Question

我有以下 DatabaseHander 类，它可以存储用户从Android手机输入的一些数据。即球员的名字和球员的评分：

public class DatabaseHandler extends SQLiteOpenHelper {
private final ArrayList<LastGameModel> lastGameModelsList = new ArrayList<>();
public DatabaseHandler(Context context) {
    super(context, Constants.DATABASE_NAME, null, Constants.DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    String CREATE_MOVIES_TABLE = "CREATE TABLE " + Constants.TABLE_NAME +
            "(" + Constants.KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT  , " + Constants.PLAYER_NAME +
            " TEXT, "  +  Constants.PLAYER_RATE + " INTEGER);";
    db.execSQL(CREATE_MOVIES_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + Constants.TABLE_NAME);

    onCreate(db);
}

//add content to table
public void addMovies(LastGameModel lastGameModel) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    //values.put(Constants.KEY_ID,lastGameModel.getId());
    values.put(Constants.PLAYER_NAME, lastGameModel.getPlayerName());
    values.put(Constants.PLAYER_RATE, lastGameModel.getPlayerRate());

    db.insert(Constants.TABLE_NAME, null, values);

    db.close();

    Log.d("Theo","heeeey!data saved");
}

//get all folders
public ArrayList<LastGameModel> getBestPlayersDetails() {

    SQLiteDatabase db = this.getReadableDatabase();

    Cursor cursor = db.query(Constants.TABLE_NAME, new String[]{
            Constants.KEY_ID, Constants.PLAYER_NAME,Constants.PLAYER_RATE}, null, null, null, null, Constants.KEY_ID + " DESC");


    if (cursor.moveToFirst()) {
        do {

            LastGameModel lgm = new LastGameModel();
            lgm.setPlayerName(cursor.getString(cursor.getColumnIndex(Constants.PLAYER_NAME)));

            lgm.setPlayerRate(cursor.getInt(cursor.getColumnIndex(Constants.PLAYER_RATE)));
            lgm.setId(Integer.parseInt(cursor.getString(cursor.getColumnIndex(Constants.KEY_ID))));



            lastGameModelsList.add(lgm);
        }while(cursor.moveToNext());


    }
    return lastGameModelsList;
}

public void deletePlayer(int id){
    SQLiteDatabase db = this.getWritableDatabase();
    db.delete(Constants.TABLE_NAME,Constants.KEY_ID + " = ? ",new String[]   
 {String.valueOf(id)});
    lastGameModelsList.clear();
    db.close();
   }
 }

现在我想用JUNIT 4测试上面的类。

所以：

@RunWith(JUnit4.class)
public class DBTesting {

public static String playerName;
public static String playerRate;
public static long playerId;


Context mMockContext;
@Test
public void testDropDB() {
    assertTrue(mMockContext.deleteDatabase(Constants.DATABASE_NAME));
 }
}

但是所有测试都失败了

testDropDB（）正在给我

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean 
android.content.Context.deleteDatabase(java.lang.String)' on a null object 
 reference

at team.football.ael.DBTesting.deleteTheDatabase(DBTesting.java:33)
at team.football.ael.DBTesting.testDropDB(DBTesting.java:30)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)

为什么会这样？ Constants.DATABASE_NAME不是空字符串。

public class Constants implements BaseColumns{
public static final String DATABASE_NAME="ratedplayersdb";
public static final int DATABASE_VERSION=2;
public static final String TABLE_NAME="ratedplayers";

public static final String PLAYER_NAME="playername";



public static final String PLAYER_RATE="player_rate";

public static final String KEY_ID="_id";



}

Answer 1

mMockContext为null，如错误消息中所述

Junit测试Sqlite给出空指针异常

1 个答案: