实现可滑动的日历

这是简单的效果，可以滑动，是用的viewpager和自定义view实现的

首先是viewpager的代码，其实和平常的使用时一样的

viewPager = (ViewPager) findViewById(R.id.view_pager).
pagerAdapter = new  CalendarPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(pagerAdapter);
viewPager.addOnPageChangeListener(this);
// 获取当天的日期所对应的position
viewPager.setCurrentItem(DateTimeUtils.getTodayMonthIndex());

重要的是fragment的创建，通过计算年份的偏移给出position

public class CalendarPagerAdapter extends FragmentStatePagerAdapter {

public CalendarPagerAdapter(FragmentManager fm) {
    super(fm);
}

@Override
public Fragment getItem(int position) {
    return CalendarPagerFragment.create(position);
}

@Override
public int getCount() {
// 计算一共有多少的position
    int years = DateTimeUtils.getMaxYear() - DateTimeUtils.getMinYear();
    return years * 12;
}
}


public class CalendarPagerFragment extends Fragment {

public static final String MONTH_INDEX = "month_index";

private int monthIndex;
private MonthDateView monthDateView;

public static CalendarPagerFragment create(int monthIndex) {
    CalendarPagerFragment fragment = new CalendarPagerFragment();
    Bundle bundle = new Bundle();
    bundle.putInt(MONTH_INDEX, monthIndex);
    fragment.setArguments(bundle);
    return fragment;
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    monthIndex = getArguments().getInt(MONTH_INDEX);
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    ViewGroup view = (ViewGroup) inflater.inflate(R.layout.view_calendar, null);
    // 动态添加自定义的日历界面
    monthDateView = new MonthDateView(getActivity(), monthIndex);
    monthDateView.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
    view.addView(monthDateView);
    monthDateView.invalidate();
    return view;
}
}

然后是自定义的日历代码：

// 获取view的宽高，用于计算显示的坐标和距离
mDisplayMetrics = getResources().getDisplayMetrics();
Calendar calendar = Calendar.getInstance();
// 初始化画笔
mPaint = new Paint();
mPaint.setAntiAlias(true);
    // 计算当前的年和月
    mSelYear = DateTimeUtils.getMinYear() + (monthIndex / 12);
    mSelMonth = monthIndex % 12;



@Override
protected void onDraw(Canvas canvas) {
    initSize();
    daysString = new int[6][7];

    String dayString;
    // 获取全部的天数
    int mMonthDays = DateUtils.getMonthDays(mSelYear, mSelMonth);
    // 月份第一天是周几
    int weekNumber = DateUtils.getFirstDayWeek(mSelYear, mSelMonth);

    Log.d("DateView", "DateView:" + mSelMonth + "月1号周" + weekNumber);
    for (int day = 0; day < mMonthDays; day++) {
        dayString = (day + 1) + "";

        // 列
        int column = (day + weekNumber - 1) % 7;
        // 行
        int row = (day + weekNumber - 1) / 7;

        // 根据行，列进行赋值
        daysString[row][column] = day + 1;
        
        if (dayString.equals(mSelDay + "")) {
        
            // 在这里可以绘制选中日期的背景色
            // 记录第几行，即第几周
            weekRow = row + 1;
            sendMessage();
        }

        // 绘制横线
        mPaint.setColor(mLineColor);
        canvas.drawLine(0, mRowSize * (row + 1), getWidth(), mRowSize * (row + 1), mPaint);

        // 绘制事务圆形标志，就是字右上角显示的事务个数
        int count = PrefUtils.getInt(getDateString(day + 1), 0);
        if (count != 0) {
            drawCircle(row, column, day + 1, count, canvas);
        }

        mPaint.setTextSize(context.getResources().getDimension(R.dimen.content_text_size));


        // 计算显示字体的坐标，ascent()、descent()两个函数的意思可以自行查找
        int startX = (int) (mColumnSize * column + (mColumnSize - mPaint
                .measureText(dayString)) / 2);
        int startY = (int) (mRowSize * row + mRowSize / 2 - (mPaint
                .ascent() + mPaint.descent()) / 2);
        
        // 绘制日期
        if (dayString.equals(mCurrDay + "")
                && mCurrMonth == mSelMonth) {
            // 正常月，选中其他日期，则今日为红色
            int startRecX = mColumnSize * column;
            int startRecY = mRowSize * row;
            mPaint.setColor(mSelectBGColor);
            canvas.drawCircle(startRecX + mColumnSize / 2, startRecY + mRowSize / 2,
                    context.getResources().getDimension(R.dimen.alarm_click_bg_margin), mPaint);

            mPaint.setColor(mSelectDayColor);
        } else if (column == 0 || column == 6) {
            // 周六日的颜色
            mPaint.setColor(mWeekendColor);
        } else {
            mPaint.setColor(mDayColor);
        }
        canvas.drawText(dayString, startX, startY, mPaint);
    }

}