Android动画下拉/向上 View 正确

Question

我正在尝试制作正确的向下滑动动画。向下滑动的 View 应将其下方的所有 View 以一种平滑的方式向下推，当它向上滑动时，所有 View 应以一种平滑的方式跟随。

我的尝试:

在代码中:

LinearLayout lin = (LinearLayout)findViewById(R.id.user_list_container);
                setLayoutAnimSlidedownfromtop(lin, this);
                lin.addView(getLayoutInflater().inflate(R.layout.user_panel,null),0);

还有:

public static void setLayoutAnimSlidedownfromtop(ViewGroup panel, Context ctx) {

      AnimationSet set = new AnimationSet(true);

      Animation animation = new AlphaAnimation(0.0f, 1.0f);
      animation.setDuration(100);
      set.addAnimation(animation);

      animation = new TranslateAnimation(
          Animation.RELATIVE_TO_SELF, 0.0f, Animation.RELATIVE_TO_SELF, 0.0f,
          Animation.RELATIVE_TO_SELF, -1.0f, Animation.RELATIVE_TO_SELF, 0.0f
      );
      animation.setDuration(500);
      set.addAnimation(animation);

      LayoutAnimationController controller =
          new LayoutAnimationController(set, 0.25f);
      panel.setLayoutAnimation(controller);

}

我的user_panel.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="40dp"
    android:orientation="vertical" >
    <ImageView 
        android:layout_alignParentLeft="true"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:src="@drawable/icon" />
</LinearLayout>

主要 XML 的顶部:

<LinearLayout
        android:id="@+id/user_list_container"
        android:layout_alignParentTop="true"
        android:orientation="vertical" 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"/>
    <LinearLayout
        android:id="@+id/container"
        android:layout_below="@+id/user_list_container"
        android:orientation="vertical" 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">

上述方法的问题是，当我首先启动动画时，会创建 View 的空白空间，然后 View 会向下滑动。我希望它可以慢慢地将所有其他 View 向下推，而不是一气呵成。

Answer 1

所以我最终在 this answer 的帮助下自己完成了这项工作。 .如果是 Android 3.0 ，我本可以使用属性动画，但不是我必须自己这样做。

这是我最终得到的结果:

import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;

/**
 * Class for handling collapse and expand animations.
 * @author Esben Gaarsmand
 *
 */
public class ExpandCollapseAnimation extends Animation {
    private View mAnimatedView;
    private int mEndHeight;
    private int mType;

    /**
     * Initializes expand collapse animation, has two types, collapse (1) and expand (0).
     * @param view The view to animate
     * @param duration
     * @param type The type of animation: 0 will expand from gone and 0 size to visible and layout size defined in XML. 
     * 1 will collapse view and set to gone
     */
    public ExpandCollapseAnimation(View view, int duration, int type) {
        setDuration(duration);
        mAnimatedView = view;
        mEndHeight = mAnimatedView.getLayoutParams().height;
        mType = type;
        if(mType == 0) {
            mAnimatedView.getLayoutParams().height = 0;
            mAnimatedView.setVisibility(View.VISIBLE);
        }
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        super.applyTransformation(interpolatedTime, t);
        if (interpolatedTime < 1.0f) {
            if(mType == 0) {
                mAnimatedView.getLayoutParams().height = (int) (mEndHeight * interpolatedTime);
            } else {
                mAnimatedView.getLayoutParams().height = mEndHeight - (int) (mEndHeight * interpolatedTime);
            }
            mAnimatedView.requestLayout();
        } else {
            if(mType == 0) {
                mAnimatedView.getLayoutParams().height = mEndHeight;
                mAnimatedView.requestLayout();
            } else {
                mAnimatedView.getLayoutParams().height = 0;
                mAnimatedView.setVisibility(View.GONE);
                mAnimatedView.requestLayout();
                mAnimatedView.getLayoutParams().height = mEndHeight;
            }
        }
    }
}

示例用法:

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class AnimationTestActivity extends Activity {
    private boolean mActive = false;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        final Button animatedButton = (Button) findViewById(R.id.animatedButton);
        
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                ExpandCollapseAnimation animation = null;
                if(mActive) {
                    animation = new ExpandCollapseAnimation(animatedButton, 1000, 1);
                    mActive = false;
                } else {
                    animation = new ExpandCollapseAnimation(animatedButton, 1000, 0);
                    mActive = true;
                }
                animatedButton.startAnimation(animation);
            }
        });
    }
}

XML:

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
    <Button
        android:id="@+id/animatedButton"
        android:visibility="gone"
        android:layout_width="fill_parent"
        android:layout_height="50dp"
        android:text="@string/hello"/>
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />
    <Button
        android:id="@+id/button"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello"/>
</LinearLayout>

---

编辑

测量 wrap_content 高度:

因此，为了使 wrap_content 能够正常工作，我在开始动画之前测量了 View 的高度，然后使用这个测量的高度作为实际高度。下面是测量 View 高度并将其设置为新高度的代码(我假设 View 使用屏幕宽度，根据您自己的需要更改):

/**
 * This method can be used to calculate the height and set it for views with wrap_content as height. 
 * This should be done before ExpandCollapseAnimation is created.
 * @param activity
 * @param view
 */
public static void setHeightForWrapContent(Activity activity, View view) {
    DisplayMetrics metrics = new DisplayMetrics();
    activity.getWindowManager().getDefaultDisplay().getMetrics(metrics);

    int screenWidth = metrics.widthPixels;
    
    int heightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
    int widthMeasureSpec = MeasureSpec.makeMeasureSpec(screenWidth, MeasureSpec.EXACTLY);

    view.measure(widthMeasureSpec, heightMeasureSpec);
    int height = view.getMeasuredHeight();
    view.getLayoutParams().height = height;
}