ViewGroup Android

讲讲ViewGroup的setPersistentDrawingCache方法

这是一篇采坑文章，灵感来源于博主某篇文章中与大佬的聊天

前言

记得在三年前，还在上一个学校，学生时代的时候，接过一个外包的Android单，里面有个需求是在一个Activity中根据用户的点击反复的执行两个动画以达到比较好的交互效果。当时在网上没有找到类似的效果，最后还是在Android官方Demo里找到的。

而本人对其案例中setPersistentDrawingCache方法的理解一直是在对其进行优化。

mContainer.setPersistentDrawingCache(ViewGroup.PERSISTENT_ANIMATION_CACHE);

并且在后续的自己开发APP中，甚至是拿了软著权准备上架的那几款APP相同情景下一直使用此方法。今天和大佬在另一篇文章中聊到性能消耗，于是测试了下setPersistentDrawingCache加与不加的性能消耗，结果发现貌似不加效果还好一点。

一、看看Demo中给出的注释

// Since we are caching large views, we want to keep their cache

//由于我们缓存的是大视图，我们希望保留它们的缓存

开始想着是动画的强度不够，加大了动画的强度，结果不加setPersistentDrawingCache还是好一点，于是去Android官方文档查看了下，才明白。

二、Android官方文档给出的介绍

此方法在APl级别28中已弃用，随着APl 11中硬件加速渲染的引入，视图绘图缓存在很大程度上已经过时了。在使用硬件加速时，中间缓存层基本上是不必要的，并且由于创建和更新该层的成本，很容易导致性能的净损失。在极少数情况下，缓存层是有用的，比如alpha动画。View.setLaverTvpe (int。android.araphics.Paint)通过硬件渲染处理这个问题。对于视图层次结构或单个视图的一小部分的软件渲染快照，建议从位图或图片创建一个Canvas，并在视图上调用View. draw(android.graphics.Canvas)。然而，这些软件渲染的用法是不鼓励的，并且与硬件渲染特性(如Config)存在兼容性问题。硬件位图，实时阴影，轮廓剪辑。对于Ul反馈报告或单元测试的屏幕截图，建议使用PixelCopy APl。

三、丢一个案例源码（此案例为官方Demo源码,根据个人修改了点效果）

代码比较简单就不解释了

1.3d动画类

public class Rotate3dAnimation extends Animation {

    private final float mFromDegrees;

    private final float mToDegrees;

    private final float mCenterX;

    private final float mCenterY;

    private final float mDepthZ;

    private final boolean mReverse;

    private Camera mCamera;



    public Rotate3dAnimation(float fromDegrees, float toDegrees,

                             float centerX, float centerY, float depthZ, boolean reverse) {

        mFromDegrees = fromDegrees;

        mToDegrees = toDegrees;

        mCenterX = centerX;

        mCenterY = centerY;

        mDepthZ = depthZ;

        mReverse = reverse;

    }


    @Override

    public void initialize(int width, int height, int parentWidth, int parentHeight) {

        super.initialize(width, height, parentWidth, parentHeight);

        mCamera = new Camera();

    }


    @Override

    protected void applyTransformation(float interpolatedTime, Transformation t) {

        final float fromDegrees = mFromDegrees;

        float degrees = fromDegrees + ((mToDegrees - fromDegrees) * interpolatedTime);


        final float centerX = mCenterX;

        final float centerY = mCenterY;

        final Camera camera = mCamera;


        final Matrix matrix = t.getMatrix();


        camera.save();

        if (mReverse) {

            camera.translate(0.0f, 0.0f, mDepthZ * interpolatedTime);

        } else {

            camera.translate(0.0f, 0.0f, mDepthZ * (1.0f - interpolatedTime));

        }

        camera.rotateY(degrees);

        camera.getMatrix(matrix);

        camera.restore();


        matrix.preTranslate(-centerX, -centerY);

        matrix.postTranslate(centerX, centerY);

    }

}

2.Activity类

public class Transition3d extends Activity implements
AdapterView.OnItemClickListener, View.OnClickListener {
private ListView mPhotosList;
private ViewGroup mContainer;
private ImageView mImageView;

//item-name
private static final String[] PHOTOS_NAMES = new String[] {
"百度关键词",
"微信公众号",
"微信小程序",
"个人网站",
"掘金",
"同id:计蒙不吃鱼"

    };
//item-img
private static final int[] PHOTOS_RESOURCES = new int[] {

            R.drawable.aaaa,

            R.drawable.aaaa1,

            R.drawable.aaaa1,

            R.drawable.aaaa,

            R.drawable.aaaa,

            R.drawable.aaaa


    };

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);


        setContentView(R.layout.animations_main_screen);


        mPhotosList = (ListView) findViewById(android.R.id.list);

        mImageView = (ImageView) findViewById(R.id.picture);

        mContainer = (ViewGroup) findViewById(R.id.container);

// 准备列表视图
final ArrayAdapter<String> adapter = new ArrayAdapter<>(this,

                android.R.layout.simple_list_item_1, PHOTOS_NAMES);

        mPhotosList.setAdapter(adapter);

        mPhotosList.setOnItemClickListener(this);
// 准备图片

        mImageView.setClickable(true);

        mImageView.setFocusable(true);

        mImageView.setOnClickListener(this);


//由于我们缓存的是大视图，我们希望在每个动画之间保持它们的缓存

        mContainer.setPersistentDrawingCache(ViewGroup.PERSISTENT_ANIMATION_CACHE);

    }

/**

     * 在容器视图上设置一个新的3D旋转。

     *

     * @param position 单击该项以显示图片，或单击-1以显示列表

     * @param start 旋转必须开始的起始角度

     * @param end •旋转的结束角度

     */
private void applyRotation(int position, float start, float end) {
//找到容器的中心
final float centerX = mContainer.getWidth() / 2.0f;
final float centerY = mContainer.getHeight() / 2.0f;

//使用提供的参数创建一个新的3D旋转
// 动画监听器用于触发网络动画
final Rotate3dAnimation rotation =
new Rotate3dAnimation(start, end, centerX, centerY, 310.0f, true);

        rotation.setDuration(500);

        rotation.setFillAfter(true);

        rotation.setInterpolator(new AccelerateInterpolator());

        rotation.setAnimationListener(new DisplayNextView(position));


        mContainer.startAnimation(rotation);

    }

public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
//预加载图像然后开始动画

        mImageView.setImageResource(PHOTOS_RESOURCES[position]);

        applyRotation(position, 0, 90);

    }

public void onClick(View v) {

        applyRotation(-1, 180, 90);

    }

/**

     这class收听动画前半部分的结尾部分。•当容器旋转90度，因此不可见时，它会发布一个新的动作，有效地交换视图。

     */
private final class DisplayNextView implements Animation.AnimationListener {
private final int mPosition;

private DisplayNextView(int position) {

            mPosition = position;

        }

public void onAnimationStart(Animation animation) {

        }

public void onAnimationEnd(Animation animation) {

            mContainer.post(new SwapViews(mPosition));

        }

public void onAnimationRepeat(Animation animation) {

        }

    }

/**

     这个类负责交换视图并启动第二个视图

     动画的一半。

     */
private final class SwapViews implements Runnable {
private final int mPosition;

public SwapViews(int position) {

            mPosition = position;

        }

public void run() {
final float centerX = mContainer.getWidth() / 2.0f;
final float centerY = mContainer.getHeight() / 2.0f;

            Rotate3dAnimation rotation;

if (mPosition > -1) {

                mPhotosList.setVisibility(View.GONE);

                mImageView.setVisibility(View.VISIBLE);

                mImageView.requestFocus();


                rotation = new Rotate3dAnimation(90, 180, centerX, centerY, 310.0f, false);

            } else {

                mImageView.setVisibility(View.GONE);

                mPhotosList.setVisibility(View.VISIBLE);

                mPhotosList.requestFocus();


                rotation = new Rotate3dAnimation(90, 0, centerX, centerY, 310.0f, false);

            }


            rotation.setDuration(500);

            rotation.setFillAfter(true);

            rotation.setInterpolator(new DecelerateInterpolator());


            mContainer.startAnimation(rotation);

        }

    }


}

3.布局文件

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">

<ListView
android:id="@android:id/list"
android:persistentDrawingCache="animation|scrolling"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layoutAnimation="@anim/layout_bottom_to_top_slide" />

<ImageView
android:id="@+id/picture"
android:scaleType="fitCenter"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:visibility="gone" />

</FrameLayout>

4.Listview的载入动画

layout_bottom_to_top_slide.xml

<layoutAnimation xmlns:android="http://schemas.android.com/apk/res/android"
android:delay="30%"
android:animationOrder="reverse"
android:animation="@anim/slide_right" />

slide_right.xml

<set xmlns:android="http://schemas.android.com/apk/res/android" android:interpolator="@android:anim/accelerate_interpolator">
<translate android:fromXDelta="-100%p" android:toXDelta="0"
android:duration="@android:integer/config_shortAnimTime" />
</set>

5.效果图

0

2021-09-01

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