android - 得到 threadid=1 : thread exiting with uncaught exception (group=0x41088930) on listview

Question

我正在制作一个在 ListView 上显示正在运行的应用程序图标的应用程序。 没有语法问题(我认为)但是当我启动应用程序并尝试运行 Activity 时， 应用程序强制关闭，我得到了 threadid=1: thread exiting with uncaught exception (group=0x41088930) 以及更多错误我该如何解决这个错误？我应该使用 Asynctask 将图像加载到 ListView 吗？或任何解决方案？

(Logcat)

02-18 14:17:46.700: W/dalvikvm(18370): threadid=1: thread exiting with uncaught exception (group=0x41088930)
02-18 14:17:46.700: E/AndroidRuntime(18370): FATAL EXCEPTION: main
02-18 14:17:46.700: E/AndroidRuntime(18370): java.lang.RuntimeException: Unable to start activity ComponentInfo{kr.hybdms.sidepanel/kr.hybdms.sidepanel.LeftSidePanel}: java.lang.NullPointerException
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2309)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2359)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.app.ActivityThread.access$600(ActivityThread.java:153)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.os.Handler.dispatchMessage(Handler.java:99)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.os.Looper.loop(Looper.java:137)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.app.ActivityThread.main(ActivityThread.java:5204)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at java.lang.reflect.Method.invokeNative(Native Method)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at java.lang.reflect.Method.invoke(Method.java:511)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:799)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at dalvik.system.NativeStart.main(Native Method)
02-18 14:17:46.700: E/AndroidRuntime(18370): Caused by: java.lang.NullPointerException
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.widget.ListView.setAdapter(ListView.java:462)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at kr.hybdms.sidepanel.LeftSidePanel.onCreate(LeftSidePanel.java:59)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.app.Activity.performCreate(Activity.java:5108)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-18 14:17:46.700: E/AndroidRuntime(18370):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2263)
02-18 14:17:46.700: E/AndroidRuntime(18370):    ... 11 more

---

(LeftSidePanel.java)

package kr.hybdms.sidepanel;


import java.util.ArrayList;
import java.util.List;


import kr.hybdms.sidepanel.PanelArrayAdapter;
import kr.hybdms.sidepanel.R;

import kr.hybdms.sidepanel.util.SystemUiHider;


import android.app.Activity;
import android.app.ActivityManager;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;

import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListView;
import android.widget.Toast;

/**
 * An example full-screen activity that shows and hides the system UI (i.e.
 * status bar and navigation/system bar) with user interaction.
 * 
 * @see SystemUiHider
 */
public class LeftSidePanel extends Activity implements
OnItemClickListener {
ListView listView;
List<PanelItemDetail> rowItems;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_left_side_panel);

ActivityManager am = (ActivityManager) this.getSystemService(ACTIVITY_SERVICE);
List<ActivityManager.RunningTaskInfo> tasks = am.getRunningTasks(10);
ArrayList<PanelItemDetail> iconarray = new ArrayList<PanelItemDetail>();
PackageManager pacMgr = getPackageManager();
  for (ActivityManager.RunningTaskInfo runningTask: tasks)
  {
    try {
        iconarray.add(new PanelItemDetail(pacMgr.getApplicationIcon(runningTask.topActivity.getPackageName())));
    } catch (NameNotFoundException e) {
      e.printStackTrace();
    }
  }

listView = (ListView) findViewById(R.id.panelcontents);
PanelArrayAdapter adapter = new PanelArrayAdapter(this,
        R.layout.panelrow, rowItems);
listView.setAdapter(adapter);
listView.setOnItemClickListener(this);
}

@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
    long id) {
Toast toast = Toast.makeText(getApplicationContext(),
    "Item " + (position + 1) + ": " + rowItems.get(position),
    Toast.LENGTH_SHORT);
toast.setGravity(Gravity.BOTTOM|Gravity.CENTER_HORIZONTAL, 0, 0);
toast.show();
}
}

---

(PanelArrayAdapter.java)

package kr.hybdms.sidepanel;

import java.util.List;

import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;

public class PanelArrayAdapter extends ArrayAdapter<PanelItemDetail> {
    Context context;
    public PanelArrayAdapter(Context context, int resourceId,
            List<PanelItemDetail> items) {
        super(context, resourceId, items);
        this.context = context;
    }
    /*private view holder class*/
    private class ViewHolder {
        ImageView imageView;
    }
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        PanelItemDetail rowItem = getItem(position);
        LayoutInflater mInflater = (LayoutInflater) context
                .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.panelrow, null);
            holder = new ViewHolder();
            holder.imageView = (ImageView) convertView.findViewById(R.id.appicon);
            convertView.setTag(holder);
        } else
            holder = (ViewHolder) convertView.getTag();
        holder.imageView.setImageDrawable(rowItem.getImageId());
        return convertView;
    }
}

---

(PanelItemDetail.java)

package kr.hybdms.sidepanel;

import android.graphics.drawable.Drawable;

public class PanelItemDetail {
    private Drawable imageId;
    public PanelItemDetail(Drawable images) {
        this.imageId = images;
    }
    public Drawable getImageId() {
        return imageId;
    }
    public void setImageId(Drawable imageId) {
        this.imageId = imageId;
    }
}

Answer 1

错误在这里

PanelArrayAdapter adapter = new PanelArrayAdapter(this,
        R.layout.panelrow, rowItems);
listView.setAdapter(adapter);

因为 rowItems 还没有初始化。