ImageView 不喜欢 TranslationX 动画

Question

我正在尝试创建一个滑块，当用户向左或向右滑动时，该滑块会动画滑动，平移动画。然而，它并没有以正确的方式工作。

package pete.android.study.home.scrollingindicator;



import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;

public class MainScreen extends Activity {

    protected ValueAnimator mScrollIndicatorAnimator;
    protected ValueAnimator mScrollator;
    protected ImageView mScrollIndicator = null;    
    protected static final int sScrollIndicatorFadeInDuration = 150;
    protected static final int sScrollIndicatorFadeOutDuration = 650;
    protected static final int sScrollIndicatorFlashDuration = 650;

    public static final int PAGE_COUNT = 4;
    private int mPageWidth = 0;

    private int mCurrentPage = 0;
    private int mIndicatorPos = 0;
    private int mIndicatorSpace = 0;

    private GestureDetector mGestureDetector;
    private static final boolean DEBUG = true;
    private static final String TAG = "indicator";
    private Handler mHandler;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        DisplayMetrics displaymetrics = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
        //ht = displaymetrics.heightPixels;
        mPageWidth = displaymetrics.widthPixels;

        mHandler = new Handler();
        setupScrollingIndicator();
        mGestureDetector = new GestureDetector(this, new LearnGestureListener());  
    }

    @Override  
    public boolean onTouchEvent(MotionEvent event) {  
      if (mGestureDetector.onTouchEvent(event))  
        return true;  
      else  
        return false;  
    }  

    public void setupScrollingIndicator() {
        if(mScrollIndicator == null) { 
            mScrollIndicator = (ImageView) findViewById(R.id.indicator);
        }

        mIndicatorSpace = mPageWidth / PAGE_COUNT;
        mIndicatorPos = mIndicatorSpace * mCurrentPage;

        if(DEBUG) {
            Log.i(TAG, "mIndicatorSpace = " + mIndicatorSpace);
            Log.i(TAG, "mCurrentPage = " + mCurrentPage);
            Log.i(TAG, "mIndicatorPos = " + mIndicatorPos);         
        }

        if(mScrollIndicator.getMeasuredWidth() != mIndicatorSpace) {
            mScrollIndicator.getLayoutParams().width = mIndicatorSpace;
            mScrollIndicator.requestLayout();           
        }

        mScrollIndicator.setTranslationX(mIndicatorPos);
        mScrollIndicator.invalidate();
    }

    public void showIndicator() {
        setupScrollingIndicator();

        mScrollIndicator.setVisibility(View.VISIBLE);
        cancelScrollingAnimations();

        mScrollIndicatorAnimator = ObjectAnimator.ofFloat(mScrollIndicator, "alpha", 1f);
        mScrollIndicatorAnimator.setDuration(sScrollIndicatorFadeInDuration);
        mScrollIndicatorAnimator.start();

        mScrollator = ObjectAnimator.ofFloat(mScrollIndicator, "translationX", mIndicatorPos);
        mScrollator.setDuration(sScrollIndicatorFlashDuration);
        mScrollator.start();
    }
    Runnable hideScrollingIndicatorRunnable = new Runnable() {
        @Override
        public void run() {
            hideIndicator();
        }
    };

    protected void flashIndicator() {        
        showIndicator();
        mHandler.postDelayed(hideScrollingIndicatorRunnable, sScrollIndicatorFlashDuration);
    }
    public void hideIndicator() {
        setupScrollingIndicator();
        cancelScrollingAnimations();

        mScrollIndicatorAnimator = ObjectAnimator.ofFloat(mScrollIndicator, "alpha", 0f);
        mScrollIndicatorAnimator.setDuration(sScrollIndicatorFadeOutDuration);
        mScrollIndicatorAnimator.addListener(new AnimatorListenerAdapter() {
            private boolean cancelled = false;
            @Override
            public void onAnimationCancel(android.animation.Animator animation) {
                cancelled = true;
            }
            @Override
            public void onAnimationEnd(Animator animation) {
                if (!cancelled) {
                    mScrollIndicator.setVisibility(View.INVISIBLE);
                }
            }
        });
        mScrollIndicatorAnimator.start();        
    }
    public void cancelScrollingAnimations() {
        if(mScrollIndicatorAnimator != null) {
            mScrollIndicatorAnimator.cancel();
        }
    }

    public void scrollToRight() {
        flashIndicator();
        mCurrentPage++; 
        if(mCurrentPage >= PAGE_COUNT) {
            mCurrentPage = 0;
        }
    }

    public void scrollToLeft() {
        flashIndicator();
        mCurrentPage--;
        if(mCurrentPage < 0) {
            mCurrentPage = PAGE_COUNT - 1;
        }
    }

    class LearnGestureListener extends GestureDetector.SimpleOnGestureListener {
        @Override  
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {  
            if(e2.getX() - e1.getX() > 50) {

                scrollToLeft();
            } else if(e2.getX() - e1.getX() < 50) {
                scrollToRight();

            } 
            return true;  
        }  
    }  

}

请帮我解决这个问题，非常感谢！

Answer 1

mScrollIndicator.setTranslationX(mIndicatorPos) 只需在新位置 mIndicatorPos 上重新绘制视图即可。它不做动画。

如果您希望 mScrollIndicator 随滚动事件一起移动，请尝试重写 onScroll 方法而不是 onFling。

或者另一种方式，创建一个 android.animation.ObjectAnimator 对象，为您的视图设置它并在 Fling 上调用 ObjectAnimator.start() 。