自动滚动的Textview

   又到了写博博的时候了！大家还好吧！

   开始做机顶盒了，所以这里就有很多的界面需要做成一个自动化的界面。因为遥控盒手机触摸毕竟不一样咯！这里而且要方便大众的视觉体验的话，我们必须要考虑到这些因素。当然，我觉着，这次的自动滚动效果一定对大家也很有帮助的哦！

  我们只要写一个类来继承我布局文件里面写的一个TextView就ok啦。

package com.example.myscroltextview.view;

import java.util.ArrayList;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Typeface;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.widget.TextView;

/**
 * 垂直滚动的textview
 * 
 * @author Catherine.Brian.William
 * 
 */
public class VertailScrollTextView extends TextView {

    public VertailScrollTextView(Context context) {
        super(context);
        init();
    }

    public VertailScrollTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public VertailScrollTextView(Context context, AttributeSet attrs,
            int defStyle) {
        super(context, attrs, defStyle);
        init();
    }

    Handler handler;

    /**
     * 是否在滚动
     */
    boolean scrolling = false;

    /**
     * 当前的位移
     */
    float currentY;
    /**
     * 每次滚动的距离
     */
    float speed = 0.2f;

    /**
     * 要显示的text
     */
    String scrollText = "";

    /**
     * 真实宽度,在配置width="xxdp"里起作用
     */
    private int exactlyWidth = -1;

    /**
     * 真实高度,在配置height="xxdip"里起作用
     */
    private int exactlyHeight = -1;

    /**
     * 实际高度：所有字显示完全需要的高度
     */
    float absloutHeight = 0;

    /**
     * handler发消息的时间间隔
     */
    int delayTime = 50;

    /**
     * 每行的字符串
     */
    ArrayList<String> lineStrings;

    Paint mPaint;

    private static final int DY = 20; // 每一行的间隔

    /**
     * 初始化
     */
    private void init() {

        // 非高亮部分
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setTextSize(20);
        mPaint.setColor(Color.WHITE);
        mPaint.setTypeface(Typeface.SERIF);

        handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                if (absloutHeight <= getHeight()) {
                    currentY = 0;
                    stop();
                    return;
                }
                switch (msg.what) {
                case 0:
                    currentY = currentY - speed;

                    resetCurrentY();
                    invalidate();
                    handler.sendEmptyMessageDelayed(0, delayTime);
                    break;
                }
                super.handleMessage(msg);
            }

            /**
             * 重置currentY(当currentY超过absolutHeight时,让它重置为0)
             */
            private void resetCurrentY() {
                if (currentY >= absloutHeight || currentY <= -absloutHeight
                        || getHeight() <= 0) {
                    currentY = 0;
                }
            }
        };

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int width = MeasureWidth(widthMeasureSpec);
        int height = MeasureHeight(width, heightMeasureSpec);
        setMeasuredDimension(width, height);
        currentY = 0;
        if (height < absloutHeight) {
            play();
        } else {
            stop();
        }
    }

    /**
     * 测量宽度
     * 
     * @param widthMeasureSpec
     * @return
     */
    private int MeasureWidth(int widthMeasureSpec) {
        int mode = MeasureSpec.getMode(widthMeasureSpec);
        int width = MeasureSpec.getSize(widthMeasureSpec);
        // 如果时候wrap_content
        if (mode == MeasureSpec.AT_MOST) {
            double abwidth = getPaint().measureText(scrollText);
            width = Math.min((int) Math.rint(abwidth), width);
            exactlyWidth = -1;
        }
        // 精确宽度
        if (mode == MeasureSpec.EXACTLY) {
            exactlyWidth = width;
        }
        return width;

    }

    /**
     * 测量高度
     * 
     * @param width
     * @param heightMeasureSpec
     * @return
     */
    private int MeasureHeight(int width, int heightMeasureSpec) {
        int mode = MeasureSpec.getMode(heightMeasureSpec);
        int height = MeasureSpec.getSize(heightMeasureSpec);
        generateTextList(width);

        int lines = lineStrings.size();

        absloutHeight = lines * (getLineHeight() + DY) + getPaddingBottom()
                + getPaddingTop();
        // 如果是wrap_content
        if (mode == MeasureSpec.AT_MOST) {
            height = (int) Math.min(absloutHeight, height);
            exactlyHeight = -1;
        } else if (mode == MeasureSpec.EXACTLY) {
            exactlyHeight = height;
        }

        return height;
    }

    /**
     * 生成多行字符串列表
     * 
     * @param MaxWidth
     */
    public void generateTextList(int MaxWidth) {
        lineStrings = new ArrayList<String>();

        String remain = scrollText; 

        while (!remain.equals("")) {
            String line = getLineText(MaxWidth, remain);
            lineStrings.add(line);
            remain = remain.substring(line.length(), remain.length());
        }

    }

    /**
     * 获取一行的字符
     * 
     * @param MaxWidth
     * @param remain
     * @return
     */
    private String getLineText(int MaxWidth, String str) {

        // 真实行
        StringBuffer trueStringBuffer = new StringBuffer();

        // 临时行
        StringBuffer tempStringBuffer = new StringBuffer();

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            String add = "";
            if (!isChinese(c) && isENWordStart(str, i)) {
                int place = getNextSpecePlace(i, str);
                // 找到下一个空格
                if (place > -1) {
                    add = str.substring(i, place) + " ";
                    if (getPaint().measureText(add) > MaxWidth) {
                        add = "" + c;
                    } else {
                        i = place;
                    }
                } else {
                    add = "" + c;
                }

            } else {
                add = "" + c;
            }
            tempStringBuffer.append(add);
            String temp = tempStringBuffer.toString();

            float width = getPaint().measureText(temp.toString());

            if (width <= MaxWidth) {
                trueStringBuffer.append(add);
            } else {
                break;
            }

        }
        return trueStringBuffer.toString();
    }

    /**
     * 找到下一个空格的地方
     * 
     * @param i
     * @param str
     * @return
     */
    int getNextSpecePlace(int i, String str) {

        for (int j = i; j < str.length(); j++) {
            char c = str.charAt(j);
            if (c == ' ') {

                return j;
            }
        }
        return -1;
    }

    /**
     * 是否为英文单词的首字母
     * 
     * @param str
     * @param i
     * @return
     */
    boolean isENWordStart(String str, int i) {

        if (i == 0) {
            return true;

        } else if (str.charAt(i - 1) == ' ') {
            return true;
        }
        return false;
    }

    /**
     * 设置textview的文字
     * 
     * @param scrollText
     */
    public void setScrollText(String scrollText) {
        this.scrollText = scrollText;
        // setText(scrollText);
        reset();
    }

    public String getScrollText() {
        return scrollText;
    }

    /**
     * 重置
     */
    private void reset() {
        requestLayout();
        invalidate();
        currentY = 0;
    }

    /**
     * 开始滚动
     */
    public void play() {
        if (!scrolling) {
            handler.sendEmptyMessage(0);
            scrolling = true;
        }
    }

    /**
     * 停止滚动
     */
    public void stop() {
        if (scrolling) {
            handler.removeMessages(0);
            scrolling = false;
        }
    }

    /**
     * 更改滚动状态
     */
    public void updateScrollStatus() {
        if (scrolling) {
            stop();
        } else {
            play();
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        super.onDraw(canvas);
        float x = getPaddingLeft();
        float y = getPaddingTop();

        float lineHeight = getLineHeight() + DY;
        float textSize = getPaint().getTextSize();

        for (int i = 0; i < lineStrings.size(); i++) {
            // currentY+=50;
            y = lineHeight * i + textSize + currentY;

            float min = 0;
            if (exactlyHeight > -1) {
                min = Math.min(min, exactlyHeight - absloutHeight);
            }
            if (y < min) {
                y = y + absloutHeight;
            } else if (y >= min && y < textSize + min) {
                // 如果最顶端的文字已经到达需要循环从下面滚出的时候
                System.out.println("x:" + x + "y:" + y);
            }
            if (y >= absloutHeight) {
                // 如果最底端的文字已经到达需要循环从上面滚出的时候
                System.out.println("x:" + x + "y:" + y);
                y = y - absloutHeight;
            }

            canvas.drawText(lineStrings.get(i), x, y, mPaint);
        }

    }

    /**
     * 判断是否为中文
     * 
     * @param c
     * @return
     */
    private static final boolean isChinese(char c) {
        Character.UnicodeBlock ub = Character.UnicodeBlock.of(c);
        if (ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS
                || ub == Character.UnicodeBlock.CJK_COMPATIBILITY_IDEOGRAPHS
                || ub == Character.UnicodeBlock.CJK_UNIFIED_IDEOGRAPHS_EXTENSION_A
                || ub == Character.UnicodeBlock.GENERAL_PUNCTUATION
                || ub == Character.UnicodeBlock.CJK_SYMBOLS_AND_PUNCTUATION
                || ub == Character.UnicodeBlock.HALFWIDTH_AND_FULLWIDTH_FORMS) {
            return true;
        }
        return false;
    }

}