java - 尝试使用数据库中的数据填充自定义 ListView 时出现 IndexOutofBoundsException 错误

Question

这个问题已经有答案了:

What is a StringIndexOutOfBoundsException? How can I fix it? (1 个回答)

已关闭 5 年前。

我正在尝试从数据库检索数据并填充自定义 ListView 。但是，我收到错误

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

并且应用程序崩溃并停止。你能告诉我如何解决这个问题吗？

我希望 ListView 像 this .

日志猫:

FATAL EXCEPTION: main Process: com.example.dell.remindme, PID: 28020 java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 at java.util.ArrayList.get(ArrayList.java:411) at com.example.dell.remindme.CustomAdapter.getView(CustomAdapter.java:68) at android.widget.AbsListView.obtainView(AbsListView.java:3170) at android.widget.ListView.measureHeightOfChildren(ListView.java:1389) at android.widget.ListView.onMeasure(ListView.java:1296) at android.view.View.measure(View.java:21126) at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715) at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461) at android.view.View.measure(View.java:21126) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6461) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139) at android.view.View.measure(View.java:21126) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6461) at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:400) at android.view.View.measure(View.java:21126) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6461) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at android.view.View.measure(View.java:21126) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6461) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1464) at android.widget.LinearLayout.measureVertical(LinearLayout.java:758) at android.widget.LinearLayout.onMeasure(LinearLayout.java:640) at android.view.View.measure(View.java:21126) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6461) at android.widget.FrameLayout.onMeasure(FrameLayout.java:185) at com.android.internal.policy.DecorView.onMeasure(DecorView.java:899) at android.view.View.measure(View.java:21126) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2612) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1664) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1915) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1537) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7183) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:959) at android.view.Choreographer.doCallbacks(Choreographer.java:734) at android.view.Choreographer.doFrame(Choreographer.java:670) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:945) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6776) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)

Dbhelper.java

public class DbHelper extends SQLiteOpenHelper {
    public static final String TAG = DbHelper.class.getSimpleName();

    // Database Version
    private static final int DATABASE_VERSION = 5;

    // Database Name
    private static final String DATABASE_NAME = "RemindMe";

    // Table Names
    private static final String TABLE_TODO = "Todo";
    private static final String TABLE_LOGIN = "Login";

    // TODO Table - column names
    private static final String TASK_ID = "task_id";
    private static final String TASK_TITLE = "task_title";
    private static final String TASK_DESCRIP = "task_descrip";
    private static final String TASK_DATE = "task_date";
    private static final String TASK_TIME = "task_time";

    // LOGIN Table - column names
    private static final String LOGIN_ID = "login_id";
    private static final String EMAIL = "email";
    private static final String PASSWORD = "password";

    // Table Create Statements
    // Todo table create statement
    private static final String CREATE_TABLE_TODO = "CREATE TABLE " + TABLE_TODO + "(" + TASK_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + TASK_TITLE + " TEXT," + TASK_DESCRIP + " TEXT," + TASK_DATE + " TEXT," + TASK_TIME + " TEXT" + ")";

    // Login table create statement
    private static final String CREATE_TABLE_LOGIN = "CREATE TABLE " + TABLE_LOGIN + "(" + LOGIN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + EMAIL + " EMAIL," + PASSWORD + " TEXT" + ")";

    public DbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        // creating required tables
        db.execSQL(CREATE_TABLE_TODO);
        db.execSQL(CREATE_TABLE_LOGIN);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // on upgrade drop older tables
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_TODO);
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_LOGIN);

        // create new tables
        onCreate(db);
    }
    //Todo table
    //add new task
    public void Add_New_Task(String task_title, String task_descrip, String task_date, String task_time){
        SQLiteDatabase db= this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(TASK_TITLE, task_title);
        values.put(TASK_DESCRIP, task_descrip);
        values.put(TASK_DATE, task_date);
        values.put(TASK_TIME, task_time);
        // insert row
        long id = db.insert(TABLE_TODO, null, values);
        db.close();
        Log.d(TAG, "New task added" + id);

    }
    //delete task
    public void Delete_Task(String title){
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_TODO,TASK_TITLE + " = ? ",new String[] {title});
        db.close();
    }
}

自定义适配器

public class CustomAdapter extends BaseAdapter {
    private Context mContext;
    DbHelper dbHelper;
    private ArrayList<String> title = new ArrayList<String>();
    private ArrayList<String> date = new ArrayList<String>();
    private ArrayList<String> time = new ArrayList<String>();
    public CustomAdapter(Context  context,ArrayList<String> title,ArrayList<String> date, ArrayList<String> time)
    {
        this.mContext = context;
        this.title = title;
        this.date = date;
        this.title = time;
    }
    @Override
    public int getCount() {

        return title.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }
    public class viewHolder {
        TextView Title;
        TextView Date;
        TextView Time;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final viewHolder holder;
        dbHelper = new DbHelper(mContext);
        LayoutInflater layoutInflater;
        if (convertView == null) {
            layoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = layoutInflater.inflate(R.layout.activity_list, null);
            holder = new viewHolder();
            holder.Title = (TextView) convertView.findViewById(R.id.task_title);
            holder.Date = (TextView) convertView.findViewById(R.id.task_date);
            holder.Time = (TextView) convertView.findViewById(R.id.task_time);
            convertView.setTag(holder);
        } else {
            holder = (viewHolder) convertView.getTag();
        }
        holder.Title.setText(title.get(position));
        holder.Date.setText(date.get(position));
        holder.Time.setText(time.get(position));
        return convertView;
    }
}

Todolist.java

public class To_Do_List extends AppCompatActivity{
    private DbHelper dbHelper;
    private SQLiteDatabase db;
    private ListView lstTask;
    //ArrayAdapter<String> myAdapter;
    private ArrayList<String> Title = new ArrayList<String>();
    private ArrayList<String> Date = new ArrayList<String>();
    private ArrayList<String> Time = new ArrayList<String>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_to__do__list);
        overridePendingTransition(R.anim.fadein, R.anim.fadeout);

        lstTask = (ListView)findViewById(R.id.List);
        dbHelper = new DbHelper(this);
        Load_List();
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        }

    //back button on actionbar
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                Intent main_activity = new Intent(To_Do_List.this, MainActivity.class);
                startActivity(main_activity);
                finish();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    //load activity_list of tasks
    private void Load_List() {
        /*ArrayList<String> taskList = dbHelper.getTaskList();
        if (myAdapter == null) {
            myAdapter = new ArrayAdapter<String>(this, R.layout.activity_list, R.id.task_title, taskList);
            lstTask.setAdapter(myAdapter);
        } else {
            myAdapter.clear();
            myAdapter.addAll(taskList);
            myAdapter.notifyDataSetChanged();
        }*/

        db = dbHelper.getReadableDatabase();
        Cursor cursor = db.rawQuery("SELECT task_title, task_date, task_time FROM  todo",null);
        Title.clear();
        Date.clear();
        Time.clear();
        if (cursor.moveToFirst()) {
            do {
                Title.add(cursor.getString(cursor.getColumnIndex("task_title")));
                Date.add(cursor.getString(cursor.getColumnIndex("task_date")));
                Time.add(cursor.getString(cursor.getColumnIndex("task_time")));
            } while (cursor.moveToNext());
        }
        CustomAdapter myadapter = new CustomAdapter(To_Do_List.this,Title,Date,Time);
        lstTask.setAdapter(myadapter);
        //code to set adapter to populate list
        cursor.close();
    }
    //add new task
    public void Add_New_Task(View view) {
        Intent intent = new Intent(To_Do_List.this, Reminder.class);
        startActivity(intent);
        finish();
    }
    //delete existing task
    public void Delete_Task(View view){
        View parent = (View)view.getParent();
        TextView taskTextView = (TextView)parent.findViewById(R.id.task_title);
        Log.e("String", (String) taskTextView.getText());
        String task = String.valueOf(taskTextView.getText());
        dbHelper.Delete_Task(task);
        Load_List();
    }
}

Answer 1

您的问题在这一行中得到了解释:

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0 at java.util.ArrayList.get(ArrayList.java:411) 

您正在尝试读取空List的第一个元素。

在尝试读取元素之前检查是否存在元素。