android - 使用 KitKat Transitions Framework 时如何实现后退堆栈

Question

我正在使用新的 KitKat Transitions Android 上的 API。我使用两种布局创建了两个 Scene 对象。我在 Fragment 中制作了从 Scene 1 到 Scene 2 的动画。我想在用户按下后退按钮时自动返回到上一个 Scene。

使用 Transitions 时是否有某种内置的后台机制，还是我必须自己动手？

调用 TransitionManager.go(scene1) 很容易，但我真的不想在所有具有 场景动画。

Answer 1

我最终推出了自己的解决方案。

让你的Activity实现这个

public interface SceneBackstackHandler {

    public void addBackstackListener(BackstackListener listener);

    public void removeBackstackListener(BackstackListener listener);

    public void removeAllBackstackListeners();

    public interface BackstackListener {
        public boolean onBackPressed();
    }
}

Activity

private final Object mBackstackListenerLock = new Object();
private List<BackstackListener> mBackstackListeners = new ArrayList<>();

@Override
public void onBackPressed() {
    synchronized (mBackstackListenerLock) {
        for (BackstackListener mBackstackListener : mBackstackListeners) {
            if (mBackstackListener.onBackPressed()) {
                // handled by fragment
                return;
            }
        }
        super.onBackPressed();
    }
}

@Override
protected void onPause() {
    super.onPause();
    removeAllBackstackListeners();
}

@Override
public void addBackstackListener(BackstackListener listener) {
    synchronized (mBackstackListenerLock) {
        mBackstackListeners.add(listener);
    }
}

@Override
public void removeBackstackListener(BackstackListener listener) {
    synchronized (mBackstackListenerLock) {
        mBackstackListeners.remove(listener);
    }
}

@Override
public void removeAllBackstackListeners() {
    synchronized (mBackstackListenerLock) {
        mBackstackListeners.clear();
    }
}

子 fragment :

public class MySceneFragment extends Fragment
        implements SceneBackstackHandler.BackstackListener {

    private Scene mCurrentScene;

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        mBackstackHandler = (SceneBackstackHandler) activity;
        mBackstackHandler.addBackstackListener(this);
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mBackstackHandler.removeBackstackListener(this);
    }

    @Override
    public boolean onBackPressed() {
        if (mCurrentScene != null && mCurrentScene.equals(mMyScene)) {
            removeMyScene();
            return true;
        }
        return false;
    }

    private void changeScene(Scene scene) {
        TransitionManager.go(scene);
        mCurrentScene = scene;
    }
}