在列表行中显示按钮，并希望用户使用该按钮将列表项添加到购物车，但每当我加载列表获取错误不幸的是，如果我不在我的代码中使用按钮没有得到任何错误，应用程序已停止。
所以在这里我的问题在我尝试使用按钮时我的代码出了什么问题？
这是我遇到错误的一行：
mImgAddCart.setOnClickListener(new OnClickListener() {
logcat的：
07-01 05:57:03.733: E/AndroidRuntime(779): FATAL EXCEPTION: main
07-01 05:57:03.733: E/AndroidRuntime(779): java.lang.NullPointerException
07-01 05:57:03.733: E/AndroidRuntime(779): at com.example.sample.ItemsActivity$MyAsyncTask.onPostExecute(ItemsActivity.java:191)
07-01 05:57:03.733: E/AndroidRuntime(779): at com.example.sample.ItemsActivity$MyAsyncTask.onPostExecute(ItemsActivity.java:1)
07-01 05:57:03.733: E/AndroidRuntime(779): at android.os.AsyncTask.finish(AsyncTask.java:631)
07-01 05:57:03.733: E/AndroidRuntime(779): at android.os.AsyncTask.access$600(AsyncTask.java:177)
07-01 05:57:03.733: E/AndroidRuntime(779): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
07-01 05:57:03.733: E/AndroidRuntime(779): at android.os.Handler.dispatchMessage(Handler.java:99)
07-01 05:57:03.733: E/AndroidRuntime(779): at android.os.Looper.loop(Looper.java:137)
07-01 05:57:03.733: E/AndroidRuntime(779): at android.app.ActivityThread.main(ActivityThread.java:5041)
07-01 05:57:03.733: E/AndroidRuntime(779): at java.lang.reflect.Method.invokeNative(Native Method)
07-01 05:57:03.733: E/AndroidRuntime(779): at java.lang.reflect.Method.invoke(Method.java:511)
07-01 05:57:03.733: E/AndroidRuntime(779): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
07-01 05:57:03.733: E/AndroidRuntime(779): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
07-01 05:57:03.733: E/AndroidRuntime(779): at dalvik.system.NativeStart.main(Native Method)
07-01 05:57:07.172: E/Trace(806): error opening trace file: No such file or directory (2)
LazyAdapter.java：
public class LazyAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
String itemTitle, itemCost;
public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.listrow_items, null);
final TextView title = (TextView)vi.findViewById(R.id.title);
final TextView cost = (TextView)vi.findViewById(R.id.cost);
ImageView thumb_image = (ImageView) vi.findViewById(R.id.list_image);
HashMap<String, String> item = new HashMap<String, String>();
item = data.get(position);
// Setting all values in listview
title.setText(item.get(ItemsActivity.KEY_TITLE));
cost.setText(item.get(ItemsActivity.KEY_COST));
imageLoader.DisplayImage(item.get(com.example.sample.ItemsActivity.KEY_THUMB_URL), thumb_image);
//Button mImgAddCart
Button mImgAddCart = (Button) vi.findViewById(R.id.btn_add_to_order);
mImgAddCart.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
itemTitle = title.getText().toString();
itemCost = cost.getText().toString();
if (Constants.sItem_Detail.size() <= 0) {
HashMap<String, String> sTempObj = new HashMap<String, String>();
sTempObj.put(KEY_TITLE, itemTitle);
sTempObj.put(KEY_COST, itemCost);
Constants.sItem_Detail.add(sTempObj);
}
AlertDialog.Builder alertdialog = new AlertDialog.Builder(
ItemsActivity.this);
alertdialog.setTitle(getResources()
.getString(R.string.app_name));
alertdialog.setMessage("Item Added to Cart");
alertdialog.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which)
{
activity.finish();
}
});
alertdialog.show();
}
});
return vi;
}
}
行：
sTempObj.put(KEY_TITLE, itemTitle);
获得：
KEY_TITLE cannot be resolved to a variable
订单
AlertDialog.Builder alertdialog = new AlertDialog.Builder(ItemsActivity.this);
获得：
No enclosing instance of the type ItemsActivity is accessible in scope
订单
alertdialog.setTitle(getResources().getString(R.string.app_name));
获得：
The method getResources() is undefined for the type new View.OnClickListener(){}
答案 0 :(得分：3)
您的 LazyAdapter 类代码应如下所示：
public class LazyAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
String itemTitle, itemCost;
TextView title, cost;
public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.listrow_items, null);
title = (TextView)vi.findViewById(R.id.title);
cost = (TextView)vi.findViewById(R.id.cost);
ImageView thumb_image = (ImageView) vi.findViewById(R.id.list_image);
HashMap<String, String> item = new HashMap<String, String>();
item = data.get(position);
// Setting all values in listview
title.setText(item.get(ItemsActivity.KEY_TITLE));
cost.setText(item.get(ItemsActivity.KEY_COST));
imageLoader.DisplayImage(item.get(com.example.sample.ItemsActivity.KEY_THUMB_URL), thumb_image);
//Button mImgAddCart
Button mImgAddCart = (Button) vi.findViewById(R.id.btn_add_to_order);
mImgAddCart.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
itemTitle = title.getText().toString();
itemCost = cost.getText().toString();
if (Constants.sItem_Detail.size() <= 0) {
HashMap<String, String> sTempObj = new HashMap<String, String>();
sTempObj.put(com.example.sample.ItemsActivity.KEY_TITLE, itemTitle);
sTempObj.put(com.example.sample.ItemsActivity.KEY_COST, itemCost);
Constants.sItem_Detail.add(sTempObj);
}
return vi;
}
}
答案 1 :(得分：1)
如果你在listrow_items.xml中使用“btn_add_to_order”按钮，那么按钮的监听器应该在你的“LazyAdapter”类中看@下面的代码
public class LazyAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.listrow_items, null);
TextView title = (TextView)vi.findViewById(R.id.title);
TextView cost = (TextView)vi.findViewById(R.id.cost);
ImageView thumb_image = (ImageView) vi.findViewById(R.id.list_image);
HashMap<String, String> item = new HashMap<String, String>();
item = data.get(position);
// Setting all values in listview
title.setText(item.get(ItemsActivity.KEY_TITLE));
cost.setText(item.get(ItemsActivity.KEY_COST));
imageLoader.DisplayImage(item.get(com.example.sample.ItemsActivity.KEY_THUMB_URL), thumb_image);
//Button mImgAddCart
Button mImgAddCart = (Button) vi.findViewById(R.id.btn_add_to_order);
mImgAddCart.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
itemTitle = txt_title.getText().toString();
itemCost = text_cost.getText().toString();
if (Constants.sItem_Detail.size() <= 0) {
HashMap<String, String> sTempObj = new HashMap<String, String>();
sTempObj.put(KEY_TITLE, itemTitle);
sTempObj.put(KEY_COST, itemCost);
Constants.sItem_Detail.add(sTempObj);
}
AlertDialog.Builder alertdialog = new AlertDialog.Builder(
ItemsActivity.this);
alertdialog.setTitle(getResources()
.getString(R.string.app_name));
alertdialog.setMessage("Item Added to Cart");
alertdialog.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which)
{
finish();
}
});
alertdialog.show();
}
});
return vi;
}
}
答案 2 :(得分：1)
快速修复LazyAdapter类中的当前问题：
<强>获得：
KEY_TITLE cannot be resolved to a variable
解决方案： 确保在ItemsActivity
中将KEY_TITLE声明为公共静态字段<强>获得：
在范围
中无法访问ItemsActivity类型的封闭实例AlertDialog.Builder alertdialog = new AlertDialog.Builder(ItemsActivity.this);
解决方案： 使用Activity上下文将AlertDialog显示为：
AlertDialog.Builder alertdialog = new AlertDialog.Builder(activity);
<强>获得：
alertdialog.setTitle(getResources().getString(R.string.app_name));
对于新的View.OnClickListener（）{}类型，未定义方法getResources（） 解决方案： 使用Activity上下文访问Resources：
alertdialog.setTitle(activity.getResources().getString(R.string.app_name));
答案 3 :(得分：1)
您刚刚初始化了按钮，然后调用方法......
看看这可能会有所帮助。
public class LazyAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
String itemTitle, itemCost;
public LazyAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.listrow_items, null);
final TextView title = (TextView)vi.findViewById(R.id.title);
final TextView cost = (TextView)vi.findViewById(R.id.cost);
ImageView thumb_image = (ImageView) vi.findViewById(R.id.list_image);
Button mImgAddCart = (Button) vi.findViewById(R.id.btn_add_to_order);
HashMap<String, String> item = new HashMap<String, String>();
item = data.get(position);
// Setting all values in listview
title.setText(item.get(ItemsActivity.KEY_TITLE));
cost.setText(item.get(ItemsActivity.KEY_COST));
imageLoader.DisplayImage(item.get(com.example.sample.ItemsActivity.KEY_THUMB_URL), thumb_image);
//Button mImgAddCart
mImgAddCart.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
itemTitle = title.getText().toString();
itemCost = cost.getText().toString();
if (Constants.sItem_Detail.size() <= 0) {
HashMap<String, String> sTempObj = new HashMap<String, String>();
sTempObj.put(KEY_TITLE, itemTitle);
sTempObj.put(KEY_COST, itemCost);
Constants.sItem_Detail.add(sTempObj);
}
AlertDialog.Builder alertdialog = new AlertDialog.Builder(
ItemsActivity.this);
alertdialog.setTitle(getResources()
.getString(R.string.app_name));
alertdialog.setMessage("Item Added to Cart");
alertdialog.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which)
{
activity.finish();
}
});
alertdialog.show();
}
});
return vi;
}
}
答案 4 :(得分：0)
您尚未在txt_title课程中初始化text_cost和ItemsActivity。
假设您有activity_item中的文字视图。
setContentView(R.layout.activity_item);
txt_title = (TextView) findViewById(R.id.title);
text_cost = (TextView) findViewById(R.id.cost);
答案 5 :(得分：0)
更改getResources行以使用活动上下文。还要在活动类中将KEY_TITLE声明为public。
AlertDialog.Builder alertdialog = new AlertDialog.Builder(
a);
alertdialog.setTitle(a.getResources()
.getString(R.string.app_name));
alertdialog.setMessage("Item Added to Cart");
alertdialog.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int which)
{
a.finish();
}
});
alertdialog.show();