问题：
当我试图更新/编辑Sqlite数据库java.lang.IndexOutOfBoundsException时出现了这个错误：索引：0,大小：0可以帮助我吗
安泰平
Process: com.example.attendance, PID: 20112
java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.get(ArrayList.java:437)
at com.example.attendance.MainActivity.updateClass(MainActivity.java:135)
at com.example.attendance.MainActivity.lambda$showUpdateDialog$4$MainActivity(MainActivity.java:131)
at com.example.attendance.-$$Lambda$MainActivity$m9twlugKZZaVnr6kCG8LrRCoXMM.onClick(Unknown Source:4)
at com.example.attendance.MyDialog.lambda$getUpdateClassDialog$1$MyDialog(MyDialog.java:94)
at com.example.attendance.-$$Lambda$MyDialog$5v1iqgaO8riJO2phwUfadWXdoyM.onClick(Unknown Source:6)
at android.view.View.performClick(View.java:8160)
at android.widget.TextView.performClick(TextView.java:16222)
at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1119)
at android.view.View.performClickInternal(View.java:8137)
at android.view.View.access$3700(View.java:888)
at android.view.View$PerformClick.run(View.java:30236)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:246)
at android.app.ActivityThread.main(ActivityThread.java:8512)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
I/Process: Sending signal. PID: 20112 SIG: 9
package com.example.attendance;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.TextView;
import android.widget.Toolbar;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
FloatingActionButton floatingActionButton;
RecyclerView recyclerView;
ClassAdapter classAdapter;
RecyclerView.LayoutManager layoutManager;
ArrayList<ClassItem> classItems = new ArrayList<>();
Toolbar toolbar;
DbHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new DbHelper(this);
floatingActionButton = findViewById(R.id.fab_main);
floatingActionButton.setOnClickListener(V -> showDialog());
loadData();
recyclerView = findViewById(R.id.att_list);
recyclerView.setHasFixedSize(true);
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
classAdapter = new ClassAdapter(this, classItems);
recyclerView.setAdapter(classAdapter);
classAdapter.setOnItemClickListener(position -> gotoItemActivity(position));
setToolbar();
}
private void loadData() {
Cursor cursor = dbHelper.getClassTable();
classItems.clear();
while (cursor.moveToNext()){
int id = cursor.getInt(cursor.getColumnIndex(DbHelper.C_ID));
String department = cursor.getString(cursor.getColumnIndex(DbHelper.CLASS_NAME_KEY));
String subject = cursor.getString(cursor.getColumnIndex(DbHelper.SUBJECT_NAME_KEY));
classItems.add(new ClassItem(id,department,subject));
}
}
private void setToolbar() {
toolbar = findViewById(R.id.toolbar);
TextView title = toolbar.findViewById(R.id.tool_title);
TextView subTitle = toolbar.findViewById(R.id.tool_sub_title);
TextView samiTitle = toolbar.findViewById(R.id.tool_sami_title);
ImageButton back = toolbar.findViewById(R.id.tool_back);
ImageButton save = toolbar.findViewById(R.id.tool_save);
title.setText("Attendance");
subTitle.setVisibility(View.GONE);
samiTitle.setVisibility(View.GONE);
save.setVisibility(View.GONE);
back.setOnClickListener(v -> onBackPressed());
}
private void gotoItemActivity(int position) {
Intent intent = new Intent(this,StudentActivity.class);
intent.putExtra("departmentName",classItems.get(position).getDepartment());
intent.putExtra("subjectName",classItems.get(position).getSubject());
intent.putExtra("position",position);
startActivity(intent);
}
private void showDialog() {
MyDialog dialog = new MyDialog();
dialog.show(getSupportFragmentManager(),MyDialog.CLASS_ADD_DIALOG);
dialog.setListener((department,subject)->addClass(department,subject));
}
private void addClass(String department, String subject) {
long cid = dbHelper.addClass(department,subject);
ClassItem classItem = new ClassItem(cid,department,subject);
classItems.add(classItem);
classAdapter.notifyDataSetChanged();
}
@Override
public boolean onContextItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()){
case 0:
showUpdateDialog(item.getGroupId());
case 1:
deleteClass(item.getGroupId());
}
return super.onContextItemSelected(item);
}
private void showUpdateDialog(int position) {
MyDialog updateDialog = new MyDialog();
updateDialog.show(getSupportFragmentManager(),MyDialog.CLASS_UPDATE_DIALOG);
updateDialog.setListener((department,subject)->updateClass(position,department,subject));
}
// when I try to Update the Data its don't work and the app will crash
private void updateClass(int position, String department, String subject) {
dbHelper.updateClass(classItems.get(position).getCid(),department,subject);
classItems.get(position).setDepartment(department);
classItems.get(position).setSubject(subject);
classAdapter.notifyItemChanged(position);
}
private void deleteClass(int position) {
dbHelper.deleteClass(classItems.get(position).getCid());
classItems.remove(position);
classAdapter.notifyItemRemoved(position);
}
}
package com.example.attendance;
import android.content.Context;
import android.view.ContextMenu;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
public class ClassAdapter extends RecyclerView.Adapter<ClassAdapter.ClassViewHolder> {
private OnItemClickListener onItemClickListener;
public interface OnItemClickListener {
void onClick(int position);
}
public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
this.onItemClickListener = onItemClickListener;
}
public ClassAdapter(Context context, ArrayList<ClassItem> classItems) {
this.classItems = classItems;
this.context = context;
}
ArrayList<ClassItem> classItems;
Context context;
public static class ClassViewHolder extends RecyclerView.ViewHolder implements View.OnCreateContextMenuListener {
TextView department, subject;
public ClassViewHolder(@NonNull View itemView,OnItemClickListener onItemClickListener) {
super(itemView);
department = itemView.findViewById(R.id.dep_tv);
subject = itemView.findViewById(R.id.sub_tv);
itemView.setOnClickListener(v -> onItemClickListener.onClick(getAdapterPosition()));
itemView.setOnCreateContextMenuListener(this);
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
menu.add(getAdapterPosition(),0,0,"EDIT");
menu.add(getAdapterPosition(),1,0,"DELETE");
}
}
@NonNull
@Override
public ClassViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.class_item, parent, false);
return new ClassViewHolder(itemView, onItemClickListener);
}
@Override
public void onBindViewHolder(@NonNull ClassViewHolder holder, int position) {
holder.department.setText(classItems.get(position).getDepartment());
holder.subject.setText(classItems.get(position).getSubject());
}
@Override
public int getItemCount() {
return classItems.size();
}
}
这里是数据库
package com.example.attendance;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import androidx.annotation.Nullable;
public class DbHelper extends SQLiteOpenHelper {
private static final int VERSION = 1;
//Class table
private static final String CLASS_TABLE_NAME= "CLASS_TABLE";
public static final String C_ID= "_CID";
public static final String CLASS_NAME_KEY= "CLASS_NAME";
public static final String SUBJECT_NAME_KEY= "SUBJECT_NAME";
private static final String CREATE_CLASS_TABLE=
"CREATE TABLE " + CLASS_TABLE_NAME + "(" +
C_ID + " INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, " +
CLASS_NAME_KEY + " TEXT NOT NULL, " +
SUBJECT_NAME_KEY + " TEXT NOT NULL, " +
" UNIQUE ( " + CLASS_NAME_KEY + "," + SUBJECT_NAME_KEY + ")" +
");";
private static final String DROP_CLASS_TABLE = "DROP TABLE IF EXISTS "+CLASS_TABLE_NAME;
private static final String SELECT_CLASS_TABLE = "SELECT * FROM "+CLASS_TABLE_NAME;
//Student table
private static final String STUDENT_TABLE_NAME= "STUDENT_TABLE";
private static final String S_ID= "_SID";
private static final String STUDENT_NAME_KEY= "STUDENT_NAME";
private static final String STUDENT_ROLL_KEY= "ROLL";
private static final String CREATE_STUDENT_TABLE=
"CREATE TABLE "+ STUDENT_TABLE_NAME +
"( "+
S_ID+ " INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "+
C_ID + " TEXT NOT NULL, "+
STUDENT_NAME_KEY + " TEXT NOT NULL, "+
STUDENT_ROLL_KEY + " INTEGER, "+
" FOREIGN KEY ( "+C_ID+ " ) REFERENCES "+ CLASS_TABLE_NAME + "("+C_ID+")"+
");";
private static final String DROP_STUDENT_TABLE = "DROP TABLE IF EXISTS "+STUDENT_TABLE_NAME;
private static final String SELECT_STUDENT_TABLE = "SELECT * FROM "+STUDENT_TABLE_NAME;
//Status table
private static final String STATUS_TABLE_NAME= "STATUS_TABLE";
private static final String STATUS_ID= "_STATUS_ID";
private static final String DATE_KEY= "STATUS_NAME";
private static final String STATUS_KEY= "STATUS";
private static final String CREATE_STATUS_TABLE=
"CREATE TABLE "+STATUS_TABLE_NAME+
"("+
STATUS_ID + " INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "+
S_ID + " INTEGER NOT NULL, "+
DATE_KEY + " DATE NOT NULL, "+
STATUS_KEY + " TEXT NOT NULL, "+
" UNIQUE ( " + S_ID + "," + DATE_KEY + ")," +
" FOREIGN KEY ( "+ S_ID+ " ) REFERENCES "+ STUDENT_TABLE_NAME + "( "+S_ID+")"+
");";
private static final String DROP_STATUS_TABLE = "DROP TABLE IF EXISTS "+ STATUS_TABLE_NAME;
private static final String SELECT_STATUS_TABLE = "SELECT * FROM "+ STATUS_TABLE_NAME;
public DbHelper(@Nullable Context context) {
super(context, "Attendance.db", null, VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_CLASS_TABLE);
db.execSQL(CREATE_STUDENT_TABLE);
db.execSQL(CREATE_STATUS_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
try {
db.execSQL(DROP_CLASS_TABLE);
db.execSQL(DROP_STUDENT_TABLE);
db.execSQL(DROP_STATUS_TABLE);
} catch (SQLException e) {
e.printStackTrace();
}
}
long addClass(String className,String subjectName){
SQLiteDatabase database = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(CLASS_NAME_KEY,className);
values.put(SUBJECT_NAME_KEY,subjectName);
return database.insert(CLASS_TABLE_NAME,null,values);
}
Cursor getClassTable(){
SQLiteDatabase database = this.getReadableDatabase();
return database.rawQuery(SELECT_CLASS_TABLE,null);
}
int deleteClass(long cid){
SQLiteDatabase database = this.getReadableDatabase();
return database.delete(CLASS_TABLE_NAME,C_ID+"=?",new String[]{String.valueOf(cid)});
}
long updateClass(long cid,String className,String subjectName){
SQLiteDatabase database = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(CLASS_NAME_KEY,className);
values.put(SUBJECT_NAME_KEY,subjectName);
return database.update(CLASS_TABLE_NAME,values,C_ID+"=?",new String[]{String.valueOf(cid)});
}
}
共有1个答案
赵雪峰
删除表后，忘记在onupgrade方法中再次创建它们。
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
try {
db.execSQL(DROP_CLASS_TABLE);
db.execSQL(DROP_STUDENT_TABLE);
db.execSQL(DROP_STATUS_TABLE);
onCreate(db);
} catch (SQLException e) {
e.printStackTrace();
}
}
另外，在每次调用.getwritabledatabase()或.getreadabledatabase()时调用.close()方法也是一个好主意。这里有一个例子...
long addClass(String className, String subjectName){
SQLiteDatabase database = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(CLASS_NAME_KEY,className);
values.put(SUBJECT_NAME_KEY,subjectName);
database.close();
long id = database.insert(CLASS_TABLE_NAME,null,values);
return id;
}
希望能有所帮助，快乐的编码！
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