我尝试按照this tutorials制作带有图标的列表视图。我按照教程的说法完成了所有操作，但当我尝试使用listview调用活动时，我收到此错误java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
我收到完整错误
03-16 11:07:10.067 3859-3859/th.ac.sd.sdschoolas E/AndroidRuntime: FATAL EXCEPTION: main
Process: th.ac.sd.sdschoolas, PID: 3859
java.lang.RuntimeException: Unable to start activity ComponentInfo{th.ac.sd.sdschoolas/th.ac.sd.sdschoolas.MoreActivity2}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at th.ac.sd.sdschoolas.MoreActivity2.onCreate(MoreActivity2.java:45)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
MoreActivity2.java （具有列表视图的活动）
package th.ac.sd.sdschoolas;
import android.app.Activity;
import android.app.ListActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
public class MoreActivity2 extends Activity{
ListView list;
String[] itemname ={
"Safari",
"Camera",
"Global",
"FireFox",
"UC Browser",
"Android Folder",
"VLC Player",
"Cold War"
};
Integer[] imgid={
R.drawable.ic_cal,
R.drawable.ic_cal,
R.drawable.ic_cal,
R.drawable.ic_cal,
R.drawable.ic_cal,
R.drawable.ic_cal,
R.drawable.ic_cal,
R.drawable.ic_cal,
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
CustomListAdapter adapter=new CustomListAdapter(this, itemname, imgid);
list=(ListView)findViewById(R.id.list);
list.setAdapter(adapter);
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// TODO Auto-generated method stub
String Slecteditem= itemname[+position];
Toast.makeText(getApplicationContext(), Slecteditem, Toast.LENGTH_SHORT).show();
}
});
}
}
activity_more2.xml （布局文件）
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="th.ac.sd.sdschoolas.MoreActivity2" >
<ListView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true" >
</ListView>
</RelativeLayout>
clist.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<ImageView
android:id="@+id/icon"
android:layout_width="60dp"
android:layout_height="60dp"
android:padding="5dp" />
<LinearLayout android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="@+id/item"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium"
android:layout_marginLeft="10dp"
android:layout_marginTop="5dp"
android:padding="2dp"
android:textColor="#33CC33" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
android:layout_marginLeft="10dp"/>
</LinearLayout>
</LinearLayout>
CustomListViewAdapter.java
package th.ac.sd.sdschoolas;
import android.app.Activity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
public class CustomListAdapter extends ArrayAdapter<String> {
private final Activity context;
private final String[] itemname;
private final Integer[] imgid;
public CustomListAdapter(Activity context, String[] itemname, Integer[] imgid) {
super(context, R.layout.clist, itemname);
// TODO Auto-generated constructor stub
this.context=context;
this.itemname=itemname;
this.imgid=imgid;
}
public View getView(int position,View view,ViewGroup parent) {
LayoutInflater inflater=context.getLayoutInflater();
View rowView=inflater.inflate(R.layout.clist, null,true);
TextView txtTitle = (TextView) rowView.findViewById(R.id.item);
ImageView imageView = (ImageView) rowView.findViewById(R.id.icon);
TextView extratxt = (TextView) rowView.findViewById(R.id.textView1);
txtTitle.setText(itemname[position]);
imageView.setImageResource(imgid[position]);
extratxt.setText("Description "+itemname[position]);
return rowView;
};
}