一、为什么我们需要造轮子?
看到标题你可能会问:系统自带Toolbar不香吗?确实香,但遇到这些场景就抓瞎了:
- 设计稿要求标题栏带渐变背景+动态波浪线
- 产品经理非要搞个不对称的返回按钮布局
- UI设计师坚持标题和副标题要45度角重叠
这时候再不自己动手撸View,就只能等着加班掉头发了!
二、从零打造ToolbarView
2.1 骨架搭建
class ToolbarView @JvmOverloads constructor(context: Context,attrs: AttributeSet? = null,defStyleAttr: Int = 0
) : ViewGroup(context, attrs, defStyleAttr) {// 三大核心组件private lateinit var backButton: ImageViewprivate lateinit var titleView: TextViewprivate lateinit var actionMenu: LinearLayout// 初始化三连init {initAttrs(attrs)initViews()setupClickListeners()}
}
关键点解析:
- 继承ViewGroup而不是直接继承Toolbar(保持最大自由度)
- 采用组合模式而不是继承(方便后续扩展)
- 初始化拆分为属性解析、视图创建、事件绑定三步
2.2 测量布局实战
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {val maxWidth = MeasureSpec.getSize(widthMeasureSpec)var totalHeight = 0// 测量返回按钮backButton.measure(MeasureSpec.makeMeasureSpec(maxWidth, MeasureSpec.AT_MOST),MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED))totalHeight = max(totalHeight, backButton.measuredHeight)// 测量标题(最多占用剩余宽度的70%)val titleMaxWidth = (maxWidth - backButton.measuredWidth) * 0.7ftitleView.measure(MeasureSpec.makeMeasureSpec(titleMaxWidth.toInt(), MeasureSpec.AT_MOST),MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED))totalHeight = max(totalHeight, titleView.measuredHeight)// 设置最终尺寸setMeasuredDimension(maxWidth, resolveSize(totalHeight + paddingTop + paddingBottom, heightMeasureSpec))
}
避坑指南:
- 处理wrap_content时需要特别注意AT_MOST模式
- 带IconFont的TextView需要单独处理CompoundDrawable测量
- 多语言文本可能导致测量抖动,需要添加layout稳定机制
2.3 自定义属性大全
<!-- res/values/attrs.xml -->
<declare-styleable name="ToolbarView"><!-- 背景相关 --><attr name="toolbarBackground" format="color|reference" /><attr name="cornerRadius" format="dimension" /><!-- 标题样式 --><attr name="titleText" format="string" /><attr name="titleTextColor" format="color" /><attr name="titleTextSize" format="dimension" /><!-- 返回按钮特殊配置 --><attr name="backIcon" format="reference" /><attr name="backIconTint" format="color" />
</declare-styleable>
属性解析黑科技:
private fun initAttrs(attrs: AttributeSet?) {context.obtainStyledAttributes(attrs, R.styleable.ToolbarView).apply {// 解析渐变背景getDrawable(R.styleable.ToolbarView_toolbarBackground)?.let {background = if (it is GradientDrawable) {it.apply { cornerRadius = getDimension(...) }} else it}// 动态创建标题ViewtitleView.text = getString(R.styleable.ToolbarView_titleText)titleView.setTextColor(getColor(R.styleable.ToolbarView_titleTextColor, Color.BLACK))// 返回按钮图标处理backButton.setImageDrawable(getDrawable(R.styleable.ToolbarView_backIcon))DrawableCompat.setTint(backButton.drawable, getColor(...))recycle()}
}
三、高级技巧加持
3.1 沉浸式状态栏适配
fun fitsSystemWindow() {val statusBarHeight = getStatusBarHeight()setPadding(paddingLeft, paddingTop + statusBarHeight, paddingRight, paddingBottom)layoutParams = layoutParams.apply { height += statusBarHeight }
}private fun getStatusBarHeight(): Int {val resourceId = resources.getIdentifier("status_bar_height", "dimen", "android")return if (resourceId > 0) resources.getDimensionPixelSize(resourceId) else 0
}
3.2 动态主题切换
fun applyDarkTheme(isDark: Boolean) {val textColor = if (isDark) Color.WHITE else Color.BLACKval iconTint = if (isDark) Color.WHITE else Color.DKGRAYtitleView.setTextColor(textColor)backButton.drawable.setTint(iconTint)actionMenu.children.forEach { (it as? ImageView)?.drawable?.setTint(iconTint) }// 带动画效果更丝滑animate().setDuration(300).alpha(0.8f).withEndAction { animate().alpha(1f) }
}
四、调试踩坑记录
4.1 触摸事件冲突
症状:滑动返回手势和按钮点击冲突
处方:重写onInterceptTouchEvent
override fun onInterceptTouchEvent(ev: MotionEvent): Boolean {return when {// 在左右边缘30dp内时交给系统处理滑动返回ev.x < 30.dp || ev.x > width - 30.dp -> false// 其他区域自己处理点击else -> super.onInterceptTouchEvent(ev)}
}
4.2 内存泄漏检测
在onDetachedFromWindow中释放资源:
override fun onDetachedFromWindow() {super.onDetachedFromWindow()// 清除动画clearAnimation()// 解绑回调backButton.setOnClickListener(null)// 释放大图资源backButton.setImageDrawable(null)
}
经验之谈:自定义View就像搭积木,先拆解设计稿,再组合基础组件,最后打磨细节。记得多用Canvas.saveLayer()来调试绘制范围!