android自带的TextView可以实现跑马灯效果，但是有很多的局限性；比如需要设置ellipsize=”marquee”，获取 focusable=”true”，设置singleLine=”true”，控件里的内容需要超过控件本身的长度，无法控制滚动速度和滚动暂停和继续滚动功能，各种限制导致用起来特别不顺手，几乎无法使用到生产环境中，在此背景下，需要自定义View实现跑马灯效果。
使用主要方法：自定义View重写onDraw方法，通过canvas.drawText()方法来显示文字，利用Handler不断地绘制文字，并控制文字开始绘制的X轴的位置，来实现连续滚动的效果。
实现步骤：
1、自定义view的class：
import android.annotation.SuppressLint;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.FontMetrics;
import android.graphics.Rect;
import android.os.Handler;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.View;
public class MarqueenView extends View {
/*
* 1、自定义View的属性 2、在View的构造方法中获得我们自定义的属性 [ 3、重写onMesure ] 4、重写onDraw
*/
/*
* 文本
*/
private String mTitleText;
/**
* 文本的颜色
*/
private int mTitleTextColor;
/**
* 文本的大小
*/
private int mTitleTextSize;
/**
* 绘制时控制文本绘制的范围
*/
private Rect mBound, usualBound;
// 画笔
private Paint mPaint;
private int spead = 15;
private int length = 3;
private int currentLength;
@SuppressLint("HandlerLeak")
private Handler handler = new Handler() {
@Override
public void handleMessage(android.os.Message msg) {
if (mBound.width() <= getWidth()) {
if (currentLength >= 120 + (getWidth() / length) * length) {
currentLength = length;
} else {
currentLength = currentLength + length;
}
} else {
if (currentLength >= (mBound.width() + 120)) {
currentLength = length;
} else {
currentLength = currentLength + length;
}
}
invalidate();
handler.sendEmptyMessageDelayed(0, spead);
};
};
public MarqueenView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
currentLength = length;
}
public MarqueenView(Context context) {
this(context, null);
}
public MarqueenView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomTitleView, defStyle, 0);
int n = a.getIndexCount();
for (int i = 0; i < n; i++) {
int attr = a.getIndex(i);
switch (attr) {
case R.styleable.CustomTitleView_titleText:
mTitleText = a.getString(attr);
break;
case R.styleable.CustomTitleView_titleTextColor:
mTitleTextColor = a.getColor(attr, Color.BLACK);
break;
case R.styleable.CustomTitleView_titleTextSize:
mTitleTextSize = a.getDimensionPixelSize(attr,
(int) TypedValue.applyDimension(PLEX_UNIT_SP, 16, getResources().getDisplayMetrics()));
break;
}
}
a.recycle();
mPaint = new Paint();
mPaint.setTextSize(mTitleTextSize);
mBound = new Rect();
usualBound = new Rect();
mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);
mPaint.getTextBounds("1234567890QqYy你好", 0, 16, usualBound);
}
/*
* EXACTLY：一般是设置了明确的值或者是MATCH_PARENT AT_MOST：表示子布局限制在一个最大值内，一般为WARP_CONTENT
* UNSPECIFIED：表示子布局想要多大就多大，很少使用
*/
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int widthSize = MeasureSpec.getSize(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int heightSize = MeasureSpec.getSize(heightMeasureSpec);
int width;
int height;
if (widthMode == MeasureSpec.EXACTLY) {
width = widthSize;
} else {
mPaint.setTextSize(mTitleTextSize);
mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);
float textWidth = mBound.width();// 字体宽度
// 控件padding
int desired = (int) (getPaddingLeft() + textWidth + getPaddingRight());
width = desired;
}
if (heightMode == MeasureSpec.EXACTLY) {
height = heightSize;
} else {
mPaint.setTextSize(mTitleTextSize);
mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);
float textHeight = mBound.height();
int desired = (int) (getPaddingTop() + textHeight + getPaddingBottom());
height = desired;
}
// setMeasuredDimension((width / length) * length, height);
setMeasuredDimension(width, height + usualBound.bottom);
}
@Override
protected void onDraw(Canvas canvas) {
mPaint.setColor(mTitleTextColor);
if (mBound.width() <= getWidth()) {
if (currentLength < mBound.width()) {
canvas.drawText(mTitleText, getPaddingLeft() - currentLength, getHeight() - usualBound.bottom, mPaint);
}
if (currentLength >= 120) {
canvas.drawText(mTitleText, getWidth() - currentLength + 120, getHeight() - usualBound.bottom, mPaint);
}
} else {
if (currentLength < mBound.width()) {
canvas.drawText(mTitleText, getPaddingLeft() - currentLength, getHeight() - usualBound.bottom, mPaint);
}
if (currentLength >= mBound.width() - getWidth() + 120) {
canvas.drawText(mTitleText, 120 - currentLength + mBound.width(), getHeight() - usualBound.bottom, mPaint);
}
}
}
public static int getFontHeight(Integer textSize) {
Paint paint = new Paint();
if (textSize != null) {
paint.setTextSize(textSize);
}
FontMetrics fm = paint.getFontMetrics();
return (int) (fm.descent - fm.ascent);
}
public void startScroll() {
handler.removeMessages(0);
handler.sendEmptyMessage(0);
}
public void stopScroll() {
handler.removeMessages(0);
currentLength = 0;
invalidate();
}
public void setScrollLength(int length) {
this.length = length;
currentLength = length;
}
public void setSpead(int spead) {
this.spead = spead;
}
public void setText(String msg) {
mTitleText = msg;
mBound = new Rect();
mPaint.getTextBounds(msg, 0, mTitleText.length(), mBound);
}
}
2、在values的attrs.xml文件中需要加入自定义的属性，字体大小、颜色、和初始内容，这里有待改进
3、在layout的布局文件中引用此控件
xmlns:custom="/apk/res/***这里写上自己的包名***"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
android:id="@+id/main_marquee_view"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
custom:titleText=" "
custom:titleTextColor="#666666"
custom:titleTextSize="14sp"/>
4、上面准备好后，就可以在activity中设置跑马灯并开始滚动了
mv = (MarqueenView) findViewById(R.id.main_marquee_view);
mv.stopScroll();
mv.setText("滚动内容");// 设置显示内容
//mv.setSpead(15);//滚动频率，默认15毫秒一次，数值太小会影响效率
//mv.setScrollLength(3);//默认每次左移3px，数值太大会有停顿感，数值太小滚动会变慢
mv.startScroll();
//记得在Ondestroy中停止滚动，方便回收
@Override
protected void onDestroy() {
try {
mv.stopScroll();
mv = null;
} catch (Throwable e) {
e.printStackTrace();
}
super.onDestroy();
}
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脚本之家。
