[英]How to initialize an interface defined in an Activity which is implemented by 3 fragments setup with ViewPager via TabLayout?
我有一个活动,其中包含带有 ViewPager 的 TabLayout 设置和 3 个片段这 3 个片段包含一些独特的方法,它们需要在单击按钮时调用,该按钮是菜单中的菜单项,以便为父活动膨胀这3个片段。
现在我无法初始化在名为 OnMenuSaveButonClickListener 的活动中定义的接口,因为我收到一个错误:
Caused by: java.lang.ClassCastException: com.blah.blah.EditProductInfoActivity cannot be cast to com.blah.blah.EditProductInfoActivity$OnMenuSaveButonClickListener
at com.blah.blah.EditProductInfoActivity.onCreate(EditProductInfoActivity.java:53)
带有 ViewPager 的父活动代码(带有 TabLayout 中的片段):
public class EditProductInfoActivity extends AppCompatActivity {
TabLayout tabLayout;
ViewPager mViewPager;
OnMenuSaveButonClickListener mCallback;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit_product_info);
tabLayout = (TabLayout) findViewById(R.id.tabs);
mViewPager = (ViewPager) findViewById(R.id.v_pager_prod);
mCallback = (OnMenuSaveButonClickListener) this; //line:53 with error
initViewPager();
private void initViewPager() {
ArrayList<Fragment> fragments = new ArrayList<>();
fragments.add(new CatalogueItemInfoFragment());
fragments.add(new CatalogueItemInventoryFragment());
fragments.add(new CatalogueItemNotesFragment());
ProductTabsViewPagerAdapter productTabs = new ProductTabsViewPagerAdapter(
getSupportFragmentManager(),this, fragments);
mViewPager.setAdapter(productTabs);
tabLayout.setupWithViewPager(mViewPager);
tabLayout.getTabAt(0).setText("Product Info");
tabLayout.getTabAt(1).setText("Inventory");
tabLayout.getTabAt(2).setText("Notes");
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.item_info_menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()){
case R.id.item_check:
mCallback.onMenuButonClick();
return true;
default: return super.onOptionsItemSelected(item);
}
}
public interface OnMenuSaveButonClickListener{
void onMenuButonClick();
}
}
ViewPager Adpater 类的代码:
public class ProductTabsViewPagerAdapter extends FragmentPagerAdapter {
private Context context;
private List<Fragment> fragments;
public ProductTabsViewPagerAdapter(FragmentManager fm, Context context, List<Fragment> fragments) {
super(fm);
this.context = context;
this.fragments = fragments;
}
@Override
public Fragment getItem(int position) {
return fragments.get(position);
}
@Override
public int getCount() {
return fragments.size();
}
}
片段 1 的代码:
public class CatalogueItemInfoFragment extends Fragment implements EditProductInfoActivity.OnMenuSaveButonClickListener {
...
...
public void setItemFromItemForm(){
productViewModel.setSize(productSizeText.getText().toString());
productViewModel.setSizeSelection(productSizeSelectionText.getText().toString());
productViewModel.setColor(productColorText.getText().toString());
}
@Override
public void onMenuButonClick() {
setItemFromItemForm();
}
}
片段 2 的代码:
public class CatalogueItemInventoryFragment extends Fragment implements EditProductInfoActivity.OnMenuSaveButonClickListener {
...
...
private void setItemInventoryInfo() {
productViewModel.setAvailableQuantity(Integer.parseInt(availableQtyText.getText().toString()));
productViewModel.setIsOutOfStock(outOfStockSwitch.isChecked());
productViewModel.setIsShowOutOfStock(showOutOfStockSwitch.isChecked());
productViewModel.setIsForceAllowOrder(forceAllowOrderSwitch.isChecked());
}
@Override
public void onMenuButonClick() {
setItemInventoryInfo();
}
}
片段 3 的代码:
public class CatalogueItemNotesFragment extends Fragment implements EditProductInfoActivity.OnMenuSaveButonClickListener {
...
...
private void setItemMoreDetails() {
mStaticProduct.setNotes(productNotesText.getText().toString());
productViewModel.setNotes(productNotesText.getText().toString());
}
@Override
public void onMenuButonClick() {
setItemMoreDetails();
}
}
从 TabLayout 获取选定的选项卡位置,以便您可以将当前片段定位为可见
int selectedTab = tabLayout.getSelectedTabPosition();
从该片段调用OnMenuSaveButonClickListener实现方法
((OnMenuSaveButonClickListener) fragment.get(selectedTab)).onMenuButonClick();
此代码在onOptionsItemSelected 中进入您的活动,您可以将该逻辑放在一个函数中,以避免为其他菜单项选项重复相同的行。
确保从代码中删除 mCallback 和它的分配。
我建议您还从您的活动中删除OnMenuSaveButonClickListener接口定义,并将其放在自己的 .java (OnMenuSaveButonClickListener.java) > 松散耦合中。
片段正在实现接口,因此调用方法如下:
((OnMenuSaveButonClickListener)fragments.get(i)).onMenuButonClick();
并删除第 53 行。
所以你在适配器中有片段列表,添加一个 getter 方法来获取片段列表
public List<Fragments> getFragments(){
return fragments;
}
然后点击这样做,
final List<Fragment> fragments = productTabs.getFragments();
for (Fragment fragment : fragments) {
if (fragment instanceof OnMenuSaveButonClickListener) {
((OnMenuSaveButonClickListener) fragment).onMenuButonClick();
}
}
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