嘿伙计们我正在为一项任务编写一个简单的待办事项列表应用程序。在我的应用程序中，单击listView项时发生错误。它应该打开一个对话框，我可以在其中编辑项目。但是，应用程序崩溃并显示此错误消息：
10-18 09:01:24.463 12767-12767/com.example.ayush.todolistapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.ayush.todolistapp, PID: 12767
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String[] java.lang.String.split(java.lang.String)' on a null object reference
at com.example.ayush.todolistapp.MainActivity.fillReplaceDialog(MainActivity.java:140)
at com.example.ayush.todolistapp.MainActivity$2.onItemClick(MainActivity.java:56)
at android.widget.AdapterView.performItemClick(AdapterView.java:310)
at android.widget.AbsListView.performItemClick(AbsListView.java:1147)
at android.widget.AbsListView$PerformClick.run(AbsListView.java:3068)
at android.widget.AbsListView$3.run(AbsListView.java:3916)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:152)
at android.app.ActivityThread.main(ActivityThread.java:5497)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
我无法找到问题的根源，所以如果有人可以帮助我，那将会非常有帮助。这是mainActivity文件：
public class MainActivity extends AppCompatActivity {
Dialog dialog;
myDatabase database = new myDatabase(this);
ArrayList<Data> list = new ArrayList<>();
int numberOfItems = 0;
ListView listView;
EditText et1;
EditText et2;
DatePicker dp1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
listView = (ListView) findViewById(R.id.mylist);
list = database.returnProduct();
CustomAdapter adapter = new CustomAdapter(MainActivity.this,list);
listView.setAdapter(adapter);
listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
database.setAsComplete(position);
Toast.makeText(MainActivity.this, "Item saved as completed", Toast.LENGTH_SHORT).show();
return false;
}
});
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
fillReplaceDialog(position);
String title = list.get(position).getTitle();
String desc = list.get(position).getDescription();
String final_date = list.get(position).getDueDate();
String[] date = final_date.split("/");//here is where the error is occurring
int day = Integer.parseInt(date[0]);
int month = Integer.parseInt(date[1]);
int year = Integer.parseInt(date[2]);
et1.setText(title);
et2.setText(desc);
dp1.updateDate(year,month,day);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.completed_tasks){
Intent intent = new Intent(MainActivity.this, Main2Activity.class);
startActivity(intent);
}
else if (id == R.id.add_items){
fillDialog();
}
return super.onOptionsItemSelected(item);
}
public void fillDialog(){
dialog = new Dialog(this);
dialog.setCanceledOnTouchOutside(false);
dialog.setContentView(R.layout.dialog_layout);
dialog.show();
Button bt_save= (Button) dialog.findViewById(R.id.button);
listView = (ListView) findViewById(R.id.mylist);
et1 = (EditText) dialog.findViewById(R.id.et_title);
et2 = (EditText) dialog.findViewById(R.id.et_description);
dp1= (DatePicker) dialog.findViewById(R.id.datePicker);
bt_save.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String title = et1.getText().toString();
String description = et2.getText().toString();
int day = dp1.getDayOfMonth();
int month = dp1.getMonth();
int year = dp1.getYear();
String final_date = day+"/"+month+"/"+year;
database.insert_Data(title,description,final_date);
numberOfItems+=1;
dialog.dismiss();
list = database.returnProduct();
CustomAdapter adapter = new CustomAdapter(MainActivity.this,list);
listView.setAdapter(adapter);
}
});
Button bt_cancel = (Button) dialog.findViewById(R.id.button2);
bt_cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//automatically dismisses the dialog on pressing the cancel button
dialog.dismiss();
}
});
}
public void fillReplaceDialog(final int position){
dialog = new Dialog(this);
dialog.setCanceledOnTouchOutside(false);
dialog.setContentView(R.layout.dialog_layout);
dialog.show();
Button bt_save= (Button) dialog.findViewById(R.id.button);
listView = (ListView) findViewById(R.id.mylist);
et1 = (EditText) dialog.findViewById(R.id.et_title);
et2 = (EditText) dialog.findViewById(R.id.et_description);
dp1= (DatePicker) dialog.findViewById(R.id.datePicker);
bt_save.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String title = et1.getText().toString();
String description = et2.getText().toString();
int day = dp1.getDayOfMonth();
int month = dp1.getMonth();
int year = dp1.getYear();
String final_date = day+"/"+month+"/"+year;
database.replaceObject(title,description,final_date, position);
dialog.dismiss();
list = database.returnProduct();
CustomAdapter adapter = new CustomAdapter(MainActivity.this,list);
listView.setAdapter(adapter);
}
});
Button bt_cancel = (Button) dialog.findViewById(R.id.button2);
bt_cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//automatically dismisses the dialog on pressing the cancel button
dialog.dismiss();
}
});
}
}
数据类：
public class Data {
String title;
String description;
String dueDate;
int status;
public String getTitle() {
return title;
}
public String getDescription() {
return description;
}
public String getDueDate() {
return dueDate;
}
public int getStatus() {
return status;
}
public void setTitle(String title) {
this.title = title;
}
public void setDescription(String description) {
this.description = description;
}
public void setDueDate(String dueDate) {
this.dueDate = dueDate;
}
public void setStatus(int status) {
this.status = status;
}
}
CustomAdapter类：
public class CustomAdapter extends BaseAdapter {
private Context mContext;
private ArrayList<Data> mData;
LayoutInflater mInflator;
public CustomAdapter(Context context, ArrayList<Data> list){
mContext = context;
mData = list;
mInflator = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
return mData.size();
}
@Override
public Object getItem(int position) {
return mData.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
convertView = mInflator.inflate(R.layout.row_layout, parent, false);
//inflates the layout
TextView tv1 = (TextView) convertView.findViewById(R.id.textView);
TextView tv2 = (TextView) convertView.findViewById(R.id.textView2);
TextView tv3 = (TextView) convertView.findViewById(R.id.textView3);
TextView header = (TextView) convertView.findViewById(R.id.header_title);
ImageView iv1 = (ImageView) convertView.findViewById(R.id.imageView);
tv1.setText(mData.get(position).getTitle());
tv2.setText(mData.get(position).getDescription());
tv3.setText(mData.get(position).getDueDate());
iv1.setImageResource(R.drawable.incomplete);
header.setText(mData.get(position).getDueDate());
return convertView;
//returns the view
}
}
我只是一个初学者，并且最近才开始学习android编程，所以请原谅任何愚蠢的错误。提前致谢
答案 0 :(得分：1)
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String[] java.lang.String.split(java.lang.String)' on a null object reference
当应用程序尝试使用时抛出NullPointerException 具有空值的对象引用。
问题来自
String final_date = list.get(position).getDueDate(); // At first value getting null
String[] date = final_date.split("/"); // Didn't find "/" in STRING that's why CRASHING .
FYI ，以 DEBUG 模式运行您的APP。你可以找到答案。
final_date 是null。您应该检查 STRING null 是否支持。
if (final_date != null && !final_date.isEmpty())
{
String[] date = final_date.split("/");
........// Your code //............
}
else
{
// Your String null ;
}
答案 1 :(得分：0)
尝试在控制台中打印值 final_date 。我认为getDueDate（）返回null，即Item可能没有截止日期。
答案 2 :(得分：-2)
检查DateFormat是否为（＆＃34; dd / mm / yyyy＆＃34;）正确与否。 如果/在DateFormat中找不到，则final_date.split（＆＃34; /＆＃34;）不起作用。
你也可以得到这样的日，月，年。
DateFormat formatter = new SimpleDateFormat("MM/dd/yyyy");
Date date = formatter.parse("10/18/2017");
int month = date.getMonth();
int day= date.getDay();
int year = date.getYear();