private SparseArray mFragmentPositionMap;
private SparseArray mFragmentPositionMapAfterUpdate;
public BaseFragmentPagerAdapter(FragmentManager fm, List fragments) {
super(fm);
mFragmentList = fragments;
mFragmentManager = fm;
mFragmentList = fragments;
mFragmentPositionMap = new SparseArray<>();
mFragmentPositionMapAfterUpdate = new SparseArray<>();
setFragmentPositionMap();
setFragmentPositionMapForUpdate();
}
/**
- 保存更新之前的位置信息，用<hashCode, position>的键值对结构来保存
*/
private void setFragmentPositionMap() {
mFragmentPositionMap.clear();
for (int i = 0; i < mFragmentList.size(); i++) {
mFragmentPositionMap.put(Long.valueOf(getItemId(i)).intValue(), String.valueOf(i));
}
}
/**
- 保存更新之后的位置信息，用<hashCode, position>的键值对结构来保存
*/
private void setFragmentPositionMapForUpdate() {
mFragmentPositionMapAfterUpdate.clear();
for (int i = 0; i < mFragmentList.size(); i++) {
mFragmentPositionMapAfterUpdate.put(Long.valueOf(getItemId(i)).intValue(), String.valueOf(i));
}
}
/**
- 在此方法中找到需要更新的位置返回POSITION_NONE，否则返回POSITION_UNCHANGED即可
*/
@Override
public int getItemPosition(Object object) {
int hashCode = object.hashCode();
//查找object在更新后的列表中的位置
String position = mFragmentPositionMapAfterUpdate.get(hashCode);
//更新后的列表中不存在该object的位置了
if (position == null) {
return POSITION_NONE;
} else {
//如果更新后的列表中存在该object的位置, 查找该object之前的位置并判断位置是否发生了变化
int size = mFragmentPositionMap.size();
for (int i = 0; i < size ; i++) {
int key = mFragmentPositionMap.keyAt(i);
if (key == hashCode) {
String index = mFragmentPositionMap.get(key);
if (position.equals(index)) {
//位置没变依然返回POSITION_UNCHANGED
return POSITION_UNCHANGED;
} else {
//位置变了
return POSITION_NONE;
}
}
}
}
return POSITION_UNCHANGED;
}
/**
-
将指定的Fragment替换/更新为新的Fragment
-
@param oldFragment 旧Fragment
-
@param newFragment 新Fragment
*/
public void replaceFragment(BaseFragment oldFragment, BaseFragment newFragment) {
int position = mFragmentList.indexOf(oldFragment);
if (position == -1) {
return;
}
//从Transaction移除旧的Fragment
removeFragmentInternal(oldFragment);
//替换List中对应的Fragment
mFragmentList.set(position, newFragment);
//刷新Adapter
notifyItemChanged();
}
/**
-
将指定位置的Fragment替换/更新为新的Fragment，同{@link #replaceFragment(BaseFragment oldFragment, BaseFragment newFragment)}
-
@param position 旧Fragment的位置
-
@param newFragment 新Fragment
*/
public void replaceFragment(int position, BaseFragment newFragment) {
BaseFragment oldFragment = mFragmentList.get(position);
removeFragmentInternal(oldFragment);
mFragmentList.set(position, newFragment);
notifyItemChanged();
}
/**
-
移除指定的Fragment
-
@param fragment 目标Fragment
*/
public void removeFragment(BaseFragment fragment) {
//先从List中移除
mFragmentList.remove(fragment);
//然后从Transaction移除
removeFragmentInternal(fragment);
//最后刷新Adapter
notifyItemChanged();
}
/**
- 移除指定位置的Fragment，同 {@link #removeFragment(B
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aseFragment fragment)}
- @param position
*/
public void removeFragment(int position) {
BaseFragment fragment = mFragmentList.get(position);
//然后从List中移除
mFragmentList.remove(fragment);
//先从Transaction移除
removeFragmentInternal(fragment);
//最后刷新Adapter
notifyItemChanged();
}
/**
-
添加Fragment
-
@param fragment 目标Fragment
*/
public void addFragment(BaseFragment fragment) {
mFragmentList.add(fragment);
notifyItemChanged();
}
/**
-
在指定位置插入一个Fragment
-
@param position 插入位置
-
@param fragment 目标Fragment
*/
public void insertFragment(int position, BaseFragment fragment) {
mFragmentList.add(position, fragment);
notifyItemChanged();
}
private void notifyItemChanged() {
//刷新之前重新收集位置信息
setFragmentPositionMapForUpdate();
notifyDataSetChanged();
setFragmentPositionMap();
}
/**
-
从Transaction移除Fragment
-
@param fragment 目标Fragment
*/
private void removeFragmentInternal(BaseFragment fragment) {
FragmentTransaction transaction = mFragmentManager.beginTransaction();
transaction.remove(fragment);
transaction.commitNow();
}
/**
- 此方法不用position做返回值即可破解fragment tag异常的错误
*/
@Override
public long getItemId(int position) {
// 获取当前数据的hashCode，其实这里不用hashCode用自定义的可以关联当前Item对象的唯一值也可以，只要不是直接返回position
return mFragmentList.get(position).hashCode();
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public List getFragments() {
return mFragmentList;
}
}
好了，现在这个类可以用来实现Fragment列表中的Fragment替换、删除、添加等操作了，并且可以实时刷新adapter, 你可以试验一下。
测试代码：
Activity代码
public class TestActivity extends FragmentActivity implements View.OnClickListener {
List mFragmentList;
ViewPager mViewPager;
public BaseFragmentPagerAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
mViewPager = findViewById(R.id.vp);
findViewById(R.id.btn_change).setOnClickListener(this);
mFragmentList = new ArrayList<>();
mFragmentList.add(getFg(“AAA”));
mFragmentList.add(getFg(“BBB”));
mFragmentList.add(getFg(“CCC”));
mFragmentList.add(getFg(“DDD”));
mAdapter = new BaseFragmentPagerAdapter(getSupportFragmentManager(), mFragmentList);
mViewPager.setAdapter(mAdapter);
}
private TestFragment getFg(String a){
TestFragment fragment = new TestFragment();
fragment.setTest(a);
return fragment;
}
@Override
public void onClick(View view) {
TestFragment eee = getFg(“EEE”);
//新增
mAdapter.addFragment(eee);
//插入
mAdapter.insertFragment(1, eee);
//删除
mAdapter.removeFragment(1);
//删除
mAdapter.removeFragment(mFragmentList.get(1));
//替换
mAdapter.replaceFragment(1, eee);
//替换
mAdapter.replaceFragment(mFragmentList.get(0), eee);
}
}
用到的TestFragment:
public class TestFragment extends Fragment {
private final static String TAG = TestFragment.class.getSimpleName();
private String test;
public View mContentView;
public void setTest(String test) {
this.test = test;
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.e(TAG, "onCreate: test = "+test);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
mContentView = inflater.inflate(R.layout.layout_fg, null);
Log.e(TAG, "onCreateView: test = "+test);
return mContentView;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
Log.e(TAG, "onViewCreated: test = "+test);
TextView testText = mContentView.findViewById(R.id.tv_test);
testText.setText(test);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.e(TAG, "onActivityCreated: test = "+test);
}
@Override
public void onDestroy() {
super.onDestroy();
Log.e(TAG, "onDestroy: test = "+test);
}
}
布局文件：