Android 实现锚点定位思路详解

public class CustomScrollView extends ScrollView { public Callbacks mCallbacks; public CustomScrollView(Context context) {  super(context); } public CustomScrollView(Context context, AttributeSet attrs) {  super(context, attrs); } public CustomScrollView(Context context, AttributeSet attrs, int defStyleAttr) {  super(context, attrs, defStyleAttr); } public void setCallbacks(Callbacks callbacks) {  this.mCallbacks = callbacks; } @Override protected void onScrollChanged(int l, int t, int oldl, int oldt) {  super.onScrollChanged(l, t, oldl, oldt);  if (mCallbacks != null) {   mCallbacks.onScrollChanged(l, t, oldl, oldt);  } } //定义接口用于回调 public interface Callbacks {  void onScrollChanged(int x, int y, int oldx, int oldy); }}

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <android.support.design.widget.TabLayout  android:id="@+id/tablayout"  android:layout_width="match_parent"  android:layout_height="wrap_content"  app:tabIndicatorColor="@color/colorPrimary"  app:tabMode="scrollable"  app:tabSelectedTextColor="@color/colorPrimary" /> <com.tabscroll.CustomScrollView  android:id="@+id/scrollView"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:fillViewport="true"  android:fitsSystemWindows="true">  <LinearLayout   android:id="@+id/container"   android:layout_width="match_parent"   android:layout_height="wrap_content"   android:orientation="vertical"   android:padding="16dp">  </LinearLayout> </com.tabscroll.CustomScrollView></LinearLayout>

private String[] tabTxt = {"客厅", "卧室", "餐厅", "书房", "阳台", "儿童房"};//内容块view的集合private List<AnchorView> anchorList = new ArrayList<>();//判读是否是scrollview主动引起的滑动，true-是，false-否，由tablayout引起的private boolean isScroll;//记录上一次位置，防止在同一内容块里滑动 重复定位到tablayoutprivate int lastPos;//模拟数据，填充scrollviewfor (int i = 0; i < tabTxt.length; i++) { AnchorView anchorView = new AnchorView(this); anchorView.setAnchorTxt(tabTxt[i]); anchorView.setContentTxt(tabTxt[i]); anchorList.add(anchorView); container.addView(anchorView);}//tablayout设置标签for (int i = 0; i < tabTxt.length; i++) { tabLayout.addTab(tabLayout.newTab().setText(tabTxt[i]));}

public class AnchorView extends LinearLayout { private TextView tvAnchor; private TextView tvContent; public AnchorView(Context context) {  this(context, null); } public AnchorView(Context context, @Nullable AttributeSet attrs) {  this(context, attrs, 0); } public AnchorView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {  super(context, attrs, defStyleAttr);  init(context); } private void init(Context context) {  View view = LayoutInflater.from(context).inflate(R.layout.view_anchor, this, true);  tvAnchor = view.findViewById(R.id.tv_anchor);  tvContent = view.findViewById(R.id.tv_content);  Random random = new Random();  int r = random.nextInt(256);  int g = random.nextInt(256);  int b = random.nextInt(256);  tvContent.setBackgroundColor(Color.rgb(r, g, b)); } public void setAnchorTxt(String txt) {  tvAnchor.setText(txt); } public void setContentTxt(String txt) {  tvContent.setText(txt); }}

scrollView.setOnTouchListener(new View.OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) {  //当由scrollview触发时，isScroll 置true  if (event.getAction() == MotionEvent.ACTION_DOWN) {   isScroll = true;  }  return false; }});scrollView.setCallbacks(new CustomScrollView.Callbacks() { @Override public void onScrollChanged(int x, int y, int oldx, int oldy) {  if (isScroll) {   for (int i = tabTxt.length - 1; i >= 0; i--) {    //根据滑动距离，对比各模块距离父布局顶部的高度判断    if (y > anchorList.get(i).getTop() - 10) {     setScrollPos(i);     break;    }   }  } }});//tablayout对应标签的切换private void setScrollPos(int newPos) { if (lastPos != newPos) {  //该方法不会触发tablayout 的onTabSelected 监听  tabLayout.setScrollPosition(newPos, 0, true); } lastPos = newPos;}tabLayout的点击切换：tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() { @Override public void onTabSelected(TabLayout.Tab tab) {  //点击标签，使scrollview滑动，isScroll置false  isScroll = false;  int pos = tab.getPosition();  int top = anchorList.get(pos).getTop();  scrollView.smoothScrollTo(0, top); } @Override public void onTabUnselected(TabLayout.Tab tab) { } @Override public void onTabReselected(TabLayout.Tab tab) { }});

//监听判断最后一个模块的高度，不满一屏时让最后一个模块撑满屏幕private ViewTreeObserver.OnGlobalLayoutListener listener;listener = new ViewTreeObserver.OnGlobalLayoutListener() { @Override public void onGlobalLayout() {  int screenH = getScreenHeight();  int statusBarH = getStatusBarHeight(MainActivity.this);  int tabH = tabLayout.getHeight();  //计算内容块所在的高度，全屏高度-状态栏高度-tablayout的高度-内容container的padding 16dp  int lastH = screenH - statusBarH - tabH - 16 * 3;  AnchorView lastView = anchorList.get(anchorList.size() - 1);  //当最后一个view 高度小于内容块高度时，设置其高度撑满  if (lastView.getHeight() < lastH) {   LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);   params.height = lastH;   lastView.setLayoutParams(params);  }  container.getViewTreeObserver().removeOnGlobalLayoutListener(listener); }};container.getViewTreeObserver().addOnGlobalLayoutListener(listener);