嘗試在空對象引用上調用虛擬方法Service.setName（java.lang.String）'

Question

我想用變量概念和proceDo填充此活動中的數組，但是當我編譯它時會拋出此異常，我不會「知道到底爲什麼，因爲我初始化的，如果

public class ConceptsActivity extends AppCompatActivity{ 
private int i; 
private AutoCompleteTextView actv; 
private TextView tvConcept; 
private TextView tvConcept2; 
private TextView warning; 
private TextView tvPrice; 
private EditText price; 
private Button addConcept; 
private String concept; 
private double priceDo; 
private List<AddConceptsListView> myConcept = new ArrayList<AddConceptsListView>(); 
private Service service[]; 

public ConceptsActivity(){ 

} 

public ConceptsActivity(Service service[]){ 
    this.service = service; 
} 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    setTitle(R.string.TitleSer); 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.concepts_layout); 

    actv = (AutoCompleteTextView) findViewById(R.id.autoCompleteTextViewConcept); 
    tvConcept = (TextView) findViewById(R.id.textViewConcept); 
    tvConcept2 = (TextView) findViewById(R.id.textViewConcept2); 
    warning = (TextView) findViewById(R.id.textViewWarning); 
    tvPrice = (TextView) findViewById(R.id.textViewPrice); 
    price = (EditText) findViewById(R.id.editTextPrice); 
    addConcept = (Button) findViewById(R.id.buttonAddConcept); 

    //Autocomplete Textview 
    String[] services = getResources().getStringArray(R.array.services_array); 
    ArrayAdapter<String> adapter = 
      new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, services); 
    actv.setAdapter(adapter); 

    actv.setOnEditorActionListener(new TextView.OnEditorActionListener() { 
     @Override 
     public boolean onEditorAction(TextView v, int actionId, KeyEvent event) { 
      boolean handled = false; 
      if (actionId == EditorInfo.IME_ACTION_DONE) { 
       //make items visible 
       tvConcept.setVisibility(View.VISIBLE); 
       tvConcept2.setVisibility(View.VISIBLE); 
       tvPrice.setVisibility(View.VISIBLE); 
       price.setVisibility(View.VISIBLE); 
       addConcept.setVisibility(View.VISIBLE); 

       concept = actv.getText()+""; 
       tvConcept2.setText(concept); 
       //To hide the keyboard 
       InputMethodManager imm = (InputMethodManager) v.getContext().getSystemService(Context.INPUT_METHOD_SERVICE); 
       imm.hideSoftInputFromWindow(v.getWindowToken(), 0); 

       handled = true; 
      } 
      return handled; 
     } 
    }); 
} 

public void onClickAddConcept(View view){ 

    if(service == null){ 
     service = new Service[1]; 
     i=0; 
    } 
    //service = new Service [i]; 

    if(price.getText().toString().equals("")){ 
     warning.setVisibility(View.VISIBLE); 
    } 
    else { 
     warning.setVisibility(View.INVISIBLE); 
     if(price.getText().toString().contains(".")){ 
      priceDo = Double.parseDouble(price.getText().toString()); 
      Toast.makeText(getApplicationContext(),"Precio: " + priceDo+ "" + "\n" 
        + "Concepto: " + concept,Toast.LENGTH_SHORT).show(); 

      service[i].setName(concept); 
      Toast.makeText(getApplicationContext(), "Array nameConcept: " + service[i].getName(), Toast.LENGTH_SHORT); 
     } 
     else{ 
      priceDo = Double.parseDouble(price.getText().toString()); 
      Toast.makeText(getApplicationContext(),"Precio: " + priceDo+ "" + "\n" 
        + "Concepto: " + concept,Toast.LENGTH_SHORT).show(); 
     } 
    } 
} 

}

陣列這裏的例外

Process: com.example.ally.helper, PID: 31717 
                    java.lang.IllegalStateException: Could not execute method for android:onClick 
                     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:275) 
                     at android.view.View.performClick(View.java:4761) 
                     at android.view.View$PerformClick.run(View.java:19767) 
                     at android.os.Handler.handleCallback(Handler.java:739) 
                     at android.os.Handler.dispatchMessage(Handler.java:95) 
                     at android.os.Looper.loop(Looper.java:135) 
                     at android.app.ActivityThread.main(ActivityThread.java:5312) 
                     at java.lang.reflect.Method.invoke(Native Method) 
                     at java.lang.reflect.Method.invoke(Method.java:372) 
                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901) 
                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696) 
                     Caused by: java.lang.reflect.InvocationTargetException 
                     at java.lang.reflect.Method.invoke(Native Method) 
                     at java.lang.reflect.Method.invoke(Method.java:372) 
                     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:270) 
                     at android.view.View.performClick(View.java:4761)  
                     at android.view.View$PerformClick.run(View.java:19767)  
                     at android.os.Handler.handleCallback(Handler.java:739)  
                     at android.os.Handler.dispatchMessage(Handler.java:95)  
                     at android.os.Looper.loop(Looper.java:135)  
                     at android.app.ActivityThread.main(ActivityThread.java:5312)  
                     at java.lang.reflect.Method.invoke(Native Method)  
                     at java.lang.reflect.Method.invoke(Method.java:372)  
                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)  
                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)  
                     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.ally.helper.Service.setName(java.lang.String)' on a null object reference 
                     at com.example.ally.helper.ConceptsActivity.onClickAddConcept(ConceptsActivity.java:107) 
                     at java.lang.reflect.Method.invoke(Native Method)  
                     at java.lang.reflect.Method.invoke(Method.java:372)  
                     at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:270)  
                     at android.view.View.performClick(View.java:4761)  
                     at android.view.View$PerformClick.run(View.java:19767)  
                     at android.os.Handler.handleCallback(Handler.java:739)  
                     at android.os.Handler.dispatchMessage(Handler.java:95)  
                     at android.os.Looper.loop(Looper.java:135)  
                     at android.app.ActivityThread.main(ActivityThread.java:5312)  
                     at java.lang.reflect.Method.invoke(Native Method)  
                     at java.lang.reflect.Method.invoke(Method.java:372)  
                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)  
                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)  

唯一的例外是在這條線

service [i] .setName（concept）;

Answer 1

當你調用

service = new Service[1]; 

你實際上並沒有實例化一個服務對象，而你只是實例化的服務陣列。

要解決這個問題，請嘗試：

service = new Service[1]; 
service[0] = new Service(); // or iterate through a loop and create