notifyDataSetChanged()引起IndexOutOfBoundsException异常

Question

这是我代码的简化版本。

public class MainActivity extends ActionBarActivity {

private ArrayList<String> entry = new ArrayList<String>();
private String[] entryString = new String[11];
private ArrayAdapter<String> aa;
private ListView entryListView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    entryListView = (ListView) findViewById(R.id.listView1);
    int listID = R.layout.entry_layout;
    aa = new EntryAdapter(this, listID, entry);
    entryListView.setAdapter(aa);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    switch (id) {
    case R.id.action_add: {
        Intent intent = new Intent(MainActivity.this, AddActivity.class);
        startActivityForResult(intent, 1);
        break;
    }
    }
    return super.onOptionsItemSelected(item);
}

@Override
public void onActivityResult(int rc, int resc, Intent i) {
    super.onActivityResult(rc, resc, i);
    entryString = i.getStringArrayExtra("Entry");
    this.onNewItemAdded(entryString);
}

public void onNewItemAdded(String[] _entry){
    String key = new String();
    key = _entry[0];
    entry.add(key);
    aa.notifyDataSetChanged();   //Runs without crashing when this is removed.
}

适配器类是一种：

@SuppressLint("Instantiatable")
public class EntryAdapter extends ArrayAdapter<String>{

private ArrayList<String> entries;
int count;
int resource;
public EntryAdapter(Context _context, int _resource, List<String> _entries){
    //TODO Auto-generated constructor stub
    super(_context, _resource, R.id.key, _entries);
    this.resource = _resource;
    this.entries = new ArrayList<String>(_entries);
    this.count = 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View row = convertView;

    if (convertView == null) {
        String inflater = Context.LAYOUT_INFLATER_SERVICE;
        LayoutInflater li;
        li = (LayoutInflater) getContext().getSystemService(inflater);
        row = li.inflate(resource, parent, false);
    }

    TextView keyView = (TextView) row.findViewById(R.id.key);
    TextView siteView = (TextView) row.findViewById(R.id.site);

    for(int c=0; c<11; c++){
        while(!entries.get(c).toString().equals("")){
            count++;
        }
    }

    keyView.setText(entries.get(position));
    siteView.setText(count + "sources");

    return row;
}
} 

通过在MainActivity中注释掉aa.notifyDataSetChanged()的调用，应用程序可以运行而不崩溃，但是当它没有被注释时会抛出IndexOutOfBoundsException: Invalid index 0, size is 0异常。

PS：XML文件完全没有问题。

编辑：

以下是日志记录：

03-18 18:38:03.840: E/AndroidRuntime(6052): FATAL EXCEPTION: main 03-18 18:38:03.840: E/AndroidRuntime(6052): 进程：com.FirstClass.alert，PID：6052 03-18 18:38:03.840: E/AndroidRuntime(6052): java.lang.IndexOutOfBoundsException: 索引0无效，大小为0 03-18 18:38:03.840: E/AndroidRuntime(6052): at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255) 03-18 18:38:03.840: E/AndroidRuntime(6052): at java.util.ArrayList.get(ArrayList.java:308) 03-18 18:38:03.840: E/AndroidRuntime(6052): at com.FirstClass.netalert.EntryAdapter.getView(EntryAdapter.java:66) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.AbsListView.obtainView(AbsListView.java:2263) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.ListView.makeAndAddView(ListView.java:1790) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.ListView.fillDown(ListView.java:691) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.ListView.fillFromTop(ListView.java:752) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.ListView.layoutChildren(ListView.java:1630) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.AbsListView.onLayout(AbsListView.java:2091) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.View.layout(View.java:14822) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.ViewGroup.layout(ViewGroup.java:4631) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.View.layout(View.java:14822) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.ViewGroup.layout(ViewGroup.java:4631) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.FrameLayout.onLayout(FrameLayout.java:388) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.View.layout(View.java:14822) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.ViewGroup.layout(ViewGroup.java:4631) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.support.v7.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:502) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.View.layout(View.java:14822) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.ViewGroup.layout(ViewGroup.java:4631) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.FrameLayout.onLayout(FrameLayout.java:388) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.View.layout(View.java:14822) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.view.ViewGroup.layout(ViewGroup.java:4631) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671) 03-18 18:38:03.840: E/AndroidRuntime(6052): at android.widget.LinearLayout

- Bob Bob

---

问题很可能出在 key = _entry[0] 这一行。在获取 0 索引之前，请检查条目大小。注释和取消注释的 notify 数据集更改可能只是一个不幸的巧合。 - user3629714

@MartínMarconcini 完成 - Bob Bob

@MartínMarconcini 对不起，我没听懂你的意思？我该如何检查呢？ - Bob Bob

第66行是for循环。感谢您让我看到那里！在@NaveenDissanayake指出我犯的错误后进行更正，程序会卡在蓝屏上。这在我试图修复代码时已经发生了几次。结果是，for循环中的while循环陷入了无限循环。 - Bob Bob

很高兴你找到了问题，教训是：下次要仔细阅读堆栈跟踪。 ;) - Martin Marconcini

Answer 1

通过实现ArrayAdapter的getCount()方法，解决了我的问题。这有助于ArrayAdapter知道在数据更改后需要调用getView()的对象数量。

@Override
public int getCount()
{
    return data.size();
}

- craned

Answer 2

如果你通过调用new ArrayList<String>(_entries);来创建一个新的ArrayList，那么在你的Adapter中引用的ArrayList将不是你的activity中的ArrayList。因此，当你更改activity中的entry ArrayList时，它不会影响Adapters ArrayList。要解决这个问题，可以改变构造函数为：

public EntryAdapter(Context _context, int _resource, List<String> _entries){
    super(_context, _resource, R.id.key, _entries);
    this.resource = _resource;
    this.entries = _entries;
    this.count = 0;
}

或者将onNewItemAdded更改为：

public void onNewItemAdded(String[] _entry){
    String key = new 
    key = _entry[0];
    aa.add(key);
    aa.notifyDataSetChanged();
}

- Naveen Dissanayake