[英]Change textView value in viewpager from Activity
我在應用程序中使用了選項卡式視圖...
我的代碼...
public class ComboGraph extends AppCompatActivity {
Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_combo_graph);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
Button next = (Button) findViewById(R.id.button8);
final TextView textView = (TextView) findViewById(R.id.textView22);
next.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
textView.setText(textView.getText().toString() + "a");
ExpensesGraph expensesGraph=(ExpensesGraph)getSupportFragmentManager().findFragmentById(R.id.fragment1);
expensesGraph.textView.setText("Hello");
}
});
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(new ExpensesGraph(), "Expenses");
adapter.addFragment(new IncomeGraph(), "Income");
viewPager.setAdapter(adapter);
}
class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
}
ExpenseGraph.java
public class ExpensesGraph extends Fragment {
TextView textView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_epenses_graph, container, false);
textView = (TextView) view.findViewById(R.id.textview_fragment);
return view;
}
}
錯誤日志
java.lang.NullPointerException:嘗試從com.gloesolutions.pocketdiary.ComboGraph $ 1.onClick(ComboGraph.java:44)上的空對象引用中從字段“ android.widget.TextView com.pocketdiary.ExpensesGraph.textView”讀取
我需要更改combograph
按鈕單擊從expensgraph
活動值的textview。 我嘗試獲取空點錯誤的每種方法。 我該如何解決這個問題。
為ExpensesGraph和IncomeGraph創建一個BaseFragment,如下所示
public abstract class BaseFragment extends Fragment {
public abstract void updateComponent();
}
在活動按鈕中
Button next = (Button) findViewById(R.id.button8);
final TextView textView = (TextView) findViewById(R.id.textView22);
next.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
(BaseFragment)viewPageAdaptor.getItem(0)).updateComponent();
}
});
在ExpensesGraph和IncomeGraph片段中,您需要相應地更新TextView。 如果要在所有片段中進行相同的回調,請使其在循環內。
片段內
public class ExpensesGraph extends BaseFragment {
TextView textView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_epenses_graph, container, false);
textView = (TextView) view.findViewById(R.id.textview_fragment);
return view;
}
public void updateComponent(){
if(textView != null){
textView.setText("Update your text Here")
}
}}
您應該在這里調用replace方法mFragmentList.add(fragment);
因為有可能片段上的onCreateView
不會重新初始化
您可以在活動中創建兩個方法getter和setter。 public String getDataToPass(){返回必需文本;},public void setDataToPass(String requiredtext){this.requiredtext = requiredtext;},以及片段按鈕中的onClick,將數據傳遞給活動方法,例如。 btn.onClick(){getActivity()。setDataToPass(“ your text”);},最后在下一個片段OnViewCreated上:將文本作為String text = getActivity()。getDataToPass();
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