我创建了一个应用程序来解析数据并将其放入字符串数组中。我在后台做这个任务。我想要实现的是，读取后台进程已解析的任何数据的字符串。为了做到这一点，我已经使数组静态，我试图从另一个类中读取它，但我的程序失败，出现以下错误。有谁可以看看，帮助我。感谢。
01-17 09:43:07.927: E/AndroidRuntime(1167): FATAL EXCEPTION: main
01-17 09:43:07.927: E/AndroidRuntime(1167): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.pro1/com.example.pro1.Secactivity}: java.lang.NullPointerException
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.os.Handler.dispatchMessage(Handler.java:99)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.os.Looper.loop(Looper.java:137)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.app.ActivityThread.main(ActivityThread.java:5039)
01-17 09:43:07.927: E/AndroidRuntime(1167): at java.lang.reflect.Method.invokeNative(Native Method)
01-17 09:43:07.927: E/AndroidRuntime(1167): at java.lang.reflect.Method.invoke(Method.java:511)
01-17 09:43:07.927: E/AndroidRuntime(1167): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-17 09:43:07.927: E/AndroidRuntime(1167): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-17 09:43:07.927: E/AndroidRuntime(1167): at dalvik.system.NativeStart.main(Native Method)
01-17 09:43:07.927: E/AndroidRuntime(1167): Caused by: java.lang.NullPointerException
01-17 09:43:07.927: E/AndroidRuntime(1167): at com.example.pro1.Secactivity.onCreate(Secactivity.java:29)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.app.Activity.performCreate(Activity.java:5104)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
01-17 09:43:07.927: E/AndroidRuntime(1167): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
01-17 09:43:07.927: E/AndroidRuntime(1167): ... 11 more
这是我执行asynctask的主要类：
public class MainActivity extends Activity {
EditText uid;
EditText password;
Button submit;
static String Sarray1[] = new String[50];
@Override
protected void onCreate(Bundle savedInstanceState) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
submit = (Button)findViewById(R.id.submit);
submit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
uid = (EditText)findViewById(R.id.id);
password = (EditText)findViewById(R.id.password);
String userid = uid.getText().toString();
String pwd = password.getText().toString();
Loginauth log = new Loginauth();
if(!userid.equals("")&&!pwd.equals(""))
{
String result = log.Login(userid,pwd);
if(result.equals(""))
{
Toast toast = Toast.makeText(getApplicationContext(), "Login Error: Check id and Password", Toast.LENGTH_LONG);
toast.show();
}
else
{
Toast toast = Toast.makeText(getApplicationContext(), "Login Successfull", Toast.LENGTH_SHORT);
toast.show();
SAXParserActivity ab = new SAXParserActivity();
ab.execute();
for (int j = 0; j<15;j++)
{
Log.d("Array",Sarray1[j].toString());
}
startActivity(new Intent("com.example.pro1.ABC"));
}
}
else
{
Toast toast = Toast.makeText(getApplicationContext(), "Invalid id or password", Toast.LENGTH_LONG);
toast.show();
}
}
});
}
class SAXParserActivity extends AsyncTask<Void,Void,Void> {
XMLGettersSetters data;
@Override
protected Void doInBackground(Void... params) {
Log.i("Abe","Abe");
try {
SAXParserFactory saxPF = SAXParserFactory.newInstance();
SAXParser saxP = saxPF.newSAXParser();
XMLReader xmlR = saxP.getXMLReader();
URL url = new URL("http://www.xmlfiles.com/examples/cd_catalog.xml"); // URL of the XML
XMLHandler myXMLHandler = new XMLHandler();
xmlR.setContentHandler(myXMLHandler);
xmlR.parse(new InputSource(url.openStream()));
} catch (Exception e) {
System.out.println(e);
}
data = XMLHandler.data;
for (int i = 0; i < data.getTitle().size(); i++) {
Sarray1[i] =data.getTitle().get(i);
//System.out.printf("Sarray",Sarray[i].toString());
//Log.d("Abe",Sarray);
//Sarray1[i]=Sarray;
Log.d("Abe",Sarray1[i].toString());
}
return null;
}
}
}
以下是我尝试访问数组的类：
package com.example.pro1;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.widget.TabHost;
public class Secactivity extends FragmentActivity {
TabHost tHost;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main1);
tHost = (TabHost) findViewById(android.R.id.tabhost);
tHost.setup();
String array[] = new String[50];
for(int i = 0;i<MainActivity.Sarray1.length;i++)
{
array[i] = MainActivity.Sarray1[i];
Log.d("Secactivity",MainActivity.Sarray1[i]);
}
/** Defining Tab Change Listener event. This is invoked when tab is changed */
TabHost.OnTabChangeListener tabChangeListener = new TabHost.OnTabChangeListener() {
@Override
public void onTabChanged(String tabId) {
android.support.v4.app.FragmentManager fm = getSupportFragmentManager();
Protab1 androidFragment = (Protab1) fm.findFragmentByTag("ST");
Protab2 appleFragment = (Protab2) fm.findFragmentByTag("CSI");
android.support.v4.app.FragmentTransaction ft = fm.beginTransaction();
/** Detaches the androidfragment if exists */
if(androidFragment!=null)
ft.detach(androidFragment);
/** Detaches the applefragment if exists */
if(appleFragment!=null)
ft.detach(appleFragment);
/** If current tab is android */
if(tabId.equalsIgnoreCase("ST")){
if(androidFragment==null){
/** Create AndroidFragment and adding to fragmenttransaction */
ft.add(R.id.realtabcontent,new Protab1(), "ST");
}else{
/** Bring to the front, if already exists in the fragmenttransaction */
ft.attach(androidFragment);
}
}else{ /** If current tab is apple */
if(appleFragment==null){
/** Create AppleFragment and adding to fragmenttransaction */
ft.add(R.id.realtabcontent,new Protab2(), "CSI");
}else{
/** Bring to the front, if already exists in the fragmenttransaction */
ft.attach(appleFragment);
}
}
ft.commit();
}
};
/** Setting tabchangelistener for the tab */
tHost.setOnTabChangedListener(tabChangeListener);
/** Defining tab builder for Andriod tab */
TabHost.TabSpec tSpecAndroid = tHost.newTabSpec("ST");
tSpecAndroid.setIndicator("ST");
tSpecAndroid.setContent(new DummyTabContent(getBaseContext()));
tHost.addTab(tSpecAndroid);
/** Defining tab builder for Apple tab */
TabHost.TabSpec tSpecApple = tHost.newTabSpec("CSI");
tSpecApple.setIndicator("CSI");
tSpecApple.setContent(new DummyTabContent(getBaseContext()));
tHost.addTab(tSpecApple);
}
}
答案 0 :(得分：0)
不要像这样使用大小合适的Array，
static String Sarray1[] = new String[50];
将其更改为ArrayList，
ArrayList<String> Sarray1 = new ArrayList<String>();
然后使用add data来使用传真，
Sarray1.add(data.getTitle().get(i));
在您的情况下，如果您使用MainActivity.Sarray1.length循环，那么即使只有10个数据条目，它仍将始终运行 50次。因此，剩余索引的获取null values会有所变化。