Question

您好我在尝试获取我创建的列表视图时遇到了一些麻烦，无法将用户输入添加到EditText视图中。当用户按下“添加”按钮但是程序刚崩溃时，应该添加内容，更不用说运行速度非常慢。我没有在下面添加我认为相关的部分。

public class ListViewActivity_Two extends Activity 
{
EditText edit;          Button add;
final List<String> data = new ArrayList<String>();

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    data.add( "Hello" );

    edit = ( EditText )findViewById( R.id.editTxt ); 
    add = ( Button ) findViewById( R.id.add );
    add.setOnClickListener( new OnClickListener() 
    {

        @Override
        public void onClick(View v) 
        {
            data.add( edit.getText().toString() );
        }
    }); 

    /**
    for( int i = 1; i <= 10; i++ )
    {
        data.add( String.format( "Item %d", i ) );
    }
    */

    // Declare an instance of our custom adapter class
    CustomAdapter adapter = new CustomAdapter( this, data );

    ListView listView = ( ListView )findViewById( android.R.id.list ); 
    listView.setAdapter( adapter );

    listView.setOnItemClickListener( new OnItemClickListener()
    {

        @Override
        public void onItemClick( AdapterView listview, View v, int pos, long id ) 
        {
            TextView textView = (TextView)v.findViewById( android.R.id.text1 );
            toast( (String) textView.getText() );
        }

    });

}

data.add（）就是为了确保我可以实际添加到ListView，我可以。我在onClickButton做同样的事情，为什么会发生这种情况？另外，我在onCreate方法上声明创建视图是正确的，还是必须在其中才能正常工作？

修改的

这是CustomAdapter类

package com.stylingandroid.listview;

import java.util.List;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class CustomAdapter extends BaseAdapter
{
private final Context context;
private final List<String> items;

public CustomAdapter( Context context, List<String> items )
{
    this.context = context;
    this.items = items;
}

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

@Override
public Object getItem(int position) 
{
    return items.get( position );
}

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

/**
 * Method getView() below is inefficent because inflating XML layouts is memory expensive
 * because it involves parsing XML and then instantiating objects to represent all of the Views
 * in the view hierarchy
 * 
 * see: http://blog.stylingandroid.com/archives/632
 * 
 * for more details.
 * 
 * The more efficient code is below it!


@Override
public View getView( int position, View convertView, ViewGroup parent ) 
{
    LayoutInflater inflater = ( LayoutInflater )context.getSystemService( Context.LAYOUT_INFLATER_SERVICE );
    View v = inflater.inflate( R.layout.item, parent, false );

    final String item = ( String ) getItem( position );
    TextView tv = ( TextView )v.findViewById( android.R.id.text1 );
    tv.setText( item );

    ImageView iv = ( ImageView )v.findViewById( R.id.imageView );
    iv.setOnClickListener( new OnClickListener() 
    {

        @Override
        public void onClick(View v) 
        {
            Toast.makeText( context, String.format( "ImageClicked: %s", item ), Toast.LENGTH_SHORT ).show();
        }

    });

    return v;
}

*/

@Override
public View getView( int position, View convertView, ViewGroup parent ) 
{
    /**
     * this method differs from the one above because, here, all we are doing is inflating a new view
     * if convertView is null. This significantly reduces the amount of object deletion and instantiation
     * that's required, and vastly improves our scrolling performance particularly on low powered devices
     */
    View v = convertView;

    if( v == null )
    {
        LayoutInflater inflater = ( LayoutInflater )context.getSystemService( Context.LAYOUT_INFLATER_SERVICE );
        v = inflater.inflate( R.layout.item, parent, false );
    }

    final String item = ( String ) getItem( position );
    TextView tv = ( TextView )v.findViewById( android.R.id.text1 );
    tv.setText( item );

    ImageView iv = ( ImageView )v.findViewById( R.id.imageView );
    iv.setOnClickListener( new OnClickListener() 
    {

        @Override
        public void onClick(View v) 
        {
            Toast.makeText( context, String.format( "ImageClicked: %s", item ), Toast.LENGTH_SHORT ).show();
        }

    });

    return v;
}

}

BTW我试图将程序的模拟器更改为API级别7;它完全破坏了程序。现在在每一个R.whatever我得到一个错误。我在Manifest文件中将它更改为7也一样重要吗？最后我清理了项目，但这没有什么区别 - 这里有什么问题？

Answer 1

我实现了一些代码并且工作正常：）

ListView mListView;
EditText mValue;
Button mAdd;

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

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.act_listview);

    data.add("Hello World");

    mListView = (ListView) findViewById(R.id.custom_list);
    mValue = (EditText) findViewById(R.id.text_to_add);
    mAdd = (Button) findViewById(R.id.add_string);

    mListView.setAdapter(new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, data));
    mAdd.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View currentView) {
            data.add(new String(mValue.getText().toString()));
        }
    });
}

Answer 2

我认为问题出在onClick上。这些变量的范围是不对的。对“数据”的引用不限于父类。与“编辑”相同。

相反，它的作用域是新的OnClickListner，因此未定义。

尝试使用

更改它以引用父类

ParentClasName.this.data.add(ParentClasName.this.edit.getText().toString());

只需将“ParentClassName”替换为您的班级名称。

让用户从EditText添加到ListView

2 个答案: