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Android自定義View實(shí)現(xiàn)豎直跑馬燈效果案例解析

 更新時(shí)間：2016年07月14日 11:47:08   作者：鳳求凰丶  
這篇文章主要為大家詳細(xì)介紹了Android自定義View實(shí)現(xiàn)豎直跑馬燈效果，文中示例代碼介紹的非常詳細(xì)，具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下

本文實(shí)例為大家分享了Android實(shí)現(xiàn)豎直跑馬燈效果的具體代碼，供大家參考，具體內(nèi)容如下

首先給出跑馬燈效果圖

中間的色塊是因?yàn)橐曨l轉(zhuǎn)成GIF造成的失真，自動(dòng)忽略哈。
大家知道，橫向的跑馬燈android自帶的TextView就可以實(shí)現(xiàn)，詳情請(qǐng)百度【Android跑馬燈效果】。但是豎直的跑馬燈效果原生Android是不支持的。網(wǎng)上也有很多網(wǎng)友實(shí)現(xiàn)了自定義的效果，但是我一貫是不喜歡看別人的代碼，所以這篇博客的思路完全是我自己的想法哈。 

首先，我們需要給自定義的控件梳理一下格局，如下圖所示： 

1、首先我們將控件分為三個(gè)區(qū)塊，上面綠色部分為消失不可見的塊，中間黑色部分為可見區(qū)域，下面紅色部分為欲出現(xiàn)不可見區(qū)域。藍(lán)色的線代表的是整個(gè)控件的上線和下線。 
2、首先我們只給出兩個(gè)文字塊在內(nèi)存中，分別是黑色部分的可見塊和紅色部分的欲出現(xiàn)塊。 
3、求出這些塊的寬度、高度與中心點(diǎn)的坐標(biāo)值。 
4、滾動(dòng)時(shí)，動(dòng)態(tài)地改變每個(gè)塊的中心點(diǎn)y坐標(biāo)，使之向上平移。 
5、當(dāng)平移結(jié)束后，可見塊位于欲消失的不可見塊，欲出現(xiàn)的可見塊位于可見區(qū)域的文字塊。此時(shí)將欲消失的文字塊移除List，并重新設(shè)置后一個(gè)索引的Text和重心坐標(biāo)值，重新加入List中，刷新。 
6、用一個(gè)Handler來(lái)處理動(dòng)畫的間隔時(shí)間。用屬性動(dòng)畫ValueAnimator來(lái)實(shí)現(xiàn)平移的動(dòng)畫效果。 

下面開始代碼講解，首先是用鏈?zhǔn)皆O(shè)置法設(shè)置一些常規(guī)屬性： 

<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>

最后一定要調(diào)用commit方法進(jìn)行提交，通過代碼可以看出來(lái)這里除了有排空措施，還有最重要的一步：設(shè)置字體的大小。
然后我抽象出一個(gè)文字塊的bean類： 

 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);
 }
 }

這個(gè)bean類，最重要的方法就是幾個(gè)重載的reset方法，通過改變centerY的值，來(lái)動(dòng)態(tài)得改變繪制文字的起點(diǎn)實(shí)現(xiàn)居中繪制。關(guān)于文字的居中繪制請(qǐng)參考百度【android canvas 居中繪制文本】。
然后是重寫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();
 //添加顯示區(qū)域的文字塊
 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);
 }
 }

在這個(gè)方法中，首先進(jìn)行非空判斷以免出現(xiàn)致命邏輯錯(cuò)誤。然后得到整個(gè)控件的寬高和重心坐標(biāo)。然后實(shí)例化兩個(gè)文字塊TextBlock，第一個(gè)文字塊通過reset設(shè)置中點(diǎn)y坐標(biāo)為整個(gè)控件的中點(diǎn)y坐標(biāo)，第二個(gè)文字塊通過reset設(shè)置中點(diǎn)y坐標(biāo)為centerY+height，意思就是置于下一個(gè)文字塊的不可見區(qū)域內(nèi)。
 然后是onDraw方法，這個(gè)方法非常簡(jiǎn)單，已經(jīng)將業(yè)務(wù)邏輯轉(zhuǎn)交給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);
 }
 }

最關(guān)鍵的就是滾動(dòng)效果的實(shí)現(xiàn)了，首先我們給出兩個(gè)方法，開始滾動(dòng)和結(jié)束滾動(dòng)。 

 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;
 }

原理很簡(jiǎn)單，首先給出一個(gè)boolean標(biāo)志isStopScroll。然后用Handler的postDelayed方法進(jìn)行循環(huán)延遲得調(diào)用scroll方法進(jìn)行滾動(dòng)。接下來(lái)給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){
 //移除第一塊
 int position = blocks.get(1).getPosition();
 TextBlock textBlock = blocks.remove(0);
 //最后一個(gè)
 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類進(jìn)行屬性動(dòng)畫，開始值為控件的中點(diǎn)y坐標(biāo)，結(jié)束值為centerY-height，意味著要從下往上移動(dòng)一個(gè)文字塊的距離。然后在動(dòng)畫更新回調(diào)方法中，進(jìn)行對(duì)文字塊的reset方法。當(dāng)動(dòng)畫結(jié)束后，得到第二個(gè)文字塊的position值，然后移除第一個(gè)文字塊，重新reset這個(gè)文字塊的索引值，再加入到List的容器中。如此循壞。
最后給一個(gè)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();
 }

上述就將這個(gè)自定義控件的所有代碼都呈現(xiàn)出來(lái)了，考慮到比較零散，這里講所有代碼都打印出來(lái)： 

/**
 * @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();
 //添加顯示區(qū)域的文字塊
 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){
 //移除第一塊
 int position = blocks.get(1).getPosition();
 TextBlock textBlock = blocks.remove(0);
 //最后一個(gè)
 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);
 }
 }
 
}

最后給出使用的方法，很簡(jiǎn)單。

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[]{
 "南海又開始動(dòng)蕩了","菲律賓到處都在肇事","這次為了一張審判廢紙，菲律賓投入了多少成本呢","測(cè)試數(shù)據(jù)4","測(cè)試數(shù)據(jù)5為了長(zhǎng)度不一樣","就把這條當(dāng)做測(cè)試數(shù)據(jù)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, "當(dāng)前的索引為：" + 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();
 //必須要調(diào)用，否則內(nèi)存中會(huì)一直無(wú)限循環(huán)
 vmView.stopScroll();
 }
}

demo就不提供了，自定義View就只有上面一個(gè)文件。

以上就是本文的全部?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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