Classcastexception：嘗試創建類對象時

Question

我有兩個java類：

PrefManager.java：

public class PrefManager {
    SharedPreferences pref;
    SharedPreferences.Editor editor;
    Context _context;
    // shared pref mode
    int PRIVATE_MODE = 0;

    // Shared preferences file name
    private static final String PREF_NAME = "welcome";
    private static final String IS_FIRST_TIME_LAUNCH = "IsFirstTimeLaunch";

    public PrefManager(WelcomeActivity context) {
        this._context = context;
        pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
        editor = pref.edit();
    }

    public void setFirstTimeLaunch(boolean isFirstTime) {
        editor.putBoolean(IS_FIRST_TIME_LAUNCH, isFirstTime);
        editor.commit();
    }

    public boolean isFirstTimeLaunch() {
        return pref.getBoolean(IS_FIRST_TIME_LAUNCH, true);
    }
}

我正在嘗試在下面創建此類的對象：

MainActivity.java ：

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        PrefManager prefManager = new PrefManager((WelcomeActivity) getApplicationContext());
        if(prefManager.isFirstTimeLaunch()){
            prefManager.setFirstTimeLaunch(false);
            startActivity(new Intent(MainActivity.this, WelcomeActivity.class));
            finish();
        }
    }
}

執行后，我在PrefManager prefManager = new PrefManager((WelcomeActivity) getApplicationContext());行中不斷收到此錯誤。 ：

原因：java.lang.ClassCastException: android.app.Application 無法轉換為 com.example.electric_viewing.WelcomeActivity

如何修復此錯誤？

Answer 1

使用通用的代碼

public PrefManager(Context context) {
        this._context = context;
        pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
        editor = pref.edit();
    }

現在可以像這樣創建對象

PrefManager prefManager = new PrefManager(this); // no need to call getApplicationContext