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<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"