学步园

转自     http://blog.csdn.net/wdaming1986/article/details/7539600

      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：

  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。

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：

 /** 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：

  /** {@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) {
           ........

   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：

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：

            // 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：

            // 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：

    /**
     * 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——>

   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：

           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：

            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--->