android动画使用三

使用ValueAnimator实现一个点击view展示次级view的效果

效果图：

代码：
MainActivity.java

package com.example.lhd.myvalueanimator;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.RelativeLayout;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private Button btn1;
    private RelativeLayout r2;

    private float mDensity;//屏幕密度
    private int r2Height;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        init();
        //将dp转换为px
        mDensity = getResources().getDisplayMetrics().density;
        //获取隐藏布局的高度 mDensity * 100dp + 0.5f
        r2Height = (int) (mDensity * 100 + 0.5);
    }

    private void init() {
        r2 = (RelativeLayout) findViewById(R.id.r2);
        btn1 = (Button) findViewById(R.id.btn_1);
        btn1.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        if (r2.getVisibility() == View.GONE) {
            //展开动画
            btn1.setText("-");
            open(r2);
        } else {
            //关闭动画
            close(r2);
            btn1.setText("+");
        }
    }

    private void open(View view) {
        view.setVisibility(View.VISIBLE);
        ValueAnimator animator = openAnimator(view, 0, r2Height);
        animator.start();
    }

    private void close(final View view) {
        int curheight = view.getHeight();
        ValueAnimator animator = openAnimator(view, curheight, 0);//由现在的高度变回为0
        animator.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                view.setVisibility(View.GONE);//动画执行结束后让布局隐藏
            }
        });
        animator.start();
    }

    private ValueAnimator openAnimator(final View view, int start, int end) {
        ValueAnimator animator = ValueAnimator.ofInt(start, end);
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {

            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                int value = (int) animation.getAnimatedValue();
                ViewGroup.LayoutParams lp = view.getLayoutParams();
                lp.height = value;//高度不断变化，由start到end
                view.setLayoutParams(lp);
            }
        });
        return animator;
    }
}

布局文件：

<?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">

    <RelativeLayout  android:id="@+id/r1" android:layout_width="match_parent" android:layout_height="40dp" android:background="#0fa">

        <TextView  android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerInParent="true" android:text="ValueAnimator" android:textSize="18sp" />

        <Button  android:id="@+id/btn_1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentRight="true" android:background="#fff" android:text="+" android:textSize="30sp" />
    </RelativeLayout>

    <!-- 隐藏布局的高度为100dp -->

    <RelativeLayout  android:visibility="gone" android:id="@+id/r2" android:layout_width="match_parent" android:layout_height="100dp" android:background="#fa0">

        <ImageView  android:layout_width="100dp" android:layout_height="100dp" android:background="@drawable/xixi" />

        <TextView  android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerInParent="true" android:text="展开的内容" android:textColor="#fff" android:textSize="20sp" />

        <Button  android:id="@+id/btn_2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentRight="true" android:layout_centerVertical="true" android:background="#0fa" android:text="(*^__^*)" android:textSize="30sp" />
    </RelativeLayout>
</LinearLayout>

图片素材：

demo下载：
http://dl.download.csdn.net/down11/20160609/7ad708a192f47edc1993f5898486d031.zip?response-content-disposition=attachment%3Bfilename%3D%22MyValueAnimator.zip%22&OSSAccessKeyId=9q6nvzoJGowBj4q1&Expires=1465699930&Signature=4ISctwgPfYaJaAq%2BvC0nkSiiPt4%3D