invalidate();
}
/**
* 设置文本颜色
* Sets the text color for this label.
* @param color ARGB value for the text
*/
public void setTextColor(int color) {
mTextPaint.setColor(color);
invalidate();
}
/**
* 测量View和它的内容，并决定测量宽度和测量高度
* 这个方法被 measure(int, int)所调用
*/
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
// 覆盖onMeasure时必须调用此方法，否则会抛出measurement 运行时异常
setMeasuredDimension(measureWidth(widthMeasureSpec),
measureHeight(heightMeasureSpec));
}
/**
* 决定这个view的宽度
* @param measureSpec A measureSpec packed into an int
* @return The width of the view, honoring constraints from measureSpec
*/
private int measureWidth(int measureSpec) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
// 如果view的宽度是确定值，那么直接获取此确定值
if (specMode == MeasureSpec.EXACTLY) {
// We were told how big to be
result = specSize;
} else { // 如果宽度不是确定值，就需要计算下
// 测量text的宽度
result = (int) mTextPaint.measureText(mText) + getPaddingLeft()
+ getPaddingRight();
if (specMode == MeasureSpec.AT_MOST) {
// Respect AT_MOST value if that was what is called for by measureSpec
result = Math.min(result, specSize);
}
}
return result;
}
/**
* 决定这个view的高度
* 注意： 字体的高度＝上坡度＋下坡度＋行间距
* ascent和top都是负数
* @param measureSpec A measureSpec packed into an int
* @return The height of the view, honoring constraints from measureSpec
*/
private int measureHeight(int measureSpec) {
int result = 0;
int specMode = MeasureSpec.getMode(measureSpec);
int specSize = MeasureSpec.getSize(measureSpec);
mAscent = (int) mTextPaint.ascent();
if (specMode == MeasureSpec.EXACTLY) {
// We were told how big to be
result = specSize;
} else {
// Measure the text (beware: ascent is a negative number)
result = (int) (-mAscent + mTextPaint.descent()) + getPaddingTop()
+ getPaddingBottom();
if (specMode == MeasureSpec.AT_MOST) {
// Respect AT_MOST value if that was what is called for by measureSpec
result = Math.min(result, specSize);
}
}
return result;
}
/**
* Render the text
* 绘制相应的界面，这里是drawText
* @see android.view.View#onDraw(android.graphics.Canvas)
*/
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawText(mText, getPaddingLeft(), getPaddingTop() - mAscent, mTextPaint);
}
}
package com.example.labelview;
// Need the following import to get access to the app resources, since this
// class is in a sub-package.
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
/**
* Example of how to write a custom subclass of View. LabelView
* is used to draw simple text views. Note that it does not handle
* s