將項目添加到微調框

Question

我想將項目添加到微調框，但出現錯誤「不幸的是，我的應用程序已停止工作」。我在strings.xml中創建了一個字符串數組，其中我有一些項目。當用戶從MainActivity中選擇添加項目時，會出現一個帶有按鈕的editText，並且我想要將editText中的任何內容傳遞給微調器。微調器位於activity_main.xml中，我正在處理addactivity.xml。我如何將新項目從EditText（在addactivity.xml和AddActivity.java中）傳遞給MainActivity.java和activity_main.xml中的微調器？

這裏是我的代碼：

public class AddActivity extends Activity{ 

Spinner spnr1; 
EditText edtxAddActivity; 
ArrayAdapter<String> spinnerAdapter; 
Button btnAddActivity; 
String[] actArray; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.addactivity); 
    addActivityButton(); 

} 

public void addActivityButton() { 
    // TODO Auto-generated method stub 
    edtxAddActivity = (EditText) findViewById(R.id.etAddActivity); 
    spnr1 = (Spinner) findViewById(R.id.spinner1); 
    actArray = getResources().getStringArray(R.array.activities_array); 
    spinnerAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,actArray); 
    spinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); 
    spnr1.setAdapter(spinnerAdapter); 
    btnAddActivity= (Button) findViewById(R.id.btAddActivity); 

    btnAddActivity.setOnClickListener(new OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      // TODO Auto-generated method stub 

      String newactivity = "" + edtxAddActivity.getText().toString(); 
      spinnerAdapter.add(newactivity); 

      spinnerAdapter.notifyDataSetChanged(); 
     }  
    }); 
} 

}

這是我的strings.xml文件：

<?xml version="1.0" encoding="utf-8"?> 

<string name="app_name">MyAdroidApp</string> 
<string name="activity_prompt">Choose an activity</string> 

<string-array name="activities_array"> 
    <item>5-a-side</item> 
    <item>Football</item> 
    <item>Basketball</item> 
    <item>Table Tennis</item> 
    <item>Add</item> 
</string-array> 

顯示的錯誤如下。

07-24 14:08:43.397: E/AndroidRuntime(24798): FATAL EXCEPTION: main 
07-24 14:08:43.397: E/AndroidRuntime(24798): Process: com.example.myAndroidApp, PID: 24798 
07-24 14:08:43.397: E/AndroidRuntime(24798): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myAndroidApp/com.example.myAndroidApp.AddActivity}: java.lang.NullPointerException 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.app.ActivityThread.access$800(ActivityThread.java:135) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.os.Handler.dispatchMessage(Handler.java:102) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.os.Looper.loop(Looper.java:136) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.app.ActivityThread.main(ActivityThread.java:5001) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at java.lang.reflect.Method.invokeNative(Native Method) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at java.lang.reflect.Method.invoke(Method.java:515) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at dalvik.system.NativeStart.main(Native Method) 
07-24 14:08:43.397: E/AndroidRuntime(24798): Caused by: java.lang.NullPointerException 
07-24 14:08:43.397: E/AndroidRuntime(24798): at com.example.myAndroidApp.AddActivity.addActivityButton(AddActivity.java:46) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at com.example.socialactivities.AddActivity.onCreate(AddActivity.java:33) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.app.Activity.performCreate(Activity.java:5231) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
07-24 14:08:43.397: E/AndroidRuntime(24798): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148) 
07-24 14:08:43.397: E/AndroidRuntime(24798): ... 11 more 

的問題是，spinnerAdapter產生一個NullPointerException，因爲列表視圖可能是空的或不初始化。我怎樣才能初始化我的數組？我的字符串數組在值中是在array.xml中。在com.example.myAndroidApp.AddActivity.addActivityButton（AddActivity.java:46）

Answer 1

NullPointerException異常

意味着你referecing和使用的東西，是空的那一刻。從外觀上看，它可能是您的視圖參考之一。我的建議是把一些調試檢查點一行代碼和執行應用程序，並按照一步步搞清楚什麼是空

Answer 2

看看R.layout.addactivity佈局，你錯過了什麼，特別是我認爲findViewById（ R.id.etAddActivity）;是空，意味着你沒有它在佈局或smtg是錯誤的，它的namie，身份證左右