添加评级栏在Android工作室应用程序中的问题

Question

我将这个评级栏添加到我的应用程序，但它的启动画面后，我的应用程序崩溃。我尝试了不同的版本，但它总是崩溃。甚至没有到达评级栏的页面。

我在做什么错？

XML文件：

<RatingBar 
     android:id="@+id/ratingBar" 
     style="@style/Widget.AppCompat.RatingBar.Small" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_gravity="center" 
     android:numStars="5" 
     android:paddingBottom="5dp" 
     android:stepSize="1" /> 

    <TextView 
     android:id="@+id/value" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_gravity="center" 
     android:text="Value: " /> 

    <Button 
     android:id="@+id/ratingButton" 
     android:layout_width="wrap_content" 
     android:layout_height="30dp" 
     android:layout_gravity="center" 
     android:background="#ff6600" 
     android:elevation="10dp" 
     android:padding="7dp" 
     android:text="Submit Rating" 
     android:textSize="12sp" /> 

MainActivity.java 

    public class MainActivity extends AppCompatActivity { 

    RatingBar ratingBar; 
    Button btn; 


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

    getSupportActionBar().setDisplayShowHomeEnabled(true); 
    getSupportActionBar().setIcon(R.drawable.ic_launcher); 

    ratingBar=(RatingBar)findViewById(R.id.ratingBar1); 
    btn=(Button)findViewById(R.id.button1); 

    // Set ChangeListener to Rating Bar 
    ratingBar.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() { 
     public void onRatingChanged(RatingBar ratingBar, float rating, 
            boolean fromUser) { 

      Toast.makeText(getApplicationContext(),"Your Selected Ratings : " + String.valueOf(rating),Toast.LENGTH_LONG).show(); 

     } 
    }); 

    btn.setOnClickListener(new View.OnClickListener() { 


     public void onClick(View arg0) { 
      // TODO Auto-generated method stub 
      float rating=ratingBar.getRating(); 
      Toast.makeText(getApplicationContext(),"Your Selected Ratings : " + String.valueOf(rating),Toast.LENGTH_LONG).show(); 
     } 
    }); 

} 


    public void openAppetizersList(View v){ 

     if(v.getId() == R.id.appetizers){ 
      Intent i = new Intent(MainActivity.this, AppetizersActivity.class); 
      startActivity(i); 

     } 
    } 

    public void openDishList(View v){ 

     if(v.getId() == R.id.maindish){ 
      Intent i = new Intent(MainActivity.this, DishActivity.class); 
      startActivity(i); 

     } 
    } 

    public void openSidesList(View v){ 

     if(v.getId() == R.id.sides){ 
      Intent i = new Intent(MainActivity.this, SidesActivity.class); 
      startActivity(i); 

     } 
    } 

    public void openDessertsList(View v) { 

     if (v.getId() == R.id.desserts) { 
      Intent i = new Intent(MainActivity.this, DessertsActivity.class); 
      startActivity(i); 

     } 
    } 

    public void openBonusButton(View v) { 

     if (v.getId() == R.id.bonus) { 
      Intent i = new Intent(MainActivity.this, BonusActivity.class); 
      startActivity(i); 

     } 
    } 

    public void openTextClick(View v) { 

     if (v.getId() == R.id.textClick) { 
      Intent i = new Intent(MainActivity.this, BonusActivity.class); 
      startActivity(i); 

     } 
    } 



    } 

Answer 1

据崩溃日志，你正在试图做setOnRatingBarChangeListener一个空物体上，这意味着你的ratingBar变量为空。让我们看一下它的声明：

ratingBar=(RatingBar)findViewById(R.id.ratingBar1); 

然而，在布局XML中，我们看到

<RatingBar 
    android:id="@+id/ratingBar" 
    ... /> 

含义有两个ID（ “ratingBar1” 和 “的RatingBar”）不匹配。您可以通过更改其中一个来匹配另一个来解决此问题。例如，ratingBar：

ratingBar=(RatingBar)findViewById(R.id.ratingBar); 

而在XML：

<RatingBar 
    android:id="@+id/ratingBar" 
    ... />