Android Java IllegalStateException：無法執行活動的方法

Question

我正在嘗試編寫一個簡單的隨機應用程序。 我有隨機發生器按鈕工作，但后來我改變了一些代碼（我認為這與隨機化程序按鈕無關），它開始崩潰並獲得“IllegalStateException：無法執行活動的方法”錯誤。 據我所知，這個錯誤非常特定於代碼是什么，因為我找不到適合我代碼的任何答案。

package com.example.randomgamechooser;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.TextView;

public class MainScreen extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main_screen);


}

public void chooseGame (View view) {
    GameList dbUtil = new GameList(this);
    dbUtil.open();
    String string = dbUtil.getRandomEntry();
    //TextView textView = new TextView(this);
    TextView textView = (TextView) findViewById(R.id.chosenbox);
    textView.setTextSize(40);
    textView.setText(string);
    //setContentView (textView);
    dbUtil.close();
}



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main_screen, menu);
    return true;
}
//starts the Game Selection activity
public void openGames (View view) {
    Intent intent = new Intent(this, GameSelction.class);
    startActivity(intent);
}

}

這是引用的GameList類

package com.example.randomgamechooser;

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 android.util.Log;

import java.util.Random;

public class GameList {

private static final String TAG = "GameList";

//database name
private static final String DATABASE_NAME = "game_list";

//database version
private static final int DATABASE_VERSION = 1;

//table name
private static final String DATABASE_TABLE = "game_list";

//table columns
public static final String KEY_NAME = "name";
public static final String KEY_GENRE = "genre";
public static final String KEY_ROWID = "_id";

//database creation sql statement
private static final String CREATE_GAME_TABLE =
    "create table " + DATABASE_TABLE + " (" + KEY_ROWID + " integer primary key autoincrement, "
    + KEY_NAME +" text not null, " + KEY_GENRE + " text not null);";

//Context
private final Context mCtx;
private DatabaseHelper mDbHelper;
private static SQLiteDatabase mDb;


 //Inner private class. Database Helper class for creating and updating database.

private static class DatabaseHelper extends SQLiteOpenHelper {
    DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

     // onCreate method is called for the 1st time when database doesn't exists.
    @Override
    public void onCreate(SQLiteDatabase db) {
        Log.i(TAG, "Creating DataBase: " + CREATE_GAME_TABLE);
        db.execSQL(CREATE_GAME_TABLE);
    }

     //onUpgrade method is called when database version changes.
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
                + newVersion);
    }
}

 //Constructor - takes the context to allow the database to be opened/created
 //@param ctx the Context within which to work
public GameList(Context ctx) {
    this.mCtx = ctx;
}

 //This method is used for creating/opening connection
 //@return instance of GameList
 //@throws SQLException
public GameList open() throws SQLException {
    mDbHelper = new DatabaseHelper(mCtx);
    mDb = mDbHelper.getWritableDatabase();
    return this;
}

 //This method is used for closing the connection.
public void close() {
    mDbHelper.close();
}


 //This method is used to create/insert new game.
 //@param name
 // @param genre
 // @return long
public long createGame(String name, String genre) {
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_NAME, name);
    initialValues.put(KEY_GENRE, genre);
    return mDb.insert(DATABASE_TABLE, null, initialValues);
}

 // This method will delete game.
 // @param rowId
 // @return boolean
public static boolean deleteGame(long rowId) {
    return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}


 // This method will return Cursor holding all the games.
 // @return Cursor
public Cursor fetchAllGames() {
    return mDb.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NAME,
            KEY_GENRE}, null, null, null, null, null);

}


 // This method will return Cursor holding the specific game.
 // @param id
 // @return Cursor
 // @throws SQLException
public Cursor fetchGame(long id) throws SQLException {
    Cursor mCursor =
        mDb.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
                KEY_NAME, KEY_GENRE}, KEY_ROWID + "=" + id, null,
                null, null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }

    return mCursor;
}

public int getAllEntries()
{
    Cursor cursor = mDb.rawQuery(
                "SELECT COUNT(name) FROM game_list", null);
            if(cursor.moveToFirst()) {
                return cursor.getInt(0);
            }
            return cursor.getInt(0);

}  

public String getRandomEntry()
{

    //id = getAllEntries();
    Random random = new Random();
    int rand = random.nextInt(getAllEntries());
    if(rand == 0)
        ++rand;
    Cursor cursor = mDb.rawQuery(
                "SELECT name FROM game_list WHERE _id = " + rand, null);
            if(cursor.moveToFirst()) {
                return cursor.getString(0);
            }
            return cursor.getString(0);

}


 // This method will update game.
 // @param id
 // @param name
 // @param standard
 // @return boolean
public boolean updateGame(int id, String name, String standard) {
    ContentValues args = new ContentValues();
    args.put(KEY_NAME, name);
    args.put(KEY_GENRE, standard);
    return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + id, null) > 0;
}
}

這是錯誤日志

07-31 14:50:45.215: D/AndroidRuntime(280): Shutting down VM
07-31 14:50:45.215: W/dalvikvm(280): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
07-31 14:50:45.236: E/AndroidRuntime(280): FATAL EXCEPTION: main
07-31 14:50:45.236: E/AndroidRuntime(280): java.lang.IllegalStateException: Could not execute method of the activity
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.view.View$1.onClick(View.java:2072)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.view.View.performClick(View.java:2408)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.view.View$PerformClick.run(View.java:8816)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.os.Handler.handleCallback(Handler.java:587)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.os.Handler.dispatchMessage(Handler.java:92)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.os.Looper.loop(Looper.java:123)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.app.ActivityThread.main(ActivityThread.java:4627)
07-31 14:50:45.236: E/AndroidRuntime(280):  at java.lang.reflect.Method.invokeNative(Native Method)
07-31 14:50:45.236: E/AndroidRuntime(280):  at java.lang.reflect.Method.invoke(Method.java:521)
07-31 14:50:45.236: E/AndroidRuntime(280):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-31 14:50:45.236: E/AndroidRuntime(280):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-31 14:50:45.236: E/AndroidRuntime(280):  at dalvik.system.NativeStart.main(Native Method)
07-31 14:50:45.236: E/AndroidRuntime(280): Caused by: java.lang.reflect.InvocationTargetException
07-31 14:50:45.236: E/AndroidRuntime(280):  at com.example.randomgamechooser.MainScreen.chooseGame(MainScreen.java:23)
07-31 14:50:45.236: E/AndroidRuntime(280):  at java.lang.reflect.Method.invokeNative(Native Method)
07-31 14:50:45.236: E/AndroidRuntime(280):  at java.lang.reflect.Method.invoke(Method.java:521)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.view.View$1.onClick(View.java:2067)
07-31 14:50:45.236: E/AndroidRuntime(280):  ... 11 more
07-31 14:50:45.236: E/AndroidRuntime(280): Caused by: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.database.AbstractCursor.checkPosition(AbstractCursor.java:580)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:214)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:41)
07-31 14:50:45.236: E/AndroidRuntime(280):  at com.example.randomgamechooser.GameList.getRandomEntry(GameList.java:153)
07-31 14:50:45.236: E/AndroidRuntime(280):  ... 15 more

Answer 1

仔細閱讀stacktrace。 答案是最后一次“引起”例外;

07-31 14:50:45.236: E/AndroidRuntime(280): Caused by: android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.database.AbstractCursor.checkPosition(AbstractCursor.java:580)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCursor.java:214)
07-31 14:50:45.236: E/AndroidRuntime(280):  at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:41)
07-31 14:50:45.236: E/AndroidRuntime(280):  at com.example.randomgamechooser.GameList.getRandomEntry(GameList.java:153)
07-31 14:50:45.236: E/AndroidRuntime(280):  ... 15 more

查詢方法getRandomEntry（）返回空結果，同時從第一個位置讀取。