java - 抽象类扩展了Java和Android的多种类型的 Activity

Question

我是 Java 和 Android 编程新手。我刚刚创建了带有登录表单和注册表单的简单应用程序。我的登录表单和注册表单现在可以使用。我创建了从 Activity 类扩展的抽象 SignedActivity 类。我希望登录后可用的每个 Activity 都继承自 SignedActivity。如果 Activity 继承自 SignedActivity，我可以确定它仅适用于签名用户。

这是 SignedActivity 的外观:

public abstract class SignedActivity extends Activity {

public static String LOG_OUT_PATH = "/logOut.php";

private String sessionId;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if (savedInstanceState != null) {
        String newSessionId = savedInstanceState.getString("sessionId");
        if (newSessionId instanceof String) {
            sessionId = newSessionId;
            return;
        }
    }
    Bundle extras = getIntent().getExtras();
    if (extras != null) {
        String newSessionId = extras.getString("sessionId");
        if (newSessionId instanceof String) {
            sessionId = newSessionId;
            return;
        }
    }

    finish();
}

public void startSignedActivity(Intent intent) {
    intent.putExtra("sessionId", getSessionId());
    this.startActivity(intent);
}

protected String getSessionId() {
    return sessionId;
}

private void setSessionId(String newSessionId) {
    sessionId = newSessionId;
}

protected void logOut() {
    new RequestLogOutTask().execute(SignedActivity.LOG_OUT_PATH);
    setSessionId("");
    Intent intent = new Intent(this, SignInActivity.class);
    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK|Intent.FLAG_ACTIVITY_NEW_TASK);
    intent.putExtra("logOut", true);
    startActivity(intent);
}

public void onClickLogOut(View v) {
    logOut();
}

@Override
protected void onSaveInstanceState(Bundle savedInstanceState) {
    savedInstanceState.putString("sessionId", sessionId);
    super.onSaveInstanceState(savedInstanceState);
}

class RequestLogOutTask extends AsyncTask<String, Void, Void> {
    protected Void doInBackground(String... params) {
        (new RESTClient(Constants.REST_URL)).post(params[0], "");
        return null;
    }
}

}

我的问题是登录后有时需要 FragmentActivity 而不是 Activity。所以我必须创建从 FragmentActivity 扩展的 SignedFragmentActivity ，它与 SignedActivity 基本相同(只有父级不同)。所以我有重复的代码 - 如何避免它？

Answer 1

您可以将 SignedActivity 代码移至 ActivityHelper 类:

class ActivityHelper {
    public static String initializeSessionId(Bundle savedInstanceState, Activity activity) {
        if (savedInstanceState != null) {
            String newSessionId = savedInstanceState.getString("sessionId");
            if (newSessionId instanceof String) {
                return newSessionId;
            }
        }
        Bundle extras = activity.getIntent().getExtras();
        if (extras != null) {
            String newSessionId = extras.getString("sessionId");
            if (newSessionId instanceof String) {
                return newSessionId;
            }
        }
        return null;
    }

    ...
}

现在您可以在每个 Activity 实例中使用它(即 FragmentActivity):

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    sessionId = ActivityHelper.initializeSessionId(savedInstanceState, this);

    finish();
}
...