为了节约资源,现在很多 app 采用了 replace() 方法来实现碎片的切换,但是在这种情宽下,如果不讲之前的碎片雅茹栈中,就无法避免之前碎片回随之销毁,所以我们采用 hide() 和 show() 方法来实现碎片的切换。
效果图项目地址--https://github.com/FishInWater-1999/android-SignInSystem
首先,定义四个成员
private Fragment mContent = new Fragment();// 记录下当前碎片 由于替换
private Fragment mPerson;
private Fragment mRanking;
private Fragment mSummary;
private FragmentTransaction transaction;
其次,在 OnCreate() 方法中,对他们进行初始化
mPerson = new Personal();
mRanking = new Ranking();
mSummary = new Summary();
fragmentManager = getSupportFragmentManager();
mContent = mRanking;
FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.add(R.id.fragment, mContent).commit();
navigation.setSelectedItemId(R.id.navigation_home);
最后,在按钮点击时调用
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.navigation_home:
switchContent(mPerson);
return true;
case R.id.navigation_dashboard:
switchContent(mRanking);
return true;
case R.id.navigation_ranking:
switchContent(mSummary);
return true;
}
return false;
}
};
private void switchContent(Fragment to) {
if (mContent != to) {
FragmentTransaction transaction = fragmentManager.beginTransaction();
if (!to.isAdded()) { // 判断是否被add过
// 隐藏当前的fragment,将 下一个fragment 添加进去
transaction.hide(mContent).add(R.id.fragment, to).commit();
} else {
// 隐藏当前的fragment,显示下一个fragment
transaction.hide(mContent).show(to).commit();
}
mContent = to;
}
}