Android如何实现文字动态高亮读取进度效果

小编给大家分享一下Android如何实现文字动态高亮读取进度效果，希望大家阅读完这篇文章之后都有所收获，下面让我们一起去探讨吧！

具体内容如下

1、效果图

类似歌词的效果。播放下面文字的音频，同时音频播放的进度和文字高亮进度保持一致。

2、代码结构和实现

简单的类图：

ISubtitleView接口代码如下：

public interface ISubtitleView {        List<SubtitleItem> getSubtitleItemList();        void setSubtitleItemList(List<SubtitleItem> linesTextList);        void setDuration(long duration);        void updatePts(long pts);        void reset();}EMSubtitleView类的代码如下：public class EMSubtitleView extends android.support.v7.widget.AppCompatTextView  implements ISubtitleView{    private int mMeasuredWidth;    private int mMeasuredHeight;    private List<SubtitleItem> mSubtitleItemList;    private List<LineEntity> mLinesTextList;    private Paint mNormalPaint;    private Paint mHLPaint;    private long mPts = 0;    private int mCurHLLine;    private float mReadSubtitleCount;    private Rect mLastHLRect;    private int mHLTextColor;    private long mDuration;    private boolean mIsPlain = false;    public EMSubtitleView(Context context) {        this(context , null);    }    public EMSubtitleView(Context context, AttributeSet attrs) {        this(context, attrs , 0);    }    public EMSubtitleView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        mSubtitleItemList = new ArrayList<>();        mLinesTextList = null;        mLastHLRect = new Rect();        mNormalPaint = null;        initAttrs(attrs , defStyleAttr);    }    private void initAttrs(AttributeSet attrs , int defStyleAttr) {        TypedArray ta = getContext().obtainStyledAttributes(attrs , R.styleable.EMSubtitleView , defStyleAttr , R.style.EMSubtitleViewDefaultTheme);        for(int i = 0 ; i < ta.getIndexCount() ; i++){            int index = ta.getIndex(i);            if (index == R.styleable.EMSubtitleView_highLightTextColor) {                mHLTextColor = ta.getColor(index, getResources().getColor(R.color.emvideovisit_color_FF9000));            }        }        ta.recycle();    }    private void initHLPaint() {        mHLPaint = new Paint(mNormalPaint);        mHLPaint.setColor(mHLTextColor);        mHLPaint.setTextSize(getTextSize());    }        public void setRichText(String text){        mIsPlain = false;        reset();        setText(text);        setDuration(mDuration , true);    }        public void setPlainText(String text){        mIsPlain = true;        reset();        setText(text);    }    @Override    protected void onDraw(Canvas canvas) {        if (mMeasuredWidth == 0 || mMeasuredHeight == 0) {            mMeasuredWidth = getMeasuredWidth();            mMeasuredHeight = getMeasuredHeight();        }        if(mIsPlain){            super.onDraw(canvas);            return;        }        if(mNormalPaint == null){            super.onDraw(canvas);            mNormalPaint = getPaint();            initHLPaint();            return;        }        if(mLinesTextList == null){            fillLinesEntityListJustOnce();        }        //没有pts，绘制        if(mPts <= 0){            drawNormalText(canvas);            return;        }        drawNormalText(canvas);        calculateReadLineAndWordsCount();        //绘制高亮部分歌词        drawHLText(canvas);    }    private void drawHLText(Canvas canvas) {        if(mCurHLLine >= 0){            int curLineTextCount = 0;            for(int i = 0 ; i < mLinesTextList.size() ; ++i){                LineEntity entity = mLinesTextList.get(i);                if(mCurHLLine > i){                    canvas.drawText( entity.lineText , entity.left , entity.baseLine , mHLPaint);                }else if(mCurHLLine == i && mReadSubtitleCount > 0 ){                    canvas.save();                    mLastHLRect.set(entity.left , entity.top , entity.left + (int) (mHLPaint.measureText(entity.lineText)*1.0f/entity.lineText.length()*(mReadSubtitleCount-curLineTextCount)), entity.bottom);                    canvas.clipRect(mLastHLRect );                    canvas.drawText( entity.lineText , entity.left , entity.baseLine , mHLPaint);                    canvas.restore();                    //遮挡的话需要滚动                    if(entity.baseLine > getHeight()){                        if(getScrollY() != entity.bottom - getHeight() + 1){                            setScrollY( entity.bottom - getHeight() + 1);                        }                    }                    break;                }                curLineTextCount += entity.lineText.length();            }        }    }    private void calculateReadLineAndWordsCount() {        float curSubtitleCount = 0;        for(SubtitleItem subtitleItem :  mSubtitleItemList){            //文字之间不可以有空隙，否则mCurHLLine可能一直为-1；            if(mPts >= subtitleItem.getStartTime() && mPts < subtitleItem.getEndTime()){                float lineOffset = (subtitleItem.getWords().length()*1.0f/(subtitleItem.getEndTime() - subtitleItem.getStartTime()))*(mPts-subtitleItem.getStartTime());                curSubtitleCount += lineOffset;                int curLineTextCount = 0;                for(int i = 0 ; i < mLinesTextList.size() ; ++i){                    curLineTextCount += mLinesTextList.get(i).lineText.length();                    if(curLineTextCount > curSubtitleCount){                        mCurHLLine = i;                        break;                    }                }                break;            }            curSubtitleCount += subtitleItem.getWords().length();        }        mReadSubtitleCount = curSubtitleCount;    }    private void fillLinesEntityListJustOnce() {        if(mLinesTextList != null){            return;        }        mLinesTextList = new ArrayList<>();        Layout layout = getLayout();        int line=getLayout().getLineCount();        String text=layout.getText().toString();        for(int i=0;i<line;i++){            int start=layout.getLineStart(i);            int end=layout.getLineEnd(i);            int left = (int) layout.getLineLeft(i);            int baseLine = layout.getLineBaseline(i);            Paint.FontMetrics fontMetrics = getPaint().getFontMetrics();            int top = (int) (baseLine + fontMetrics.top);            int bottom = (int) (baseLine + fontMetrics.bottom);            int ascent = (int) (baseLine + fontMetrics.ascent);            int descent = (int) (baseLine + fontMetrics.descent);            mLinesTextList.add(new LineEntity(text.substring(start, end) , top , bottom , ascent , descent ,baseLine , left));        }    }    private void drawNormalText(Canvas canvas) {        for(LineEntity entity : mLinesTextList){            canvas.drawText(entity.lineText, entity.left,  entity.baseLine , mNormalPaint);        }    }    public List<SubtitleItem> getSubtitleItemList() {        return mSubtitleItemList;    }        public void setSubtitleItemList(List<SubtitleItem> linesTextList) {        if(mSubtitleItemList != null){            mSubtitleItemList.clear();            mSubtitleItemList.addAll(linesTextList);        }else{            this.mSubtitleItemList = linesTextList;        }    }        public void setDuration(long duration){        setDuration( duration , false);    }    private void setDuration(long duration , boolean force){        if((duration > 0 && mDuration != duration) || force){            mDuration = duration;            if(mSubtitleItemList != null){                mSubtitleItemList.clear();            }else{                this.mSubtitleItemList = new ArrayList<>();            }            mSubtitleItemList.add(new SubtitleItem(getText().toString() , 0 , duration));        }    }        public void updatePts(long pts){        mPts = pts;        postInvalidate();    }        public void reset(){        mPts = 0;        mCurHLLine = 0;        mReadSubtitleCount = 0;        mLinesTextList = null;        mNormalPaint = null;        setScrollY(0);        postInvalidate();    }    static class LineEntity{       String lineText;       int top;       int bottom;       int ascent;       int descent;       int baseLine;       int left;        public LineEntity(String lineText, int top, int bottom, int ascent, int descent, int baseLine, int left) {            this.lineText = lineText;            this.top = top;            this.bottom = bottom;            this.ascent = ascent;            this.descent = descent;            this.baseLine = baseLine;            this.left = left;        }    }}

布局文件里使用类似如下：

<com.eastmoney.emvideovisit.view.EMSubtitleView        android:id="@+id/play_text"        android:layout_width="match_parent"        android:layout_height="@dimen/emvideovisit_dp_60"        android:layout_marginLeft="@dimen/emvideovisit_dp_60"        android:layout_marginRight="@dimen/emvideovisit_dp_60"        android:gravity="center_horizontal"        android:layout_marginTop="@dimen/emvideovisit_dp_20"        android:textColor="#fff"        app:highLightTextColor="#A6EA5504"        android:text="@string/emvideovisit_string_headset_tips"        android:textSize="@dimen/emvideovisit_dp_16"        android:layout_marginBottom="@dimen/emvideovisit_dp_4"/>

3、其它

处理过程中文字位置的参数需要注意：

Android是什么

Android是一种基于Linux内核的自由及开放源代码的操作系统，主要使用于移动设备，如智能手机和平板电脑，由美国Google公司和开放手机联盟领导及开发。

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