public class ExemptListView extends Activity {
DbHandler dbHandler;
Cursor c;
ArrayList<Devices> list;
MycustomAdapter adapter;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.listview);
//final ListView listview_var = (ListView) findViewById(R.id.listView1);
dbHandler = new DbHandler(getApplicationContext());
list = new ArrayList<Devices>();
generateListofDevices();
for (int i = 0; i < list.size(); i++) {
Log.i("Dhiraj", list.get(i).devicename + " : "
+ list.get(i).IpAddress + " : " + list.get(i).checked);
}
adapter = new MycustomAdapter(this, android.R.layout.simple_list_item_1,list);
ListView lv=(ListView)findViewById(R.id.listView1);
lv.setAdapter(adapter);
Log.i("Dhiraj"," Adapter set");
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
Log.i("Dhiraj","lv.setitemclicklistener");
Devices dv=(Devices)arg0.getItemAtPosition(arg2);
//Toast.makeText(getApplicationContext(),
// "Clicked on Row: " + dv.devicename,
// Toast.LENGTH_LONG).show();
}
});
checkbuttonclick();
}
private void generateListofDevices() {
c = dbHandler.GetCursor(dbHandler.Devices_List_db);
Log.i("Dhiraj", "generating lsit ");
if (c != null) {
if (c.moveToFirst())
do {
Boolean Checked = false;
Log.i("Dhiraj", c.getString(1) + " : " + c.getString(2)
+ " : " + c.getString(3));
if (c.getString(3) == "Y")
Checked = true;
Devices d = new Devices(c.getString(1), c.getString(2),
Checked);
list.add(d);
} while (c.moveToNext());
}
}
public class Devices {
String devicename = null;
String IpAddress = null;
Boolean checked = false;
Devices(String devicename, String IpAddress, Boolean checked2) {
this.devicename = devicename;
this.IpAddress = IpAddress;
this.checked = checked2;
}
public void setSelected(boolean selected) {
this.checked = selected;
}
}
private class MycustomAdapter extends ArrayAdapter<Devices> {
private ArrayList<Devices> Deviceslist;
public MycustomAdapter(Context context, int resource,
ArrayList<Devices> DeviceList) {
super(context, resource, DeviceList);
this.Deviceslist = new ArrayList<Devices>();
this.Deviceslist.addAll(DeviceList);
Log.i("Dhiraj","MycustomAdapter constructor cmpleted");
}
private class ViewHolder {
TextView Name;
TextView IP;
CheckBox Exempt;
}
public View getView(int position, View convertview, ViewGroup parent) {
Log.i("Dhiraj"," GET View");
ViewHolder holder = null;
if (convertview == null) {
Log.i("Dhiraj","convertview is null");
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertview = vi.inflate(R.layout.custom_checkboxlist, null);
Log.i("Dhiraj", convertview.toString());
Log.i("Dhiraj","NEw Holder");
holder = new ViewHolder();
holder.Name = (TextView) findViewById(R.id.DEVNAME);
holder.IP = (TextView) findViewById(R.id.DEVADDR);
holder.Exempt = (CheckBox) findViewById(R.id.EXEMPT);
convertview.setTag(holder);
Log.i("Dhiraj","convertview.setTag(holder)");
holder.Exempt.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Log.i("Dhiraj"," on click listener");
CheckBox cb = (CheckBox) v;
Devices devices = (Devices) cb.getTag();
Toast.makeText(
getApplicationContext(),
"Clicked on Checkbox: " + cb.getText() + " is "
+ cb.isChecked(), Toast.LENGTH_LONG)
.show();
devices.setSelected(cb.isChecked());
}
});
}
else
{
Log.i("Dhiraj","Else");
holder=(ViewHolder)convertview.getTag();
}
Log.i("Dhiraj","Done with null and else");
Devices device=Deviceslist.get(position);Log.i("Dhiraj",Deviceslist.get(position)+"");
holder.Name.setText(device.devicename);Log.i("Dhiraj",device.devicename);
holder.IP.setText(device.IpAddress);Log.i("Dhiraj",device.IpAddress);
holder.Exempt.setChecked(device.checked);Log.i("Dhiraj",device.checked.toString());
Log.i("Dhiraj"," View Over");
return convertview;
}
}
public void checkbuttonclick(){
Button Apply=(Button)findViewById(R.id.Apply);
Log.i("Dhiraj","chcek button");
ArrayList<Devices> deviceslist=adapter.Deviceslist;
for(int i=0;i<deviceslist.size();i++){
Devices d=deviceslist.get(i);
if(d.checked)
Log.i("Dhiraj", d.devicename +" is Exempted");
}
}
}
logcat显示以下错误
10-14 08:51:18.486: I/Dhiraj(25481): Database Name: DevicesList
10-14 08:51:18.494: I/Dhiraj(25481): returning all Values
10-14 08:51:18.494: I/Dhiraj(25481): generating lsit
10-14 08:51:18.494: I/Dhiraj(25481): Ujgffbb : Vhncfcv : N
10-14 08:51:18.494: I/Dhiraj(25481): Uj : Vh : N
10-14 08:51:18.494: I/Dhiraj(25481): Ihdecv : Ibswchj : N
10-14 08:51:18.494: I/Dhiraj(25481): Ih : Ib : N
10-14 08:51:18.494: I/Dhiraj(25481): Hhbb : Plhb : N
10-14 08:51:18.494: I/Dhiraj(25481): Ujgffbb : Vhncfcv : false
10-14 08:51:18.494: I/Dhiraj(25481): Uj : Vh : false
10-14 08:51:18.494: I/Dhiraj(25481): Ihdecv : Ibswchj : false
10-14 08:51:18.494: I/Dhiraj(25481): Ih : Ib : false
10-14 08:51:18.502: I/Dhiraj(25481): Hhbb : Plhb : false
10-14 08:51:18.502: I/Dhiraj(25481): MycustomAdapter constructor cmpleted
10-14 08:51:18.502: I/Dhiraj(25481): Adapter set
10-14 08:51:18.502: I/Dhiraj(25481): chcek button
10-14 08:51:18.518: I/Dhiraj(25481): GET View
10-14 08:51:18.518: I/Dhiraj(25481): convertview is null
10-14 08:51:18.518: I/Dhiraj(25481): android.widget.LinearLayout@41418e10
10-14 08:51:18.518: I/Dhiraj(25481): NEw Holder
10-14 08:51:18.518: I/Dhiraj(25481): convertview.setTag(holder)
10-14 08:51:18.525: W/dalvikvm(25481): threadid=1: thread exiting with uncaught exception (group=0x40ab5210)
10-14 08:51:18.533: E/AndroidRuntime(25481): FATAL EXCEPTION: main
10-14 08:51:18.533: E/AndroidRuntime(25481): java.lang.NullPointerException
10-14 08:51:18.533: E/AndroidRuntime(25481): at com.dhiraj.projectsierra_v1.ExemptListView$MycustomAdapter.getView(ExemptListView.java:136)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.AbsListView.obtainView(AbsListView.java:2144)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.ListView.measureHeightOfChildren(ListView.java:1244)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.ListView.onMeasure(ListView.java:1155)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.View.measure(View.java:12751)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.LinearLayout.measureVertical(LinearLayout.java:660)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.View.measure(View.java:12751)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.FrameLayout.onMeasure(FrameLayout.java:295)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.View.measure(View.java:12751)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.View.measure(View.java:12751)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4698)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.widget.FrameLayout.onMeasure(FrameLayout.java:295)
10-14 08:51:18.533: E/AndroidRuntime(25481): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2120)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.View.measure(View.java:12751)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1106)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2558)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.os.Handler.dispatchMessage(Handler.java:99)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.os.Looper.loop(Looper.java:137)
10-14 08:51:18.533: E/AndroidRuntime(25481): at android.app.ActivityThread.main(ActivityThread.java:4697)
10-14 08:51:18.533: E/AndroidRuntime(25481): at java.lang.reflect.Method.invokeNative(Native Method)
10-14 08:51:18.533: E/AndroidRuntime(25481): at java.lang.reflect.Method.invoke(Method.java:511)
10-14 08:51:18.533: E/AndroidRuntime(25481): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
10-14 08:51:18.533: E/AndroidRuntime(25481): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
10-14 08:51:18.533: E/AndroidRuntime(25481): at dalvik.system.NativeStart.main(Native Method)
我没有弄错它。 Layout中是否有错误。
我使用的LinearLayout包含2个TextViews和一个复选框。此layout用于生成ListView
答案 0 :(得分：1)
您好像没有正确使用findViewById()。如果DEVNAME中的DEVADDR，EXEMPT和id为custom_checkboxlist.xml，那么应该引用它们
holder.Name = (TextView) convertview.findViewById(R.id.DEVNAME);
holder.Name = (TextView) convertview.findViewById(R.id.DEVADDR);
holder.Name = (TextView) convertview.findViewById(R.id.EXEMPT);
你需要查看膨胀的layout内部。否则，他们会看到之前layout来自setContentView()的{{1}}。{/ p>
为了清晰起见而编辑
查找由onCreate（Bundle）中处理的XML中的id属性标识的视图
所以你这样做的方法是查看最初用layout充气的setContentView()。现在您已经夸大了另一个xml文件，该文件包含您尝试访问的View，因此您需要在layout之前放置新膨胀findViewById()的变量，以便应用知道查看 layout而不是最初处理过的layout。