android自定义View实现跑马灯效果

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(TypedValue.COMPLEX_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

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

 <attr name="titleText" format="string" />
 <attr name="titleTextColor" format="color" />
 <attr name="titleTextSize" format="dimension" />

 <declare-styleable name="CustomTitleView">
  <attr name="titleText" />
  <attr name="titleTextColor" />
  <attr name="titleTextSize" />
 </declare-styleable>
</resources>

3、在layout的布局文件中引用此控件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:custom="http://schemas.android.com/apk/res/***这里写上自己的包名***"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical" >

 <com.example.MarqueenView
 android:id="@+id/main_marquee_view"
 android:layout_width="fill_parent"
 android:layout_height="wrap_content"
 custom:titleText=" "
 custom:titleTextColor="#666666"
 custom:titleTextSize="14sp"/>
 </LinearLayout>

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我们。