StaticLayout如何在Android中使用？
作者：互联网
我需要构建自己的自定义TextView,所以我一直在学习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.只有一个含糊的提及StaticLayout.Builder是更新的方式.
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.
解决方法:
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：
>测量布局后多行文字的大小.
>在位图图像上绘制文本.
>创建一个处理自己的文本布局的自定义视图(而不是使用嵌入的TextView创建复合视图). TextView本身使用StaticLayout internally.
测量文字大小
单线
如果您只有一行文本,则可以使用Paint或TextPaint进行测量.
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();
多行
但是,如果有换行并且您需要高度,那么最好使用StaticLayout.您提供宽度,然后您可以从StaticLayout获取高度.
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额外设置：
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();
在图像上写文字
我可能会在将来扩展它,但是现在请参阅this post以获取使用StaticLayout并返回位图的方法的示例.
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.它的行为类似于简单的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.
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>
笔记
> This,this和this对于学习如何创建自定义文本处理视图很有用.
>如果要添加可以从代码或xml设置的自定义属性,请参阅Creating a View Class.
标签：android,text,canvas,android-custom-view,staticlayout 来源： https://codeday.me/bug/20190918/1810707.html