Android自定义View实现竖直跑马灯效果案例解析

本文实例为大家分享了Android实现竖直跑马灯效果的具体代码，供大家参考，具体内容如下

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小牛知识库。