Question

我想在单击按钮时在列表视图中添加行，但我的应用程序每次都会崩溃。这是我的代码：

public class MTCRichGraphicsActivity extends Activity {
int ELEMENT_COUNT = 3;
int position=0;
Button bAddView;
String[] elements = new String[ELEMENT_COUNT];

int r =0 ;   


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    bAddView = (Button) findViewById(R.id.bNewEvent);
   final ListView list = (ListView) findViewById(R.id.list3d);
    bAddView.setOnClickListener(new View.OnClickListener() {


        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            switch(v.getId())
            {
            case R.id.bNewEvent :
                for (int i = 0; i< ELEMENT_COUNT; i++) {
                    elements[i] = String.valueOf(i);
                }
                final MyAdapter adapter = new MyAdapter(MTCRichGraphicsActivity.this,elements);
                adapter.notifyDataSetChanged();
                //list.setScrollY(currentPosition);
                //list.setTranslationY(currentPosition);
                list.setDivider( null ); 
                list.setAdapter(adapter);

                adapter.notifyDataSetChanged();

                ELEMENT_COUNT = ELEMENT_COUNT + 3;
            }

        }
    });

}

}

这里我想在每次点击一个按钮（即bNewEvent）时添加3行，所以我每次都将ELEMENT_COUNT递增3。它第一次工作正常，但是当我第二次按下按钮时它会崩溃。

这是我的适配器类：

public class MyAdapter extends BaseAdapter {

private final LayoutInflater mInflater;
private final String[] mItems;
TextView t;
ViewHolder holder;
public MyAdapter(Activity c,String[] objects) {
    mInflater = c.getLayoutInflater();
    mItems = objects;
}

public int getCount() {
    return mItems.length;
}


@Override
public View getView(int position, View convertView, ViewGroup parent) {
    TextView t;
    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.listitem2, parent,false);
}
    holder = new ViewHolder();
    holder.t1 = (TextView) convertView.findViewById(R.id.tv1); 
    holder.t2 = (TextView) convertView.findViewById(R.id.tv2);
    holder.t3 = (TextView) convertView.findViewById(R.id.tv3);
    holder.t4 = (TextView) convertView.findViewById(R.id.tv4);
    holder.t1.setText("Title"+position);
    position = position + 3;

    //((ImageView)convertView).setTextAlignment(1);

    return convertView;
}

@Override
public Object getItem(int position) {
    return mItems[position];
}

@Override
public long getItemId(int position) {
    return position;
}

}

Answer 1

你不能使用像这样的数组..

String[] elements = new String[ELEMENT_COUNT];

导致数组与ELEMENT_COUNT的初始值具有相同数量的元素，然后您不能将ELEMENT_COUNT增加3并尝试

        for (int i = 0; i< ELEMENT_COUNT; i++) {
            elements[i] = String.valueOf(i);
        }

因为数组只包含最初定义的元素。您需要将'elements'更改为ArrayList。

ArrayList<string> elements;

Answer 2

U define

int ELEMENT_COUNT = 3;
String[] elements = new String[ELEMENT_COUNT];

但是你不能调整数组大小

 for (int i = 0; i< ELEMENT_COUNT; i++) {
                elements[i] = String.valueOf(i);
            }

这样你就得到了例外

将阵列更改为列表

喜欢

List<String> element =new ArrayList<String>();



   for (int i = 0; i< ELEMENT_COUNT; i++) {
                element.add("String.valueOf(i)")
            }

和更改适配器也喜欢这个

使用按钮动态添加新行

2 个答案: