java - 如何在不同的 fragment 中更改不同样式的操作栏标题？

Question

我正在尝试用不同的标题更改我的 2 个 fragment 操作栏。但是，我在这些行中收到变量fragment可能未初始化错误:

ProfileFragment fragment = (ProfileFragment)fragment.get(0);

StartingTestFragment fragment2 = (StartingTestFragment) fragment2.get(0);

在 onPageSelected 方法中的 CombineFragmentActivity 中。感谢您的帮助。

CombineFragmentActivity.java

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.Gravity;

import java.util.ArrayList;
import java.util.List;
import java.util.Vector;

public class CombineFragmentActivity extends AppCompatActivity {
    private PagerAdapter mPagerAdapter;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.combine_fragment_activity);
        initialisePaging();
    }

    private void initialisePaging() {

        List<Fragment> fragments = new ArrayList<>();
        fragments.add(new StartingTestFragment());
        fragments.add(new ProfileFragment());
        mPagerAdapter = new PagerAdapter1(this.getSupportFragmentManager(),fragments);

        ViewPager pager = (ViewPager)findViewById(R.id.viewpager);
        pager.setAdapter(mPagerAdapter);

        pager.addOnPageChangeListener(new ViewPager.OnPageChangeListener(){
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {
                if(position == 0) {
                    ProfileFragment fragment = (ProfileFragment) fragment.get(0);
                    fragment.setActionBarTitle("Profil");
                } else {
                    StartingTestFragment fragment2 = (StartingTestFragment) fragment2.get(0);
                    fragment2.setActionBarTitle("Anasayfa");
                }

            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }

        });
    }
}

ProfileFragment.java

import android.graphics.Color;
import android.graphics.Typeface;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;


public class ProfileFragment extends Fragment implements AdapterView.OnItemSelectedListener {
    public ProfileFragment() {
        // Required empty public constructor
    }


    public static ProfileFragment newInstance() {
        ProfileFragment fragment = new ProfileFragment();
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_profile, container, false);

    }

    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Typeface ubuntu_MI = Typeface.createFromAsset(getActivity().getAssets(),"Ubuntu-MI.ttf");
        Typeface ubuntu_L = Typeface.createFromAsset(getActivity().getAssets(),"Ubuntu-L.ttf");
        Typeface ubuntu_R = Typeface.createFromAsset(getActivity().getAssets(),"Ubuntu-R.ttf");


        /**
         * Be carefull when trying to find a view element from a layout if the name is already defined in any layout
         * AndroidStudio will not hint an error and you will end up with with ugly null pointer error
        TextView question = (TextView) view.findViewById(R.id.textView7);
        question.setTypeface(ubuntu_R);
         TextView info = (TextView) view.findViewById(R.id.textView6);
         info.setTypeface(ubuntu_R);

         */


    }
    public void setActionBarTitle(String title) {
        Typeface ubuntu_MI = Typeface.createFromAsset(getActivity().getAssets(),"Ubuntu-MI.ttf");
        // Get the ActionBar
        android.support.v7.app.ActionBar ab = ((AppCompatActivity)getActivity()).getSupportActionBar();


        // Create a TextView programmatically.
        TextView tv = new TextView(getActivity());

        // Create a LayoutParams for TextView
        RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                RelativeLayout.LayoutParams.MATCH_PARENT, // Width of TextView
                RelativeLayout.LayoutParams.WRAP_CONTENT); // Height of TextView

        // Apply the layout parameters to TextView widget
        tv.setLayoutParams(lp);

        // Set text to display in TextView
        // This will set the ActionBar title text
        tv.setText(title);

        // Set the text color of TextView
        // This will change the ActionBar title text color
        tv.setTextColor(Color.parseColor("#FFF5EE"));

        // Center align the ActionBar title
        tv.setGravity(Gravity.CENTER_HORIZONTAL);

        // Set the serif font for TextView text
        // This will change ActionBar title text font
        tv.setTypeface(ubuntu_MI);

        // Underline the ActionBar title text
        // tv.setPaintFlags(tv.getPaintFlags()| Paint.UNDERLINE_TEXT_FLAG);

        // Set the ActionBar title font size
        tv.setTextSize(TypedValue.COMPLEX_UNIT_DIP,24);

        // Display a shadow around ActionBar title text
        //tv.setShadowLayer(
        //      1.f, // radius
        //    2.0f, // dx
        //  2.0f, // dy
        //  Color.parseColor("#FF8C00") // shadow color
        //);

        // Set the ActionBar display option
        ab.setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);

        // Finally, set the newly created TextView as ActionBar custom view
        ab.setCustomView(tv);
    }
    public boolean onOptionsItemSelected(MenuItem item) {
    //Action Bar' daki settings kısmına basıldığında ne yapacağını söylüyoruz.
        if(item.getItemId() == R.id.settings){
            Toast.makeText(getActivity(), "Ayarlara basıldı", Toast.LENGTH_SHORT).show();
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        super.onCreateOptionsMenu(menu, inflater);
        inflater.inflate(R.menu.menu_profile_activity, menu);

    }
    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {

    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {

    }

}

StartingTestFragment.java

import android.graphics.Color;
import android.graphics.Typeface;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.RelativeLayout;
import android.widget.Spinner;
import android.widget.TextView;


public class StartingTestFragment extends Fragment implements AdapterView.OnItemSelectedListener {
    private Spinner spinner;
    ArrayAdapter<CharSequence> adapter;



    public StartingTestFragment() {
        // Required empty public constructor
    }


    public static StartingTestFragment newInstance() {
        StartingTestFragment fragment = new StartingTestFragment();
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_startingtest, container, false);
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        spinner = (Spinner)view.findViewById(R.id.spinner);
        adapter = ArrayAdapter.createFromResource(getActivity(),R.array.simple_spinner_dropdown_item,R.layout.spinner_item);
        adapter.setDropDownViewResource(R.layout.spinner_dropdown_item);

        spinner.setAdapter(adapter);
        spinner.setOnItemSelectedListener(this);


        Typeface ubuntu_L = Typeface.createFromAsset(getActivity().getAssets(),"Ubuntu-L.ttf");
        Typeface ubuntu_R = Typeface.createFromAsset(getActivity().getAssets(),"Ubuntu-R.ttf");

        TextView info = (TextView) view.findViewById(R.id.textView6);
        TextView question = (TextView) view.findViewById(R.id.textView7);

        info.setTypeface(ubuntu_R);
        question.setTypeface(ubuntu_R);



    }
    public void setActionBarTitle(String title) {
        Typeface ubuntu_MI = Typeface.createFromAsset(getActivity().getAssets(),"Ubuntu-MI.ttf");
        // Get the ActionBar
        android.support.v7.app.ActionBar ab = ((AppCompatActivity)getActivity()).getSupportActionBar();


        // Create a TextView programmatically.
        TextView tv = new TextView(getActivity());

        // Create a LayoutParams for TextView
        RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                RelativeLayout.LayoutParams.MATCH_PARENT, // Width of TextView
                RelativeLayout.LayoutParams.WRAP_CONTENT); // Height of TextView

        // Apply the layout parameters to TextView widget
        tv.setLayoutParams(lp);

        // Set text to display in TextView
        // This will set the ActionBar title text
        tv.setText(title);

        // Set the text color of TextView
        // This will change the ActionBar title text color
        tv.setTextColor(Color.parseColor("#FFF5EE"));

        // Center align the ActionBar title
        tv.setGravity(Gravity.CENTER_HORIZONTAL);

        // Set the serif font for TextView text
        // This will change ActionBar title text font
        tv.setTypeface(ubuntu_MI);

        // Underline the ActionBar title text
        // tv.setPaintFlags(tv.getPaintFlags()| Paint.UNDERLINE_TEXT_FLAG);

        // Set the ActionBar title font size
        tv.setTextSize(TypedValue.COMPLEX_UNIT_DIP,24);

        // Display a shadow around ActionBar title text
        //tv.setShadowLayer(
        //      1.f, // radius
        //    2.0f, // dx
        //  2.0f, // dy
        //  Color.parseColor("#FF8C00") // shadow color
        //);

        // Set the ActionBar display option
        ab.setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);

        // Finally, set the newly created TextView as ActionBar custom view
        ab.setCustomView(tv);
    }

    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        switch (position) {
            case 0:
                // Whatever you want to happen when the first item gets selected
                break;
            case 1:
                // Whatever you want to happen when the second item gets selected
                break;
            case 2:
                // Whatever you want to happen when the thrid item gets selected
                break;

        }
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {

    }
}

ERROR: FATAL EXCEPTION: main java.lang.ClassCastException: com.example.khas.memorizingwords.ProfileFragment cannot be cast to com.example.khas.memorizingwords.StartingTestFragment at com.example.khas.memorizingwords.CombineFragmentActivity$1.onPageSelected(CombineFragmentActivity.java:46) at android.support.v4.view.ViewPager.dispatchOnPageSelected(ViewPager.java:1862) at android.support.v4.view.ViewPager.scrollToItem(ViewPager.java:625) at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:609) at android.support.v4.view.ViewPager.onTouchEvent(ViewPager.java:2176) at android.view.View.dispatchTouchEvent(View.java:7127) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2170) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1905) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2176) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1919) at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1925) at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1379) at android.app.Activity.dispatchTouchEvent(Activity.java:2396) at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:60) at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1873) at android.view.View.dispatchPointerEvent(View.java:7307) at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3172) at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3117) at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4153) at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4132) at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4224) at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:171) at android.os.MessageQueue.nativePollOnce(Native Method) at android.os.MessageQueue.next(MessageQueue.java:125) at android.os.Looper.loop(Looper.java:124) at android.app.ActivityThread.main(ActivityThread.java:4745) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) at dalvik.system.NativeStart.main(Native Method)

Answer 1

您的 fragment 变量未初始化，您正在对其进行调用。这也不是正确的方法。尝试下面的代码

@Override
                public void onPageSelected(int position) {
                    if(position == 0) {
                        ProfileFragment fragment = (ProfileFragment) getSupportFragmentManager().getFragments().get(1)
                        fragment.setActionBarTitle("Profil");
                    } else {
                        StartingTestFragment fragment2 = (StartingTestFragment) getSupportFragmentManager().getFragments().get(0);
                        fragment2.setActionBarTitle("Anasayfa");
                    }

                }

这是一个更好的版本，更通用

@Override
        public void onPageSelected(int position) {
            Fragment fragment1 = getActivity().getSupportFragmentManager().getFragments().get(position);
                if(fragment1 instanceof ProfileFragment) {
                    ProfileFragment fragment = (ProfileFragment) fragment1;
                    fragment.setActionBarTitle("Profil" );
                }
                else{
                    StartingTestFragment fragment = (StartingTestFragment) fragment1;
                    fragment.setActionBarTitle("Anasayfa");
                }
            } 

        }

这是改变标题的方法

setActionBarTitle(YOUR_TITLE);

使用它代替fragment.setACtionBarTitle

我认为不能保证从管理器检索 fragment 时的顺序。所以只需这样做

@Override
            public void onPageSelected(int position) {
                Fragment fragment1 = fragments.get(position);
                if(fragment1 instanceof ProfileFragment) {
                    ProfileFragment fragment = (ProfileFragment) fragment1;
                    fragment.setActionBarTitle("Profil" );
                }
                else{
                    StartingTestFragment fragment = (StartingTestFragment) fragment1;
                    fragment.setActionBarTitle("Anasayfa");
                }

            }

注意:通过执行此操作使您的 fragment 列表最终

final List<Fragment> fragments = new ArrayList<>();