Android中如何使用StaticLayout? [英] How is StaticLayout used in Android?
问题描述
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，否则文档表示.但是，文档没有提供任何有关此操作的示例.仅有模糊的参考引用了 StaticLayout.Builder 的方法.
I need to build my own custom TextView so I have been learning about StaticLayout to draw text on a canvas. This is preferable to using Canvas.drawText() directly, or so the documentation says. However, the documentation doesn't give any examples for how do it. There is only a vague reference to StaticLayout.Builder being the newer way to do it.
我在此处找到了一个示例，但似乎有点过时了
I found an example here but it seems a little dated.
我终于做到了，但是我在下面添加了解释.
I finally worked though how to do it so I am adding my explanation below.
推荐答案
StaticLayout(类似至DynamicLayout和BoringLayout )用于在画布上布局和绘制文本.通常用于以下任务:
StaticLayout (similar to DynamicLayout and BoringLayout) is used to layout and draw text on a canvas. It is commonly used for the following tasks:
- 测量布局后多行文本的大小.
- 在位图图像上绘制文本.
- 制作一个可处理其自己的文本布局的自定义视图(与使用嵌入式
TextView制作复合视图相反).TextView本身在内部使用StaticLayout/a>.
- Measuring how big multiline text would be after being laid out.
- Drawing text on a bitmap image.
- Making a custom view that handles its own text layout (as opposed to making a composite view with an embedded
TextView).TextViewitself uses aStaticLayoutinternally.
单行
如果只有一行文本，则可以使用Paint或TextPaint进行测量.
If you only have a single line of text, you can measure it with Paint or TextPaint.
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，如果有换行并且需要高度，那么最好使用StaticLayout.您提供宽度，然后可以从StaticLayout获取高度.
However, if there is line wrapping and you need the height, then it is better to use a StaticLayout. You provide the width and then you can get the height from the StaticLayout.
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
如果您想使用更新的 StaticLayout.Builder (可从API 23获得)，您可以按照以下方式获取布局:
If you want to use the newer StaticLayout.Builder (available from API 23), you can get your layout like this:
StaticLayout.Builder builder = StaticLayout.Builder.obtain(text, 0, text.length(), myTextPaint, width);
StaticLayout myStaticLayout = builder.build();
您可以使用点符号来附加设置:
You can tack on addition settings using dot notation:
StaticLayout.Builder builder = StaticLayout.Builder.obtain(text, 0, text.length(), myTextPaint, width)
.setAlignment(Layout.Alignment.ALIGN_NORMAL)
.setLineSpacing(spacingAddition, spacingMultiplier)
.setIncludePad(includePadding)
.setMaxLines(5);
StaticLayout myStaticLayout = builder.build();
在图像上写文字
Writing text on an image
I may expand this more in the future, but for now see this post for an example of a method that uses StaticLayout and returns a bitmap.
这是使用StaticLayout的自定义视图的示例.它的行为就像一个简单的TextView.当文本太长而无法在屏幕上显示时，它会自动换行并增加其高度.
Here is an example of a custom view using a StaticLayout. It behaves like a simple TextView. When the text is too long to fit on the screen, it automatically line wraps and increases its height.
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(0, 1) // add, multiplier
// .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
<?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>
注释
This, this, and this were useful in learning how to make a custom text handling view.
请参阅创建视图类.想要添加可以从代码或xml设置的自定义属性.
See Creating a View Class if you would like to add custom attributes that can be set from code or xml.
这篇关于Android中如何使用StaticLayout?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
