android - 获取ListView的项目视图时的nullPointerException

时间：2015-03-04 07:22:38

标签： android android-listview nullpointerexception

我想在这里提出几点：

  1. listview的每个项目包含一个imageButton，2个TextView和一个imageView

  2. 我想在活动中获取itemView的imageButton 位置而不是点击事件，因为我想将badgeView添加到imageButton

  3. 错误信息如下：

    4. --------------------错误信息---------------- 

    03-04 07:03:07.226: D/dalvikvm(712): GC_CONCURRENT freed 48K, 3% free 10270K/10503K, paused 8ms+7ms
03-04 07:03:07.816: D/gralloc_goldfish(712): Emulator without GPU emulation detected.
03-04 07:03:17.307: D/AndroidRuntime(712): Shutting down VM
03-04 07:03:17.307: W/dalvikvm(712): threadid=1: thread exiting with uncaught exception (group=0x409961f8)
03-04 07:03:17.366: E/AndroidRuntime(712): FATAL EXCEPTION: main
03-04 07:03:17.366: E/AndroidRuntime(712): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.list_1/com.example.list_1.ClinicMessage}: java.lang.NullPointerException
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.os.Looper.loop(Looper.java:137)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.app.ActivityThread.main(ActivityThread.java:4340)
03-04 07:03:17.366: E/AndroidRuntime(712):  at java.lang.reflect.Method.invokeNative(Native Method)
03-04 07:03:17.366: E/AndroidRuntime(712):  at java.lang.reflect.Method.invoke(Method.java:511)
03-04 07:03:17.366: E/AndroidRuntime(712):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
03-04 07:03:17.366: E/AndroidRuntime(712):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
03-04 07:03:17.366: E/AndroidRuntime(712):  at dalvik.system.NativeStart.main(Native Method)
03-04 07:03:17.366: E/AndroidRuntime(712): Caused by: java.lang.NullPointerException
**03-04 07:03:17.366: E/AndroidRuntime(712):    at com.example.list_1.ClinicMessage.getViewByPosition(ClinicMessage.java:122)
03-04 07:03:17.366: E/AndroidRuntime(712):  at com.example.list_1.ClinicMessage.AddBadgeView(ClinicMessage.java:104)**
03-04 07:03:17.366: E/AndroidRuntime(712):  at com.example.list_1.ClinicMessage.onCreate(ClinicMessage.java:49)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.app.Activity.performCreate(Activity.java:4465)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
03-04 07:03:17.366: E/AndroidRuntime(712):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
03-04 07:03:17.366: E/AndroidRuntime(712):  ... 11 more
03-04 07:03:19.176: I/Process(712): Sending signal. PID: 712 SIG: 9

    --------------------我的代码---------------------- ---- 

    public class ClinicMessage extends Activity {

List<HashMap<String,Object>> mList= new ArrayList();
HashMap<String,Object> map=new HashMap();
private ListView mListView;
private ImageButton mIBBack;
private ImageButton mIBWrite;
private ImageButton imageButtonWithBadge; 

MyBaseAdapter mBaseAdapter;
private ActionBar actionbar;
private BadgeView badge;



@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);

    setContentView(R.layout.list1_clinic_message);
    actionbar=getActionBar();
    actionbar.hide();

    initComponent();
    initList();
    **AddBadgeView();**
    dealWithTitleBarEvents();
    dealWithListEvents();


}

public void initComponent()
{
    mListView=(ListView)findViewById(R.id.lvClinicMessage);
    mIBBack=(ImageButton)findViewById(R.id.ibBack);
    mIBWrite=(ImageButton)findViewById(R.id.ibWrite);

}


public void initList()
{
    for(int i=0;i<8;i++)
    {
        map.put("ItemLeftPic",getResources().getDrawable(R.drawable.ib_cmsg_left));
        map.put("ItemNext", getResources().getDrawable(R.drawable.im_arrow));
        map.put("ItemTitle", "上海怡康家园");
        map.put("ItemText", "医生你好，本周有空吗");
        map.put("ItemTime", "14/12/14 17:30");
        mList.add(map);
    }

    Toast.makeText(ClinicMessage.this, mList.size()+"项",Toast.LENGTH_LONG).show();
}

public void AddBadgeView()
{
    **View view=getViewByPosition(0, mListView);**


    ImageButton imageButtonWithBadge=(ImageButton) view.findViewById(R.id.ibClinicMessageLeft);


    badge=new BadgeView(this, imageButtonWithBadge);
    badge.setText(5);
    badge.setBadgePosition(BadgeView.POSITION_TOP_RIGHT);
    badge.show();

}

public View getViewByPosition(int pos, ListView listView) {
    final int firstListItemPosition = listView.getFirstVisiblePosition();
    final int lastListItemPosition = firstListItemPosition + listView.getChildCount() - 1;

    if (pos < firstListItemPosition || pos > lastListItemPosition ) {
        return listView.getAdapter().getView(pos, null, listView);
    } else {
        final int childIndex = pos - firstListItemPosition;
        return listView.getChildAt(childIndex);
    }
}

    感谢帮助我T ^ T

    -------------------------添加信息-------------

    也许我没有把整个代码放进去，但是我通过setAdapter初始化了listView（你可以在dealWithListEvents（）函数中看到它，并在oncreate（）中调用。）。这里是dealWithListEvents（）： 

    public void dealWithListEvents()
    {
        mBaseAdapter=new MyBaseAdapter(mList, this);
        mListView.setAdapter(mBaseAdapter);
        mListView.setOnItemClickListener(new OnItemClickListener()  
        {
            public void onItemClick(AdapterView<?> parent, View arg1, int position,long id) 
            {
                Toast.makeText(ClinicMessage.this, "你点击了第"+position+"项",Toast.LENGTH_LONG).show();

            }   
        });
    }

    ----------------- MyBaseAdapter --------------------- 

        package com.example.list_1;

import java.util.HashMap;
import java.util.List;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;

public class MyBaseAdapter extends BaseAdapter {

private LayoutInflater mInflater; //得到一个LayoutInfalter对象用来导入布局
private List<HashMap<String,Object>>mList;

class ViewHolder
{
    private ImageButton ibLeftPic;
    private TextView tvTitle;
    private TextView tvText;
    private TextView tvTime;
    private ImageView ivNext;

}


public MyBaseAdapter(List<HashMap<String,Object>> list,Context context) {

    this.mInflater=LayoutInflater.from(context);
    this.mList=list;
}
@Override
public int getCount() {
    // TODO Auto-generated method stub
    return mList.size();
}

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

@Override
public long getItemId(int position) {
    // TODO Auto-generated method stub
    return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder viewholder;
    //convertView就是由于滑动被隐藏回收的ItemView
    //viewHolder就是一个来接收它的缓存
    if(convertView==null)
    {
        convertView=mInflater.inflate(R.layout.list1_listitem_clinicmessage, null);
        viewholder=new ViewHolder();
        viewholder.ibLeftPic=(ImageButton)convertView.findViewById(R.id.ibClinicMessageLeft);
        viewholder.ivNext=(ImageView)convertView.findViewById(R.id.ivItemArrow);
        viewholder.tvTitle=(TextView)convertView.findViewById(R.id.tvClinicMessagetTitle);
        viewholder.tvText=(TextView)convertView.findViewById(R.id.tvClinicMessageText);
        viewholder.tvTime=(TextView)convertView.findViewById(R.id.tvClinicMessageTime);
        convertView.setTag(viewholder);     
    }
    else
    {
        viewholder=(ViewHolder)convertView.getTag();
    }

    viewholder.ibLeftPic.setBackgroundDrawable((Drawable) mList.get(position).get("ItemLeftPic"));
    viewholder.ibLeftPic.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

        }
    });
    viewholder.ivNext.setImageDrawable((Drawable)   

    mList.get(position).get("ItemNext"));

viewholder.tvTitle.setText(mList.get(position).get("ItemTitle").toString());


viewholder.tvText.setText(mList.get(position).get("ItemText").toString());
        `     `viewholder.tvTime.setText(mList.get(position).get("ItemTime").toString());`
return convertView;
}

public void refresh(List<HashMap<String,Object>> list)
{
    list=mList;
    notifyDataSetChanged();
}

    }

2 个答案:

答案 0 :(得分：1)

*假设您对listview的初始化是正确的。

然后你的代码问题很可能就是

listView.getAdapter().getView(pos, null, listView);

您尚未初始化适配器，也没有为此listview

设置适配器 
mBaseAdapter = new MyBaseAdapter(.....);
mListView.setAdapter(mBaseAdapter);

修改

发布新代码后。您必须切换调用初始化adapter的方法以及调用它的方法的顺序。使用以下顺序

dealWithListEvents();
AddBadgeView();

答案 1 :(得分：0)

您在不使用适配器的情况下手动将项目添加到列表视图中。哪个是完全错误的。

您需要为列表视图设置自定义适配器，然后您的getViewByPosition(int pos, ListView listView)方法才有效。

initComponent();
initList();
dealWithTitleBarEvents();
dealWithListEvents();
**AddBadgeView();**

试试这个..希望它有效

相关问题
最新问题