Почему я получаю исключение null-указателя при попытке установить значение в рейтинге в рейтинге?

Question

Я вижу, что исключение происходит при "rtb.setRating (8.0f);" Кроме того, я могу установить рейтинг вручную в XML-файле и который дает ожидаемый результат, например. андроид: рейтинг = "3,7"

static String ingredients[] = {"Ingredient1","Ingredient2","Ingredient3","Ingredient4","Ingredient5","Ingredient6","Ingredient7","Ingredient8","Ingredient9","Ingredient10","Ingredient11","Ingredient12","Ingredient13","Ingredient14","Ingredient15","Ingredient16","Ingredient17","Ingredient18","Ingredient19","Ingredient20"}; 
static String steps[] = {"Step1","Step2","Step3","Step4","Step5","Step6","Step7","Step8","Step9","Step10"}; 


String url = "http://192.168.1.2/cricketjson.txt"; 


private ListView mDrawerList; 
private ArrayAdapter<String> mAdapter; 
static int[] ids = {1,2,3,4,5}; 



/** 
* Fragment managing the behaviors, interactions and presentation of the navigation drawer. 
*/ 
private NavigationDrawerFragment mNavigationDrawerFragment; 

/** 
* Used to store the last screen title. For use in {@link #restoreActionBar()}. 
*/ 
private CharSequence mTitle; 
private CharSequence mStep; 



@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    RatingBar rtb = (RatingBar) findViewById(R.id.rb); 
    rtb.setRating(8.0f); 

    setContentView(R.layout.activity_recipe); 
    mDrawerList = (ListView)findViewById(R.id.navList); 
    //set visual features 
    //set string values 
    TextView[] txtStep = {(TextView) findViewById(R.id.txtStep1),  (TextView) findViewById(R.id.txtStep2)}; 


    //txtStep1.setText("ftUr"); 

//set font Title 
    TextView mRecipeTitle = (TextView) findViewById(R.id.Title); 
    Typeface face = Typeface.createFromAsset(getAssets(), 
      "Italianno-Regular.ttf"); 
    mRecipeTitle.setTypeface(face); 
    mRecipeTitle.setTextSize(TypedValue.COMPLEX_UNIT_SP, 77); 
// set scrollview as transparent 
    findViewById(R.id.recipScrollView).setBackgroundColor(getResources().getColor(android.R.color.transparent)); 

    // PD = new ProgressDialog(this); 
    // PD.setMessage("Loading....."); 

    mNavigationDrawerFragment = (NavigationDrawerFragment) 
      getSupportFragmentManager().findFragmentById(R.id.navigation_drawer); 
    mTitle = getTitle(); 




    // Set up the drawer. 
    mNavigationDrawerFragment.setUp(
      R.id.navigation_drawer, 
      (DrawerLayout) findViewById(R.id.drawer_layout)); 


    mDrawerList.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
      Toast.makeText(RecipeActivity.this, "Time for an upgrade!", Toast.LENGTH_SHORT).show(); 
     } 
    }); 

    //here*#8*#* put in the steps to the func.jsonrq 


    // Funcs.makejsonobjreq(ingredients, url, this,steps,id); 
    Funcs.makejsonobjreq(ingredients, url, this); 
    Funcs.makejsonobjreqrecipe(ingredients, url, this, steps, ids[0], txtStep); 


} 


@Override 
public void onNavigationDrawerItemSelected(int position) { 
    // update the main content by replacing fragments 
    FragmentManager fragmentManager = getSupportFragmentManager(); 
    fragmentManager.beginTransaction() 
      .replace(R.id.container, PlaceholderFragment.newInstance(position + 1)) 
      .commit(); 
} 

public void onSectionAttached(int number) { 
    switch (number) { 
     case 1: 
      mTitle = getString(R.string.title_Recipe); 
      break; 
     case 2: 
      mTitle = ingredients[0]; 

      break; 
     case 3: 
      mTitle = ingredients[1]; 
      break; 
     case 4: 
      mTitle = ingredients[2]; 
      break; 
     case 5: 
      mTitle = ingredients[3]; 
      break; 
     case 6: 
      mTitle = ingredients[4]; 
      break; 
     case 7: 
      mTitle = ingredients[5]; 
      break; 
     case 8: 
      mTitle = ingredients[6]; 
      break; 
     case 9: 
      mTitle = ingredients[7]; 
      break; 
     case 10: 
      mTitle = ingredients[8]; 
      break; 
     case 11: 
      mTitle = ingredients[9]; 
      break; 
     case 12: 
      mTitle = ingredients[10]; 
      break; 
     case 13: 
      mTitle = ingredients[11]; 
      break; 
     case 14: 
      mTitle = ingredients[12]; 
      break; 
     case 15: 
      mTitle = ingredients[13]; 
      break; 
     case 16: 
      mTitle = ingredients[14]; 
      break; 
     case 17: 
      mTitle = ingredients[15]; 
      break; 
     case 18: 
      mTitle = ingredients[16]; 
      break; 
     case 19: 
      mTitle = ingredients[17]; 
      break; 
     case 20: 
      mTitle = ingredients[18]; 
      break; 
     case 21: 
      mTitle = ingredients[19]; 
      break; 
    } 
} 

public void restoreActionBar() { 
    ActionBar actionBar = getSupportActionBar(); 
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD); 
    actionBar.setDisplayShowTitleEnabled(true); 
    actionBar.setTitle(mTitle); 
} 


@Override 
public boolean onCreateOptionsMenu(Menu menu) { 

    if (!mNavigationDrawerFragment.isDrawerOpen()) { 
     // Only show items in the action bar relevant to this screen 
     // if the drawer is not showing. Otherwise, let the drawer 
     // decide what to show in the action bar. 
     getMenuInflater().inflate(R.menu.recipe, menu); 
     restoreActionBar(); 
     return true; 
    } 
    return super.onCreateOptionsMenu(menu); 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 

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

    return super.onOptionsItemSelected(item); 
} 

/** 
* A placeholder fragment containing a simple view. 
*/ 
public static class PlaceholderFragment extends Fragment { 
    /** 
    * The fragment argument representing the section number for this 
    * fragment. 
    */ 
    private static final String ARG_SECTION_NUMBER = "section_number"; 

    /** 
    * Returns a new instance of this fragment for the given section 
    * number. 
    */ 
    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; 
    } 

    public PlaceholderFragment() { 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.fragment_recipe, container, false); 
     return rootView; 
    } 

    @Override 
    public void onAttach(Activity activity) { 
     super.onAttach(activity); 
     ((RecipeActivity) activity).onSectionAttached(
       getArguments().getInt(ARG_SECTION_NUMBER)); 
    } 
} 



} 

И coressponding XML:

<!-- As the main content view, the view below consumes the entire 
    space available using match_parent in both dimensions. --> 
<FrameLayout android:id="@+id/container" android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    > 


    <LinearLayout 
     android:background="@drawable/background8" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:orientation="vertical" 
     android:paddingTop="20dip" 
     android:layout_gravity="right|center_vertical" 
     android:weightSum="1"> 

     <TextView 
      android:layout_marginTop="0dp" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:text="New Text" 
      android:id="@+id/Creator" 
      android:layout_alignLeft="@id/title" 
      android:textSize="20dp" 
      android:layout_gravity="center_horizontal" /> 

     <TextView 
      android:layout_marginTop="30dp" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:textAppearance="?android:attr/textAppearanceLarge" 
    android:text="Large Text" 
    android:id="@+id/Title" 
    android:layout_below="@id/Creator" 
      android:layout_gravity="center_horizontal" /> 

     <ScrollView android:layout_width="match_parent" 
      android:layout_marginTop="0dp" 
      android:layout_marginLeft="30dp" 
      android:layout_marginRight="30dp" 
      android:layout_height="198dp" 
      android:background="#ffffff" 
      android:id="@+id/recipScrollView"> 

      <LinearLayout 
       android:layout_marginLeft="30dp" 

       android:layout_width="match_parent" 
       android:layout_height="wrap_content" 
       android:orientation="vertical" 
       android:paddingTop="20dip" 
       android:weightSum="1"> 

       <TextView 
        android:layout_marginTop="0dp" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="New Txt" 
        android:id="@+id/txtStep1" /> 

       <TextView 
        android:layout_marginTop="30dp" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:text="New Txt" 
        android:id="@+id/txtStep2" 
        android:layout_below="@id/txtStep1"/>/> 

      </LinearLayout> 
     </ScrollView> 

     <RatingBar 
      android:layout_marginTop="30dp" 
      android:layout_marginLeft="30dp" 
      android:id="@+id/rb" 
      style="?android:attr/ratingBarStyleSmall" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:max="10" 
      android:numStars="10" 
      android:rating="3.7" 
      android:stepSize="0.0" /> 


    </LinearLayout> 

</FrameLayout> 

<!-- android:layout_gravity="start" tells DrawerLayout to treat 
    this as a sliding drawer on the left side for left-to-right 
    languages and on the right side for right-to-left languages. 
    If you're not building against API 17 or higher, use 
    android:layout_gravity="left" instead. --> 
<!-- The drawer is given a fixed width in dp and extends the full height of 
    the container. --> 
<fragment android:id="@+id/navigation_drawer" 
    android:layout_width="@dimen/navigation_drawer_width" android:layout_height="match_parent" 
    android:layout_gravity="start" android:name="com.example.finnb.rcp.NavigationDrawerFragment" 
    tools:layout="@layout/fragment_navigation_drawer" /> 

<ListView 
    android:id="@+id/navList" 
    android:layout_width="200dp" 
    android:layout_height="match_parent" 
    android:layout_gravity="left|start" 
    android:background="#ffeeeeee"/> 

И ошибка LogCat:

03-08 04:52:30.350 1946-1946/com.example.finnb.rcp D/dalvikvm﹕ Not late-enabling CheckJNI (already on) 
03-08 04:52:30.460 1946-1946/com.example.finnb.rcp D/AndroidRuntime﹕ Shutting down VM 
03-08 04:52:30.460 1946-1946/com.example.finnb.rcp W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb0ca2b20) 
03-08 04:52:30.460 1946-1946/com.example.finnb.rcp E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.example.finnb.rcp, PID: 1946 
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.finnb.rcp/com.example.finnb.rcp.RecipeActivity}: java.lang.NullPointerException 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195) 
      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
      at android.app.ActivityThread.access$800(ActivityThread.java:135) 
      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
      at android.os.Handler.dispatchMessage(Handler.java:102) 
      at android.os.Looper.loop(Looper.java:136) 
      at android.app.ActivityThread.main(ActivityThread.java:5017) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:515) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
      at dalvik.system.NativeStart.main(Native Method) 
    Caused by: java.lang.NullPointerException 
      at com.example.finnb.rcp.RecipeActivity.onCreate(RecipeActivity.java:62) 
      at android.app.Activity.performCreate(Activity.java:5231) 
      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159) 
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245) 
            at android.app.ActivityThread.access$800(ActivityThread.java:135) 
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
            at android.os.Handler.dispatchMessage(Handler.java:102) 
            at android.os.Looper.loop(Looper.java:136) 
            at android.app.ActivityThread.main(ActivityThread.java:5017) 
            at java.lang.reflect.Method.invokeNative(Native Method) 
            at java.lang.reflect.Method.invoke(Method.java:515) 
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
            at dalvik.system.NativeStart.main(Native Method) 

Answer 1

Я считаю, что это потому что вы повторно настроив представление контента после настройки RatingBar. Попробуйте переместить

setContentView(R.layout.activity_recipe); 

вверх до

RatingBar rtb = (RatingBar) findViewById(R.id.rb); 
    rtb.setRating(8.0f 

Answer 2

setContentView(R.layout.activity_recipe); эта линия должна быть чуть ниже этой линии super.onCreate(savedInstanceState); После этого вы должны получить доступ к/инстанцирует мнения.

Вы пытаетесь получить доступ к рейтинговой панели перед связыванием макета xml.

Answer 3

Это просто. Давайте предположим, что вы используете правильный макет в setContentView:

Ниже приведен правильный порядок инициализации:

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_recipe); 

    RatingBar rtb = (RatingBar) findViewById(R.id.rb); 
    rtb.setRating(8.0f); 

Вы можете просто ссылаться на рейтинг бар, если расположение задается с помощью setContentView(), не ранее ...