Android自定义View实现竖直跑马灯效果案例解析

2019-12-12 05:59:00

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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武林网。

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