当我按下运行我的应用程序时，我收到此消息。 CAnanyone请帮帮我吗？我在这里发布我的LogCat：
09-10 21:40:54.102: E/AndroidRuntime(11894): FATAL EXCEPTION: main
09-10 21:40:54.102: E/AndroidRuntime(11894): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.shoppingapp/com.example.shoppingapp.CurrencyConverter}: java.lang.NullPointerException
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2114)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2139)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.app.ActivityThread.access$700(ActivityThread.java:143)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1241)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.os.Handler.dispatchMessage(Handler.java:99)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.os.Looper.loop(Looper.java:137)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.app.ActivityThread.main(ActivityThread.java:4963)
09-10 21:40:54.102: E/AndroidRuntime(11894): at java.lang.reflect.Method.invokeNative(Native Method)
09-10 21:40:54.102: E/AndroidRuntime(11894): at java.lang.reflect.Method.invoke(Method.java:511)
09-10 21:40:54.102: E/AndroidRuntime(11894): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
09-10 21:40:54.102: E/AndroidRuntime(11894): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
09-10 21:40:54.102: E/AndroidRuntime(11894): at dalvik.system.NativeStart.main(Native Method)
09-10 21:40:54.102: E/AndroidRuntime(11894): Caused by: java.lang.NullPointerException
09-10 21:40:54.102: E/AndroidRuntime(11894): at com.example.shoppingapp.CurrencyConverter.onCreate(CurrencyConverter.java:36)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.app.Activity.performCreate(Activity.java:5184)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
09-10 21:40:54.102: E/AndroidRuntime(11894): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2078)
09-10 21:40:54.102: E/AndroidRuntime(11894): ... 11 more
我在这里发布了CurrencyConverter类。我见过第36行。也许错误就在那里，因为我在R.java中找不到simple_spinner_item ......我该怎么办？
package com.example.shoppingapp;
import com.example.shoppingapp.ConvertECB;
import com.example.shoppingapp.R;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
public class CurrencyConverter extends Activity{
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.start_app);
final Button button = (Button) findViewById(R.id.exit);
final Button count = (Button) findViewById(R.id.ok);
final AlertDialog.Builder builder = new AlertDialog.Builder(this);
final EditText curr = (EditText) findViewById(R.id.entry);
final TextView result = (TextView) findViewById(R.id.converted);
final TextView date = (TextView) findViewById(R.id.date);
final Spinner spinner = (Spinner) findViewById(R.id.spinner);
final Spinner spinner1 = (Spinner) findViewById(R.id.spinner1);
// stworzenie parsera
final ConvertECB cp = new ConvertECB (this);
date.setText("Last updated: " + cp.getPubDate()
+ ". Data received from ECB.");
// tablica z symbolami walut
final String spinner_array[] = new String[cp.currencyCode.size()];
// przypisanie pobranych symboli do tablicy
for (int i = 0; i < cp.currencyCode.size(); i++) {
spinner_array[i] = cp.currencyCode.get(i);
}
// ustawienie tablicy z symbolami walut jako listy dla spinnerow oraz
// wygladu
ArrayAdapter adapter = new ArrayAdapter(this,
android.R.layout.simple_spinner_item, spinner_array);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
spinner1.setAdapter(adapter);
// okienko pytajace przy probie wyjscia z programu
builder.setMessage("Are you sure you want to exit?")
.setCancelable(false)
.setPositiveButton("Yes",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
finish();
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
// listnery do przyciskow
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
final AlertDialog alert;
alert = builder.create();
alert.show();
}
});
count.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
try {
float value = Float.parseFloat(curr.getText().toString());
value = value
* cp.getRelativeExchange(spinner.getSelectedItem()
.toString(), spinner1.getSelectedItem()
.toString());
result.setText(String.valueOf(value));
} catch (Exception ex) {
result.setText(R.string.error);
}
}
});
}
}
答案 0 :(得分：3)
java.lang.NullPointerException是什么意思？
这意味着您正在尝试使用变量，可能是通过在其上设置方法或侦听器。以下是我们阅读它的方式。
09-10 21：40：54.102：E / AndroidRuntime（11894）：致命异常：主
这告诉我们该应用程序停止工作。第一行告诉我们
造成了什么Caused by: java.lang.NullPointerException
告诉我们NPE。然后，引用你的项目之后的下一行是一个很好的起点。
at com.example.shoppingapp.CurrencyConverter.onCreate（CurrencyConverter.java:36）
第36行CurrencyConverter。有些东西null那里......试图找出原因和原因。如果您需要更多帮助，请发布相关代码。