機器人：複選框空對象引用

-2

所有我想要做的就是編程選中一個複選框。這是代碼：

CheckBox mycheck; 
mycheck = (CheckBox) getView().findViewById(R.id.edu1415_3); 
mycheck.setChecked(true);

我認爲問題是在一個片段中。我只是不知道如何解決它。我試圖在這兩個的onCreate方法，但我得到這個錯誤：試圖調用虛擬方法無效android.widget.CheckBox.setChecked（布爾）'對空對象引用

我缺少什麼？我感謝幫助！

這裏是我的文件：

checklist1415_2.java：

package com.abc.paplanningforthefuturechecklist; 

import android.content.Context; 
import android.content.SharedPreferences; 
import android.support.design.widget.TabLayout; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 

import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentPagerAdapter; 
import android.support.v4.view.ViewPager; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 

import android.widget.CheckBox; 
import android.widget.TextView; 

public class checklist1415_2 extends AppCompatActivity { 


    private SectionsPagerAdapter mSectionsPagerAdapter; 

    private ViewPager mViewPager; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_checklist1415_2); 

     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager()); 

     // Set up the ViewPager with the sections adapter. 
     mViewPager = (ViewPager) findViewById(R.id.container); 
     mViewPager.setAdapter(mSectionsPagerAdapter); 

     TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs); 
     tabLayout.setupWithViewPager(mViewPager); 

     FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
     fab.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG) 
         .setAction("Action", null).show(); 
      } 
     }); 

     //checkTheBoxes(); 



    } 

    public void onChecklistChecked(View view){ 
     boolean checked = ((CheckBox) view).isChecked(); 
     String checkedItem = getResources().getResourceEntryName(view.getId()); 
     SharedPreferences sharedPref = getPreferences(Context.MODE_PRIVATE); 
     SharedPreferences.Editor editor = sharedPref.edit(); 
     int checkVal = 1; 
     String pref_key = checkedItem; 
     if(checked){ 
      editor.putInt(pref_key, checkVal); 
      editor.commit(); 
     } else { 
      editor.putInt(pref_key, -1); 
      editor.commit(); 
     } 
     System.out.println(pref_key); 
    }  

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     getMenuInflater().inflate(R.menu.menu_checklist1415_2, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     int id = item.getItemId(); 

     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 

    public static class PlaceholderFragment extends Fragment { 


     private static final String ARG_SECTION_NUMBER = "section_number"; 

     public PlaceholderFragment() { 
     } 

     public static PlaceholderFragment newInstance(int sectionNumber) { 
      PlaceholderFragment fragment = new PlaceholderFragment(); 
      Bundle args = new Bundle(); 
      args.putInt(ARG_SECTION_NUMBER, sectionNumber); 
      fragment.setArguments(args); 
      return fragment; 
     } 


     @Override 
     public View onCreateView(LayoutInflater inflater, ViewGroup container, 
           Bundle savedInstanceState) { 
      View A = inflater.inflate(R.layout.edu1415, container, false); 
      View B = inflater.inflate(R.layout.employ1415, container, false); 
      View C = inflater.inflate(R.layout.comm1415, container, false); 

      switch (getArguments().getInt(ARG_SECTION_NUMBER)){ 
       case 1: 
        return A; 
       case 2: 
        return B; 
       case 3: 
        return C; 
      } 

      return null; 
     } 
    } 

    public class SectionsPagerAdapter extends FragmentPagerAdapter { 

     public SectionsPagerAdapter(FragmentManager fm) { 
      super(fm); 
     } 

     @Override 
     public Fragment getItem(int position) { 
      return PlaceholderFragment.newInstance(position + 1); 
     } 

     @Override 
     public int getCount() { 
      // Show 3 total pages. 
      return 3; 
     } 

     @Override 
     public CharSequence getPageTitle(int position) { 
      switch (position) { 
       case 0: 
        return "SECTION 1"; 
       case 1: 
        return "SECTION 2"; 
       case 2: 
        return "SECTION 3"; 
      } 
      return null; 
     } 
    } 
}

edu1415.xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:orientation="vertical"> 

    <CheckBox 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/edu1415_1" 
     android:text="@string/edu1415_1" 
     android:paddingTop="20dp" /> 

    <CheckBox 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/edu1415_2" 
     android:text="@string/edu1415_2" /> 

    <CheckBox 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:id="@+id/edu1415_3" 
     android:text="@string/edu1415_3" 
     android:onClick="onChecklistChecked"/> 

</LinearLayout>

fragment_checklist1415_2.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    tools:context="com.abc.paplanningforthefuturechecklist.checklist1415_2$PlaceholderFragment"> 

    <TextView 
     android:id="@+id/section_label" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" /> 

</RelativeLayout>

來源

2016-09-12 SinTek Solutions

確保'edu1415.xml'文件已加載到內存中。順便說一下，我在'checklist1415_2.java'文件中找不到'findViewById（）'。 –

如何將「edu1415.xml」加載到內存？我拿出'findViewById（）'，因爲它一直在打破。 –

問題中的findViewById不在您粘貼的代碼 – njzk2

，如果你想找到一個片段的觀點，做到在onCreateView()，如：只onCreateView()後

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup Bundle savedInstanceState) { 
    View root = inflater.inflate(R.layout.edu1415, container, false); 
    CheckBox checkbox = (CheckBox) root.findViewById(R.id.checkbox); 
    return root; 
}

由於getView()的作品，可以不使用它裏面onCreate()，片段的onCreateView()方法。

來源

2016-09-12 02:15:49 AssIstne

非常感謝！ –

機器人：複選框空對象引用

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