應用拋出空指針異常，當我們試圖捕捉在Android的

Question

與現場的EditText提交按鈕我有一個網格佈局在屏幕的頂部選擇複選框的IDS。我正在實現基礎適配器來填充網格佈局的值。

我使用的代碼如下。我的主要活動

public class MainActivityDynamic extends Activity{ 

GridView gridView; 
GridObject[] planets; 
ArrayList<GridObject> myObjects; 
Button Go; 
ImageAdapter adapter; 
int position; 
boolean[] itemChecked; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.gridlayout); 
    Go = (Button)findViewById(R.id.bGO); 
    gridView = (GridView) findViewById(R.id.gV); 
    String[] primarycontext = {"first","second","third","fourth","fifth","sixth","seventh","eighth","ninth","tenth","leventh","twelth","thirteenth","fouteenth","fifteenth","sixteenth","seventeenth","eighteenth","nineteenth","twenteth","twentyfirst","twentysecond", "twentythird","twentythird","twentyfouth"}; 

    gridView.setAdapter(new ImageAdapter(this, primarycontext)); 
    gridView.setOnItemClickListener(new GridView.OnItemClickListener(){ 

     public void onItemClick(AdapterView<?> arg0, View v, int position, 
       long id) { 
      // TODO Auto-generated method stub 
      //myObjects.get(position).setState(1); 
      //myAdapter.notifyDataSetChanged(); 

      Toast.makeText(getBaseContext(), "clicked on "+position, Toast.LENGTH_SHORT).show(); 
     } 

    }); 


    Go.setOnClickListener(new View.OnClickListener() { 

     public void onClick(View v) { 
      // TODO Auto-generated method stub 
      //adapter.notifyDataSetChanged(); 
      int len = 10; 
      int cnt = 0; 
      String selectImages = ""; 
      for (int i = 0;i<len; i++){ 
       if (adapter.itemChecked[i]){ 
        cnt++; 
       } 
      } 
      if(cnt == 0){ 
       Toast.makeText(getBaseContext(), "please select atleast one", Toast.LENGTH_SHORT).show(); 
      }else 
      { 
       Toast.makeText(getBaseContext(), "you have selected" + cnt + "boxes", Toast.LENGTH_SHORT).show(); 
      } 
      String item = (String) adapter.getItem(position); 
      Toast.makeText(getBaseContext(), "selected fields"+item, Toast.LENGTH_SHORT).show(); 
     } 
    }); 
    } 

} 

public class ImageAdapter extends BaseAdapter 
{ 
    Context mContext; 
    public ImageAdapter(Context c,String[] primarycontext) 
    { 
     mContext = c; 
    this.primarycontext = primarycontext; 
    } 
    @Override 
    public int getCount() 
    { 
     // TODO Auto-generated method stub 
     return providers.length; 
    } 
public Object getItem(int position) { 
    // TODO Auto-generated method stub 
    return primarycontext[position]; 
} 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) 
    { 
     // TODO Auto-generated method stub 
     View v; 
    if(convertView==null){ 
    LayoutInflater li = (LayoutInflater) mContext 
     .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    v = new View(mContext); 
    v = li.inflate(R.layout.icon, null); 
    } 
    else 
    { 
    v = convertView; 
     } 
     ImageView iv = (ImageView)v.findViewById(R.id.grid_item_image); 
    iv.setImageResource(R.drawable.folder_0); 
    CheckBox CBx = (CheckBox)v.findViewById(R.id.cBIon); 
    CBx.setText(primarycontext[position]); 
     CBx.setChecked(isItemChecked(position)); 
     return v; 
    } 
private boolean isItemChecked(int position) { 
    // TODO Auto-generated method stub 
    System.out.println("the returning items="+itemChecked); 
    return itemChecked; 
} 
} 
} 

在主要佈局我用文字和圖像一個複選框佔據一個gridview。我有一個Submit（Go）按鈕，點擊時應該捕獲在主要活動中選中的選中框的所有名稱。我怎樣才能做到這一點？當我運行此代碼並單擊Go時，應用程序崩潰並返回空指針異常。

錯誤

11-25 05:43:50.390: E/AndroidRuntime(519): FATAL EXCEPTION: main 
11-25 05:43:50.390: E/AndroidRuntime(519): java.lang.NullPointerException 
11-25 05:43:50.390: E/AndroidRuntime(519): at com.example.kam1.MainActivityDynamic$2.onClick(MainActivityDynamic.java:73) 
11-25 05:43:50.390: E/AndroidRuntime(519): at android.view.View.performClick(View.java:2408) 
11-25 05:43:50.390: E/AndroidRuntime(519): at android.view.View$PerformClick.run(View.java:8816) 
11-25 05:43:50.390: E/AndroidRuntime(519): at android.os.Handler.handleCallback(Handler.java:587) 

Answer 1

我沒有看到你在任何地方初始化adapter變量。替換此：

gridView.setAdapter(new ImageAdapter(this, primarycontext)); 

與

adapter = new ImageAdapter(this, primarycontext); 
gridView.setAdapter(adapter); 

也不要使用getBaseContext()。您應該使用MainActivityDynamic.this。

它看起來你用吐司用於調試目的 - 我建議切換到Log（see docs）