常用的方法、知识（三）

1、Fragment中写onTouchevent，监听Fragment的触碰事件，主要用于滚屏监听隐藏显示某个控件：

首先在Fragment的父Activity中写一个回调接口：

public interface MyTouchListener {
        public void onTouchEvent(MotionEvent event);
    }

    // 保存MyTouchListener接口的列表
    private ArrayList<MyTouchListener> myTouchListeners = new ArrayList<MainActivity.MyTouchListener>();

    /**
     * 提供给Fragment通过getActivity()方法来注册自己的触摸事件的方法
     * @param listener
     */
    public void registerMyTouchListener(MyTouchListener listener) {
        myTouchListeners.add(listener);
    }

    /**
     * 提供给Fragment通过getActivity()方法来取消注册自己的触摸事件的方法
     * @param listener
     */
    public void unRegisterMyTouchListener(MyTouchListener listener) {
        myTouchListeners.remove( listener );
    }

    /**
     * 分发触摸事件给所有注册了MyTouchListener的接口
     */
    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        for (MyTouchListener listener : myTouchListeners) {
            listener.onTouchEvent(ev);
        }
        return super.dispatchTouchEvent(ev);
    }

然后在Fragment中，其中在触碰事件中，判断是上滑动还是下滑动，从而做一个悬浮按钮的显示、隐藏：

 //Fragment的OnTouchevent，滚动隐藏显示备忘录图标
        MainActivity.MyTouchListener myTouchListener = new MainActivity.MyTouchListener() {
            @Override
            public void onTouchEvent(MotionEvent event) {
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    y1 = event.getY();
                }
                if (event.getAction() == MotionEvent.ACTION_UP) {
                    y2 = event.getY();
                    if (y1 - y2 > 50) {
                        //向上滑动
                        if (fabReportMemo.getVisibility() == View.VISIBLE) {
                            fabReportMemo.setVisibility(View.GONE);
                            fabReportMemo.setAnimation(BaseMethod.HideAnimation(getContext()));
                        }
                    } else if (y2 - y1 > 50) {
                        //向下滑动
                        if (fabReportMemo.getVisibility() == View.GONE) {
                            fabReportMemo.setVisibility(View.VISIBLE);
                            fabReportMemo.setAnimation(BaseMethod.ShowAnimation(getContext()));
                        }
                    }
                }
                // 处理手势事件
            }
        };

        // 将myTouchListener注册到分发列表
        ((MainActivity) this.getActivity()).registerMyTouchListener(myTouchListener);

2、双击标题栏，布局滚动到顶部：

  int count = 0;
  long firClick,secClick;


 //双击标题栏回到顶部
        llReportTitle.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                if (MotionEvent.ACTION_DOWN == event.getAction()) {
                    count++;
                    if (count == 1) {
                        firClick = System.currentTimeMillis();
                    } else if (count == 2) {
                        secClick = System.currentTimeMillis();
                        if (secClick - firClick < 1000) {
                            svReport.smoothScrollTo(0, 0);
                            if (fabReportMemo.getVisibility() == View.GONE) {
                                fabReportMemo.setVisibility(View.VISIBLE);
                                fabReportMemo.setAnimation(BaseMethod.ShowAnimation(getContext()));
                            }
                        }
                        count = 0;
                        firClick = 0;
                        secClick = 0;
                    }
                }
                return true;
            }
        });

3、双击退出程序（新写法）：

private long exitTime = 0;

    public void doExitApp() {
        if ((System.currentTimeMillis() - exitTime) > 2000) {
            Toast.makeText(this, R.string.press_again_exit_app, Toast.LENGTH_SHORT).show();
            exitTime = System.currentTimeMillis();
        } else {
            finish();
        }
    }

    @Override
    public void onBackPressed() {
                doExitApp();
    }