如果写一个点击view带动画的下滑展开显示隐藏内容的控件

原理是在onMeasure中得到隐藏内容的高度，点击这个view的时候对隐藏的view startAnimation,让它的高度从0增长到onMeasure得到的这个View的measureHeight

具体这样写:

public class ExpandableLayout extends LinearLayout {

	private Context mContext;
	private LinearLayout mHandleView;
	private RelativeLayout mContentView;
	private ImageView mIconExpand;
	int mContentHeight = 0;
	int mTitleHeight = 0;
	private boolean isExpand;
	private Animation animationDown;
	private Animation animationUp;

	public ExpandableLayout(Context context, AttributeSet attrs) {
		super(context, attrs);
		this.mContext = context;
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		if (this.mContentHeight == 0) {
			this.mContentView.measure(widthMeasureSpec, 0);
			this.mContentHeight = this.mContentView.getMeasuredHeight();
		}
		if (this.mTitleHeight == 0) {
			this.mHandleView.measure(widthMeasureSpec, 0);
			this.mTitleHeight = this.mHandleView.getMeasuredHeight();
		}
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
	}

	@Override
	protected void onFinishInflate() {
		super.onFinishInflate();
		this.mHandleView = (LinearLayout) this
				.findViewById(R.id.collapse_value);
		this.mContentView = (RelativeLayout) this.findViewById(R.id.expand_value);
		this.mIconExpand = (ImageView) this.findViewById(R.id.icon_value);

		this.mHandleView.setOnClickListener(new ExpandListener());
		this.mContentView.setOnClickListener(new ExpandListener());
		mContentView.setVisibility(View.GONE);
	}

	private class ExpandListener implements View.OnClickListener {
		@Override
		public final void onClick(View paramView) {
			//clearAnimation是view的方法
			clearAnimation();
			if (!isExpand) {
				if (animationDown == null) {
					animationDown = new DropDownAnim(mContentView,
							mContentHeight, true);
					animationDown.setDuration(200); // SUPPRESS CHECKSTYLE
				}
				startAnimation(animationDown);
				mContentView.startAnimation(AnimationUtils.loadAnimation(
						mContext, R.anim.animalpha));
				mIconExpand.setImageResource(R.drawable.update_detail_up);
				isExpand = true;
			} else {
				isExpand = false;
				if (animationUp == null) {
					animationUp = new DropDownAnim(mContentView,
							mContentHeight, false);
					animationUp.setDuration(200); // SUPPRESS CHECKSTYLE
				}
				startAnimation(animationUp);
				mIconExpand.setImageResource(R.drawable.update_detail_down);
			}
		}
	}

	class DropDownAnim extends Animation {
		/** 目标的高度 */
		private int targetHeight;
		/** 目标view */
		private View view;
		/** 是否向下展开 */
		private boolean down;

		/**
		 * 构造方法
		 *
		 * @param targetview
		 *            需要被展现的view
		 * @param vieweight
		 *            目的高
		 * @param isdown
		 *            true:向下展开，false:收起
		 */
		public DropDownAnim(View targetview, int vieweight, boolean isdown) {
			this.view = targetview;
			this.targetHeight = vieweight;
			this.down = isdown;
		}
		//down的时候，interpolatedTime从0增长到1，这样newHeight也从0增长到targetHeight
		@Override
		protected void applyTransformation(float interpolatedTime,
				Transformation t) {
			int newHeight;
			if (down) {
				newHeight = (int) (targetHeight * interpolatedTime);
			} else {
				newHeight = (int) (targetHeight * (1 - interpolatedTime));
			}
			view.getLayoutParams().height = newHeight;
			view.requestLayout();
			if (view.getVisibility() == View.GONE) {
				view.setVisibility(View.VISIBLE);
			}
		}

		@Override
		public void initialize(int width, int height, int parentWidth,
				int parentHeight) {
			super.initialize(width, height, parentWidth, parentHeight);
		}

		@Override
		public boolean willChangeBounds() {
			return true;
		}
	}
}

Layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FFFFFF" >

    <com.example.view.ExpandableLayout
        android:id="@+id/app_detail_safety_info"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical" >

        <LinearLayout
            android:id="@+id/collapse_value"
            android:layout_width="fill_parent"
            android:layout_height="34dip"
            android:layout_marginLeft="14dip"
            android:gravity="center_vertical"
            android:orientation="horizontal" >

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="30dp"
                android:text="点击我会显示隐藏的内容"
                android:textColor="#000000"
                android:textSize="18sp" >
            </TextView>

            <LinearLayout
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:gravity="right|center_vertical"
                android:orientation="horizontal" >

                <ImageView
                    android:id="@+id/icon_value"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginRight="22dip"
                    android:src="@drawable/update_detail_down" />
            </LinearLayout>
        </LinearLayout>

        <RelativeLayout
            android:id="@+id/expand_value"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:background="@drawable/app_detail_safety_info_bg"
            android:orientation="horizontal"
            android:paddingBottom="8dip"
            android:paddingTop="8dip" >

            <ImageButton
                android:id="@+id/btn"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerVertical="true"
                android:layout_marginLeft="30dp"
                android:background="@null"
                android:src="@drawable/btn_icon"
                android:textColor="#0A84BD"
                android:textSize="16sp" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="30dp"
                android:layout_toRightOf="@id/btn"
                android:text="隐藏的内容"
                android:textColor="#000000"
                android:textSize="18sp" >
            </TextView>
        </RelativeLayout>
    </com.example.view.ExpandableLayout>

</RelativeLayout>

只要在这个activity中setContentView这个layout,点击view就可以执行展开动画

代码:http://download.csdn.net/detail/baidu_nod/7812705