[置顶] 记录：Android api 24+的TabLayout问题处理

API 24的TabLayout更新了一些方法 用着有些问题 比如像我遇到的自定义处理某些tab点击时想要不切换viewPager 而是弹出一个activity

下面是一个简单的懒人处理方式 附带源码分析

ViewPager vp = (ViewPager)findViewById(R.id.viewPager);
TabLayout tabLayout = (TabLayout)findViewById(R.id.tabLayout);
tabLayout.setupWithViewPager(vp);//看看这个方法做了什么

private void setupWithViewPager(@Nullable final ViewPager viewPager, boolean autoRefresh,
boolean implicitSetup) {
if (mViewPager != null) {
// If we've already been setup with a ViewPager, remove us from it
if (mPageChangeListener != null) {
mViewPager.removeOnPageChangeListener(mPageChangeListener);
}
if (mAdapterChangeListener != null) {
mViewPager.removeOnAdapterChangeListener(mAdapterChangeListener);
}
}

if (mCurrentVpSelectedListener != null) {
// If we already have a tab selected listener for the ViewPager, remove it
removeOnTabSelectedListener(mCurrentVpSelectedListener);
mCurrentVpSelectedListener = null;
}

if (viewPager != null) {
mViewPager = viewPager;

// Add our custom OnPageChangeListener to the ViewPager
if (mPageChangeListener == null) {
mPageChangeListener = new TabLayoutOnPageChangeListener(this);
}
mPageChangeListener.reset();
viewPager.addOnPageChangeListener(mPageChangeListener);

// Now we'll add a tab selected listener to set ViewPager's current item
mCurrentVpSelectedListener = new ViewPagerOnTabSelectedListener(viewPager);
addOnTabSelectedListener(mCurrentVpSelectedListener);//这里给你添加了一个OnTabSelectedListener

final PagerAdapter adapter = viewPager.getAdapter();
if (adapter != null) {
// Now we'll populate ourselves from the pager adapter, adding an observer if
// autoRefresh is enabled
setPagerAdapter(adapter, autoRefresh);
}

// Add a listener so that we're notified of any adapter changes
if (mAdapterChangeListener == null) {
mAdapterChangeListener = new AdapterChangeListener();
}
mAdapterChangeListener.setAutoRefresh(autoRefresh);
viewPager.addOnAdapterChangeListener(mAdapterChangeListener);

// Now update the scroll position to match the ViewPager's current item
setScrollPosition(viewPager.getCurrentItem(), 0f, true);
} else {
// We've been given a null ViewPager so we need to clear out the internal state,
// listeners and observers
mViewPager = null;
setPagerAdapter(null, false);
}

mSetupViewPagerImplicitly = implicitSetup;
}

看上面的源码你会发现 这个方法里 TabLayout会帮你add一个OnTabSelectedListener 就是下面这个

class ViewPagerOnTabSelectedListener implements TabLayout.OnTabSelectedListener {
private final ViewPager mViewPager;

public ViewPagerOnTabSelectedListener(ViewPager viewPager) {
mViewPager = viewPager;
}

@Override
public void onTabSelected(TabLayout.Tab tab) {
mViewPager.setCurrentItem(tab.getPosition());//强行帮你选中你不希望选中的viewPager的某个页面
}

@Override
public void onTabUnselected(TabLayout.Tab tab) {
// No-op
}

@Override
public void onTabReselected(TabLayout.Tab tab) {
// No-op
}
}

然后罪魁祸首是TabLayout的这个方法 从上面可以看出来 在你addOnTabSelectedListener之前已经有一个OnTabSelectedListener了

所以 执行完你自己加的OnTabSelectedListener的onTabSelected之后 总会执行TabLayout会帮你add那个OnTabSelectedListener的onTabSelected

private void dispatchTabSelected(@NonNull final Tab tab) {
for (int i = mSelectedListeners.size() - 1; i >= 0; i--) {
mSelectedListeners.get(i).onTabSelected(tab);
}
}

所以 我想到的解决方案是强行remove掉它给你加的那个OnTabSelectedListener 可以 这很反射 当然 你要换成github上的一些TabLayout也无妨

Field fields[] = tabLayout.getClass().getDeclaredFields();
String[] name = new String[fields.length];
Object[] value = new Object[fields.length];

try {
Field.setAccessible(fields, true);
for (int i = 0; i < name.length; i++) {
name[i] = fields[i].getName();
value[i] = fields[i].get(tabLayout);
if (name[i].equals("mCurrentVpSelectedListener")) {
tabLayout.removeOnTabSelectedListener((TabLayout.OnTabSelectedListener) value[i]);
}
}
} catch (Exception e) {
e.printStackTrace();
}

然后自定义自己的OnTabSelectedListener

OnTabSelectedListener mTabSelectedListener = new TabLayout.ViewPagerOnTabSelectedListener(vp) {

@Override
public void onTabSelected(TabLayout.Tab tab) {
int position = (int) tab.getTag();
if (position == 0) {
vp.setCurrentItem(tab.getPosition());
}else if (position == 1) {
if (condition) {//condition：自己写的某些条件
if (tab != null) {
vp.setCurrentItem(tab.getPosition());//手动调用viewPager的setCurrentItem
}
} else {
doSomething();//可以做些其他事情 这里不用调用viewPager的setCurrentItem 就不会切到不想切换的viewPager那个页面了
}
}
}

@Override
public void onTabUnselected(TabLayout.Tab tab) {
}

@Override
public void onTabReselected(TabLayout.Tab tab) {
//之所以要在这里添加reslect的处理 主要是你之前点击tab的时候虽然没选中并切换Viewpager的页面
//但是 TabLayout的状态其实已经被选中了 再次点击时肯定是不会走onTabSelected方法的
//但是会走这个onTabReselected 另外 选中时一些UI上的图标、文字切换效果什么的需要自己在onTabSelected中处理
int position = (int) tab.getTag();
L.e(TAG, position + " onTabReselected");
mTabSelectedListener.onTabSelected(tab);
}
};

最后addOnTabSelectedListener

tabLayout.addOnTabSelectedListener(mTabSelectedListener);

release版本开了混淆的话在proguard-rules.pro加上

-keepclasseswithmembernames class android.support.design.widget.TabLayout {
*;
}