Android 上下滚动字幕实现

首先values文件夹下添加或创建attrs文件，如下：

<?xml version="1.0" encoding="utf-8"?>
<resources>


<!--//垂直滚动字幕-->
    <declare-styleable name="VerticalRollingTextView">
        <!--文字颜色-->
        <attr name="android:textColor"/>
        <!--文字大小-->
        <attr name="android:textSize"/>
        <!--滚动动画时长-->
        <attr name="android:duration"/>
        <!--两次动画之间的间隔-->
        <attr name="animInterval" format="integer"/>
    </declare-styleable>

</resources>

1、自定义上下滚动字幕textview、VerticalRollingTextView

/**
 * 作者：created by meixi
 * 邮箱：[email protected]
 * 日期：2018/8/30 10
 */

public class VerticalRollingTextView extends View {

    DataSetAdapter mDataSetAdapter;

    private final Paint mPaint;

    private int mCurrentIndex;
    private int mNextIndex;

    Rect bounds = new Rect();

    private float mCurrentOffsetY;

    private float mOrgOffsetY = -1;

    private final float mTextTopToAscentOffset;
    private float mOffset;

    private InternalAnimation mAnimation = new InternalAnimation();

    /*防止动画结束的回调触发以后动画继续进行出现的错乱问题*/
    private boolean mAnimationEnded;

    private boolean isRunning;
    /*动画时间*/
    private int mDuration = 1000;
    /*动画间隔*/
    private int mAnimInterval = 5000;

    public VerticalRollingTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaint.setColor(Color.BLACK);
        mPaint.setTypeface(Typeface.DEFAULT);

        parseAttrs(context, attrs);

        Paint.FontMetricsInt metricsInt = mPaint.getFontMetricsInt();
        mTextTopToAscentOffset = metricsInt.ascent - metricsInt.top;

        mAnimation.setDuration(mDuration);
    }

    private void parseAttrs(Context context, AttributeSet attrs) {
        float density = getResources().getDisplayMetrics().density;
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.VerticalRollingTextView);
        mPaint.setColor(typedArray.getColor(R.styleable.VerticalRollingTextView_android_textColor, Color.BLACK));
        mPaint.setTextSize(typedArray.getDimensionPixelOffset(R.styleable.VerticalRollingTextView_android_textSize, (int) (density * 14)));
        mDuration = typedArray.getInt(R.styleable.VerticalRollingTextView_android_duration, mDuration);
        mAnimInterval = typedArray.getInt(R.styleable.VerticalRollingTextView_animInterval, mAnimInterval);

        typedArray.recycle();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // 绘制文本
        if (mDataSetAdapter == null || mDataSetAdapter.isEmpty()) {
            return;
        }

        String text1 = mDataSetAdapter.getText(mCurrentIndex);
        String text2 = mDataSetAdapter.getText(mNextIndex);

        //只需要进行一次测量
        if (mOrgOffsetY == -1) {
            mPaint.getTextBounds(text1, 0, text1.length(), bounds);
            mOffset = (getHeight() + bounds.height()) * 0.5f;
            mOrgOffsetY = mCurrentOffsetY = mOffset - mTextTopToAscentOffset;
            mAnimation.updateValue(mOrgOffsetY, -2 * mTextTopToAscentOffset);
        }

        canvas.drawText(text1, 0, mCurrentOffsetY, mPaint);
        canvas.drawText(text2, 0, mCurrentOffsetY + mOffset + mTextTopToAscentOffset, mPaint);
    }

    public void setDataSetAdapter(DataSetAdapter dataSetAdapter) {
        mDataSetAdapter = dataSetAdapter;
        confirmNextIndex();
        invalidate();
    }

    /**
     * 开始转动,界面可见的时候调用
     */
    public void run() {
        if (isRunning) {
            return;
        }

        isRunning = true;
        mAnimation.updateValue(mCurrentOffsetY, -2 * mTextTopToAscentOffset);
        post(mRollingTask);
    }

    /**
     * @return true代表正在转动
     */
    public boolean isRunning() {
        return isRunning;
    }

    /**
     * 停止转动,界面不可见的时候调用
     */
    public void stop() {
        isRunning = false;
        removeCallbacks(mRollingTask);
    }

    Runnable mRollingTask = new Runnable() {
        @Override
        public void run() {
            mAnimationEnded = false;
            startAnimation(mAnimation);
            postDelayed(this, mAnimInterval);
        }
    };


    public void animationEnd() {
        //1.角标+1
        mCurrentIndex++;
        //2.计算出正确的角标
        mCurrentIndex = mCurrentIndex < mDataSetAdapter.getItemCount() ? mCurrentIndex : mCurrentIndex % mDataSetAdapter.getItemCount();
        //3.计算下一个待显示文字角标
        confirmNextIndex();
        //3.位置复位
        mCurrentOffsetY = mOrgOffsetY;
        mAnimationEnded = true;
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        removeCallbacks(mRollingTask);
        if (isRunning()) {
            mAnimation.cancel();
        }
    }

    /**
     * 计算第二个角标
     */
    private void confirmNextIndex() {
        //3.计算第二个角标
        mNextIndex = mCurrentIndex + 1;
        //4.计算出正确的第二个角标
        mNextIndex = mNextIndex < mDataSetAdapter.getItemCount() ? mNextIndex : 0;
    }

    /**
     * float估值器
     *
     * @param fraction
     * @param startValue
     * @param endValue
     * @return
     */
    float evaluate(float fraction, float startValue, float endValue) {
        return startValue + fraction * (endValue - startValue);
    }

    @Override
    public void setOnClickListener(OnClickListener l) {

    }

    public void setOnItemClickListener(final OnItemClickListener onItemClickListener) {
        super.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                onItemClickListener.onItemClick(VerticalRollingTextView.this, mCurrentIndex);
            }
        });
    }

    public interface OnItemClickListener {
        void onItemClick(VerticalRollingTextView view, int index);
    }

    class InternalAnimation extends Animation {

        float startValue;
        float endValue;

        @Override
        protected void applyTransformation(float interpolatedTime, Transformation t) {
            if (mAnimationEnded) return;

            mCurrentOffsetY = evaluate(interpolatedTime, startValue, endValue);
            if (mCurrentOffsetY == endValue) {
                try {
                    animationEnd();
                }catch (Exception e) {
                    e.printStackTrace();
                }

            }
            postInvalidate();
        }

        public void updateValue(float startValue, float endValue) {
            this.startValue = startValue;
            this.endValue = endValue;
        }

    }

}

2、layout.xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">



    <com.administrator.tests.VerticalRollingTextView
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:background="@color/numtext"
        android:textColor="@color/colorAccent"
        android:id="@+id/myvtext"/>

</LinearLayout>

3、activity调用自定义textview赋值

VerticalRollingTextView  verticalRollingTextView = (VerticalRollingTextView)findViewById(R.id.myvtext);
 TestEntity testEntity = new TestEntity();
 testEntity.setHttps("baidu.com");
 testEntity.setTitle("百度。com");
 TestEntity testEntity1 = new TestEntity();
 testEntity1.setTitle("谷歌。com");
 testEntity1.setHttps("guge.com");

 testEntities.add(testEntity);
 testEntities.add(testEntity1);

verticalRollingTextView.setDataSetAdapter(new DataSetAdapter<TestEntity>(testEntities) {
    @Override
    protected String text(TestEntity s) {
        return s.getTitle();
    }
});
verticalRollingTextView.run();
verticalRollingTextView.setOnItemClickListener(new VerticalRollingTextView.OnItemClickListener() {
    @Override
    public void onItemClick(VerticalRollingTextView view, int index) {//点击链接
        String url = testEntities.get(index).getHttps();
            Toast.makeText(MainActivity.this,url,Toast.LENGTH_LONG).show();
    }
});