条码动画，移植到 ConstraintLayout答案

【问题标题】：Barcode animation, port to ConstraintLayout条码动画，移植到 ConstraintLayout
【发布时间】：2020-04-30 16:05:49
【问题描述】：

我发现此代码可以为红色条（条形码扫描仪）设置动画。然而，它是为具有固定尺寸的相对布局而设计的。我需要找到一个浮点值（相对于容器）而不是一个固定值。

这里是布局：

    <RelativeLayout
        android:id="@+id/trackBox"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_centerInParent="true"
        android:background="@drawable/background_border"
        app:layout_constraintBottom_toTopOf="@+id/guidelineBarcodeScanner04"
        app:layout_constraintEnd_toStartOf="@+id/guidelineBarcodeScanner01"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="@+id/guidelineBarcodeScanner02"
        app:layout_constraintTop_toTopOf="@+id/guidelineBarcodeScanner03"
        app:layout_constraintVertical_bias="0.0">

        <RelativeLayout
            android:id="@+id/midLine"
            android:layout_width="match_parent"
            android:layout_height="2dp"
            android:background="#FF0000" />

    </RelativeLayout>

其中midLine为红色条，trackBox为白色边框，条需要上下滑动。

这里是实际代码：

    public void slideToAbove() {

        Animation slide = new TranslateAnimation(Animation.RELATIVE_TO_SELF, 0.0f,
                Animation.RELATIVE_TO_SELF, 0.0f, Animation.RELATIVE_TO_SELF,
                0.0f, Animation.RELATIVE_TO_SELF, -300);
        slide.setDuration(2000);

        midLine.startAnimation(slide);

        slide.setAnimationListener(new Animation.AnimationListener() {
            @Override
            public void onAnimationStart(Animation animation) {

            }

            @Override
            public void onAnimationEnd(Animation animation) {
                midLine.clearAnimation();
                RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                        midLine.getWidth(), midLine.getHeight());
                lp.addRule(RelativeLayout.ALIGN_PARENT_TOP);
                midLine.setLayoutParams(lp);

                slideToDown();
            }

            @Override
            public void onAnimationRepeat(Animation animation) {

            }
        });

    }

    public void slideToDown() {

        Animation slide = new TranslateAnimation(Animation.RELATIVE_TO_SELF, 0.0f,
                Animation.RELATIVE_TO_SELF, 0.0f, Animation.RELATIVE_TO_SELF,
                0.0f, Animation.RELATIVE_TO_SELF, 300);
        slide.setDuration(2000);

        midLine.startAnimation(slide);

        slide.setAnimationListener(new Animation.AnimationListener() {
            @Override
            public void onAnimationStart(Animation animation) {

            }

            @Override
            public void onAnimationEnd(Animation animation) {
                midLine.clearAnimation();
                RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
                        midLine.getWidth(), midLine.getHeight());
                lp.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
                midLine.setLayoutParams(lp);

                slideToAbove();
            }

            @Override
            public void onAnimationRepeat(Animation animation) {

            }
        });

要查找的值实际上是固定的 300。框是受限制的（以屏幕的百分比表示），因此固定值根本不好。

我刚刚尝试了 trackBox.getHeight()，但不是这样。

刚试过：

        int i;
        i = trackBox.getBottom() - trackBox.getTop();

不工作...

【问题讨论】：

标签： java android animation layout

【解决方案1】：

ConstraintLayout 中终于有一款很棒的条码扫描器了！

首先你需要在 Res->anim 文件夹中创建 2 个动画文件：

barcode_to_above_anim.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- translating button from bottomt to top -->
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:shareInterpolator="false">
    <translate
        android:fromXDelta="0%" android:toXDelta="0%"
        android:fromYDelta="97%p" android:toYDelta="3%p"
        android:duration="2000"
        />
</set>

barcode_to_down_anim.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- translating button from top to bottom -->
<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:shareInterpolator="false">
    <translate
        android:fromXDelta="0%" android:toXDelta="0%"
        android:fromYDelta="3%p" android:toYDelta="97%p"
        android:duration="2000"
        />
</set>

那么你的活动应该和我的类似：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/linearLayoutBarcodeScanner"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#292929"
    android:screenOrientation="landscape">

    <SurfaceView
        android:id="@+id/surfaceViewBarcodeScanner"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintDimensionRatio="16:9"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <RelativeLayout
        android:id="@+id/trackBox"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_centerInParent="true"
        android:background="@drawable/background_border"
        android:paddingStart="2dp"
        android:paddingLeft="2dp"
        android:paddingEnd="2dp"
        android:paddingRight="2dp"
        app:layout_constraintBottom_toTopOf="@+id/guidelineBarcodeScanner04"
        app:layout_constraintEnd_toStartOf="@+id/guidelineBarcodeScanner01"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="@+id/guidelineBarcodeScanner02"
        app:layout_constraintTop_toTopOf="@+id/guidelineBarcodeScanner03"
        app:layout_constraintVertical_bias="0.0">

        <RelativeLayout
            android:id="@+id/midLine"
            android:layout_width="match_parent"
            android:layout_height="2dp"
            android:background="#FF0000" />

    </RelativeLayout>

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guidelineBarcodeScanner01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.8" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guidelineBarcodeScanner02"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.2" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guidelineBarcodeScanner03"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_percent="0.25" />

    <androidx.constraintlayout.widget.Guideline
        android:id="@+id/guidelineBarcodeScanner04"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_percent="0.75" />

</androidx.constraintlayout.widget.ConstraintLayout>

最后是您在 yourActivity.java 中需要的代码：声明

public class BarcodeScannerActivity extends Activity {

    RelativeLayout midLine, trackBox;
    //your other code

引用对象并开始第一个动画：

    private void init(){
        setContentView(R.layout.barcodescanner_activity);
        midLine = findViewById(R.id.midLine);
        trackBox = findViewById(R.id.trackBox);
        slideToDown();
    }

让我们制作动画吧！

    public void slideToAbove() {
        Animation slide= AnimationUtils.loadAnimation(getBaseContext(), R.anim.barcode_to_above_anim);
        midLine.startAnimation(slide);

        slide.setAnimationListener(new Animation.AnimationListener() {
            @Override
            public void onAnimationStart(Animation animation) {

            }

            @Override
            public void onAnimationEnd(Animation animation) {
                slideToDown();
            }

            @Override
            public void onAnimationRepeat(Animation animation) {

            }
        });
    }

    public void slideToDown() {

        Animation slide= AnimationUtils.loadAnimation(getBaseContext(), R.anim.barcode_to_down_anim);
        midLine.startAnimation(slide);

        slide.setAnimationListener(new Animation.AnimationListener() {
            @Override
            public void onAnimationStart(Animation animation) {

            }

            @Override
            public void onAnimationEnd(Animation animation) {
                slideToAbove();
            }

            @Override
            public void onAnimationRepeat(Animation animation) {

            }
        });

    }

我应该向你保证，这是一个非常酷的效果！希望能帮助大家制作出炫酷的条码扫描效果。

请注意：

    <translate
        android:fromXDelta="0%" android:toXDelta="0%"
        android:fromYDelta="97%p" android:toYDelta="3%p"
        android:duration="2000"
    />

%p 表示引用父视图（或容器或屏幕）的百分比。

【讨论】：