现在的App就用越来越人性化了，为了满足用户的体验欲望，从各个方面都进行了仔细处理。比如我们点击第一次点击Back键的时候，会温馨提示“再按一次返回键退出应用”等，今天 就记录下自己在项目中写的这个小功能：

首先写个工具类：

public class DoubleClickExitApp {       private Context mcontext;     /**是否是再次点击back键*/     private boolean isOnKeyBack;     private Handler mHandler;     /**退出提示Toast*/     private Toast mExitToast;       public DoubleClickExitApp(Context context) {        this.mcontext = context;        this.mHandler = new Handler(Looper.getMainLooper());     }       /**所在Activity中的点击返回事件处理*/     public boolean onKeyDown(int keyCode, KeyEvent event) {        if(keyCode != KeyEvent.KEYCODE_BACK) {//如果不是点击的返回键，则返回false           return false;        }        if(isOnKeyBack) {           mHandler.removeCallbacks(onBackExitRunnable);           if(mExitToast != null){              mExitToast.cancel();           }           /**直接退出*/           AppManager.getAppManager().AppExit(mcontext);           return true;        } else {           isOnKeyBack = true;           if(mExitToast == null) {              mExitToast = Toast.makeText(mcontext, "再按一次返回键退出应用", Toast.LENGTH_SHORT);           }           mExitToast.show();           mHandler.postDelayed(onBackExitRunnable, 2000);           return true;        }     }       private Runnable onBackExitRunnable = new Runnable() {          @Override        public void run() {           isOnKeyBack = false;           if(mExitToast != null){              mExitToast.cancel();           }        }     };  }

然后在对应的Activity或是主页面中直接调用：

public class MainActivity extends Activity{       private DoubleClickExitApp mDoubleClickExitApp;        @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);             mDoubleClickExitApp = new DoubleClickExitApp(this);        }    @Override    protected void onDestroy() {        super.onDestroy();    }   /**在处理onKeyDown事件中调用我们写的工具类方法就可以*/    @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {        if (keyCode == KeyEvent.KEYCODE_BACK) {               return mDoubleClickExitApp.onKeyDown(keyCode, event);        }else{              return super.onKeyDown(keyCode, event);           }           }