实现的的效果

描述：一开始是完全显示的，然后高度慢慢减少，图片自上而下消失。还有就是左右慢慢展开

分析：这个效果看似很简单，但是实际上根据常规的android机制，是很难以实现的。

解决方案

想了很久，突然联想到MeasureSpec的三种情况（自适应，合父布局一样和绝对大小）。感觉图像设置为绝对大小并且靠底部对齐。然后自上而下减少外布局高度，应该可以实现效果。

一、慢慢折叠与向下展开动画

1.自定义绝对大小的Imageview

package com.ruidde.csndresourcedemo.img;

import android.annotation.SuppressLint;
import android.content.Context;
import android.util.AttributeSet;
import android.widget.ImageView;

import androidx.annotation.Nullable;

@SuppressLint("AppCompatCustomView")
public class AnimImageView extends ImageView {
    private static final int IMAGE_HEIGHT = 500;

    public AnimImageView(Context context) {
        super(context);
    }


    public AnimImageView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs, 0);
    }

    public AnimImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr, 0);

    }

    /**
     * 设置的高度最好是bitmap的高度，这样不好压缩变形。这里写死了
     * @param widthMeasureSpec 宽度
     * @param heightMeasureSpec 高度
     */
    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        setMeasuredDimension(widthMeasureSpec, IMAGE_HEIGHT);
//        setMeasuredDimension(widthMeasureSpec, heightMeasureSpec);
    }
}

实现效果的关键不过就是一行代码：

setMeasuredDimension(widthMeasureSpec, CommonUtil.dip2px(IMAGE_HEIGHT));

2.XML文件

<?xml version="1.0" encoding="utf-8"?>
<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="@color/white"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/bt_scale_big"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="30dp"
        android:text="向上展开" />

    <Button
        android:id="@+id/bt_scale_small"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/bt_scale_big"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="10dp"
        android:text="慢慢折叠" />

    <RelativeLayout
        android:id="@+id/ll_content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="30dp"
        android:layout_below="@+id/bt_scale_small">

        <com.ruidde.csndresourcedemo.img.AnimImageView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:scaleType="fitXY"
            android:src="@mipmap/two" />
    </RelativeLayout>


</RelativeLayout>

3.Activity中代码

package com.ruidde.csndresourcedemo;

import android.animation.ValueAnimator;
import android.app.Activity;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.View;
import android.view.animation.LinearInterpolator;
import android.widget.RelativeLayout;

import androidx.annotation.Nullable;

public class AnimImageActivity extends Activity implements View.OnClickListener {
    private RelativeLayout mContentLayout;
    private RelativeLayout.LayoutParams mLayoutParams;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_anim);
        if (BuildConfig.DEBUG) {
            StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectAll().penaltyLog().build());
            StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder().detectAll().penaltyLog().build());
        }
        findIds();

    }

    private void findIds() {
        mContentLayout = findViewById(R.id.ll_content);
        findViewById(R.id.bt_scale_big).setOnClickListener(this);
        findViewById(R.id.bt_scale_small).setOnClickListener(this);
        mLayoutParams = (RelativeLayout.LayoutParams) mContentLayout.getLayoutParams();

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.bt_scale_big:
                animScaleBig();
                break;
            case R.id.bt_scale_small:
                animScaleSmall();
                break;
            default:
                break;
        }

    }

    private void animScaleBig() {
        ValueAnimator scaleBig = ValueAnimator.ofFloat(100, 500);
        scaleBig.setInterpolator(new LinearInterpolator());
        scaleBig.setDuration(1000);
        scaleBig.addUpdateListener(mListener);
        scaleBig.start();
    }

    private ValueAnimator.AnimatorUpdateListener mListener = new ValueAnimator
            .AnimatorUpdateListener() {

        @Override
        public void onAnimationUpdate(ValueAnimator animation) {
            mLayoutParams.height = (int) (float) animation.getAnimatedValue();
            mContentLayout.setLayoutParams(mLayoutParams);
        }
    };

    private void animScaleSmall() {
        ValueAnimator scaleBig = ValueAnimator.ofFloat(500, 100);
        scaleBig.setInterpolator(new LinearInterpolator());
        scaleBig.setDuration(1000);
        scaleBig.addUpdateListener(mListener);
        scaleBig.start();
    }

}

二、左右慢慢展开

1.XML文件

<?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="match_parent"
    android:orientation="vertical">
    
    <!-- 这里imageView的src定义为clipdrawable资源 -->
    <ImageView
        android:id="@+id/image"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:src="@drawable/drawable_clip" />
</LinearLayout>

2.Activity代码

package com.ruidde.csndresourcedemo;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.graphics.drawable.ClipDrawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;

import androidx.annotation.Nullable;

import java.util.Timer;
import java.util.TimerTask;

/**
 * 图片的慢慢展开动画
 */
public class ClipDrawableActivity extends Activity {
    private ImageView imageView;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_clip_drawable);
        imageView = (ImageView) findViewById(R.id.image);
        //获取图片所显示的ClipDrawble对象
        ClipDrawable clipdrawable = (ClipDrawable) imageView.getDrawable();
        initDate(clipdrawable);

    }

    public void initDate(final ClipDrawable clipdrawable) {
        /**
         * Handler
         * */
        @SuppressLint("HandlerLeak") final Handler handler = new Handler() {
            public void handleMessage(Message msg) {
                if (msg.what == 0x1233) {
                    //修改ClipDrawable的level值
                    clipdrawable.setLevel(clipdrawable.getLevel() + 500);
                }
            }
        };
        /**
         * 计时器
         * */
        final Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            public void run() {
                Message msg = new Message();
                msg.what = 0x1233;
                //发送消息,通知应用修改ClipDrawable对象的level值
                handler.sendMessage(msg);
                //取消定时器
                if (clipdrawable.getLevel() >= 10000) {
                    timer.cancel();
                }
            }
        }, 0, 300);
    }
}