一. 图示
支付宝效果
实现的效果
二. 思路讲解
TabLayout+ScrollView实现即可。每一个tab对应scrollview中包裹的一层布局，以上有4个tab，也就需要inflate 4个布局文件，用来表示每一层的样式内容。
1.页面加载完毕后，记住每一层父布局在Screen中所要滑动至顶部的距离Distance；
2.操作：
a. 当点击tab时：滑动scrollview该层的距离Distance；
b. 当滑动scrollview至对应的层时： 选定对应的tab。
三. 代码
1. 布局代码
布局代码很简单，可能会有的疑问点有：
a. wrapperFl是用来干啥的？
b. ObservableScrollView又是个什么东西？
（后面说明）
2. 逻辑代码
public class MainActivity extends AppCompatActivity implements ObservableScrollView.ScrollViewListener {
private static final String TAG = "MainActivity";
private FrameLayout wrapperFl;
private TabLayout tabLayout;
private ObservableScrollView scrollView;
private LinearLayout containerLl;
private boolean firstAlreadyInflated = true;
private ViewGroup firstFloorVg;
private ViewGroup secondFloorVg;
private ViewGroup thirdFloorVg;
private ViewGroup fourthFloorVg;
private int secondFloorVgPositionDistance;//第二层滑动至顶部的距离
private int thirdFloorVgPositionDistance;
private int fourthFloorVgPositionDistance;
private int currentPosition = 0;
private boolean tabInterceptTouchEventTag = true;//标志位，用来区分是点击了tab还是手动滑动scrollview
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initViews();
initListeners();
}
private void initViews() {
wrapperFl = (FrameLayout) findViewById(R.id.wrapperFl);
tabLayout = (TabLayout) findViewById(R.id.tabLayout);
scrollView = (ObservableScrollView) findViewById(R.id.scrollView);
containerLl = (LinearLayout) findViewById(R.id.containerLl);
for (int i = 0; i < 4; i++) {
tabLayout.addTab(tabLayout.newTab().setText("tab" + (i + 1)));
}
firstFloorVg = (ViewGroup) LayoutInflater.from(this).inflate(R.layout.item_floor_first, null);
secondFloorVg = (ViewGroup) LayoutInflater.from(this).inflate(R.layout.item_floor_second, null);
thirdFloorVg = (ViewGroup) LayoutInflater.from(this).inflate(R.layout.item_floor_third, null);
fourthFloorVg = (ViewGroup) LayoutInflater.from(this).inflate(R.layout.item_floor_fourth, null);
containerLl.addView(firstFloorVg);
containerLl.addView(secondFloorVg);
containerLl.addView(thirdFloorVg);
containerLl.addView(fourthFloorVg);
}
@Override
public void onWindowFocusChanged(boolean hasFocus) {
super.onWindowFocusChanged(hasFocus);
if (firstAlreadyInflated) {//获取各层离screen顶部的位置以及计算滑动值相应顶部所需要的距离
firstAlreadyInflated = false;
int[] firstFloorVgPosition = new int[2];
int[] secondFloorVgPosition = new int[2];
int[] thirdFloorVgPosition = new int[2];
int[] fourthFloorVgPosition = new int[2];
firstFloorVg.getLocationOnScreen(firstFloorVgPosition);
secondFloorVg.getLocationOnScreen(secondFloorVgPosition);
thirdFloorVg.getLocationOnScreen(thirdFloorVgPosition);
fourthFloorVg.getLocationOnScreen(fourthFloorVgPosition);
int firstFloorVgPositionAnchor = firstFloorVgPosition[1];
int secondFloorVgPositionAnchor = secondFloorVgPosition[1];
int thirdFloorVgPositionAnchor = thirdFloorVgPosition[1];
int fourthFloorVgPositionAnchor = fourthFloorVgPosition[1];
Log.d(TAG, "第一层距离屏幕的距离是：" + firstFloorVgPosition[1]);
Log.d(TAG, "第二层距离屏幕的距离是：" + secondFloorVgPosition[1]);
Log.d(TAG, "第三层距离屏幕的距离是：" + thirdFloorVgPosition[1]);
Log.d(TAG, "第四层距离屏幕的距离是：" + fourthFloorVgPosition[1]);
secondFloorVgPositionDistance = secondFloorVgPositionAnchor - firstFloorVgPositionAnchor;
thirdFloorVgPositionDistance = thirdFloorVgPositionAnchor - firstFloorVgPositionAnchor;
fourthFloorVgPositionDistance = fourthFloorVgPositionAnchor - firstFloorVgPositionAnchor;
}
}
private void initListeners() {
wrapperFl.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.d(TAG,"wrapperFl onTouch");
tabInterceptTouchEventTag = true;//让tab来处理滑动
return false;
}
});
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
currentPosition = tab.getPosition();
if(!tabInterceptTouchEventTag){//手动滑动页面时则不再次处理滑动
return;
}
scrollView.computeScroll();
switch (currentPosition) {
case 0:
scrollView.smoothScrollTo(0, 0);
break;
case 1:
scrollView.smoothScrollTo(0, secondFloorVgPositionDistance);
break;
case 2:
scrollView.smoothScrollTo(0, thirdFloorVgPositionDistance);
break;
case 3:
scrollView.smoothScrollTo(0, fourthFloorVgPositionDistance);
break;
default:
break;
}
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
scrollView.setScrollViewListener(this);
scrollView.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
Log.d(TAG, "scrollView onTouch");
tabInterceptTouchEventTag = false;//让scrollview处理滑动
return false;
}
});
}
@Override
public void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy) {
if (tabInterceptTouchEventTag) {//让tab来处理滑动
return;
}
Log.d(TAG, "当前scrollView的位置——>" + y);
if (y < secondFloorVgPositionDistance) {
if (currentPosition != 0) {
scrollView.computeScroll();
tabLayout.getTabAt(0).select();
}
} else if (y < thirdFloorVgPositionDistance) {
if (currentPosition != 1) {
scrollView.computeScroll();
tabLayout.getTabAt(1).select();
}
} else if (y < fourthFloorVgPositionDistance) {
if (currentPosition != 2) {
scrollView.computeScroll();
tabLayout.getTabAt(2).select();
}
} else {
if (currentPosition != 3) {
scrollView.computeScroll();
tabLayout.getTabAt(3).select();
}
}
}
}
a. tabInterceptTouchEventTag 作为标志位是为了防止因scrollview触发了tab Selected从而再次引起scrollview滑动导致的滑动不流畅。
b. wrapperFl的存在则是要去给 tabInterceptTouchEventTag 赋值，因为TabLayout的Touch、Click、Focus等事件被消化掉了，无法在这些事件中监听到对应的值的变化，所以通过wrapperFl来进行Touch事件的监听。
c. ObservableScrollView 是继承自Scrollview，新增和改变了其中的以下方法：
public void setScrollViewListener(ScrollViewListener scrollViewListener) {
this.scrollViewListener = scrollViewListener;
}
@Override
protected void onScrollChanged(int x, int y, int oldx, int oldy) {
super.onScrollChanged(x, y, oldx, oldy);
if (scrollViewListener != null) {
scrollViewListener.onScrollChanged(this, x, y, oldx, oldy);
}
}
public interface ScrollViewListener {
void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy);
}
这样就可以在activity主界面中监听到scrollview的滑动事件，从而获取当前整个scrollview所处的位置，进而去判定是否需要选定对应的tab。
ps：如果要做成支付宝那样TabLayout上还有个TopView的内容样式，则可以参考之前写过的博客的做法：View滑动固定效果实现>>
最后，完整代码可以查看GitHub>>