您好我在运行我的应用程序时遇到空指针异常。 这是我的代码：
ProductAdapter.java
public class ProductAdapter extends BaseAdapter {
Context context;
List<Product> products = new ArrayList<Product>();
private boolean showCheckbox;
public ProductAdapter(Context context, List<Product> products,
boolean showCheckbox) {
super();
this.context = context;
this.products = products;
this.showCheckbox = showCheckbox;
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return products.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return products.get(position);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null){
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
inflater.inflate(R.layout.new_item, null);
}
Product myProduct = products.get(position);
TextView title = (TextView) convertView.findViewById(R.id.txt_title);
title.setText(myProduct.getTitle());
TextView cost = (TextView) convertView.findViewById(R.id.txt_cost);
cost.setText(myProduct.getCost());
ImageView image = (ImageView) convertView.findViewById(R.id.imageView1);
CheckBox selectBox = (CheckBox) convertView.findViewById(R.id.CheckBoxSelect1);
if(!showCheckbox){
selectBox.setVisibility(View.GONE);
}
else{
if(myProduct.selected == true)
selectBox.setChecked(true);
else
selectBox.setChecked(false);
}
return convertView;
}
}
这是我的布局xml文件
new_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_launcher" />
<TextView
android:id="@+id/txt_title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Large Text"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/txt_cost"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Medium Text"
android:textAppearance="?android:attr/textAppearanceMedium" />
<CheckBox
android:id="@+id/CheckBoxSelect1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
这里我得到一个nullpointer异常请帮帮我。 这是我的logcat。
09-26 16:37:23.894: D/AndroidRuntime(2611): Shutting down VM
09-26 16:37:23.894: W/dalvikvm(2611): threadid=1: thread exiting with uncaught exception (group=0x409951f8)
09-26 16:37:23.904: E/AndroidRuntime(2611): FATAL EXCEPTION: main
09-26 16:37:23.904: E/AndroidRuntime(2611): java.lang.NullPointerException
09-26 16:37:23.904: E/AndroidRuntime(2611): at com.shoppingcart.ProductAdapter.getView(ProductAdapter.java:59)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.AbsListView.obtainView(AbsListView.java:2033)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.ListView.makeAndAddView(ListView.java:1772)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.ListView.fillDown(ListView.java:672)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.ListView.fillFromTop(ListView.java:732)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.ListView.layoutChildren(ListView.java:1625)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.AbsListView.onLayout(AbsListView.java:1863)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.View.layout(View.java:11158)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.View.layout(View.java:11158)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.View.layout(View.java:11158)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.View.layout(View.java:11158)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.View.layout(View.java:11158)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1462)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2382)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.os.Handler.dispatchMessage(Handler.java:99)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.os.Looper.loop(Looper.java:137)
09-26 16:37:23.904: E/AndroidRuntime(2611): at android.app.ActivityThread.main(ActivityThread.java:4340)
09-26 16:37:23.904: E/AndroidRuntime(2611): at java.lang.reflect.Method.invokeNative(Native Method)
09-26 16:37:23.904: E/AndroidRuntime(2611): at java.lang.reflect.Method.invoke(Method.java:511)
09-26 16:37:23.904: E/AndroidRuntime(2611): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
09-26 16:37:23.904: E/AndroidRuntime(2611): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
09-26 16:37:23.904: E/AndroidRuntime(2611): at dalvik.system.NativeStart.main(Native Method)
谢谢。 这是我的Logcat。
09-26 16:58:35.205: D/AndroidRuntime(2749): Shutting down VM
09-26 16:58:35.205: W/dalvikvm(2749): threadid=1: thread exiting with uncaught exception (group=0x409951f8)
09-26 16:58:35.225: E/AndroidRuntime(2749): FATAL EXCEPTION: main
09-26 16:58:35.225: E/AndroidRuntime(2749): java.lang.ClassCastException: android.widget.TextView cannot be cast to android.widget.ImageView
09-26 16:58:35.225: E/AndroidRuntime(2749): at com.shoppingcart.ProductAdapter.getView(ProductAdapter.java:66)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.AbsListView.obtainView(AbsListView.java:2033)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.ListView.makeAndAddView(ListView.java:1772)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.ListView.fillDown(ListView.java:672)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.ListView.fillFromTop(ListView.java:732)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.ListView.layoutChildren(ListView.java:1625)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.AbsListView.onLayout(AbsListView.java:1863)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.View.layout(View.java:11158)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.View.layout(View.java:11158)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.View.layout(View.java:11158)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.View.layout(View.java:11158)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.View.layout(View.java:11158)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.ViewGroup.layout(ViewGroup.java:4197)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1462)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2382)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.os.Handler.dispatchMessage(Handler.java:99)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.os.Looper.loop(Looper.java:137)
09-26 16:58:35.225: E/AndroidRuntime(2749): at android.app.ActivityThread.main(ActivityThread.java:4340)
09-26 16:58:35.225: E/AndroidRuntime(2749): at java.lang.reflect.Method.invokeNative(Native Method)
09-26 16:58:35.225: E/AndroidRuntime(2749): at java.lang.reflect.Method.invoke(Method.java:511)
09-26 16:58:35.225: E/AndroidRuntime(2749): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
09-26 16:58:35.225: E/AndroidRuntime(2749): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
09-26 16:58:35.225: E/AndroidRuntime(2749): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
第一次将convertView充值的xml文件分配给null。
if(convertView == null){
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.new_item, null);
}
答案 1 :(得分：0)
public View getView(int position, View convertView, ViewGroup parent) {
if(convertView == null){
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
inflater.inflate(R.layout.new_item, null);
}
将上述代码更改为
public View getView(int position, View convertView, ViewGroup parent) {
LinearLayout rowLayout = null;
if (rowLayout == null) {
rowLayout = (LinearLayout) LayoutInflater.from(context)
.inflate(R.layout.new_item, parent, false);
}
Product myProduct = products.get(position);
TextView title = (TextView) rowLayout.findViewById(R.id.txt_title);
title.setText(myProduct.getTitle());
TextView cost = (TextView) rowLayout.findViewById(R.id.txt_cost);
cost.setText(myProduct.getCost());
ImageView image = (ImageView) rowLayout.findViewById(R.id.imageView1);
CheckBox selectBox = (CheckBox) rowLayout.findViewById(R.id.CheckBoxSelect1);
if(!showCheckbox){
selectBox.setVisibility(View.GONE);
}
else{
if(myProduct.selected == true)
selectBox.setChecked(true);
else
selectBox.setChecked(false);
}
return rowLayout;
}
}