java - 如何从非 Activity 类获取上下文

Question

这个问题已经有答案了:

get Context in non-Activity class [duplicate] (1 个回答)

已关闭 6 年前。

我在 Android Studio 中创建了一个游戏，现在我尝试将分数插入数据库。我在 SQL 中创建了一个脚本，可以很好地创建数据库，但现在我尝试插入信息，但没有上下文。

这是我的DBAdapter:

public class DBAdapter {

private SQLiteDatabase database;
private ScriptSQL dbHelper;
private String[] allColumns = {ScriptSQL.ID, ScriptSQL.PONTUACAO};

public DBAdapter(Context ctx) {
    dbHelper = new ScriptSQL(ctx);
}

public void open() throws SQLException {
    database = dbHelper.getWritableDatabase();
}

public void openRead() throws SQLException {
    database = dbHelper.getReadableDatabase();
}

public void close() {
    dbHelper.close();
}

public Score createScore(String pontuacao) {
    ContentValues values = new ContentValues();
    values.put(dbHelper.PONTUACAO, pontuacao);
    long insertId = database.insert(dbHelper.TABLE_NAME, null, values);
    // To show how to query
    Cursor cursor = database.query(dbHelper.TABLE_NAME, allColumns, dbHelper.ID + " = " + insertId, null, null, null, null);
    cursor.moveToFirst();
    return cursorToScore(cursor);
}

这是我试图获取上下文的非 Activity 类。

World.java

public class World {

static final int WORLD_WIDTH = 10; //largura
static final int WORLD_HEIGHT = 13; //altura
static final int SCORE_INCREMENT = 10; //incremento do score
static final float TICK_INITIAL = 0.8f; //velocidade inicial do jogo
static final float TICK_DECREMENT = 0.2f; //velocidade de decremento

public Dog dog;
public Elements element;
public boolean EndGame = false;
public int score = 0;

static int put_element = 0;
public List<Elements> elements = new ArrayList<Elements>();
Random random = new Random();
float timeTick = 0;
static float tick = TICK_INITIAL;

public World(){
    dog = new Dog();
}

/*...*/

DBAdapter datasource;
private Context context;

public void update_database(){

    datasource = new DBAdapter(context.getApplicationContext());

    try {
        datasource.open();
        String point = Integer.toString(score);
        Score c = datasource.createScore(point);
        datasource.close();

    }
    catch (SQLException ex) { }

}

问题上线了:

datasource = new DBAdapter(context.getApplicationContext());

我也尝试这样做，但它给出了一个错误，因为这是一个非 Activity 类。

datasource = new DBAdapter(this);

我能做什么？

Answer 1

Context 存在于您的应用程序内部，并不属于特定的 Activity，但是您仍然需要访问它......

您可以将 Context 传递给非 Activity 类方法

public void update_database(Context yourAppContext){

    datasource = new DBAdapter(yourAppContext);
    //Other Stuff........
}