我正在开发一个应用程序，我在其中CustomListview使用一个图标、raitingbar、复选框来实现。现在一切正常，但是当我插入一个按钮时，它让我出现 nullpointer 错误。我知道 nullpointer 错误会导致在未初始化控件的情况下......但到目前为止我已经尝试过，但不明白这里有什么问题。 ...
我采取了一个 viewHold 来声明所有 Row 项目..
package com.AppFavorits;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.ImageView;
import android.widget.RatingBar;
import android.widget.TextView;
class ViewHolder {
public ImageView imgvFavrowiconappicon;
public TextView txvxFavrowiconappname;
public RatingBar ratingBar1;
public CheckBox chkbxFavrowsel;
public Button btnFavrowOpen;
ViewHolder(View base) {
this.ratingBar1=(RatingBar)base.findViewById(R.id.ratingBar1);
this.ratingBar1.setFocusable(false);
this.txvxFavrowiconappname=(TextView)base.findViewById(R.id.txvxFavrowiconappname);
this.imgvFavrowiconappicon=(ImageView)base.findViewById(R.id.imgvFavrowiconappicon);
this.chkbxFavrowsel = (CheckBox)base.findViewById(R.id.chkbxFavrowsel);
this.btnFavrowOpen= (Button)base.findViewWithTag(R.id.btnFavrowOpen);
this.chkbxFavrowsel.setFocusable(false);
}
}
自定义适配器
class RatingAdapter extends ArrayAdapter<RowModel> implements OnClickListener {
private ArrayList<Model> mlist;
boolean[] checkBoxState;
RatingAdapter(ArrayList<RowModel> list, ArrayList<Model> mlist) {
super(Favorites.this, R.layout.rowfavorites,
R.id.txvxFavrowiconappname, list);
checkBoxState = new boolean[list.size()];
this.mlist = mlist;
}
public View getView(final int position, View convertView,
ViewGroup parent) {
View row = super.getView(position, convertView, parent);
holder = (ViewHolder) row.getTag();
if (convertView == null) {
holder = new ViewHolder(row);
row.setTag(holder);
} else {
row = convertView;
((ViewHolder) row.getTag()).chkbxFavrowsel.setTag(mlist
.get(position));
}
RatingBar.OnRatingBarChangeListener l = new RatingBar.OnRatingBarChangeListener() {
public void onRatingChanged(RatingBar ratingBar, float rating,
boolean fromTouch) {
Integer myPosition = (Integer) ratingBar.getTag();
RowModel model = getModel(myPosition);
model.rating = rating;
flFavRate[position] = rating;
// stored listitem rating in array
datasource.open();
datasource.UpdateRating(String.valueOf(rating), String.valueOf(position+1));
datasource.close();
}
};
holder.ratingBar1.setOnRatingBarChangeListener(l);
holder.chkbxFavrowsel
.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView,
boolean isChecked) {
Model element = (Model) holder.chkbxFavrowsel
.getTag();
element.setSelected(buttonView.isChecked());
bSelected[position] = isChecked;
element.setsizeInc(sizeincrement);
// if (holder.chkbxFavrowsel.isChecked() ==
// isChecked) {
boolean bAlreadyfav = false;
String prefixlink = "https://play.google.com/store/apps/details?id=";
ShrdDatasource.open();
ArrayList<Comment> alDSPackagenm = ShrdDatasource.getAllPackage();
ArrayList<Comment> alDSRating = ShrdDatasource.getAllRating();
ArrayList<Comment> alDSID = ShrdDatasource.getID();
Log.i(TAG, "First Package cmp"+ alDSPackagenm);
ShrdDatasource.close();
int i = 0 ;
if (alDSPackagenm != null) {
for (i = 0; i < alDSPackagenm.size(); i++) {
if(alDSPackagenm.get(i).toString().equalsIgnoreCase(prefixlink + alPackagenm.get(position).toString() + "1x2optrue") || alDSPackagenm.get(i).toString().equalsIgnoreCase(prefixlink + alPackagenm.get(position).toString() + "1x2opfalse"))
{
bAlreadyfav = true;
break;
}
}
}
GolbPosition = position;
if (bAlreadyfav == true) {
Log.i(TAG, "Share positionis "+i);
Log.i(TAG, "Current positionis "+position);
Log.i(TAG,"ShrdDatasource Rating" + alDSRating.get(i).toString());
Log.i(TAG,"Favorite Rating" + String.valueOf(flFavRate[GolbPosition]));
if(alDSRating.get(i).toString().equalsIgnoreCase(String.valueOf(flFavRate[GolbPosition])))
{
Toast.makeText(getBaseContext(), " App already in Share list ",
Toast.LENGTH_LONG).show();
}
else
{
//alid
/*GolbPosition = position;
new GETFavTask().execute();*/
//UpdateRating
ShrdDatasource.open();
ShrdDatasource.UpdateRating(String.valueOf(flFavRate[GolbPosition]), alDSID.get(i).toString());
ShrdDatasource.close();
//Update Query fire
}
} else {
//Log.i(TAG, "First Package cmp"+ alDSPackagenm.get(position).toString());
Log.i(TAG, "Second Package cmp"+ alPackagenm.get(position).toString());
GolbPosition = position;
new GETFavTask().execute();
// add item in Database when user get select
}
}
});
RowModel model = getModel(position);
ViewHolder holder = (ViewHolder) row.getTag();
holder.ratingBar1.setTag(new Integer(position));
//holder.btnFavrowOpen.setTag(mlist.get(position));
holder.ratingBar1.setRating(model.rating);
holder.imgvFavrowiconappicon.setImageDrawable(drblAlIcon[position]);
holder.txvxFavrowiconappname.setText(alAppName.get(position)
.toString());
holder.chkbxFavrowsel.setChecked(mlist.get(position).isSelected());
holder.chkbxFavrowsel.setTag(mlist.get(position));
holder.btnFavrowOpen.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// OpenApp(alPackagenm.get(position).toString());
}
});
try
{
if (alAppRating.get(position) == null | alAppRating.get(position).toString().equalsIgnoreCase("null")) {
holder.ratingBar1.setRating(0.0f);
} else {
holder.ratingBar1.setRating(Float.parseFloat(alAppRating
.get(position).toString()));
}
}catch (Exception e) {
e.printStackTrace();
}
//holder.ratingBar1.setRating(Float.parseFloat(alAppRating.get(position).toString()));
return (row);
}
在这里，您可以看到holder.btnFavrowOpen带有 onclicklistner 的按钮，我在该行得到了空指针，这与此处发生的情况非常相关....如果我在适配器中删除按钮代码，它会正常工作...但是当我再次编写按钮代码时，它会出现错误空指针