將數據從非活動類傳遞到活動時（通過意圖）

Question

我嘗試從OnClickListener調用另一個活動，但遇到NullPointerException。我使用https://stackoverflow.com/a/7325248/1291619提供的建議將數據傳遞給其他活動。

該類用於監聽列表，並在單擊某個項目時用選定的uri啓動VCardActivity.java。它發送URI的意圖沿着：

public class StaffListListener implements OnItemClickListener { 

    ArrayList<String> items; 
    Activity activity; 

    public StaffListListener(ArrayList<String> items, Activity activity) { 
     this.items = items; 
     this.activity = activity; 
    } 

    /** 
    * Send user to view with contact details 
    */ 
    public void onItemClick(AdapterView<?> parent, View view, int pos, long id) { 

     //items.get(pos) returns the UPI needed. Append to http://www.cs.auckland.ac.nz/our_staff/vcard.php?upi=  
     Uri.Builder b = Uri.parse("http://www.cs.auckland.ac.nz/our_staff/vcard.php").buildUpon(); 
     b.appendQueryParameter("upi", items.get(pos)); 
     Uri uri = b.build(); 
     Log.d("URL of staff", uri.toString()); 

     Intent i = new Intent(activity.getApplicationContext(), VCardActivity.class); 
     i.putExtra("URI",uri); 
     activity.startActivity(i);  
    } 
} 

此類旨在接收的意圖，與URI一起，並解析該數據並顯示它。我還沒有整理出來的數據格式化和解析的是，簡單地使用日誌作爲一個佔位符：

public class VCardActivity extends ListActivity { 
    private VCardActivity local; 
    private String uri; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_vcard); 
     local = this; 

     Bundle extras = getIntent().getExtras(); 
     if (extras != null) { 
      uri = extras.getString("URI"); 
     } 

     try { 
      URL url = new URL(uri.toString()); 
      HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection(); 

      InputStream stream = urlConnection.getInputStream(); 
      StringBuffer fileContent = new StringBuffer(""); 
      int ch; 
      while((ch = stream.read()) != -1){ 
       fileContent.append((char)ch); 
       } 
      String data = new String(fileContent); 
      Log.i("TAG", "data: " + data); 
      } 
     catch (IOException e) { 
      e.printStackTrace(); 
      }   
    } 
} 

我的例外：

06-01 10:06:13.293: E/AndroidRuntime(903): FATAL EXCEPTION: main 
06-01 10:06:13.293: E/AndroidRuntime(903): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.lim.assignment/com.lim.json.VCardActivity}: java.lang.NullPointerException 
06-01 10:06:13.293: E/AndroidRuntime(903): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 

如果有人能告訴我，我要去哪裏錯了，會非常感激。這樣

Intent i = new Intent(getApplicationContext(), VCardActivity.class); 
     i.putExtra("URI",uri.toString()); 
     startActivity(i); 

通過意向

Answer 1

傳遞數據和這樣的

Bundle extras = getIntent().getExtras(); 
     if (extras != null) { 
      uri = extras.getString("URI"); 
     }