转自：http://blog.csdn.net/twoicewoo/article/details/7385876
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自定义一个layout，覆写dispatchKeyEventPreIme(KeyEvent event)方法，请看QuickSearchBox的源码
1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.quicksearchbox.ui; 18 19 import android.app.Activity; 20 import android.content.Context; 21 import android.util.AttributeSet; 22 import android.view.KeyEvent; 23 import android.view.inputmethod.InputMethodManager; 24 import android.widget.RelativeLayout; 25 26 /** 27 * Finishes the containing activity on BACK, even if input method is showing. 28 */ 29 public class SearchActivityView extends RelativeLayout { 30 31 public SearchActivityView(Context context) { 32 super(context); 33 } 34 35 public SearchActivityView(Context context, AttributeSet attrs) { 36 super(context, attrs); 37 } 38 39 public SearchActivityView(Context context, AttributeSet attrs, int defStyle) { 40 super(context, attrs, defStyle); 41 } 42 43 private Activity getActivity() { 44 Context context = getContext(); 45 if (context instanceof Activity) { 46 return (Activity) context; 47 } else { 48 return null; 49 } 50 } 51 52 /** 53 * Hides the input method. 54 */ 55 protected void hideInputMethod() { 56 InputMethodManager imm = (InputMethodManager) 57 getContext().getSystemService(Context.INPUT_METHOD_SERVICE); 58 if (imm != null) { 59 imm.hideSoftInputFromWindow(getWindowToken(), 0); 60 } 61 } 62 63 /** 64 * Overrides the handling of the back key to dismiss the activity. 65 */ 66 @Override 67 public boolean dispatchKeyEventPreIme(KeyEvent event) { 68 Activity activity = getActivity(); 69 if (activity != null && event.getKeyCode() == KeyEvent.KEYCODE_BACK) { 70 KeyEvent.DispatcherState state = getKeyDispatcherState(); 71 if (state != null) { 72 if (event.getAction() == KeyEvent.ACTION_DOWN 73 && event.getRepeatCount() == 0) { 74 state.startTracking(event, this); 75 return true; 76 } else if (event.getAction() == KeyEvent.ACTION_UP 77 && !event.isCanceled() && state.isTracking(event)) { 78 hideInputMethod(); 79 activity.onBackPressed(); 80 return true; 81 } 82 } 83 } 84 return super.dispatchKeyEventPreIme(event); 85 } 86 }