Android上如何让应用截获系统按键

本文章主要讲述Android智能机上，应用捕获按键的处理。遥控器上按键分为两种，普通按键和热键。普通按键就是我们常用的数字键，上下左右功能键，设置，返回，确认等按键。而在android上，对于遥控器的映射中，规定某些按键应用是无法拦截到的，我们称此为热键，如静音键，电源键,HOME键，直播键等等。

1. 应用拦截普通按键的处理：

// 拦截系统热键
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
int key = event.getKeyCode();
Log.i(TAG, "[test] dispatchKeyEvent  event = " + event);
if (key == KeyEvent.KEYCODE_VOLUME_DOWN
|| key == KeyEvent.KEYCODE_VOLUME_UP) {
Log.i(TAG, "[test] catch  event!! return true! ");
return true;
}
return super.dispatchKeyEvent(event);
}

在按键的处理过程中，若应用重写了dispatchKeyEvent,并且对响应的按键进行了处理完后，直接return true,则系统将不再处理此按键的响应。如果不写return true,super.dispatchKeyEvent(event)将会将按键再次交给系统进行处理。

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2.应用拦截热键的处理：

[1]在Activity中重写onAttachedToWindow方法，设置一个0x80000000的flags下去。//仅一个标志而已

@Override
public void onAttachedToWindow() {
System.out.println("onAttachedToWindow  ............");
this.getWindow().addFlags(0x80000000);//
super.onAttachedToWindow();
}

[2]修改phoneWindownManager.java.在相应按键的事件派发前进行如下处理：【以home键为例】

在进行事件处理前，先获取当前WindowManager.LayoutParams，通过flags可以判断应用是否可以处理该按键消息，若可以，直接return 0,不再进行按键处理，交留给应用去处理。如果flags判断应用无法获取该按键消息，将还会进行系统原有的按键处理流程。

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 if(mHoldHomePressed == true){
mHoldHomePressed = false;
}else{
mHoldHomePressed = false;
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;
}
}

/**
* 特殊处理，让应用程序能拦截HOME按键
*/
final int attrFlags = attrs.flags;
if((attrFlags & 0x80000000) != 0) {
return 0;
}

}

if (down) {
if (repeatCount == 0) {
mHomePressed = true;
} else if ((event.getFlags() & KeyEvent.FLAG_LONG_PRESS) != 0) {
if (!keyguardOn) {
//handleLongPressOnHome();
mHoldHomePressed = true;
Intent intentShowRecent = new Intent("hi_action_show_recent");
mContext.sendBroadcast(intentShowRecent);
}
}
}
return -1;
}

[3]热键在应用中的处理：

参照普通按键的处理流程。重写dispatchKeyEvent。