Android自定义View实现竖直跑马灯效果案例解析

首先给出跑马灯效果图

 

中间的色块是因为视频转成gif造成的失真，自动忽略哈。
大家知道，横向的跑马灯android自带的textview就可以实现，详情请百度【android跑马灯效果】。但是竖直的跑马灯效果原生android是不支持的。网上也有很多网友实现了自定义的效果，但是我一贯是不喜欢看别人的代码，所以这篇博客的思路完全是我自己的想法哈。 

首先，我们需要给自定义的控件梳理一下格局，如下图所示： 

1、首先我们将控件分为三个区块，上面绿色部分为消失不可见的块，中间黑色部分为可见区域，下面红色部分为欲出现不可见区域。蓝色的线代表的是整个控件的上线和下线。 
2、首先我们只给出两个文字块在内存中，分别是黑色部分的可见块和红色部分的欲出现块。 
3、求出这些块的宽度、高度与中心点的坐标值。 
4、滚动时，动态地改变每个块的中心点y坐标，使之向上平移。 
5、当平移结束后，可见块位于欲消失的不可见块，欲出现的可见块位于可见区域的文字块。此时将欲消失的文字块移除list，并重新设置后一个索引的text和重心坐标值，重新加入list中，刷新。 
6、用一个handler来处理动画的间隔时间。用属性动画valueanimator来实现平移的动画效果。 

下面开始代码讲解，首先是用链式设置法设置一些常规属性： 

<span style="font-size:14px;"> public verticalmarqueeview color(int color){
  this.color = color;
  return this;
 }
 
 public verticalmarqueeview textsize(int textsize){
  this.textsize = textsize;
  return this;
 }
 
 public verticalmarqueeview datas(string[] datas){
  this.datas = datas;
  return this;
 }
 
 public void commit(){
  if(this.datas == null || datas.length == 0){
   log.e("verticalmarqueeview", "the datas's length is illegal");
   throw new illegalstateexception("may be not invoke the method named datas(string[])");
  }
  paint.setcolor(color);
  paint.settextsize(textsize);
 }</span>

最后一定要调用commit方法进行提交，通过代码可以看出来这里除了有排空措施，还有最重要的一步：设置字体的大小。
然后我抽象出一个文字块的bean类： 

 public class textblock {
  private int width;
  private int height;
  private string text;
  private int drawx;
  private int drawy;
  private paint paint;
  private int position;
  
  public textblock(int width, int height, paint paint){
   this.width = width;
   this.height = height;
   this.paint = paint;
  }
  
  public void reset(int centery){
   reset(text, centerx, centery, position);
  }
  
  public void reset(string text, int centery){
   reset(text, centerx, centery, position);
  }
  
  public void reset(string text, int centery, int position){
   reset(text, centerx, centery, position);
  }
  
  public void reset(string text, int centerx, int centery, int position){
   this.text = text;
   this.position = position;
   int measurewidth = (int)paint.measuretext(text);
   drawx = (width - measurewidth) / 2;
   fontmetrics metrics = paint.getfontmetrics();
   drawy = (int)(centery + (metrics.bottom - metrics.top) / 2 - metrics.bottom);
  }
  
  public int getposition(){
   return position;
  }
  
  public void draw(canvas canvas){
   canvas.drawtext(text, drawx, drawy, paint);
  }
 }

这个bean类，最重要的方法就是几个重载的reset方法，通过改变centery的值，来动态得改变绘制文字的起点实现居中绘制。关于文字的居中绘制请参考百度【android canvas 居中绘制文本】。
然后是重写onmeasure方法 

 @override
 protected void onmeasure(int widthmeasurespec, int heightmeasurespec){
  super.onmeasure(widthmeasurespec, heightmeasurespec);
  if(this.datas == null || this.datas.length == 0){
   log.e("verticalmarqueeview", "the datas's length is illegal");
   return;
  }
  width = measurespec.getsize(widthmeasurespec) - getpaddingleft() - getpaddingright();
  height = measurespec.getsize(heightmeasurespec) - getpaddingtop() - getpaddingbottom();
  centerx = width / 2;
  centery = height / 2;
  blocks.clear();
  //添加显示区域的文字块
  textblock block1 = new textblock(width, height, paint);
  block1.reset(datas[0], centerx, centery, 0);
  blocks.add(block1);
  if(datas.length > 1){   
   textblock block2 = new textblock(width, height, paint);
   block2.reset(datas[1], centerx, centery + height, 1);
   blocks.add(block2);
  }
 }

在这个方法中，首先进行非空判断以免出现致命逻辑错误。然后得到整个控件的宽高和重心坐标。然后实例化两个文字块textblock，第一个文字块通过reset设置中点y坐标为整个控件的中点y坐标，第二个文字块通过reset设置中点y坐标为centery+height，意思就是置于下一个文字块的不可见区域内。
 然后是ondraw方法，这个方法非常简单，已经将业务逻辑转交给textblock的draw方法了。 

 @override
 protected void ondraw(canvas canvas){
  for(int i = 0; i < blocks.size(); i++){
   blocks.get(i).draw(canvas);
  }
 }

最关键的就是滚动效果的实现了，首先我们给出两个方法，开始滚动和结束滚动。 

 public void startscroll(){
  isstopscroll = false;
  if(datas == null || datas.length == 0 || datas.length == 1){
   log.e("verticalmarqueeview", "the datas's length is illegal");
   return;
  }
  if(!isstopscroll){
   handler.postdelayed(new runnable(){
    
    @override
    public void run(){
     scroll();
     if(!isstopscroll){
      handler.postdelayed(this, duration_scroll);
     }
    }
   }, duration_scroll);
  }
 }
 
 public void stopscroll(){
  this.isstopscroll = true;
 }

原理很简单，首先给出一个boolean标志isstopscroll。然后用handler的postdelayed方法进行循环延迟得调用scroll方法进行滚动。接下来给出全文最重要的方法，scroll方法。 

private void scroll(){
  valueanimator animator = valueanimator.ofpropertyvaluesholder(propertyvaluesholder.ofint("scrolly", centery, centery - height));
  animator.setduration(duration_animator);
  animator.addupdatelistener(new animatorupdatelistener(){
   
   @override
   public void onanimationupdate(valueanimator animation){
    int scrolly = (int)animation.getanimatedvalue("scrolly");
    blocks.get(0).reset(scrolly);
    blocks.get(1).reset(scrolly + height);
    invalidate();
   }
  });
  animator.addlistener(new animatorlistener(){
   
   @override
   public void onanimationstart(animator animation){
   }
   
   @override
   public void onanimationrepeat(animator animation){
   }
   
   @override
   public void onanimationend(animator animation){
    //移除第一块
    int position = blocks.get(1).getposition();
    textblock textblock = blocks.remove(0);
    //最后一个
    if(position == datas.length - 1){
     position = 0;
    }else{
     position ++;
    }
    textblock.reset(datas[position], centery + height, position);
    blocks.add(textblock);
    invalidate();
   }
   
   @override
   public void onanimationcancel(animator animation){
   }
  });
  animator.start();
 }

首先采用valueanimator类进行属性动画，开始值为控件的中点y坐标，结束值为centery-height，意味着要从下往上移动一个文字块的距离。然后在动画更新回调方法中，进行对文字块的reset方法。当动画结束后，得到第二个文字块的position值，然后移除第一个文字块，重新reset这个文字块的索引值，再加入到list的容器中。如此循坏。
最后给一个get方法返回position吧。 

 public int getcurrentposition(){
  if(datas == null || datas.length == 0){
   return -1;
  }
  if(datas.length == 1 && blocks.size() == 1){
   return 0;
  }
  return blocks.get(0).getposition();
 }

上述就将这个自定义控件的所有代码都呈现出来了，考虑到比较零散，这里讲所有代码都打印出来： 

/**
 * @filename: verticalmarqueeview.java
 * @author 
 * @description:
 * @date 2016年7月13日 上午9:32:27
 * @copyright cnp corporation
 */
package cc.wxf.component;

import android.animation.animator;
import android.animation.animator.animatorlistener;
import android.animation.propertyvaluesholder;
import android.animation.valueanimator;
import android.animation.valueanimator.animatorupdatelistener;
import android.content.context;
import android.graphics.canvas;
import android.graphics.color;
import android.graphics.paint;
import android.graphics.paint.fontmetrics;
import android.os.handler;
import android.util.attributeset;
import android.util.log;
import android.view.view;

import java.util.arraylist;
import java.util.list;

public class verticalmarqueeview extends view{
 
 public static final int duration_scroll = 3000;
 public static final int duration_animator = 1000;
 private int color = color.black;
 private int textsize = 30;
 private string[] datas = null;
 
 private int width;
 private int height;
 private int centerx;
 private int centery;
 
 private list<textblock> blocks = new arraylist<textblock>(2);
 private paint paint = new paint(paint.anti_alias_flag);
 private handler handler = new handler();
 private boolean isstopscroll = false;
 
 public verticalmarqueeview(context context, attributeset attrs, int defstyleattr){
  super(context, attrs, defstyleattr);
 }

 public verticalmarqueeview(context context, attributeset attrs){
  super(context, attrs);
 }

 public verticalmarqueeview(context context){
  super(context);
 }
 
 public verticalmarqueeview color(int color){
  this.color = color;
  return this;
 }
 
 public verticalmarqueeview textsize(int textsize){
  this.textsize = textsize;
  return this;
 }
 
 public verticalmarqueeview datas(string[] datas){
  this.datas = datas;
  return this;
 }
 
 public void commit(){
  if(this.datas == null || datas.length == 0){
   log.e("verticalmarqueeview", "the datas's length is illegal");
   throw new illegalstateexception("may be not invoke the method named datas(string[])");
  }
  paint.setcolor(color);
  paint.settextsize(textsize);
 }

 @override
 protected void onmeasure(int widthmeasurespec, int heightmeasurespec){
  super.onmeasure(widthmeasurespec, heightmeasurespec);
  if(this.datas == null || this.datas.length == 0){
   log.e("verticalmarqueeview", "the datas's length is illegal");
   return;
  }
  width = measurespec.getsize(widthmeasurespec) - getpaddingleft() - getpaddingright();
  height = measurespec.getsize(heightmeasurespec) - getpaddingtop() - getpaddingbottom();
  centerx = width / 2;
  centery = height / 2;
  blocks.clear();
  //添加显示区域的文字块
  textblock block1 = new textblock(width, height, paint);
  block1.reset(datas[0], centerx, centery, 0);
  blocks.add(block1);
  if(datas.length > 1){   
   textblock block2 = new textblock(width, height, paint);
   block2.reset(datas[1], centerx, centery + height, 1);
   blocks.add(block2);
  }
 }
 
 @override
 protected void ondraw(canvas canvas){
  for(int i = 0; i < blocks.size(); i++){
   blocks.get(i).draw(canvas);
  }
 }
 
 public void startscroll(){
  isstopscroll = false;
  if(datas == null || datas.length == 0 || datas.length == 1){
   log.e("verticalmarqueeview", "the datas's length is illegal");
   return;
  }
  if(!isstopscroll){
   handler.postdelayed(new runnable(){
    
    @override
    public void run(){
     scroll();
     if(!isstopscroll){
      handler.postdelayed(this, duration_scroll);
     }
    }
   }, duration_scroll);
  }
 }
 
 public void stopscroll(){
  this.isstopscroll = true;
 }
 
 private void scroll(){
  valueanimator animator = valueanimator.ofpropertyvaluesholder(propertyvaluesholder.ofint("scrolly", centery, centery - height));
  animator.setduration(duration_animator);
  animator.addupdatelistener(new animatorupdatelistener(){
   
   @override
   public void onanimationupdate(valueanimator animation){
    int scrolly = (int)animation.getanimatedvalue("scrolly");
    blocks.get(0).reset(scrolly);
    blocks.get(1).reset(scrolly + height);
    invalidate();
   }
  });
  animator.addlistener(new animatorlistener(){
   
   @override
   public void onanimationstart(animator animation){
   }
   
   @override
   public void onanimationrepeat(animator animation){
   }
   
   @override
   public void onanimationend(animator animation){
    //移除第一块
    int position = blocks.get(1).getposition();
    textblock textblock = blocks.remove(0);
    //最后一个
    if(position == datas.length - 1){
     position = 0;
    }else{
     position ++;
    }
    textblock.reset(datas[position], centery + height, position);
    blocks.add(textblock);
    invalidate();
   }
   
   @override
   public void onanimationcancel(animator animation){
   }
  });
  animator.start();
 }
 
 public int getcurrentposition(){
  if(datas == null || datas.length == 0){
   return -1;
  }
  if(datas.length == 1 && blocks.size() == 1){
   return 0;
  }
  return blocks.get(0).getposition();
 }
 
 public class textblock {
  private int width;
  private int height;
  private string text;
  private int drawx;
  private int drawy;
  private paint paint;
  private int position;
  
  public textblock(int width, int height, paint paint){
   this.width = width;
   this.height = height;
   this.paint = paint;
  }
  
  public void reset(int centery){
   reset(text, centerx, centery, position);
  }
  
  public void reset(string text, int centery){
   reset(text, centerx, centery, position);
  }
  
  public void reset(string text, int centery, int position){
   reset(text, centerx, centery, position);
  }
  
  public void reset(string text, int centerx, int centery, int position){
   this.text = text;
   this.position = position;
   int measurewidth = (int)paint.measuretext(text);
   drawx = (width - measurewidth) / 2;
   fontmetrics metrics = paint.getfontmetrics();
   drawy = (int)(centery + (metrics.bottom - metrics.top) / 2 - metrics.bottom);
  }
  
  public int getposition(){
   return position;
  }
  
  public void draw(canvas canvas){
   canvas.drawtext(text, drawx, drawy, paint);
  }
 }
 
}

最后给出使用的方法，很简单。

package cc.wxf.androiddemo;

import android.app.activity;
import android.content.context;
import android.os.bundle;
import android.view.view;
import android.widget.toast;

import cc.wxf.component.verticalmarqueeview;

public class mainactivity extends activity {

 private verticalmarqueeview vmview;

 @override
 public void oncreate(bundle savedinstancestate) {
  super.oncreate(savedinstancestate);
  setcontentview(r.layout.activity_main);

  vmview = (verticalmarqueeview)findviewbyid(r.id.vmview);
  string[] datas = new string[]{
    "南海又开始动荡了","菲律宾到处都在肇事","这次为了一张审判废纸，菲律宾投入了多少成本呢","测试数据4","测试数据5为了长度不一样","就把这条当做测试数据吧"
  };
  vmview.color(getresources().getcolor(android.r.color.black))
    .textsize(sp2px(this, 15))
    .datas(datas).commit();
  vmview.startscroll();
  vmview.setonclicklistener(new view.onclicklistener(){

   @override
   public void onclick(view v){
    toast.maketext(mainactivity.this, "当前的索引为：" + vmview.getcurrentposition(), toast.length_short).show();
   }
  });
 }

 private int sp2px(context context, int sp){
  float density = context.getresources().getdisplaymetrics().scaleddensity;
  return (int) (sp * density + 0.5f);
 }

 @override
 protected void ondestroy() {
  super.ondestroy();
  //必须要调用，否则内存中会一直无限循环
  vmview.stopscroll();
 }
}

demo就不提供了，自定义view就只有上面一个文件。

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。