月份：2018年2月

Android中，在自定义View中通过Canvas绘制文字时，经常需要测量文字的宽度和高度。这里记录下几种比较常用的方法，仅作备忘。

1. Paint.measureText （测量文本的宽度）

Paint paint = new Paint();
paint.setTextSize(size);
float strWidth = paint.measureText(str);

2. Paint.getTextBounds (获得文字所在矩形区域，可以得到宽高)

Paint paint = new Paint();
Rect rect = new Rect();  
paint.getTextBounds(str, 0, str.length(), rect);  
int w = rect.width();  
int h = rect.height();

3. Paint.getTextWidths(获得每个字符的宽度)

float width = 0;
int len = str.length();  
Paint paint = new Paint();
float[] widths = new float[len];  
paint.getTextWidths(str, widths);  
for (int i = 0; i < len; i++) {  
     width += widths[i];  
}

4. 通过Paint.FontMetrics or Paint.FontMetricsInt来获取高度

这两者的含义相同，只不过精度不同，一个float、一个int。关于Paint.FontMetrics，可以参考这里。

Paint paint = new Paint();
paint.setTextSize(size);//设置字体大小
paint.setTypeface(Typeface.xx);//设置字体
FontMetrics fontMetrics = getFontMetrics();
float height1 = fontMetrics.descent - fontMetrics.ascent;
float height2 = fontMetrics.bottom - fontMetrics.top;

这里获取的两个高度略有不同，height2的高度会略大于height1，这样在文本的顶部和底部就会有一些留白。具体使用哪个高度，要看具体需求了。

此外，还可以通过Paint.getFontSpacing和Paint.getFontMetrics(null)来获得高度，其实前者也是调用后者来实现的。这里的值和通过fontMetrics.descent - fontMetrics.ascent获得的大小是一致的。

5. Layout.getDesiredWidth (获得宽度)

TextPaint textPaint = new TextPaint();
paint.setTextSize(size);//设置字体大小
paint.setTypeface(Typeface.xx);//设置字体
float width = Layout.getDesiredWidth(str,textPaint);

之前碰到一个问题，TextView在布局上占用的高度和属性textSize的大小不一样，要比textSize的值大一些（比如textSize=”12dp”，实际的高度大概有14-16dp），仔细看的话会发现文字的上方和下发留有空白。查了下文档，发现可以通过设置android:includeFontPadding来控制是否包含上下空白。

String str = "Hello";
canvas.drawText( str , x , y , paint);

//1. 粗略计算文字宽度
Log.d(TAG, "measureText=" + paint.measureText(str));

//2. 计算文字所在矩形，可以得到宽高
Rect rect = new Rect();
paint.getTextBounds(str, 0, str.length(), rect);
int w = rect.width();
int h = rect.height();
Log.d(TAG, "w=" +w+"  h="+h);

//3. 精确计算文字宽度
int textWidth = getTextWidth(paint, str);
Log.d(TAG, "textWidth=" + textWidth);

    public static int getTextWidth(Paint paint, String str) {
        int iRet = 0;
        if (str != null && str.length() > 0) {
            int len = str.length();
            float[] widths = new float[len];
            paint.getTextWidths(str, widths);
            for (int j = 0; j < len; j++) {
                iRet += (int) Math.ceil(widths[j]);
            }
        }
        return iRet;
    }

public class XRTextView extends AppCompatTextView {
    private boolean mEnabled = true;

    public XRTextView(Context context) {
        super(context);
    }

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

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

    public void setAutoSplitEnabled(boolean enabled) {
        mEnabled = enabled;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        if (MeasureSpec.getMode(widthMeasureSpec) == MeasureSpec.EXACTLY
                && MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.EXACTLY
                && getWidth() > 0
                && getHeight() > 0
                && mEnabled) {
            String newText = autoSplitText(this);
            if (!TextUtils.isEmpty(newText)) {
                setText(newText);
            }
        }
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    private String autoSplitText(final TextView tv) {
        final String rawText = tv.getText().toString(); //原始文本
        final Paint tvPaint = tv.getPaint(); //paint，包含字体等信息
        final float tvWidth = tv.getWidth() - tv.getPaddingLeft() - tv.getPaddingRight(); //控件可用宽度

        //将原始文本按行拆分
        String[] rawTextLines = rawText.replaceAll("\r", "").split("\n");
        StringBuilder sbNewText = new StringBuilder();
        for (String rawTextLine : rawTextLines) {
            if (tvPaint.measureText(rawTextLine) <= tvWidth) {
                //如果整行宽度在控件可用宽度之内，就不处理了
                sbNewText.append(rawTextLine);
            } else {
                //如果整行宽度超过控件可用宽度，则按字符测量，在超过可用宽度的前一个字符处手动换行
                float lineWidth = 0;
                for (int cnt = 0; cnt != rawTextLine.length(); ++cnt) {
                    char ch = rawTextLine.charAt(cnt);
                    lineWidth += tvPaint.measureText(String.valueOf(ch));
                    if (lineWidth <= tvWidth) {
                        sbNewText.append(ch);
                    } else {
                        sbNewText.append("\n");
                        lineWidth = 0;
                        --cnt;
                    }
                }
            }
            sbNewText.append("\n");
        }

        //把结尾多余的\n去掉
        if (!rawText.endsWith("\n")) {
            sbNewText.deleteCharAt(sbNewText.length() - 1);
        }

        return sbNewText.toString();
    }

    public void setFont(String textFont) {
        Typeface lastTypeFace = getTypeface();
        boolean isBold = lastTypeFace != null ? lastTypeFace.isBold() : false;
        Typeface typeface = FontUtil.getTypeface(textFont, getContext());
        //使用字体
        setTypeface(typeface);
        //中文字体设置加粗
        TextPaint paint = getPaint();
        paint.setFakeBoldText(isBold);
    }
}

public class JustifyTextView extends AppCompatTextView {

    private int mLineY;
    private int mViewWidth;
    public static final String TWO_CHINESE_BLANK = "  ";

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

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        TextPaint paint = getPaint();
        paint.setColor(getCurrentTextColor());
        paint.drawableState = getDrawableState();
        mViewWidth = getMeasuredWidth();
        String text = getText().toString();
        mLineY = 0;
        mLineY += getTextSize();
        Layout layout = getLayout();

        // layout.getLayout()在4.4.3出现NullPointerException
        if (layout == null) {
            return;
        }

        Paint.FontMetrics fm = paint.getFontMetrics();

        int textHeight = (int) (Math.ceil(fm.descent - fm.ascent));
        textHeight = (int) (textHeight * layout.getSpacingMultiplier() + layout.getSpacingAdd());
        //解决了最后一行文字间距过大的问题
        for (int i = 0; i < layout.getLineCount(); i++) {
            int lineStart = layout.getLineStart(i);
            int lineEnd = layout.getLineEnd(i);
            float width = StaticLayout.getDesiredWidth(text, lineStart, lineEnd, getPaint());
            String line = text.substring(lineStart, lineEnd);

            if(i < layout.getLineCount() - 1) {
                if (needScale(line)) {
                    drawScaledText(canvas, lineStart, line, width);
                } else {
                    canvas.drawText(line, 0, mLineY, paint);
                }
            } else {
                canvas.drawText(line, 0, mLineY, paint);
            }
            mLineY += textHeight;
        }
    }

    private void drawScaledText(Canvas canvas, int lineStart, String line, float lineWidth) {
        float x = 0;
        if (isFirstLineOfParagraph(lineStart, line)) {
            String blanks = "  ";
            canvas.drawText(blanks, x, mLineY, getPaint());
            float bw = StaticLayout.getDesiredWidth(blanks, getPaint());
            x += bw;

            line = line.substring(3);
        }

        int gapCount = line.length() - 1;
        int i = 0;
        if (line.length() > 2 && line.charAt(0) == 12288 && line.charAt(1) == 12288) {
            String substring = line.substring(0, 2);
            float cw = StaticLayout.getDesiredWidth(substring, getPaint());
            canvas.drawText(substring, x, mLineY, getPaint());
            x += cw;
            i += 2;
        }

        float d = (mViewWidth - lineWidth) / gapCount;
        for (; i < line.length(); i++) {
            String c = String.valueOf(line.charAt(i));
            float cw = StaticLayout.getDesiredWidth(c, getPaint());
            canvas.drawText(c, x, mLineY, getPaint());
            x += cw + d;
        }
    }

    private boolean isFirstLineOfParagraph(int lineStart, String line) {
        return line.length() > 3 && line.charAt(0) == ' ' && line.charAt(1) == ' ';
    }

    private boolean needScale(String line) {
        if (line == null || line.length() == 0) {
            return false;
        } else {
            return line.charAt(line.length() - 1) != '\n';
        }
    }
}

StaticLayout是android中处理文字换行的一个工具类，StaticLayout已经实现了文本绘制换行处理。它跟TextView的效果是一样的，其实TextView也是调用StaticLayout来实现换行的。

public StaticLayout(CharSequence source,
                    int bufstart,
                    int bufend,
                    TextPaint paint,
                    int outerwidth,
                    Layout.Alignment align,
                    float spacingmult,
                    float spacingadd,
                    boolean includepad,
                    TextUtils.TruncateAt ellipsize,
                    int ellipsizedWidth)

1.需要分行的字符串
2.需要分行的字符串从第几的位置开始
3.需要分行的字符串到哪里结束
4.画笔对象
5.layout的宽度，字符串超出宽度时自动换行。
6.layout的对其方式，有ALIGN_CENTER， ALIGN_NORMAL， ALIGN_OPPOSITE 三种。
7.相对行间距，相对字体大小，1.5f表示行间距为1.5倍的字体高度。
8.在基础行距上添加多少
实际行间距等于这两者的和。
9.参数未知
10.从什么位置开始省略
11.超过多少开始省略
需要指出的是这个layout是默认画在Canvas的(0,0)点的，如果需要调整位置只能在draw之前移Canvas的起始坐标
canvas.translate(x,y);

生成长图功能的实现：

public static Bitmap getBitmap(Context context, EditText mEditText) {
        Editable editable = mEditText.getText();
        TextPaint textPaint = new TextPaint();
        textPaint.setARGB(0xFF, 0, 0, 0);
        textPaint.setTextSize(mEditText.getTextSize() - DisplayUtils.sp2px(context, 2));

        // 设置字体
        String fontPath = Cache.read_String(SharedPreferencesKey.KEY_FONT, "");
        if (!TextUtils.isEmpty(fontPath)) {
            File fontFile = new File(fontPath);
            if (fontFile.isFile() && fontFile.exists())
                textPaint.setTypeface(Typeface.createFromFile(fontFile));
        }
        ScreenInfo mScreenInfo = ScreenInfo.getInstance();

        float bitmapWidth = mScreenInfo.getWidthPixels()
                - DisplayUtils.dip2px(context, 10);
        float padding = DisplayUtils.dip2px(context, 15);

        StaticLayout layout = new StaticLayout(editable, textPaint,
                (int) (bitmapWidth - padding * 4), Alignment.ALIGN_NORMAL,
                1.2F, 0.0F, true);

        float bitmapHeight = layout.getHeight() + padding * 10;

        Bitmap bitmap = null;
        try {
            bitmap = Bitmap.createBitmap((int) bitmapWidth, (int) bitmapHeight,
                    Bitmap.Config.ARGB_8888);
        } catch (OutOfMemoryError e) {
            e.printStackTrace();
            return null;
        }
        Canvas paper = new Canvas(bitmap);
        paper.drawColor(ColorSelectView.getColor(2));

        paper.translate(padding * 2, padding * 4);

        layout.draw(paper);

        paper.translate(-padding * 2, -padding * 4);

        Paint mPaint = new Paint(Paint.DITHER_FLAG);
        mPaint.setColor(Color.GRAY);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(DisplayUtils.dip2px(context, 0.5f));

        float offset = DisplayUtils.dip2px(context, 2);

        paper.drawRect(new Rect((int) (padding), (int) (padding * 2),
                (int) (bitmapWidth - padding),
                (int) (bitmapHeight - padding * 4)), mPaint);

        paper.drawRect(new Rect((int) (padding - offset),
                (int) (padding * 2 - offset), (int) (padding),
                (int) (padding * 2)), mPaint);

        paper.drawRect(new Rect((int) (bitmapWidth - padding),
                (int) (padding * 2 - offset),
                (int) (bitmapWidth - padding + offset), (int) (padding * 2)),
                mPaint);

        paper.drawRect(new Rect((int) (padding - offset),
                (int) (bitmapHeight - padding * 4), (int) (padding),
                (int) (bitmapHeight - padding * 4 + offset)), mPaint);

        paper.drawRect(new Rect((int) (bitmapWidth - padding),
                (int) (bitmapHeight - padding * 4), (int) (bitmapWidth
                        - padding + offset),
                (int) (bitmapHeight - padding * 4 + offset)), mPaint);

        paper.drawRect(new Rect((int) (padding + offset),
                (int) (padding * 2 + offset),
                (int) (bitmapWidth - padding - offset), (int) (bitmapHeight
                        - padding * 4 - offset)), mPaint);

        TextPaint fromTextPaint = new TextPaint();
        fromTextPaint.setColor(Color.GRAY);
        fromTextPaint.setTextSize(DisplayUtils.sp2px(context, 12));
        StaticLayout fromLayout = new StaticLayout(Cache.read_String(
                KEY_SHARE_TAIL, context.getString(R.string.share_image_info)),
                fromTextPaint, (int) (bitmapWidth - padding * 3.5),
                Alignment.ALIGN_NORMAL, 1.0F, 0.0F, true);
        paper.translate(padding, bitmapHeight - padding * 3);
        fromLayout.draw(paper);

        return bitmap;
    }

static public Boolean printBill(Activity context) {

        try {
            int height = 50 + 14 * 30;
            // 打印高度计算：每多一行加50
            Bitmap bitmap = Bitmap
                    .createBitmap(WIDTH, height, Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(bitmap);
            canvas.drawColor(Color.WHITE);
            TextPaint paint = new TextPaint(Paint.ANTI_ALIAS_FLAG);
            paint.setStrokeWidth(1);
            paint.setColor(Color.BLACK);
            paint.setTypeface(Typeface.SANS_SERIF);

            String content = "";
            StaticLayout layout;

            // 打印标题--购物小票
            paint.setTextSize(32);
            content = "备注信息";
                layout = new StaticLayout(content, paint, (int) (400),
                    Layout.Alignment.ALIGN_CENTER, 1F, 0, false);
            canvas.translate(0, 0);
            layout.draw(canvas);

            // 分割线
            content = "======================\r\n";
            layout = new StaticLayout(content, paint, (int) (400),
                    Layout.Alignment.ALIGN_NORMAL, 1F, 0, false);
            canvas.translate(0, 50);
            layout.draw(canvas);
            // 打印客户姓名
            content = "客户姓名： " + customerName + "\r\n";
            layout = new StaticLayout(content, paint, (int) (400),
                    Layout.Alignment.ALIGN_NORMAL, 1F, 0, false);
            canvas.translate(0, 50);
            layout.draw(canvas);


            // 打印门店名称
            content = "门店名称： " + orgName + "\r\n";
            layout = new StaticLayout(content, paint, (int) (400),
                    Layout.Alignment.ALIGN_NORMAL, 1F, 0, false);
            canvas.translate(0, 50);
            layout.draw(canvas);

            // 打印款项
            content = "款项类型： " + type + "\r\n";
            layout = new StaticLayout(content, paint, (int) (400),
                    Layout.Alignment.ALIGN_NORMAL, 1F, 0, false);
            canvas.translate(0, 50);
            layout.draw(canvas);

            // 打印ERP单号
            content = "ERP单号： " + erpCode + "\r\n";
            layout = new StaticLayout(content, paint, (int) (400),
                    Layout.Alignment.ALIGN_NORMAL, 1F, 0, false);
            canvas.translate(0, 50);
            layout.draw(canvas);

            // 打印HY单号
            content = "HY单号: " + jtlOrderNo + "\r\n";
            layout = new StaticLayout(content, paint, (int) (400),
                    Layout.Alignment.ALIGN_NORMAL, 1F, 0, false);
            canvas.translate(0, 50);
            layout.draw(canvas);



            canvas.save(Canvas.ALL_SAVE_FLAG);
            canvas.restore();
            String path = Environment.getExternalStorageDirectory()
                    + "/image.png";
            System.out.println(path);
            FileOutputStream os = new FileOutputStream(new File(path));
            bitmap.compress(Bitmap.CompressFormat.PNG, 100, os);
            os.flush();
            os.close();
            AppHelper.callPrint(context, path);
            return true;

        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }

    }

在include某个布局的时候，被include的布局顶部使用merge布局可以有效减少布局嵌套，如果是替换LinearLayout等其他布局更是有效提高性能

tools:parentTag=”LinearLayout” 和 tools:orientation=”horizontal” 都是让android studio预览的时候可以以LinearLayout形式观看

<merge xmlns:android="http://schemas.android.com/apk/res/android"  
      xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"     
      android:layout_height="match_parent" 
      tools:parentTag="LinearLayout" 
      tools:orientation="horizontal"> 

      <TextView 
          android:layout_width="wrap_content" 
         android:layout_height="wrap_content" 
         android:text="Some text" 
          android:textSize="20sp"/> 
     <TextView 
           android:layout_width="wrap_content" 
           android:layout_height="wrap_content" 
          android:text="Some other text"/> 

</merge>