java - Android - 显示/隐藏 ActionBar 项目时淡入/淡出

Question

有什么简单的方法可以在显示/隐藏时使用淡入/淡出动画为 ActionBar 项目设置动画？也许是这样的:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getSupportMenuInflater().inflate(R.menu.menu, menu);

    if (visible) {
        menu.findItem(R.id.randomItemID).setVisible(true);
    else {
        menu.findItem(R.id.randomItemID).setVisible(false);
    }
    return true;
}


private void showHideActionItem() {

    if (visible) {
        // Fade Out animation here
        visible = false;
        invalidateOptionsMenu();
    } else {
        // Fade In animation here
        visible = true;
        invalidateOptionsMenu();
    }
}

谢谢，托尼。

Answer 1

我发现这个问题真的很有趣，所以我决定找到一个解决方案(所以请原谅我，如果这个解决方案不是最佳的，它只是一个展示方法的例子)。

经过一些研究，我决定使用 Android timer : 全局的想法是有一个计时器，它会定期更新 actionBar 背景(所以为了制作 fade_in 效果，我只需要保持相同的背景并改变它的不透明度)。

这里是我的实现:

首先:我的自定义类将完成大部分工作:

public class ToolbarAnimator {
    private final static String TAG = ToolbarAnimator.class.getSimpleName();
    private final int ALPHA_MAX = 255;//just look at the documentation
    private final int NUMBER_OF_TICK = 255;//can go from 1 to 255, it's the number of tick
    private final int ALPHA_PER_TICK = ALPHA_MAX / NUMBER_OF_TICK;//alpha we'll remove/add on every tick
    private long DELAY = 1000;//amount of time in milliseconds before animation execution.
    private final AppCompatActivity mActivity;

    /*
    ** Private field
     */
    private ActionBar mActionBar;
    private Timer mTimer;
    private int mCurrentAlpha;
    private int mActionBarBackgroundColor;

    /*
    ** Constructor
     */
    public ToolbarAnimator(@NonNull AppCompatActivity activity, @NonNull final ActionBar actionBar, final int actionBarBackgroundColor) {
        mActivity = activity;
        mActionBar = actionBar;
        mTimer = new Timer();
        mCurrentAlpha = 0;
        mActionBarBackgroundColor = actionBarBackgroundColor;
    }

    /*
    ** Public method
     */
    public void start(final long duration) {
        final long period = duration / NUMBER_OF_TICK;//time beetwen 2 run() call

        Log.d(TAG, "start");
        Log.d(TAG, "delay = " + DELAY);
        Log.d(TAG, "period = " + period);
        Log.d(TAG, "duration = " + duration);
        Log.d(TAG, "alphaPerTick = " + ALPHA_PER_TICK);

        //init a timer which will updateActionBarColor on every each period
        mTimer.schedule(new TimerTask() {
            @Override
            public void run() {
                //update the actionBar
                updateActionBarColor();
            }
        }, DELAY, period);
    }

    /*
    ** Private method
     */
    private void updateActionBarColor() {
        //We have to go to the main thread for updating the interface.
        mActivity.runOnUiThread(new TimerTask() {
            @Override
            public void run() {
                //check if the animation is finish
                if (mCurrentAlpha > 255 || mCurrentAlpha < 0) {
                    Log.d(TAG, "cancel timer");
                    mTimer.cancel();
                    mTimer.purge();
                    return;
                }
                //create the new backgroundColorDrawable
                final Drawable backgroundDrawable = new ColorDrawable(mActionBarBackgroundColor);
                backgroundDrawable.setAlpha(mCurrentAlpha);

                //apply the new color
                mActionBar.setBackgroundDrawable(backgroundDrawable);

                //upgrade alpha
                mCurrentAlpha += ALPHA_PER_TICK;
            }
        });
    }
}

当你有这个类时，你可以从任何 Activity 或 fragment 开始动画:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    //just inflate the actionBar
    getMenuInflater().inflate(R.menu.menu_main, menu);

    //Check if the supportActionBar has been enable
    final ActionBar actionBar = getSupportActionBar();
    if (actionBar != null) {
        //Start a 2s animation on the actionBar
        new ToolbarAnimator(this, actionBar, Color.RED).start(2 * 1000);
    }
    return true;
}

更新:

我已经做了一个实现更多功能的示例应用程序(例如，您可以选择淡入淡出或淡入淡出)，您可以找到源代码here .