Android跑马灯MarqueeView源码解析

跑马灯效果，大家可以去原作者页面浏览

下面看自定义控件的代码

public class MarqueeView extends ViewFlipper {

 private Context mContext;
 private List<String> 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<String> 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<String> getNotices() {
  return notices;
 }

 public void setNotices(List<String> 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<String> 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"

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持呐喊教程。