Android技能树 — Fragment总体小结，2024年最新腾讯面试gm

xmlns:android=“http://schemas.android.com/apk/res/android”
xmlns:app=“http://schemas.android.com/apk/res-auto”
xmlns:tools=“http://schemas.android.com/tools”
android:orientation=“vertical”
android:layout_width=“match_parent”
android:layout_height=“match_parent”>

Button button = new Button(mActivity);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams( LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.WRAP_CONTENT);
button.setLayoutParams(params);
container.addView(button);

Fragment one = new FragmentOne();//自定义的Fragment类
//要先获取FragmentManager对象
FragmentManager fragmentManager = getSupportFragmentManager();
//开启一个FragmentTransaction事务
FragmentTransaction transaction = fragmentManager.beginTransaction();
transaction.add(R.id.framelayout_view,one).commit();

/**
• Return the FragmentManager for interacting with fragments associated
• with this activity.
• 
• @deprecated Use {@link android.support.v4.app.FragmentActivity#getSupportFragmentManager()}
*/
@Deprecated
public FragmentManager getFragmentManager() {
return mFragments.getFragmentManager();
}

Class xxxFragment extends Fragment {
private Context mContext;
//‘高版本后，都是回调这个方法’
@Override
public void onAttach(Context context) {
super.onAttach(context);
mContext = context;
}
//‘API低于 23 的版本的时候，是会回调这个方法’
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
mContext = activity;
}
}

public class FragmentAdapter extends FragmentPagerAdapter{
private ArrayList list;
//通过构造获取fragment集合
public Fragment_pager(FragmentManager fm,ArrayList list) {
super(fm);
this.list=list;
}
//设置具体position的fragment
@Override
public Fragment getItem(int position) {
// TODO Auto-generated method stub
return list.get(position);
}
//设置有多少个fragment
@Override
public int getCount() {
// TODO Auto-generated method stub
return list.size();
}
}

public abstract class FragmentPagerAdapter extends PagerAdapter {
//‘初始化创建Item:’
@NonNull
public Object instantiateItem(@NonNull ViewGroup container, int position) {
if (this.mCurTransaction == null) {
this.mCurTransaction = this.mFragmentManager.beginTransaction();
}
long itemId = this.getItemId(position);
String name = makeFragmentName(container.getId(), itemId);
Fragment fragment = this.mFragmentManager.findFragmentByTag(name);
if (fragment != null) {
//‘后面使用fragment是通过FragmentTransaction.attach方式加进来的，’
//‘只是重新绘制了UI,fragment对象还在。’
this.mCurTransaction.attach(fragment);
} else {
//‘我们知道刚返回fragment使用的是getItem(position)方法’
//‘我们可以看到第一次使用fragment是通过FragmentTransaction.add方式加进来的’
fragment = this.getItem(position);
this.mCurTransaction.add(container.getId(), fragment, makeFragmentName(container.getId(), itemId));
}
if (fragment != this.mCurrentPrimaryItem) {
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
}
return fragment;
}
//‘销毁item:’
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
if (this.mCurTransaction == null) {
this.mCurTransaction = this.mFragmentManager.beginTransaction();
}
//‘我们可以看到FragmentTransaction只是单纯的detach了fragment,视图不在了，但是fragment对象还在’
this.mCurTransaction.detach((Fragment)object);
}
}

public abstract class FragmentStatePagerAdapter extends PagerAdapter {
@NonNull
public Object instantiateItem(@NonNull ViewGroup container, int position) {
Fragment fragment;
if (this.mFragments.size() > position) {
fragment = (Fragment)this.mFragments.get(position);
if (fragment != null) {
return fragment;
}
}
if (this.mCurTransaction == null) {
this.mCurTransaction = this.mFragmentManager.beginTransaction();
}
fragment = this.getItem(position);
if (this.mSavedState.size() > position) {
SavedState fss = (SavedState)this.mSavedState.get(position);
if (fss != null) {
fragment.setInitialSavedState(fss);
}
}
while(this.mFragments.size() <= position) {
this.mFragments.add((Object)null);
}
fragment.setMenuVisibility(false);
fragment.setUserVisibleHint(false);
this.mFragments.set(position, fragment);
//‘我们可以看到fragment都是add进来的’
this.mCurTransaction.add(container.getId(), fragment);
return fragment;
}
public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
Fragment fragment = (Fragment)object;
if (this.mCurTransaction == null) {
this.mCurTransaction = this.mFragmentManager.beginTransaction();
}
while(this.mSavedState.size() <= position) {
this.mSavedState.add((Object)null);
}
this.mSavedState.set(position, fragment.isAdded() ? this.mFragmentManager.saveFragmentInstanceState(fragment) : null);
this.mFragments.set(position, (Object)null);
//‘可以看到都是通过remove的方式移除了’
this.mCurTransaction.remove(fragment);
}