大致了解我想要做什么：我有一个名为 Events 的类，它将包含一个日期对象、一些字符串和一些布尔值。我使用在 DiaryMain.java 中调用 startActivityForResult 时传回的数据创建它。我想把那个对象放入一个名为 Diary 的 ArrayList 中。我得到一个NullPointer Exception(DiaryMain.java:111)，这diary.add(new Event(date, lengthOfEvent, typeOfEvent, trigger, notes, amb_called, amb_needed, awake));是DiaryMain.onActivityResult(). 我已经包含了 DiaryMain.java、DiaryEventCreate.java 和 Event.java 的相关代码。我没有正确地将数据传递回 DiaryMain 还是我的 ArrayList 没有正确初始化？
谢谢您的帮助。
DiaryMain.java - 我的应用程序的主要活动
package org.daringer.EpApp;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.GregorianCalendar;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.widget.Toast;
import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.app.ActionBar.Tab;
import com.actionbarsherlock.app.SherlockFragment;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuInflater;
import com.actionbarsherlock.view.MenuItem;
public class DiaryMain extends SherlockFragmentActivity {
public static Context appContext;
public ArrayList<Event> diary;
...
public boolean onOptionsItemSelected(MenuItem item){
switch(item.getItemId()){
...
case R.id.menu_add_event:{
makeToast("add event");
Intent i = new Intent(DiaryMain.this,DiaryEventCreate.class);
startActivityForResult(i, 0);
break;
}
}
return true;
}
/* (non-Javadoc)
* @see android.support.v4.app.FragmentActivity#onActivityResult(int, int, android.content.Intent)
*/
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// TODO Auto-generated method stub
if(resultCode == RESULT_OK){
if(requestCode == 0){ //new event [add this event to the end of the diary]
String notes, lengthOfEvent, typeOfEvent, trigger;
boolean amb_called, amb_needed, awake;
GregorianCalendar date;
makeToast("CREATED NEW EVENT");
date = (GregorianCalendar) data.getSerializableExtra("date");
notes = data.getStringExtra("notes").toString();
lengthOfEvent = data.getStringExtra("lengthOfEvent").toString();
typeOfEvent = data.getStringExtra("typeOfEvent").toString();
trigger = data.getStringExtra("trigger").toString();
amb_called = data.getBooleanExtra("amb_called", false);
amb_needed = data.getBooleanExtra("amb_needed", false);
awake = data.getBooleanExtra("awake", false);
diary.add(new Event(date, lengthOfEvent, typeOfEvent, trigger, notes, amb_called, amb_needed, awake));
}
else if(requestCode == 1){ //edit event [HAVE TO REFERENCE THE EVENTS INDEX]
}
}
super.onActivityResult(requestCode, resultCode, data);
}
}
DiaryEventCreate.java - 接受输入并将其发送回 DiaryMain.java 的活动
package org.daringer.EpApp;
import java.util.GregorianCalendar;
import net.kapati.widgets.DatePicker;
import android.content.Intent;
import android.os.Bundle;
import android.text.format.DateFormat;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;
import com.actionbarsherlock.app.SherlockActivity;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuInflater;
import com.actionbarsherlock.view.MenuItem;
public class DiaryEventCreate extends SherlockActivity{
private GregorianCalendar date;
private String lengthOfEvent;
private String typeOfEvent;
private String trigger;
private String notes;
private boolean amb_called;
private boolean amb_needed;
private boolean awake;
private DatePicker ETDate;
private EditText ELength;
private EditText EType;
private EditText ETrigger;
private EditText ENotes;
private CheckBox EAmbCalled;
private CheckBox EAmbNeeded;
private CheckBox EAwake;
private void saveEvent(){
int day = ETDate.getDay();
int month= ETDate.getMonth()+1;
int year = ETDate.getYear();
date = new GregorianCalendar(year, month, day);
makeToast("Saving event...");
lengthOfEvent = ELength.getText().toString();
typeOfEvent = EType.getText().toString();
trigger = ETrigger.getText().toString();
notes = ENotes.getText().toString();
amb_called = EAmbCalled.isChecked();
amb_needed = EAmbNeeded.isChecked();
awake = EAwake.isChecked();
if(isInteger(lengthOfEvent)){
int len = Integer.parseInt(lengthOfEvent);
if(len>0){
Intent i = getIntent();
i.putExtra("lengthOfEvent", lengthOfEvent);
i.putExtra("date", date);
i.putExtra("typeOfEvent", typeOfEvent);
i.putExtra("trigger", trigger);
i.putExtra("notes", notes);
i.putExtra("amb_called", amb_called);
i.putExtra("amb_needed", amb_needed);
i.putExtra("awake", awake);
setResult(RESULT_OK, i);
finish();
}
else
makeToast("Length of event cannot less than 0");
}
else{
makeToast("Length of Event is not an integer");
}
}
public boolean onOptionsItemSelected(MenuItem item){
switch(item.getItemId()){
...
case R.id.event_discard:{
makeToast("Discarding all entries...");
finish();
break;
}
case R.id.event_save:{
saveEvent();
break;
}
}
return true;
}
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
MenuInflater inflater = getSupportMenuInflater();
inflater.inflate(R.menu.diary_create_event_menu, menu);
return super.onCreateOptionsMenu(menu);
}
}
事件.java
package org.daringer.EpApp;
import java.util.GregorianCalendar;
public class Event{
private GregorianCalendar date;
private String lengthOfEvent;
private String typeOfEvent;
private String trigger;
private String notes;
private boolean amb_called;
private boolean amb_needed;
private boolean awake;
public Event(GregorianCalendar date, String lengthOfEvent, String typeOfEvent, String trigger, String notes, boolean amb_called, boolean amb_needed, boolean awake){
this.date = date;
this.lengthOfEvent = lengthOfEvent;
this.typeOfEvent = typeOfEvent;
this.trigger = trigger;
this.notes = notes;
this.amb_called = amb_called;
this.amb_needed = amb_needed;
this.awake = awake;
}
/**
* @return the amb_called
*/
public boolean isAmb_called() {
return amb_called;
}
/**
* @param amb_called the amb_called to set
*/
public void setAmb_called(boolean amb_called) {
this.amb_called = amb_called;
}
/**
* @return the amb_needed
*/
public boolean isAmb_needed() {
return amb_needed;
}
/**
* @param amb_needed the amb_needed to set
*/
public void setAmb_needed(boolean amb_needed) {
this.amb_needed = amb_needed;
}
/**
* @return the awake
*/
public boolean isAwake() {
return awake;
}
/**
* @param awake the awake to set
*/
public void setAwake(boolean awake) {
this.awake = awake;
}
/**
* @return the date
*/
public GregorianCalendar getDate() {
return date;
}
/**
* @param date the date to set
*/
public void setDate(GregorianCalendar date) {
this.date = date;
}
/**
* @return the lengthOfEvent
*/
public String getLengthOfEvent() {
return lengthOfEvent;
}
/**
* @param lengthOfEvent the lengthOfEvent to set
*/
public void setLengthOfEvent(String lengthOfEvent) {
this.lengthOfEvent = lengthOfEvent;
}
/**
* @return the typeOfEvent
*/
public String getTypeOfEvent() {
return typeOfEvent;
}
/**
* @param typeOfEvent the typeOfEvent to set
*/
public void setTypeOfEvent(String typeOfEvent) {
this.typeOfEvent = typeOfEvent;
}
/**
* @return the trigger
*/
public String getTrigger() {
return trigger;
}
/**
* @param trigger the trigger to set
*/
public void setTrigger(String trigger) {
this.trigger = trigger;
}
/**
* @return the notes
*/
public String getNotes() {
return notes;
}
/**
* @param notes the notes to set
*/
public void setNotes(String notes) {
this.notes = notes;
}
}
日志猫
04-24 14:38:45.978: E/AndroidRuntime(6137): FATAL EXCEPTION: main
04-24 14:38:45.978: E/AndroidRuntime(6137): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=0, result=-1, data=Intent { cmp=org.daringer.EpApp/.DiaryEventCreate (has extras) }} to activity {org.daringer.EpApp/org.daringer.EpApp.DiaryMain}: java.lang.NullPointerException
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.app.ActivityThread.deliverResults(ActivityThread.java:3319)
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.app.ActivityThread.handleSendResult(ActivityThread.java:3362)
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.app.ActivityThread.access$1100(ActivityThread.java:141)
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1282)
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.os.Handler.dispatchMessage(Handler.java:99)
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.os.Looper.loop(Looper.java:137)
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.app.ActivityThread.main(ActivityThread.java:5041)
04-24 14:38:45.978: E/AndroidRuntime(6137): at java.lang.reflect.Method.invokeNative(Native Method)
04-24 14:38:45.978: E/AndroidRuntime(6137): at java.lang.reflect.Method.invoke(Method.java:511)
04-24 14:38:45.978: E/AndroidRuntime(6137): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-24 14:38:45.978: E/AndroidRuntime(6137): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-24 14:38:45.978: E/AndroidRuntime(6137): at dalvik.system.NativeStart.main(Native Method)
04-24 14:38:45.978: E/AndroidRuntime(6137): Caused by: java.lang.NullPointerException
04-24 14:38:45.978: E/AndroidRuntime(6137): at org.daringer.EpApp.DiaryMain.onActivityResult(DiaryMain.java:111)
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.app.Activity.dispatchActivityResult(Activity.java:5293)
04-24 14:38:45.978: E/AndroidRuntime(6137): at android.app.ActivityThread.deliverResults(ActivityThread.java:3315)
04-24 14:38:45.978: E/AndroidRuntime(6137): ... 11 more