我在android中有以下代码，但是当我运行它时，它会抱怨：不幸的是已停止：
package com.example.trave;
import java.util.List;
import com.example.trave.data.NoteDataSource;
import com.example.trave.data.NoteItem;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
public class MainActivity extends Activity {
private NoteDataSource dataSource;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dataSource = new NoteDataSource(this);
List<NoteItem> notes = dataSource.findAll();
NoteItem note = notes.get(0);
note.setText("Updated!");
dataSource.update(note);
notes = dataSource.findAll();
note = notes.get(0);
Log.i("NOTES", note.getKey() + ": " + note.getText());
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
package com.example.trave.data;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.SortedSet;
import java.util.TreeSet;
import android.content.Context;
import android.content.SharedPreferences;
public class NoteDataSource {
private static final String PREFKEY = "notes";
private SharedPreferences notePrefs;
public NoteDataSource(Context context) {
notePrefs = context.getSharedPreferences(PREFKEY, Context.MODE_PRIVATE);
}
public List<NoteItem> findAll() {
Map<String, ?> notesMap = notePrefs.getAll();
SortedSet<String> keys = new TreeSet<String>(notesMap.keySet());
List<NoteItem> noteList = new ArrayList<NoteItem>();
for (String key : keys) {
NoteItem note = new NoteItem();
note.setKey(key);
note.setText((String)note.getKey());
noteList.add(note);
}
return noteList;
}
public boolean update(NoteItem note) {
SharedPreferences.Editor editor = notePrefs.edit();
editor.putString(note.getKey(), note.getText());
editor.commit();
return true;
}
public boolean remove(NoteItem note) {
if (notePrefs.contains(note.getKey())) {
SharedPreferences.Editor editor = notePrefs.edit();
editor.remove(note.getKey());
editor.commit();
}
return true;
}
}
package com.example.trave.data;
import android.annotation.SuppressLint;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
public class NoteItem {
private String key;
private String text;
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
@SuppressLint("SimpleDateFormat")
public static NoteItem getNew() {
Locale locale = new Locale("en_US");
Locale.setDefault(locale);
String pattern = "yyyy-MM-dd HH:mm:ss Z";
SimpleDateFormat formatter = new SimpleDateFormat(pattern);
String key = formatter.format(new Date());
NoteItem note = new NoteItem();
note.setKey(key);
note.setText("");
return note;
}
}
问题是什么以及如何解决？
logCat：
09-08 11:15:23.674: E/SurfaceFlinger(37): ro.sf.lcd_density must be defined as a build property
09-08 11:15:23.793: E/Trace(1552): error opening trace file: No such file or directory (2)
09-08 11:15:24.533: D/AndroidRuntime(1552): Shutting down VM
09-08 11:15:24.533: W/dalvikvm(1552): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
09-08 11:15:24.543: E/AndroidRuntime(1552): FATAL EXCEPTION: main
09-08 11:15:24.543: E/AndroidRuntime(1552): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.trave/com.example.trave.MainActivity}: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.app.ActivityThread.access$600(ActivityThread.java:141)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.os.Handler.dispatchMessage(Handler.java:99)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.os.Looper.loop(Looper.java:137)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.app.ActivityThread.main(ActivityThread.java:5041)
09-08 11:15:24.543: E/AndroidRuntime(1552): at java.lang.reflect.Method.invokeNative(Native Method)
09-08 11:15:24.543: E/AndroidRuntime(1552): at java.lang.reflect.Method.invoke(Method.java:511)
09-08 11:15:24.543: E/AndroidRuntime(1552): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
09-08 11:15:24.543: E/AndroidRuntime(1552): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
09-08 11:15:24.543: E/AndroidRuntime(1552): at dalvik.system.NativeStart.main(Native Method)
09-08 11:15:24.543: E/AndroidRuntime(1552): Caused by: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
09-08 11:15:24.543: E/AndroidRuntime(1552): at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:251)
09-08 11:15:24.543: E/AndroidRuntime(1552): at java.util.ArrayList.get(ArrayList.java:304)
09-08 11:15:24.543: E/AndroidRuntime(1552): at com.example.trave.MainActivity.onCreate(MainActivity.java:25)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.app.Activity.performCreate(Activity.java:5104)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
09-08 11:15:24.543: E/AndroidRuntime(1552): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
09-08 11:15:24.543: E/AndroidRuntime(1552): ... 11 more
09-08 11:15:24.552: W/ActivityManager(291): Force finishing activity com.example.trave/.MainActivity
09-08 11:15:24.562: W/WindowManager(291): Failure taking screenshot for (246x410) to layer 21015
答案 0 :(得分：1)
你在
得到了IndexOutOfBoundsExceptionList<NoteItem> notes = dataSource.findAll();
NoteItem note = notes.get(0);
或
notes = dataSource.findAll();
note = notes.get(0);
因为列表似乎是空的，你应该检查大小
List<NoteItem> notes = dataSource.findAll();
if (notes.size()>0)
NoteItem note = notes.get(0);
并检查您提供给列表的数据
答案 1 :(得分：0)
您获得IndexOutOfBoundsException，因为NoteList为空。最有可能的是：
NoteItem note = notes.get(0);
onCreate方法中的。您需要检查NoteDataSource.findAll()的空结果，如下所示：
List<NoteItem> notes = dataSource.findAll();
if(notes.isEmpty())
return; // Or whatever you must do in your App
else {
NoteItem note = notes.get(0);
// ... The rest of your onCreate code...
此外，在您的NoteDataSource.update()和NoteDataSource.remove()中，请返回commit()的结果，而不是合同中的SharedPreferences.Editor.commit
否则返回布尔值没什么意义。