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handleShortPressOnHome
private 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。