[置顶] Android(安卓)自定义View实现竖直跑马灯效果

首先给出效果图

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。

另外，尊重原创哈。转载需要说明哦。

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