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我有一个网格布局，屏幕顶部有一个 EditText 字段。我正在实现基本适配器来填充网格布局的值。

我正在使用的代码如下。我的主要活动

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;
}
}
}

在主布局中，我有一个网格视图，上面有一个带有文本和图像的复选框。我有一个 Submit(Go) 按钮，单击该按钮应捕获在主要活动中选中的复选框的所有名称。我怎样才能做到这一点？当我运行此代码并单击 Go 时，应用程序崩溃并返回空指针异常。

错误

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)
4

1 回答 1

1

我没有看到您adapter在任何地方初始化变量。替换这个：

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

和

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

也不要使用getBaseContext()。你应该MainActivityDynamic.this改用。

And it looks you use Toast for debug purposes - I'd suggest to switch to Log (see docs)

于 2012-11-25T11:28:41.703 回答