我们顶部的标题栏用的是一个PagerTab的类来做的代码如下
public class PagerTab extends ViewGroup {
private ViewPager mViewPager;
private PageListener mPageListener = new PageListener();//用于注册给ViewPager监听状态和滚动
private OnPageChangeListener mDelegatePageListener;//用于通知外界ViewPager的状态和滚动
private BaseActivity mActivity;
private int mDividerPadding = 12;// 分割线上下的padding
private int mDividerWidth = 1;// 分割线的宽度
private int mDividerColor = 0x1A000000;//分割线颜色
private Paint mDividerPaint;//分割线的画笔
private int mIndicatorHeight = 4;//指示器的高度
private int mIndicatorWidth;//指示器的宽度，是动态的随着tab的宽度变化
private int mIndicatorLeft;//指示器的距离左边的距离
private int mIndicatorColor = 0xFF0084FF;//指示器颜色
private Paint mIndicatorPaint; //指示器的画笔
private int mContentWidth;//记录自身内容的宽度
private int mContentHeight;//记录自身内容的高度
private int mTabPadding = 24;// tab左右的内边距
private int mTabTextSize = 16; //tab文字大小
private int mTabBackgroundResId = R.drawable.bg_tab_text;// tab背景资源
private int mTabTextColorResId = R.color.bg_text_color; //tab文字颜色
private int mTabCount;//tab的个数
private int mCurrentPosition = 0;//当前光标所处的tab，规则是以光标的最左端所在的item的position
private float mCurrentOffsetPixels;//光标左边距离当前光标所处的tab的左边距离
private int mSelectedPosition = 0; //当前被选中的tab，用于记录手指点击tab的position
private boolean mIsBeingDragged = false;//是否处于拖动中
private float mLastMotionX;//上一次手指触摸的x坐标
private VelocityTracker mVelocityTracker;//用于记录速度的帮助类
private int mMinimumVelocity;//系统默认的最小满足fling的速度
private int mMaximumVelocity;//系统默认最大的fling速度
private int mTouchSlop;//系统默认满足滑动的最小位移
private ScrollerCompat mScroller;//处理滚动的帮助者
private int mLastScrollX;//记录上一次滚动的x位置，这是用于处理overScroll，实际位置可能会受到限制
private int mMaxScrollX = 0;// 控件最大可滚动的距离
private int mSplitScrollX = 0;// 根据item的个数，计算出每移动一个item控件需要移动的距离
private EdgeEffectCompat mLeftEdge;//处理overScroll的反馈效果
private EdgeEffectCompat mRightEdge;
public PagerTab(Context context) {
this(context, null);
}
public PagerTab(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public PagerTab(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
if (context instanceof BaseActivity) {
mActivity = (BaseActivity) context;
}
init();
initPaint();
}
/** 初始化一些常量 */
private void init() {
//把一个值从dip转换成px
mIndicatorHeight = UIUtils.dip2px(mIndicatorHeight);
mDividerPadding = UIUtils.dip2px(mDividerPadding);
mTabPadding = UIUtils.dip2px(mTabPadding);
mDividerWidth = UIUtils.dip2px(mDividerWidth);
mTabTextSize = UIUtils.dip2px(mTabTextSize);
//创建一个scroller
mScroller = ScrollerCompat.create(mActivity);
//获取一个系统关于View的常量配置类
final ViewConfiguration configuration = ViewConfiguration.get(mActivity);
//获取滑动的最小距离
mTouchSlop = configuration.getScaledTouchSlop();
//获取fling的最小速度
mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
//获取fling的最大速度
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
mLeftEdge = new EdgeEffectCompat(mActivity);
mRightEdge = new EdgeEffectCompat(mActivity);
}
/** 初始化笔 */
private void initPaint() {
mIndicatorPaint = new Paint();
mIndicatorPaint.setAntiAlias(true);
mIndicatorPaint.setStyle(Paint.Style.FILL);
mIndicatorPaint.setColor(mIndicatorColor);
mDividerPaint = new Paint();
mDividerPaint.setAntiAlias(true);
mDividerPaint.setStrokeWidth(mDividerWidth);
mDividerPaint.setColor(mDividerColor);
}
/** 设置ViewPager */
public void setViewPager(ViewPager viewPager) {
if (viewPager == null || viewPager.getAdapter() == null) {
throw new IllegalStateException("ViewPager is null or ViewPager does not have adapter instance.");
}
mViewPager = viewPager;
onViewPagerChanged();
}
private void onViewPagerChanged() {
mViewPager.setOnPageChangeListener(mPageListener);//给ViewPager设置监听
mTabCount = mViewPager.getAdapter().getCount();//有多少个tab需要看ViewPager有多少个页面
for (int i = 0; i < mTabCount; i++) {
if (mViewPager.getAdapter() instanceof IconTabProvider) {//如果想要使用icon作为tab，则需要adapter实现IconTabProvider接口
addIconTab(i, ((IconTabProvider) mViewPager.getAdapter()).getPageIconResId(i));
} else {
addTextTab(i, mViewPager.getAdapter().getPageTitle(i).toString());
}
}
ViewTreeObserver viewTreeObserver = getViewTreeObserver();
if (viewTreeObserver != null) {//监听第一个的全局layout事件，来设置当前的mCurrentPosition，显示对应的tab
viewTreeObserver.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
getViewTreeObserver().removeGlobalOnLayoutListener(this);//只需要监听一次，之后通过listener回调即可
mCurrentPosition = mViewPager.getCurrentItem();
if (mDelegatePageListener != null) {
mDelegatePageListener.onPageSelected(mCurrentPosition);
}
}
});
}
}
/** 设置监听，因为Tab会监听ViewPager的状态，所以不要给ViewPager设置监听了，设置给Tab，由Tab转发 */
public void setOnPageChangeListener(OnPageChangeListener listener) {
mDelegatePageListener = listener;
}
/** 添加文字tab */
private void addTextTab(final int position, String title) {
TextView tab = new TextView(mActivity);
tab.setText(title);
tab.setGravity(Gravity.CENTER);
tab.setSingleLine();
tab.setTextSize(TypedValue.COMPLEX_UNIT_PX, mTabTextSize);
tab.setTypeface(Typeface.defaultFromStyle(Typeface.BOLD));
tab.setTextColor(UIUtils.getColorStateList(mTabTextColorResId));
tab.setBackgroundDrawable(UIUtils.getDrawable(mTabBackgroundResId));
tab.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT));
addTab(position, tab);
}
/** 添加图片icon */
private void addIconTab(final int position, int resId) {
ImageButton tab = new ImageButton(mActivity);
tab.setImageResource(resId);
tab.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
addTab(position, tab);
}
private void addTab(final int position, View tab) {
tab.setFocusable(true);
//设置tab的点击事件，当tab被点击时候切换pager的页面
tab.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
mViewPager.setCurrentItem(position);
}
});
tab.setPadding(mTabPadding, 0, mTabPadding, 0);
addView(tab, position);
}
/** 测量时的回调 */
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// 获取控件自身的宽高,模式
int widthSize = MeasureSpec.getSize(widthMeasureSpec) - getPaddingLeft() - getPaddingRight();
int heightSize = MeasureSpec.getSize(heightMeasureSpec) - getPaddingBottom() - getPaddingBottom();
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int totalWidth = 0;
int highest = 0;
int goneChildCount = 0;
for (int i = 0; i < mTabCount; i++) {
final View child = getChildAt(i);
if (child == null || child.getVisibility() == View.GONE) {
goneChildCount--;
continue;
}
int childWidthMeasureSpec;
int childHeightMeasureSpec;
LayoutParams childLayoutParams = child.getLayoutParams();
if (childLayoutParams == null) {
childLayoutParams = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
}
if (childLayoutParams.width == LayoutParams.MATCH_PARENT) {
childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(widthSize, MeasureSpec.EXACTLY);
} else if (childLayoutParams.width == LayoutParams.WRAP_CONTENT) {
childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(widthSize, MeasureSpec.AT_MOST);
} else {
childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(childLayoutParams.width, MeasureSpec.EXACTLY);
}
if (childLayoutParams.height == LayoutParams.MATCH_PARENT) {
childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(heightSize, MeasureSpec.EXACTLY);
} else if (childLayoutParams.height == LayoutParams.WRAP_CONTENT) {
childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(heightSize, MeasureSpec.AT_MOST);
} else {
childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(childLayoutParams.height, MeasureSpec.EXACTLY);
}
child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
int childWidth = child.getMeasuredWidth();
int childHeight = child.getMeasuredHeight();
totalWidth += childWidth;
highest = highest < childHeight ? childHeight : highest;
}
if (totalWidth <= widthSize) {//如果子Tab的总宽度小于PagerTab，则采用平分模式
int splitWidth = (int) (widthSize / (mTabCount - goneChildCount + 0.0f) + 0.5f);
for (int i = 0; i < mTabCount; i++) {
final View child = getChildAt(i);
if (child == null || child.getVisibility() == View.GONE) {
continue;
}
int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(splitWidth, MeasureSpec.EXACTLY);
int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(child.getMeasuredHeight(), MeasureSpec.EXACTLY);
child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}
mMaxScrollX = 0;
mSplitScrollX = 0;
} else {//如果所有子View大于控件的宽度
mMaxScrollX = totalWidth - widthSize;
mSplitScrollX = (int) (mMaxScrollX / (mTabCount - goneChildCount - 1.0f) + 0.5f);
}
if (widthMode == MeasureSpec.EXACTLY) {
mContentWidth = widthSize;
} else {
mContentWidth = totalWidth;
}
if (heightMode == MeasureSpec.EXACTLY) {
mContentHeight = heightSize;
} else {
mContentHeight = highest;
}
int measureWidth = mContentWidth + getPaddingLeft() + getPaddingRight();
int measureHeight = mContentHeight + getPaddingTop() + getPaddingBottom();
setMeasuredDimension(measureWidth, measureHeight);
}
/** 布局时的回调 */
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {//这里简化了，没有考虑margin的情况
if (changed) {
int height = b - t;//控件供子View显示的高度
int left = l;
for (int i = 0; i < mTabCount; i++) {
final View child = getChildAt(i);
if (child == null || child.getVisibility() == View.GONE) {
continue;
}
int top = (int) ((height - child.getMeasuredHeight()) / 2.0f + 0.5f);//如果控件比tab要高，则居中显示
int right = left + child.getMeasuredWidth();
child.layout(left, top, right, top + child.getMeasuredHeight());//摆放tab
left = right;//因为是水平摆放的，所以为下一个准备left值
}
}
}
/** 绘制时的回调 */
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
final int height = getHeight();
//画指示器
canvas.drawRect(mIndicatorLeft, height - mIndicatorHeight, mIndicatorLeft + mIndicatorWidth, height, mIndicatorPaint);
// 画分割线
for (int i = 0; i < mTabCount - 1; i++) {//分割线的个数比tab的个数少一个
final View child = getChildAt(i);
if (child == null || child.getVisibility() == View.GONE) {
continue;
}
if (child != null) {
canvas.drawLine(child.getRight(), mDividerPadding, child.getRight(), mContentHeight - mDividerPadding, mDividerPaint);
}
}
// 因为overScroll效果是一个持续效果，所以需要持续画
boolean needsInvalidate = false;
if (!mLeftEdge.isFinished()) {//如果效果没停止
final int restoreCount = canvas.save();//先保存当前画布
final int heightEdge = getHeight() - getPaddingTop() - getPaddingBottom();
final int widthEdge = getWidth();
canvas.rotate(270);
canvas.translate(-heightEdge + getPaddingTop(), 0);
mLeftEdge.setSize(heightEdge, widthEdge);
needsInvalidate |= mLeftEdge.draw(canvas);
canvas.restoreToCount(restoreCount);
}
if (!mRightEdge.isFinished()) {
final int restoreCount = canvas.save();
final int widthEdge = getWidth();
final int heightEdge = getHeight() - getPaddingTop() - getPaddingBottom();
canvas.rotate(90);
canvas.translate(-getPaddingTop(), -(widthEdge + mMaxScrollX));
mRightEdge.setSize(heightEdge, widthEdge);
needsInvalidate |= mRightEdge.draw(canvas);
canvas.restoreToCount(restoreCount);
}
if (needsInvalidate) {
postInvalidate();
}
}
/** 触摸事件是否拦截的方法 */
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
if (mIsBeingDragged && action == MotionEvent.ACTION_MOVE) {//当已经处于拖动，并且当前事件是MOVE，直接消费掉
return true;
}
switch (action) {
case MotionEvent.ACTION_DOWN: {
final float x = ev.getX();
mLastMotionX = x; //记录住当前的x坐标
mIsBeingDragged = !mScroller.isFinished();//如果按下的时候还在滚动，则把状态处于拖动状态
break;
}
case MotionEvent.ACTION_MOVE: {
final float x = ev.getX();
final int xDiff = (int) Math.abs(x - mLastMotionX);//计算两次的差值
if (xDiff > mTouchSlop) {//如果大于最小移动的距离，则把状态改变为拖动状态
mIsBeingDragged = true;
mLastMotionX = x;
ViewParent parent = getParent();//并请求父View不要再拦截自己触摸事件，交给自己处理
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
break;
}
case MotionEvent.ACTION_CANCEL://当手指离开或者触摸事件取消的时候，把拖动状态取消掉
case MotionEvent.ACTION_UP:
mIsBeingDragged = false;
break;
}
return mIsBeingDragged;//如果是拖动状态，则拦截事件，交给自己的onTouch处理
}
/** 触摸事件的处理方法 */
public boolean onTouchEvent(MotionEvent ev) {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(ev);
final int action = ev.getAction();
switch (action) {
case MotionEvent.ACTION_DOWN: {//如果是down事件，记录住当前的x坐标
final float x = ev.getX();
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
mLastMotionX = x;
break;
}
case MotionEvent.ACTION_MOVE: {
final float x = ev.getX();
final float deltaX = x - mLastMotionX;
if (!mIsBeingDragged) {//如果还没有处于拖动，则判断两次的差值是否大于最小拖动的距离
if (Math.abs(deltaX) > mTouchSlop) {
mIsBeingDragged = true;
}
}
if (mIsBeingDragged) {//如果处于拖动状态，记录住x坐标
mLastMotionX = x;
onMove(deltaX);
}
break;
}
case MotionEvent.ACTION_UP: {
if (mIsBeingDragged) {
final VelocityTracker velocityTracker = mVelocityTracker;
//先对速度进行一个调整，第一个参数是时间单位，1000毫秒，第二个参数是最大速度。
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
float velocity = velocityTracker.getXVelocity();//获取水平方向上的速度
onUp(velocity);
}
}
case MotionEvent.ACTION_CANCEL: {
mIsBeingDragged = false;
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
break;
}
}
return true;
}
private void onMove(float x) {
if (mMaxScrollX <= 0) {
if (mViewPager.isFakeDragging() || mViewPager.beginFakeDrag()) {
mViewPager.fakeDragBy(x);
}
} else {
int scrollByX = -(int) (x + 0.5);
if (getScrollX() + scrollByX < 0) {
scrollByX = 0 - getScrollX();
mLeftEdge.onPull(Math.abs(x) / getWidth());
}
if (getScrollX() + scrollByX > mMaxScrollX) {
scrollByX = mMaxScrollX - getScrollX();
mRightEdge.onPull(Math.abs(x) / getWidth());
}
scrollBy(scrollByX, 0);
ViewCompat.postInvalidateOnAnimation(this);
}
}
private void onUp(float velocity) {
if (mMaxScrollX <= 0) {
if (mViewPager.isFakeDragging()) mViewPager.endFakeDrag();
} else {
if (Math.abs(velocity) <= mMinimumVelocity) {
return;
}
mScroller.fling(getScrollX(), 0, -(int) (velocity + 0.5), 0, 0, mMaxScrollX, 0, 0, 270, 0);
ViewCompat.postInvalidateOnAnimation(this);
}
}
@Override
public void computeScroll() {
if (mScroller.computeScrollOffset()) {
int oldX = mLastScrollX;
mLastScrollX = mScroller.getCurrX();
if (mLastScrollX < 0 && oldX >= 0) {
mLeftEdge.onAbsorb((int) mScroller.getCurrVelocity());
} else if (mLastScrollX > mMaxScrollX && oldX <= mMaxScrollX) {
mRightEdge.onAbsorb((int) mScroller.getCurrVelocity());
}
int x = mLastScrollX;
if (mLastScrollX < 0) {
x = 0;
} else if (mLastScrollX > mMaxScrollX) {
x = mMaxScrollX;
}
scrollTo(x, 0);
}
ViewCompat.postInvalidateOnAnimation(this);
}
/** 检测mIndicatorOffset的合法性，并计算出其他有关tab的属性值 */
private void checkAndcalculate() {
// 如果指示器起始位置比第一个tab的起始位置还要小，纠正为第一个tab的起始位置，指示器宽度就是第一个tab的宽度
final View firstTab = getChildAt(0);
if (mIndicatorLeft < firstTab.getLeft()) {
mIndicatorLeft = firstTab.getLeft();
mIndicatorWidth = firstTab.getWidth();
}
// 如果指示器起始位置比最后一个tab的起始位置还要大，纠正为最后一个tab的起始位置，指示器宽度就是最后一个tab的宽度
View lastTab = getChildAt(mTabCount - 1);
if (mIndicatorLeft > lastTab.getLeft()) {
mIndicatorLeft = lastTab.getLeft();
mIndicatorWidth = lastTab.getWidth();
}
// 通过指示器的起始位置计算出当前处于第几个position，并且计算出已经偏移了多少，偏移量是以当前所处的tab的宽度的百分比
for (int i = 0; i < mTabCount; i++) {
View tab = getChildAt(i);
if (mIndicatorLeft < tab.getLeft()) {
mCurrentPosition = i - 1;
View currentTab = getChildAt(mCurrentPosition);
mCurrentOffsetPixels = (mIndicatorLeft - currentTab.getLeft()) / (currentTab.getWidth() + 0.0f);
break;
}
}
}
/** 滚动到指定的child */
public void scrollSelf(int position, float offset) {
if (position >= mTabCount) {
return;
}
final View tab = getChildAt(position);
mIndicatorLeft = (int) (tab.getLeft() + tab.getWidth() * offset + 0.5);
int rightPosition = position + 1;
if (offset > 0 && rightPosition < mTabCount) {
View rightTab = getChildAt(rightPosition);
mIndicatorWidth = (int) (tab.getWidth() * (1 - offset) + rightTab.getWidth() * offset + 0.5);
} else {
mIndicatorWidth = tab.getWidth();
}
checkAndcalculate();
int newScrollX = position * mSplitScrollX + (int) (offset * mSplitScrollX + 0.5);
if (newScrollX < 0) {
newScrollX = 0;
}
if (newScrollX > mMaxScrollX) {
newScrollX = mMaxScrollX;
}
//scrollTo(newScrollX, 0);//滑动
int duration = 100;
if (mSelectedPosition != -1) {
duration = (Math.abs(mSelectedPosition - position)) * 100;
}
mScroller.startScroll(getScrollX(), 0, (newScrollX - getScrollX()), 0, duration);
ViewCompat.postInvalidateOnAnimation(this);
}
/** 选中指定位置的Tab */
private void selectTab(int position) {
for (int i = 0; i < mTabCount; i++) {
View tab = getChildAt(i);
if (tab != null) {
tab.setSelected(position == i);
}
}
}
/** ViewPager的OnPageChangeListener实现类，因为我们需要在PagerTab中获取PagerView的监听，以便可以调整tab */
private class PageListener implements OnPageChangeListener {
@Override
public void onPageScrolled(int position, float positionOffset, final int positionOffsetPixels) {
//根据VierPager的偏移值来滚动tab
scrollSelf(position, positionOffset);
if (mDelegatePageListener != null) {//这个是提供给外部的
mDelegatePageListener.onPageScrolled(position, positionOffset, positionOffsetPixels);
}
}
@Override
public void onPageScrollStateChanged(int state) {
if (state == ViewPager.SCROLL_STATE_IDLE) {
mSelectedPosition = -1;
}
if (mDelegatePageListener != null) {
mDelegatePageListener.onPageScrollStateChanged(state);
}
}
@Override
public void onPageSelected(int position) {
System.out.println("onPageSelected:" + position);
mSelectedPosition = position;
selectTab(position);
if (mDelegatePageListener != null) {
mDelegatePageListener.onPageSelected(position);
}
}
}
/** 如果指示器希望是图片，则继承该接口 */
public interface IconTabProvider {
public int getPageIconResId(int position);
public int getPageSelectedIconResId();
}
}在ViewPager中载入我们的fragment
public class MainActivity extends BaseActivity {
private PagerTab mPagerTab;
private ViewPager mViewPager;
private MyAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mPagerTab = (PagerTab) findViewById(R.id.pager_tab);
mViewPager = (ViewPager) findViewById(R.id.viewpager);
mAdapter = new MyAdapter(getSupportFragmentManager());//得到一个fragment传进去Activity要继承FragmentActivity
mViewPager.setAdapter(mAdapter);
mPagerTab.setViewPager(mViewPager);//将指针和viewpager绑定在一起
mPagerTab.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageSelected(int position) {
BaseFragment fragment = FragmentFactory.createFragment(position);
//开始加载数据
fragment.loadData();
}
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
}
class MyAdapter extends FragmentPagerAdapter{
private String[] mTabNames;
public MyAdapter(FragmentManager fm) {
super(fm);
mTabNames = UIUtils.getStringArray(R.array.tab_names);//加载页面标题数组
}
@Override
public CharSequence getPageTitle(int position) {
return mTabNames[position];
}
//返回当前页面位置的fragment对象
@Override
public Fragment getItem(int position) {
BaseFragment fragment = FragmentFactory.createFragment(position);
return fragment;
}
//fragment数量
@Override
public int getCount() {
return mTabNames.length;
}
}
}我们的Fragment是通过一个工厂类来进行生产的
/** * 生产fragment工厂 * Created by matri on 2017/5/11. */
public class FragmentFactory {
private static HashMap<Integer,BaseFragment> mFragmentMap = new HashMap<Integer,BaseFragment>();
public static BaseFragment createFragment(int pos){
//先从集合中取，如果没有，才创建对象，提高性能
BaseFragment fragment = mFragmentMap.get(pos);
if(fragment == null) {
switch (pos) {
case 0:
fragment = new HomeFragment();
break;
case 1:
fragment = new AppFragment();
break;
case 2:
fragment = new GameFragment();
break;
case 3:
fragment = new SubjectFragment();
break;
case 4:
fragment = new RecommendFragment();
break;
case 5:
fragment = new CategoryFragment();
break;
case 6:
fragment = new HotFragment();
break;
default:
break;
}
mFragmentMap.put(pos, fragment);//将fragment保存在集合中
}
return fragment;
}
}
这些Fragment都继承了BaseFragment
public abstract class BaseFragment extends Fragment{
@Nullable
private LoadingPage mLoadingPage;
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
//使用textview显示当前类的类名
// TextView view = new TextView(UIUtils.getContext());
// view.setText(getClass().getSimpleName());
mLoadingPage = new LoadingPage(UIUtils.getContext()){
@Override
public View onCreateSuccessView() {
//注意：此处一定要调用BaseFragment的onCreateView，否则栈溢出
return BaseFragment.this.onCreateSuccessView();
}
@Override
public ResultState onLoad() {
return BaseFragment.this.onLoad();
}
};
return mLoadingPage;
}
//加载成功的布局，必须由子类来实现
public abstract View onCreateSuccessView();
//加载网络数据必须由子类实现
public abstract LoadingPage.ResultState onLoad();
//开始加载数据
public void loadData(){
if(mLoadingPage != null){
mLoadingPage.loadData();
}
}
}
虽然看上去各个Fragment的展示页面是不同的但其实细分还有这么几种状态：
-未加载 -加载中 -加载失败 -数据为空 -加载成功
所以我们可以写一个LoadingPage类来根据不同的情况展现不同的页面
有两个抽象方法需要我们注意它需要子类来实现，这样才能在数据请求成功后回调这些方法展示我们想要看到的页面
/** * 根据当前状态来显示不同页面的自定义控件 * * - 未加载 - 加载中 - 加载失败 - 数据为空 - 加载成功 * * @author Kevin * @date 2015-10-27 */
public abstract class LoadingPage extends FrameLayout {
private static final int STATE_LOAD_UNDO = 1;// 未加载
private static final int STATE_LOAD_LOADING = 2;// 正在加载
private static final int STATE_LOAD_ERROR = 3;// 加载失败
private static final int STATE_LOAD_EMPTY = 4;// 数据为空
private static final int STATE_LOAD_SUCCESS = 5;// 加载成功
private int mCurrentState = STATE_LOAD_UNDO;// 当前状态
private View mLoadingPage;
private View mErrorPage;
private View mEmptyPage;
private View mSuccessPage;
public LoadingPage(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initView();
}
public LoadingPage(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}
public LoadingPage(Context context) {
super(context);
initView();
}
private void initView() {
// 初始化加载中的布局
if (mLoadingPage == null) {
mLoadingPage = UIUtils.inflate(R.layout.page_loading);
addView(mLoadingPage);// 将加载中的布局添加给当前的帧布局
}
// 初始化加载失败布局
if (mErrorPage == null) {
mErrorPage = UIUtils.inflate(R.layout.page_error);
addView(mErrorPage);
}
// 初始化数据为空布局
if (mEmptyPage == null) {
mEmptyPage = UIUtils.inflate(R.layout.page_empty);
addView(mEmptyPage);
}
showRightPage();
}
// 根据当前状态,决定显示哪个布局
private void showRightPage() {
// if (mCurrentState == STATE_LOAD_UNDO
// || mCurrentState == STATE_LOAD_LOADING) {
// mLoadingPage.setVisibility(View.VISIBLE);
// } else {
// mLoadingPage.setVisibility(View.GONE);
// }
mLoadingPage
.setVisibility((mCurrentState == STATE_LOAD_UNDO || mCurrentState == STATE_LOAD_LOADING) ? View.VISIBLE
: View.GONE);
mErrorPage
.setVisibility(mCurrentState == STATE_LOAD_ERROR ? View.VISIBLE
: View.GONE);
mEmptyPage
.setVisibility(mCurrentState == STATE_LOAD_EMPTY ? View.VISIBLE
: View.GONE);
// 当成功布局为空,并且当前状态为成功,才初始化成功的布局
if (mSuccessPage == null && mCurrentState == STATE_LOAD_SUCCESS) {
mSuccessPage = onCreateSuccessView();
if (mSuccessPage != null) {
addView(mSuccessPage);
}
}
if (mSuccessPage != null) {
mSuccessPage
.setVisibility(mCurrentState == STATE_LOAD_SUCCESS ? View.VISIBLE
: View.GONE);
}
}
// 开始加载数据
public void loadData() {
if (mCurrentState != STATE_LOAD_LOADING) {// 如果当前没有加载, 就开始加载数据
mCurrentState = STATE_LOAD_LOADING;
new Thread() {
@Override
public void run() {
final ResultState resultState = onLoad();
// 运行在主线程
UIUtils.runOnUIThread(new Runnable() {
@Override
public void run() {
if (resultState != null) {
mCurrentState = resultState.getState();// 网络加载结束后,更新网络状态
// 根据最新的状态来刷新页面
showRightPage();
}
}
});
}
}.start();
}
}
// 加载成功后显示的布局, 必须由调用者来实现
public abstract View onCreateSuccessView();
// 加载网络数据, 返回值表示请求网络结束后的状态
public abstract ResultState onLoad();
public enum ResultState {
STATE_SUCCESS(STATE_LOAD_SUCCESS), STATE_EMPTY(STATE_LOAD_EMPTY), STATE_ERROR(
STATE_LOAD_ERROR);
private int state;
private ResultState(int state) {
this.state = state;
}
public int getState() {
return state;
}
}
public static class Person {
public static Person P1 = new Person(10);
public static Person P2 = new Person(12);
public static Person P3 = new Person(19);
public Person(int age) {
}
}
// public enum Person {
// P1,P2,P3;
// }
}
结构示意图如下
上面BaseFragment的代码已经给出以HomeFragment为例
/** * 首页 * Created by matri on 2017/5/11. */
public class HomeFragment extends BaseFragment {
//如果加载数据成功，回调此方法,在主线程运行
@Override
public View onCreateSuccessView() {
TextView view = new TextView(UIUtils.getContext());
view.setText(getClass().getSimpleName());
return view;
}
//运行在子线程，可以直接执行耗时网络操作
@Override
public LoadingPage.ResultState onLoad() {
//请求网络
return LoadingPage.ResultState.STATE_SUCCESS;
}
}
数据请求部分我们在后面的文章中学习完成