问题描述
我试图将长时间单击的列表中的一项发送到另一个活动的列表。但是第二个活动，即MySchedule不会更新到一项以上。 这是我的代码
我从哪里发送字符串的活动（没有添加字符串的代码）
public class CloudEvents extends AppCompatActivity {
static int scheduleId = -1;
@Override
protected void onCreate(Bundle savedInstanceState) {
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
new AlertDialog.Builder(CloudEvents.this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Save Event")
.setMessage("Do you want to save this event into your schedule?")
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
scheduleId++;
Toast.makeText(CloudEvents.this,"Saved",Toast.LENGTH_LONG).show();
SharedPreferences sharedPreferences = getApplicationContext().getSharedPreferences("com.yatin.whatshappeningdtu", Context.MODE_PRIVATE);
sharedPreferences.edit().putString("CloudEvent",listView.getItemAtPosition(position).toString()).apply();
Intent i = new Intent(CloudEvents.this,MySchedule.class);
startActivity(i);
//myArrayAdapter.notifyDataSetChanged();
}
})
.setNegativeButton("No",null)
.show();
return true;
}
});
练习接收字符串并列出清单
public class MySchedule extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my_schedule);
final ArrayList<String> schedule = new ArrayList<>();
final ListView scheduleListView = (ListView)findViewById(R.id.scheduleListView);
String key = "CloudEvent";
String myEvent ="";
SharedPreferences sharedPreferences = getApplicationContext().getSharedPreferences("com.yatin.whatshappeningdtu", Context.MODE_PRIVATE);
if(sharedPreferences.contains(key))
{
myEvent = sharedPreferences.getString(key,"");
schedule.add(CloudEvents.scheduleId,myEvent);
}
final ArrayAdapter myArrayAdapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,schedule);
scheduleListView.setAdapter(myArrayAdapter);
scheduleListView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
new AlertDialog.Builder(MySchedule.this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Are you sure ?")
.setMessage("Do you want to delete this note")
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
schedule.remove(position);
myArrayAdapter.notifyDataSetChanged();
CloudEvents.scheduleId--;
}
})
.setNegativeButton("No",null)
.show();
return true;
}
});
}
}
（添加一项后）
Error:Caused by: java.lang.IndexOutOfBoundsException: Index: 1, Size: 0
at java.util.ArrayList.add(ArrayList.java:457)
at com.yatin.whatshappeningdtu.MySchedule.onCreate(MySchedule.java:35)
现在让我的大脑绞尽脑汁数小时。请帮助谢谢！
1楼
只需尝试commit（）而不是apply（）
在2.3中添加了apply（），它提交时没有返回表示成功或失败的布尔值。
如果保存有效，则commit（）返回true，否则返回false。
另外，请确认用于读取数据的共享首选项实例与写入数据的实例相同。
2楼
首次添加项目时，您的CloudEvents.scheduleId从-1设置为0。
假设您的字符串是"FirstEvent" ，您将其保存在CloudEvent项中，然后在MySchedule活动MySchedule其添加到schedule arraylist的0位置，并且可以正常工作。
现在，当您返回CloudEvents活动时，您的CloudEvents.scheduleId为0，因为它是statica变量，然后添加另一个项目，例如"SecondEvent" ，因此CloudEvents.scheduleId将从0更改为1，并保存了"SecondEvent"字符串在CloudEvent再次sharedpreference键，使以前的值"FirstEvent"将覆盖"SecondEvent" ，这意味着在MySchedule活动中，你将只能得到"SecondEvent"从sharedpreference，但你在第一的位置加入此schedule ArrayList和第零位置schedule arraylist将保留为空。
现在，您要在Listview适配器中传递此数组列表，该数组列表的第0位为空值，这就是它IndexOutOfBoundsException异常的方式。
要解决此问题，您可以维护一个ArrayList<String> 。在CloudEvents活动中进行以下更改。
private ArrayList<String> eventList = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState){
SharedPreferences sharedPreferences = getApplicationContext().getSharedPreferences("com.yatin.whatshappeningdtu", Context.MODE_PRIVATE);
Collections.addAll(eventList, prefManager.getString("CloudEvent", "").split(","));
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
new AlertDialog.Builder(CloudEvents.this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Save Event")
.setMessage("Do you want to save this event into your schedule?")
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
scheduleId++;
eventList.add(listView.getItemAtPosition(position).toString());
Toast.makeText(CloudEvents.this, "Saved", Toast.LENGTH_LONG).show();
Intent i = new Intent(CloudEvents.this, MySchedule.class);
i.putStringArrayListExtra("EventList", eventList);
startActivity(i);
//myArrayAdapter.notifyDataSetChanged();
}
})
.setNegativeButton("No", null)
.show();
return true;
}
});
}
现在，在MySchedule活动中进行以下更改。
公共类MySchedule扩展了AppCompatActivity {
ArrayList<String> schedule = new ArrayList<>();
SharedPreferences sharedPreferences;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my_schedule);
sharedPreferences = getApplicationContext().getSharedPreferences("com.yatin.whatshappeningdtu", Context.MODE_PRIVATE);
schedule = getIntent().getStringArrayListExtra("EventList");
ListView scheduleListView = (ListView)findViewById(R.id.scheduleListView);
final ArrayAdapter myArrayAdapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,schedule);
scheduleListView.setAdapter(myArrayAdapter);
scheduleListView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
new AlertDialog.Builder(MySchedule.this)
.setIcon(android.R.drawable.ic_dialog_alert)
.setTitle("Are you sure ?")
.setMessage("Do you want to delete this note")
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
schedule.remove(position);
myArrayAdapter.notifyDataSetChanged();
String events = "";
for(int i=0; i<schedule.size(); i++){
events = events + schedule.get(i);
if(i != (schedule.size() - 1)){
events = events + ",";
}
}
sharedPreferences.edit().putString("CloudEvent", events).apply();
}
})
.setNegativeButton("No",null)
.show();
return true;
}
});
}
}