android - 以最佳编码风格(最少重复)向 Android 的 Activity(父类)和 FragmentActivity(子类)添加功能

Question

在 Android 库中，FragmentActivity延伸Activity .我想添加一些方法，并覆盖原始 Activity 的一些方法.

import android.app.Activity

public class Activiti extends Activity {
    public void myNewMethod() { ... }
}

由于原始层次结构，FragmentActivity延伸Activity ，myNewMethod() 也应该出现在我的库的 FragmentActiviti

中

import android.support.v4.app.FragmentActivity;

public abstract class FragmentActiviti extends FragmentActivity {
    public void myNewMethod() { ... }
}

但这会导致重复代码，我不希望这种情况发生。 有没有办法避免这种重复？

---

编辑:使用场景

Activiti.java

public abstract class Activiti extends Activity {
    private int current_orientation = Configuration.ORIENTATION_UNDEFINED;  // ORIENTATION_UNDEFINED = 0

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        current_orientation = this.getResources().getConfiguration().orientation;
    }
    protected boolean isDevicePortrait() { return current_orientation == Configuration.ORIENTATION_PORTRAIT; }
}

FragmentActiviti.java

public abstract class FragmentActiviti extends FragmentActivity {
    /* This onCreate() can be omitted. Just putting here explicitly. */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    protected void someUtilsForFragments() { /* not used yet */ }
}

E_fragtest_06.java

public class E_fragtest_06 extends FragmentActiviti {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        System.out.printf(isDevicePortrait());      // this NOT WORK for now
    }
}

---

编辑 2:尝试使用 Util 类

我认为使用 Decorator Class将是解决此问题的最好方法(无重复代码)。但是 Decorator Pattern只是有点难以(或不可能)应用于 Android Activity 场景。

我尝试实现@hazzik 的方法，但我仍然遇到一些问题。

ActivityUtil.java

public abstract class ActivityUtil {
    private int current_orientation = Configuration.ORIENTATION_UNDEFINED;  // ORIENTATION_UNDEFINED = 0

    public void onCreate(Activity activity, Bundle savedInstanceState) {
        activity.onCreate(savedInstanceState);
        current_orientation = activity.getResources().getConfiguration().orientation;
    }
    public boolean isDevicePortrait() { return current_orientation == Configuration.ORIENTATION_PORTRAIT; }
}

Activiti.java

public class Activiti extends Activity {
    private ActivityUtil activityUtil;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        activityUtil.onCreate(this, savedInstanceState);
    }
    protected boolean isDevicePortrait() { return activityUtil.isDevicePortrait(); }
}

FragmentActiviti.java

public abstract class FragmentActiviti extends FragmentActivity {
    private ActivityUtil activityUtil;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        activityUtil.onCreate(this, savedInstanceState);
    }
    protected boolean isDevicePortrait() { return activityUtil.isDevicePortrait(); }
}

在 ActivityUtil.onCreate() 中，activity.onCreate(savedInstanceState); 导致此编译错误:

The method onCreate(Bundle) from the type Activity is not visible.

如果我将 Activity 更改为 Activiti:

public abstract class ActivityUtil {
    public void onCreate(Activiti activity, Bundle savedInstanceState) { ... }
    ...
}

这将导致 FragmentActiviti.onCreate() 的 activityUtil.onCreate() 中的另一个编译错误:

The method onCreate(Activiti, Bundle) in the type ActivityUtil is not applicable for the arguments (FragmentActiviti, Bundle)

我明白为什么会出现这些错误。但我只是不知道如何避免它们。

---

感谢所有为这个问题做出贡献的人，特别是@flup 指导我了解 Decorator Pattern 、@hazzik 和@donramos 感谢你们的广泛努力，我在这里发帖

我增强的 Android 的 Activity 和 FragmentActivity 类。

如果您也在开发 Android 应用程序，我希望我的代码可以在某些方面对您有所帮助:-)

ActivityCore.java

package xxx.android;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.res.Configuration;
import android.os.Bundle;

public final class ActivityCore {
    public interface ActivityCallbackInterface {
        public void onCreateCallback(Bundle savedInstanceState);
        public void onBeforeSaveInstanceState(Bundle outState);
        public void onSaveInstanceStateCallback(Bundle outState);
    }

    private final Activity activity;
    /**
     * This current_orientation variable should be once set, never changed during the object life-cycle.
     * But Activity.getResources() is not yet ready upon the object constructs.
     * That's why THIS CLASS is wholly responsible to maintain THIS VARIABLE UNCHANGED.
     */
    private int current_orientation = Configuration.ORIENTATION_UNDEFINED;  // ORIENTATION_UNDEFINED = 0

    public ActivityCore(Activity activity) { this.activity = activity; }

    public void onCreate(Bundle savedInstanceState) {
        ((ActivityCallbackInterface) activity).onCreateCallback(savedInstanceState);
        current_orientation = activity.getResources().getConfiguration().orientation;
    }

    public void onSaveInstanceState(Bundle outState) {
        /**
         * THIS is the best ever place i have found, to unload unwanted Fragments,
         * thus prevent re-creating of un-needed Fragments in the next state of Activity.
         *   (state e.g. Portrait-to-Landscape, or Landscape-to-Portrait)
         * 
         * The KEY is to do it BEFORE super.onSaveInstanceState()
         *   (my guess for this reason is, in super.onSaveInstanceState(),
         *    it saves the layout hierarchy, thus saved the Fragments into the Bundle also.
         *    Thus restored.
         *    Note that Fragments NOT IN LAYOUT, having ONLY TAGS, are also restored.)
         */
        ((ActivityCallbackInterface) activity).onBeforeSaveInstanceState(outState);
        ((ActivityCallbackInterface) activity).onSaveInstanceStateCallback(outState);
    }

    public int getCurrentOrientation() { return current_orientation; }

    public boolean isDevicePortrait() { return current_orientation == Configuration.ORIENTATION_PORTRAIT; }
    public boolean isDeviceLandscape() { return current_orientation == Configuration.ORIENTATION_LANDSCAPE; }
    public boolean isNewDevicePortrait() { return activity.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT; }
    public boolean isNewDeviceLandscape() { return activity.getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE; }
    public boolean isPortrait2Landscape() { return isDevicePortrait() && isNewDeviceLandscape(); }
    public boolean isLandscape2Portrait() { return isDeviceLandscape() && isNewDevicePortrait(); }

    public String describeCurrentOrientation() { return describeOrientation(current_orientation); }
    public String getCurrentOrientationTag() { return getOrientationTag(current_orientation); }
    public String describeNewOrientation() { return describeOrientation(activity.getResources().getConfiguration().orientation); }
    public String getNewOrientationTag() { return getOrientationTag(activity.getResources().getConfiguration().orientation); }
    private String describeOrientation(final int orientation) {
        switch (orientation) {
            case Configuration.ORIENTATION_UNDEFINED: return "ORIENTATION_UNDEFINED";   // 0
            case Configuration.ORIENTATION_PORTRAIT: return "ORIENTATION_PORTRAIT";     // 1
            case Configuration.ORIENTATION_LANDSCAPE: return "ORIENTATION_LANDSCAPE";   // 2
            case Configuration.ORIENTATION_SQUARE: return "ORIENTATION_SQUARE";         // 3
            default: return null;
        }
    }
    @SuppressLint("DefaultLocale")
    private String getOrientationTag(final int orientation) {
        return String.format("[%d:%s]", orientation, describeOrientation(orientation).substring(12, 16).toLowerCase());
    }
}

Activity.java

package xxx.android.app;

import xxx.android.ActivityCore;
import xxx.android.ActivityCore.ActivityCallbackInterface;
import android.os.Bundle;

public abstract class Activity extends android.app.Activity implements ActivityCallbackInterface {
    private final ActivityCore activityCore;

    public Activity() { super(); activityCore = new ActivityCore(this); }

    @Override
    protected void onCreate(Bundle savedInstanceState) { activityCore.onCreate(savedInstanceState); }
    @Override public void onCreateCallback(Bundle savedInstanceState) { super.onCreate(savedInstanceState); }

    @Override
    public void onBeforeSaveInstanceState(Bundle outState) {}       // Optionally: let child class override
    @Override
    protected void onSaveInstanceState(Bundle outState) { activityCore.onSaveInstanceState(outState); }
    @Override public void onSaveInstanceStateCallback(Bundle outState) { super.onSaveInstanceState(outState); }

    public final int getCurrentOrientation() { return activityCore.getCurrentOrientation(); }

    public final boolean isDevicePortrait() { return activityCore.isDevicePortrait(); }
    public final boolean isDeviceLandscape() { return activityCore.isDeviceLandscape(); }
    public final boolean isNewDevicePortrait() { return activityCore.isNewDevicePortrait(); }
    public final boolean isNewDeviceLandscape() { return activityCore.isNewDeviceLandscape(); }
    public final boolean isPortrait2Landscape() { return activityCore.isPortrait2Landscape(); }
    public final boolean isLandscape2Portrait() { return activityCore.isLandscape2Portrait(); }

    public final String describeCurrentOrientation() { return activityCore.describeCurrentOrientation(); }
    public final String getCurrentOrientationTag() { return activityCore.getCurrentOrientationTag(); }
    public final String describeNewOrientation() { return activityCore.describeNewOrientation(); }
    public final String getNewOrientationTag() { return activityCore.getNewOrientationTag(); }
}

FragmentActivity.java

package xxx.android.support.v4.app;

import xxx.android.ActivityCore;
import xxx.android.ActivityCore.ActivityCallbackInterface;
import android.os.Bundle;

public abstract class FragmentActivity extends android.support.v4.app.FragmentActivity implements ActivityCallbackInterface {
    private final ActivityCore activityCore;

    public FragmentActivity() { super(); activityCore = new ActivityCore(this); }

    @Override
    protected void onCreate(Bundle savedInstanceState) { activityCore.onCreate(savedInstanceState); }
    @Override public void onCreateCallback(Bundle savedInstanceState) { super.onCreate(savedInstanceState); }

    @Override
    public void onBeforeSaveInstanceState(Bundle outState) {}       // Optionally: let child class override
    @Override
    protected void onSaveInstanceState(Bundle outState) { activityCore.onSaveInstanceState(outState); }
    @Override public void onSaveInstanceStateCallback(Bundle outState) { super.onSaveInstanceState(outState); }

    public final int getCurrentOrientation() { return activityCore.getCurrentOrientation(); }

    public final boolean isDevicePortrait() { return activityCore.isDevicePortrait(); }
    public final boolean isDeviceLandscape() { return activityCore.isDeviceLandscape(); }
    public final boolean isNewDevicePortrait() { return activityCore.isNewDevicePortrait(); }
    public final boolean isNewDeviceLandscape() { return activityCore.isNewDeviceLandscape(); }
    public final boolean isPortrait2Landscape() { return activityCore.isPortrait2Landscape(); }
    public final boolean isLandscape2Portrait() { return activityCore.isLandscape2Portrait(); }

    public final String describeCurrentOrientation() { return activityCore.describeCurrentOrientation(); }
    public final String getCurrentOrientationTag() { return activityCore.getCurrentOrientationTag(); }
    public final String describeNewOrientation() { return activityCore.describeNewOrientation(); }
    public final String getNewOrientationTag() { return activityCore.getNewOrientationTag(); }
}

最后，我真的要感谢你们的帮助，并不断与我更新解决进度!你们都是使 stackoverflow 成为程序员完美站点的关键人物。如果您在我的代码中发现任何问题，或者有任何需要改进的地方，请随时再次帮助我:-)

一些改进？

因为onBeforeSaveInstanceState()是在使用时实现的，所以三个类都需要保持抽象。这导致成员变量 current_orientation 重复。如果 current_orientation 可以放入 class ActivityBase 中，或者将其分组到其他地方，那就更好了!

愚蠢的我。我已经修好了:-)

Answer 1

在我看来，这里最好的解决方案是将逻辑委托(delegate)给某个类，我们称它为 CustomActivityLogic。

如果您想从逻辑类中访问 Activity 类的一些数据或方法，您还需要为您的 Activity 创建通用接口(interface) (CustomActivity)。

要调用 protected 虚拟重写方法，有两种解决方案:

• 从覆盖的方法中调用 supper 的方法
• 在子类中创建一个新方法并从这个新方法调用 super 方法。从共享逻辑调用新方法。

CustomActivity.java

public interface CustomActivity {
    void someMethod();
}

Activiti.java

import android.app.Activity

public class Activiti 
    extends Activity 
    implements CustomActivity {

    private CustomActivityLogic logic = new CustomActivityLogic();

    public void someMethod() { /***/ }

    public void myNewMethod() { logic.myNewMethod(this); }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        logic.onCreate(this, savedInstanceState); // call shared logic
        super.onCreate(savedInstanceState); // call super
    }
}

FragmentActivitii.java

import android.support.v4.app.FragmentActivity;

public class FragmentActivitii 
    extends FragmentActivity 
    implements CustomActivity {

    private CustomActivityLogic logic = new CustomActivityLogic();

    public void someMethod() { /***/ }

    public void myNewMethod() { logic.myNewMethod(this); }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        logic.onCreate(this, savedInstanceState); // call shared logic
        super.onCreate(savedInstanceState); // call super
    }
}

CustomActivityLogic.java

 public class CustomActivityLogic {
     public void myNewMethod(CustomActivity activity) { /*...*/ }
     public void onCreate(Activity activity, Bundle savedInstanceState) { 
         /* shared creation logic */
     }
 }

使 onCreate 可通过 CustomActivity 接口(interface)从外部调用的方法

CustomActivity.java

public interface CustomActivity {
    void someMethod();
    void onCreateSuper(Bundle savedInstanceState);
}

Activiti.java

import android.app.Activity

public class Activiti 
    extends Activity 
    implements CustomActivity {

    private CustomActivityLogic logic = new CustomActivityLogic();

    public void someMethod() { /***/ }

    public void myNewMethod() { logic.myNewMethod(this); }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        logic.onCreate(this, savedInstanceState); // call shared logic
    }

    public void onCreateSuper(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState); // call super
    }
}

FragmentActivitii.java

import android.support.v4.app.FragmentActivity;

public class FragmentActivitii 
    extends FragmentActivity 
    implements CustomActivity {

    private CustomActivityLogic logic = new CustomActivityLogic();

    public void someMethod() { /***/ }

    public void myNewMethod() { logic.myNewMethod(this); }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        logic.onCreate(this, savedInstanceState); // call shared logic
    }

    public void onCreateSuper(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState); // call super
    }
}

CustomActivityLogic.java

 public class CustomActivityLogic {
     public void myNewMethod(CustomActivity activity) { /*...*/ }
     public void onCreate(CustomActivity activity, Bundle savedInstanceState) { 
         /* shared creation logic */
         activity.onCreateSuper(savedInstanceState); // call-back super
     }
 }