MarqueeView源码简单分析笔记

跑马灯效果，大家可以去原作者浏览https://github.com/sfsheng0322/MarqueeView
下面看自定义控件的代码

public class MarqueeView extends ViewFlipper {

    private Context mContext;
    private List notices;
    private boolean isSetAnimDuration = false;
    private OnItemClickListener onItemClickListener;

    private int interval = 2000;
    private int animDuration = 500;
    private int textSize = 14;
    private int textColor = 0xffffffff;

    private int gravity = Gravity.LEFT | Gravity.CENTER_VERTICAL;
    private static final int TEXT_GRAVITY_LEFT = 0, TEXT_GRAVITY_CENTER = 1, TEXT_GRAVITY_RIGHT = 2;

    public MarqueeView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs, 0);
    }

    private void init(Context context, AttributeSet attrs, int defStyleAttr) {
        this.mContext = context;
        if (notices == null) {
            notices = new ArrayList<>();
        }

        TypedArray typedArray = getContext().obtainStyledAttributes(attrs, R.styleable.MarqueeViewStyle, defStyleAttr, 0);
        interval = typedArray.getInteger(R.styleable.MarqueeViewStyle_mvInterval, interval);
        isSetAnimDuration = typedArray.hasValue(R.styleable.MarqueeViewStyle_mvAnimDuration);
        animDuration = typedArray.getInteger(R.styleable.MarqueeViewStyle_mvAnimDuration, animDuration);
        if (typedArray.hasValue(R.styleable.MarqueeViewStyle_mvTextSize)) {
            textSize = (int) typedArray.getDimension(R.styleable.MarqueeViewStyle_mvTextSize, textSize);
            textSize = DisplayUtil.px2sp(mContext, textSize);
        }
        textColor = typedArray.getColor(R.styleable.MarqueeViewStyle_mvTextColor, textColor);
        int gravityType = typedArray.getInt(R.styleable.MarqueeViewStyle_mvGravity, TEXT_GRAVITY_LEFT);
        switch (gravityType) {
            case TEXT_GRAVITY_CENTER:
                gravity = Gravity.CENTER;
                break;
            case TEXT_GRAVITY_RIGHT:
                gravity = Gravity.RIGHT | Gravity.CENTER_VERTICAL;
                break;
        }
        typedArray.recycle();

        setFlipInterval(interval);

        Animation animIn = AnimationUtils.loadAnimation(mContext, R.anim.anim_marquee_in);
        if (isSetAnimDuration) animIn.setDuration(animDuration);
        setInAnimation(animIn);

        Animation animOut = AnimationUtils.loadAnimation(mContext, R.anim.anim_marquee_out);
        if (isSetAnimDuration) animOut.setDuration(animDuration);
        setOutAnimation(animOut);
    }

    // 根据公告字符串启动轮播
    public void startWithText(final String notice) {
        if (TextUtils.isEmpty(notice)) return;
        getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                getViewTreeObserver().removeGlobalOnLayoutListener(this);
                startWithFixedWidth(notice, getWidth());
            }
        });
    }

    // 根据公告字符串列表启动轮播
    public void startWithList(List notices) {
        setNotices(notices);
        start();
    }

    // 根据宽度和公告字符串启动轮播
    private void startWithFixedWidth(String notice, int width) {
        int noticeLength = notice.length();
        int dpW = DisplayUtil.px2dip(mContext, width);
        int limit = dpW / textSize;
        if (dpW == 0) {
            throw new RuntimeException("Please set MarqueeView width !");
        }

        if (noticeLength <= limit) {
            notices.add(notice);
        } else {
            int size = noticeLength / limit + (noticeLength % limit != 0 ? 1 : 0);
            for (int i = 0; i < size; i++) {
                int startIndex = i * limit;
                int endIndex = ((i + 1) * limit >= noticeLength ? noticeLength : (i + 1) * limit);
                notices.add(notice.substring(startIndex, endIndex));
            }
        }
        start();
    }

    // 启动轮播
    public boolean start() {
        if (notices == null || notices.size() == 0) return false;
        removeAllViews();

        for (int i = 0; i < notices.size(); i++) {
            final TextView textView = createTextView(notices.get(i), i);
            final int finalI = i;
            textView.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (onItemClickListener != null) {
                        onItemClickListener.onItemClick(finalI, textView);
                    }
                }
            });
            addView(textView);
        }

        if (notices.size() > 1) {
            startFlipping();
        }
        return true;
    }

    // 创建ViewFlipper下的TextView
    private TextView createTextView(String text, int position) {
        TextView tv = new TextView(mContext);
        tv.setGravity(gravity);
        tv.setText(text);
        tv.setTextColor(textColor);
        tv.setTextSize(textSize);
        tv.setTag(position);
        return tv;
    }

    public int getPosition() {
        return (int) getCurrentView().getTag();
    }

    public List getNotices() {
        return notices;
    }

    public void setNotices(List notices) {
        this.notices = notices;
    }

    public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    public interface OnItemClickListener {
        void onItemClick(int position, TextView textView);
    }

}

跑马灯view是继承ViewFlipper，可以看到他的结构体

其实ViewFlipper工作机制很简单，如上图，就是将添加到ViewFlipper中的子View按照顺序定时的显示是其中一个子View，其他的子View设置为Gone状态

private Context mContext;
    private List notices;
    private boolean isSetAnimDuration = false;
    private OnItemClickListener onItemClickListener;

    private int interval = 2000;
    private int animDuration = 500;
    private int textSize = 14;
    private int textColor = 0xffffffff;

    private int gravity = Gravity.LEFT | Gravity.CENTER_VERTICAL;
    private static final int TEXT_GRAVITY_LEFT = 0, TEXT_GRAVITY_CENTER = 1, TEXT_GRAVITY_RIGHT = 2;

看出view的一些属性，上下文，集合，是否动画延迟，点击事件，跑马灯的时间间隔，动画延迟时间，字体大小颜色，设置位置在靠左垂直中间对齐，文字的位置常量。

修改MarqueeView的构造方法，我们可以在右键generate快速生成。

<declare-styleable name="MarqueeViewStyle">
        <attr name="mvInterval" format="integer|reference"/>
        <attr name="mvAnimDuration" format="integer|reference"/>
        <attr name="mvTextSize" format="dimension|reference"/>
        <attr name="mvTextColor" format="color|reference"/>
        <attr name="mvGravity">
            <enum name="left" value="0"/>
            <enum name="center" value="1"/>
            <enum name="right" value="2"/>
        attr>
    declare-styleable>

TypedArray typedArray = getContext().obtainStyledAttributes(attrs, R.styleable.MarqueeViewStyle, defStyleAttr, 0);

首先获取属性集合，获取一个mv的间隔，默认值2000

 isSetAnimDuration = typedArray.hasValue(R.styleable.MarqueeViewStyle_mvAnimDuration);

是否设置动画时间的延迟

 if (typedArray.hasValue(R.styleable.MarqueeViewStyle_mvTextSize)) {
            textSize = (int) typedArray.getDimension(R.styleable.MarqueeViewStyle_mvTextSize, textSize);
            textSize = DisplayUtil.px2sp(mContext, textSize);
        }

假如设置有自定义文字大小，就获取然后px转成sp
获取控件位置，自由设置
在后面要回收

  typedArray.recycle();

setFlipInterval(interval);设置滚屏间隔，单位毫秒

 Animation animIn = AnimationUtils.loadAnimation(mContext, R.anim.anim_marquee_in);
        if (isSetAnimDuration) animIn.setDuration(animDuration);
        setInAnimation(animIn);

        Animation animOut = AnimationUtils.loadAnimation(mContext, R.anim.anim_marquee_out);
        if (isSetAnimDuration) animOut.setDuration(animDuration);
        setOutAnimation(animOut);

一进一出的动画效果

// 根据公告字符串启动轮播
public void startWithText(final String notice)
暴露个公共方法，里面有测量view的getViewTreeObserver方法，里面内部类调用了startWithFixedWidth(notice, getWidth());方法

 // 根据宽度和公告字符串启动轮播
    private void startWithFixedWidth(String notice, int width) {
        int noticeLength = notice.length();
        int dpW = DisplayUtil.px2dip(mContext, width);
        int limit = dpW / textSize;
        if (dpW == 0) {
            throw new RuntimeException("Please set MarqueeView width !");
        }

        if (noticeLength <= limit) {
            notices.add(notice);
        } else {
            int size = noticeLength / limit + (noticeLength % limit != 0 ? 1 : 0);
            for (int i = 0; i < size; i++) {
                int startIndex = i * limit;
                int endIndex = ((i + 1) * limit >= noticeLength ? noticeLength : (i + 1) * limit);
                notices.add(notice.substring(startIndex, endIndex));
            }
        }
        start();
    }

转换得到一个dp的宽度，限制字数长度大小。假如字符串小于直接add。假如过长取余得到行数。然后循环，获取那行的头尾，末尾假如2行字数还是比总体长度大就取总体长度，假如小于总体长度，就取那行的末尾下表。
然后开始播放

 // 启动轮播
    public boolean start() {
        if (notices == null || notices.size() == 0) return false;
        removeAllViews();

        for (int i = 0; i < notices.size(); i++) {
            final TextView textView = createTextView(notices.get(i), i);
            final int finalI = i;
            textView.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (onItemClickListener != null) {
                        onItemClickListener.onItemClick(finalI, textView);
                    }
                }
            });
            addView(textView);
        }

        if (notices.size() > 1) {
            startFlipping();
        }
        return true;
    }

创建部署每行的tv

 // 创建ViewFlipper下的TextView
    private TextView createTextView(String text, int position) {
        TextView tv = new TextView(mContext);
        tv.setGravity(gravity);
        tv.setText(text);
        tv.setTextColor(textColor);
        tv.setTextSize(textSize);
        tv.setTag(position);
        return tv;
    }

然后将所有的textview add起来，然后开始播放。后面就是做个点击回调，然后set get这个公告的集合。
最后不要忘了在布局顶层加入

    xmlns:app="http://schemas.android.com/apk/res-auto"