测量文字大小

Question

我需要构建自己的自定义TextView，因此我一直在学习StaticLayout在画布上绘制文本。这比直接使用Canvas.drawText()更好，或者documentation说。但是，文档没有给出任何示例。 StaticLayout.Builder只是一个模糊的提法，是更新的方法。

我找到了一个例子here，但似乎有点过时了。

我终于工作了，但是我在下面添加了我的解释。

Answer 1

StaticLayout（similar to DynamicLayout and BoringLayout）用于在画布上布局和绘制文本。它通常用于以下任务：

衡量布局后多行文字的大小。
在位图图像上绘制文本。
创建一个自定义视图来处理自己的文本布局（而不是使用嵌入式TextView创建复合视图）。 TextView本身使用StaticLayout internally。

测量文字大小

单行

如果您只有一行文字，则可以使用Paint或TextPaint进行衡量。

String text = "This is some text."

TextPaint myTextPaint = new TextPaint();
mTextPaint.setAntiAlias(true);
mTextPaint.setTextSize(16 * getResources().getDisplayMetrics().density);
mTextPaint.setColor(0xFF000000);

float width = mTextPaint.measureText(text);
float height = -mTextPaint.ascent() + mTextPaint.descent();

<强>多

但是，如果有换行并且你需要高度，那么最好使用StaticLayout。您提供宽度，然后您可以从StaticLayout获得高度。

String text = "This is some text. This is some text. This is some text. This is some text. This is some text. This is some text.";

TextPaint myTextPaint = new TextPaint();
myTextPaint.setAntiAlias(true);
myTextPaint.setTextSize(16 * getResources().getDisplayMetrics().density);
myTextPaint.setColor(0xFF000000);

int width = 200;
Layout.Alignment alignment = Layout.Alignment.ALIGN_NORMAL;
float spacingMultiplier = 1;
float spacingAddition = 0;
boolean includePadding = false;

StaticLayout myStaticLayout = new StaticLayout(text, myTextPaint, width, alignment, spacingMultiplier, spacingAddition, includePadding);

float height = myStaticLayout.getHeight();

新API

如果您想使用较新的StaticLayout.Builder（可从API 23获得），您可以获得如下布局：

StaticLayout.Builder builder = StaticLayout.Builder.obtain(text, 0, text.length(), myTextPaint, width);
StaticLayout myStaticLayout = builder.build();

您可以使用点表示法来添加设置：

StaticLayout.Builder builder = StaticLayout.Builder.obtain(text, 0, text.length(), myTextPaint, width)
        .setAlignment(Layout.Alignment.ALIGN_NORMAL)
        .setLineSpacing(spacingMultiplier, spacingAddition)
        .setIncludePad(includePadding)
        .setMaxLines(5);
StaticLayout myStaticLayout = builder.build();

在图像上书写文字

我将来可能会对此进行更多扩展，但现在请参阅this post以获取使用StaticLayout并返回位图的方法示例。

进行自定义文本处理视图

以下是使用StaticLayout的自定义视图的示例。它表现得像一个简单的TextView。当文本太长而无法放在屏幕上时，它会自动换行并增加其高度。

代码

MyView.java

public class MyView extends View {

    String mText = "This is some text.";
    TextPaint mTextPaint;
    StaticLayout mStaticLayout;

    // use this constructor if creating MyView programmatically
    public MyView(Context context) {
        super(context);
        initLabelView();
    }

    // this constructor is used when created from xml
    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initLabelView();
    }

    private void initLabelView() {
        mTextPaint = new TextPaint();
        mTextPaint.setAntiAlias(true);
        mTextPaint.setTextSize(16 * getResources().getDisplayMetrics().density);
        mTextPaint.setColor(0xFF000000);

        // default to a single line of text
        int width = (int) mTextPaint.measureText(mText);
        mStaticLayout = new StaticLayout(mText, mTextPaint, (int) width, Layout.Alignment.ALIGN_NORMAL, 1.0f, 0, false);

        // New API alternate
        //
        // StaticLayout.Builder builder = StaticLayout.Builder.obtain(mText, 0, mText.length(), mTextPaint, width)
        //        .setAlignment(Layout.Alignment.ALIGN_NORMAL)
        //        .setLineSpacing(1, 0) // multiplier, add
        //        .setIncludePad(false);
        // mStaticLayout = builder.build();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // Tell the parent layout how big this view would like to be
        // but still respect any requirements (measure specs) that are passed down.

        // determine the width
        int width;
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthRequirement = MeasureSpec.getSize(widthMeasureSpec);
        if (widthMode == MeasureSpec.EXACTLY) {
            width = widthRequirement;
        } else {
            width = mStaticLayout.getWidth() + getPaddingLeft() + getPaddingRight();
            if (widthMode == MeasureSpec.AT_MOST) {
                if (width > widthRequirement) {
                    width = widthRequirement;
                    // too long for a single line so relayout as multiline
                    mStaticLayout = new StaticLayout(mText, mTextPaint, width, Layout.Alignment.ALIGN_NORMAL, 1.0f, 0, false);
                }
            }
        }

        // determine the height
        int height;
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightRequirement = MeasureSpec.getSize(heightMeasureSpec);
        if (heightMode == MeasureSpec.EXACTLY) {
            height = heightRequirement;
        } else {
            height = mStaticLayout.getHeight() + getPaddingTop() + getPaddingBottom();
            if (heightMode == MeasureSpec.AT_MOST) {
                height = Math.min(height, heightRequirement);
            }
        }

        // Required call: set width and height
        setMeasuredDimension(width, height);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // do as little as possible inside onDraw to improve performance

        // draw the text on the canvas after adjusting for padding
        canvas.save();
        canvas.translate(getPaddingLeft(), getPaddingTop());
        mStaticLayout.draw(canvas);
        canvas.restore();
    }
}

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/activity_vertical_margin"
    tools:context="com.example.layoutpractice.MainActivity">

    <com.example.layoutpractice.MyView
        android:layout_centerHorizontal="true"
        android:background="@color/colorAccent"
        android:padding="10dp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
</RelativeLayout>

备注

This，this和this有助于学习如何制作自定义文字处理视图。

如果您想添加可以从代码或xml设置的自定义属性，请参阅Creating a View Class。

Answer 2

这是我在画布上绘制多行文字的说明。

声明Paint对象。使用TextPaint，它是Paint的扩展。

TextPaint textPaint;

初始化Paint对象。设置自己的颜色，大小等。

textPaint = new TextPaint();
textPaint.setAntiAlias(true);
textPaint.setTextSize(16 * getResources().getDisplayMetrics().density);
textPaint.setColor(Color.YELLOW);

添加getTextHeight函数

private float getTextHeight(String text, Paint paint) {
    Rect rect = new Rect();
    paint.getTextBounds(text, 0, text.length(), rect);
    return rect.height();
}

在onDraw函数中，将以下几行放入

@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    String text = "This is a lengthy text. We have to render this properly. If layout mess users review will mess. Is that so ? ";

    Rect bounds = canvas.getClipBounds();

    StaticLayout sl = new StaticLayout(text, textPaint, bounds.width(),
            Layout.Alignment.ALIGN_CENTER, 1, 1, true);

    canvas.save();

    //calculate X and Y coordinates - In this case we want to draw the text in the
    //center of canvas so we calculate
    //text height and number of lines to move Y coordinate to center.
    float textHeight = getTextHeight(text, textPaint);
    int numberOfTextLines = sl.getLineCount();
    float textYCoordinate = bounds.exactCenterY() -
            ((numberOfTextLines * textHeight) / 2);

    //text will be drawn from left
    float textXCoordinate = bounds.left;

    canvas.translate(textXCoordinate, textYCoordinate);

    //draws static layout on canvas
    sl.draw(canvas);
    canvas.restore();
}

礼貌转到KOC's post

StaticLayout如何在Android中使用？

2 个答案:

测量文字大小

在图像上书写文字

进行自定义文本处理视图