Java 类之间的设置值(通过set/get方法)
我有一个用于定义变量的模型类,当我试图将MainActivity中的一些值设置为模型类时,会出现错误 从我的主课Java 类之间的设置值(通过set/get方法),java,android,Java,Android,我有一个用于定义变量的模型类,当我试图将MainActivity中的一些值设置为模型类时,会出现错误 从我的主课 public class MainActivity extends Activity { private ListView productList; private OfferModel offerModel; @Override protected void onCreate (Bundle savedInstanceState){
public class MainActivity extends Activity {
private ListView productList;
private OfferModel offerModel;
@Override
protected void onCreate (Bundle savedInstanceState){
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.activity_main);
productList = (ListView)findViewById(R.id.listView1);
...many codes here...
productList.setOnItemClickListener(new OnItemClickListener() {
@SuppressWarnings("deprecation")
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int position,
long arg3) {
offerModel.setProductName(arg0.getItemAtPosition(position).toString());
}
});
}}
这是我的日志结果
08-01 11:17:46.446: W/dalvikvm(2305): threadid=1: thread exiting with uncaught exception (group=0xa4b70648)
08-01 11:17:46.446: E/AndroidRuntime(2305): FATAL EXCEPTION: main
08-01 11:17:46.446: E/AndroidRuntime(2305): java.lang.NullPointerException
08-01 11:17:46.446: E/AndroidRuntime(2305): at stok.kontrol.noyagrup.MainActivity$2.onItemClick(MainActivity.java:71)
08-01 11:17:46.446: E/AndroidRuntime(2305): at android.widget.AdapterView.performItemClick(AdapterView.java:298)
08-01 11:17:46.446: E/AndroidRuntime(2305): at android.widget.AbsListView.performItemClick(AbsListView.java:1100)
08-01 11:17:46.446: E/AndroidRuntime(2305): at android.widget.AbsListView$PerformClick.run(AbsListView.java:2788)
08-01 11:17:46.446: E/AndroidRuntime(2305): at android.widget.AbsListView$1.run(AbsListView.java:3463)
08-01 11:17:46.446: E/AndroidRuntime(2305): at android.os.Handler.handleCallback(Handler.java:730)
08-01 11:17:46.446: E/AndroidRuntime(2305): at android.os.Handler.dispatchMessage(Handler.java:92)
08-01 11:17:46.446: E/AndroidRuntime(2305): at android.os.Looper.loop(Looper.java:137)
08-01 11:17:46.446: E/AndroidRuntime(2305): at android.app.ActivityThread.main(ActivityThread.java:5103)
08-01 11:17:46.446: E/AndroidRuntime(2305): at java.lang.reflect.Method.invokeNative(Native Method)
08-01 11:17:46.446: E/AndroidRuntime(2305): at java.lang.reflect.Method.invoke(Method.java:525)
08-01 11:17:46.446: E/AndroidRuntime(2305): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
08-01 11:17:46.446: E/AndroidRuntime(2305): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-01 11:17:46.446: E/AndroidRuntime(2305): at dalvik.system.NativeStart.main(Native Method)
我错过了什么
提前感谢。
OfferModel OfferModel
未实例化,为null
。因此,当您调用offerModel.setProductName(arg0.getItemAtPosition(position.toString())时代码>您将得到一个异常。您尚未初始化私有OfferModel OfferModel代码>在您的代码中,您正在使用offerModel.setProductName(arg0.getItemAtPosition(position.toString())代码>因为它将抛出NPE
因此,首先初始化它,而且productName
是null
,它尚未初始化,但您可以使用参数化的构造函数来初始化它(您必须先添加构造函数)
并添加构造函数
public OfferModel(String pro){
productName=pro;
}
或者从代码中我可以看到你喜欢这个
关键字,所以你可以像这个
productList.setOnItemClickListener(新的OnItemClickListener(){
@抑制警告(“弃用”)
@凌驾
公共单击(适配器视图arg0,视图arg1,内部位置,
长arg3){
offerModel=新的offerModel();
offerModel.setProductName(arg0.getItemAtPosition(position.toString());
}
});
什么?错了!此.productName=pName不会引发任何异常。offerModel.setProductName(arg0.getItemAtPosition(position.toString());将抛出它。可能是
offerModel=new OfferModel(productNameValue);//Pass initial value of `productName`
//So it will first initialize your productName
public OfferModel(String pro){
productName=pro;
}
public OfferModel(String productName){
this.productName=productName;
}
productList.setOnItemClickListener(new OnItemClickListener() {
@SuppressWarnings("deprecation")
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int position,
long arg3) {
offerModel= new OfferModel();
offerModel.setProductName(arg0.getItemAtPosition(position).toString());
}
});