALOG_REASON_RECENT_APPS)) {                    // RECENT_APPS键                    Toast.makeText(arg0, "RECENT_APPS", Toast.LENGTH_SHORT).show();                }            }        }    }

这样就可以监听Home的是否被按下。

3、在Frameworks层拦截Home键

在frameworks\base\policy\src\com\android\internal\policy\impl\PhoneWindowManager.java文件中我们首先看一下interceptKeyBeforeDispatching()方法。

public long interceptKeyBeforeDispatching(WindowState win, KeyEvent event, int policyFlags) {    //......    if (keyCode == KeyEvent.KEYCODE_HOME) {        //......        handleShortPressOnHome();    }}//进入handleShortPressOnHomeprivate void handleShortPressOnHome() {        // If there's a dream running then use home to escape the dream        // but don't actually go home.        if (mDreamManagerInternal != null && mDreamManagerInternal.isDreaming()) {            mDreamManagerInternal.stopDream(false /*immediate*/);            return;        }        // Go home!        launchHomeFromHotKey();    }

进入launchHomeFromHotKey方法。

static public final String SYSTEM_DIALOG_REASON_KEY = "reason";    static public final String SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS = "globalactions";    static public final String SYSTEM_DIALOG_REASON_RECENT_APPS = "recentapps";    static public final String SYSTEM_DIALOG_REASON_HOME_KEY = "homekey";    static public final String SYSTEM_DIALOG_REASON_ASSIST = "assist";void launchHomeFromHotKey() {        if (isKeyguardShowingAndNotOccluded()) {            // don't launch home if keyguard showing        } else if (!mHideLockScreen && mKeyguardDelegate.isInputRestricted()) {            // when in keyguard restricted mode, must first verify unlock            // before launching home            mKeyguardDelegate.verifyUnlock(new OnKeyguardExitResult() {                @Override                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) {            }            if (mRecentsVisible) {                // Hide Recents and notify it to launch Home                awakenDreams();                sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);                hideRecentApps(false, true);            } else {                // Otherwise, just launch Home                sendCloseSystemWindows(SYSTEM_DIALOG_REASON_HOME_KEY);                //启动Launcher界面                startDockOrHome();            }        }    }

以上方法可处理Home键的拦截操作，接下来我们进入startDockOrHome方法。

void startDockOrHome() {        if (OptConfig.LC_RAM_SUPPORT) {            try {                ActivityManagerNative.getDefault().startHomePre();            } catch (RemoteException re) {            }        }        awakenDreams();        Intent dock = createHomeDockIntent();        if (dock != null) {            try {                startActivityAsUser(dock, UserHandle.CURRENT);                return;            } catch (ActivityNotFoundException e) {            }        }        //intent的相关设置        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);        startActivityAsUser(mHomeIntent, UserHandle.CURRENT);    }

好啦，这里就对Home键进行简单的监听和拦截。

1、在应用中按下Home键的逻辑处理

2、在应用中监听Home键

3、在Frameworks层拦截Home键

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