注:该笔记是整理学习鸿洋大神自定义View系列博客的部分知识点。
自定义View(自定义控件)四大步骤:
1. 自定义View的属性
2. 在View的构造方法中获取自定义的属性
3. 重写onMesure() 不是选项
4. 重写onDraw()
自定义View属性
/** 在res/values下建立一个attrs.xml文件 */
<resources>
<attr name="titleText" format="string" />
<attr name="titleTextSize" format="dimension" />
<attr name="titleTextColor" format="color" />
<attr name="image" format="reference" />
<attr name="imageScaleType">
<enum name="fillXY" value="0" />
<enum name="center" value="1" />
</attr>
<declare-styleable name="CustomImageView">
<attr name="titleText" />
<attr name="titleTextSize" />
<attr name="titleTextColor" />
<attr name="image" />
<attr name="imageScaleType" />
</declare-styleable>
</resources>
注:format的取值类型有:
string — 字符串
color — 颜色值
demension — 尺寸值
integer — 整型值
float — 浮点值
reference — 参考某一资源ID
boolean — 布尔值
fraction — 百分数
enum — 枚举值
flag — 位或运算
获取自定义的样式属性
public CustomTitleView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
/**
* 获得我们所定义的自定义样式属性
*/
TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomTitleView, defStyle, 0);
int n = a.getIndexCount();
for (int i = 0; i < n; i++)
{
int attr = a.getIndex(i);
switch (attr)
{
case R.styleable.CustomTitleView_titleText:
mTitleText = a.getString(attr);
break;
case R.styleable.CustomTitleView_titleTextColor:
// 默认颜色设置为黑色
mTitleTextColor = a.getColor(attr, Color.BLACK); //参数:a.getColor(输入值, 默认值)
break;
case R.styleable.CustomTitleView_titleTextSize:
// 默认设置为16sp,TypeValue也可以把sp转化为px
mTitleTextSize = a.getDimensionPixelSize(attr, (int) TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_SP, 16, getResources().getDisplayMetrics()));
break;
}
}
a.recycle(); //将TypedArray回收
/**
* 获得绘制文本的宽和高
*/
mPaint = new Paint();
mPaint.setTextSize(mTitleTextSize);
// mPaint.setColor(mTitleTextColor);
mBound = new Rect();
mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound); //通过 getTextBound(String text,int start,int end,Rect bounds) 或者 getTextBound(char[] text,int index,int count,Rect bounds) 获取绘制的大小
}
重写onMeasure()
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
{
// super.onMeasure(widthMeasureSpec, heightMeasureSpec);
/**
* 设置宽度
*/
int specMode = MeasureSpec.getMode(widthMeasureSpec);
int specSize = MeasureSpec.getSize(widthMeasureSpec);
if (specMode == MeasureSpec.EXACTLY)// match_parent , accurate
{
mWidth = specSize;
} else{
// 由图片决定的宽
int desireByImg = getPaddingLeft() + getPaddingRight() + mImage.getWidth();
// 由字体决定的宽
int desireByTitle = getPaddingLeft() + getPaddingRight() + mTextBound.width();
if (specMode == MeasureSpec.AT_MOST)// wrap_content
{
int desire = Math.max(desireByImg, desireByTitle); //取 desireByImg, desireByTitle中最大值
mWidth = Math.min(desire, specSize);
}
}
/**
* 设置高度
*/
specMode = MeasureSpec.getMode(heightMeasureSpec);
specSize = MeasureSpec.getSize(heightMeasureSpec);
if (specMode == MeasureSpec.EXACTLY)// match_parent , accurate
{
mHeight = specSize;
} else {
int desire = getPaddingTop() + getPaddingBottom() + mImage.getHeight() + mTextBound.height();
if (specMode == MeasureSpec.AT_MOST)// wrap_content
{
mHeight = Math.min(desire, specSize);
}
}
setMeasuredDimension(mWidth, mHeight);
}