View-＞View测量布局中requestLayout和forceLayout的区别

XML文件

<com.gallery20.app.MyLinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/my_ll"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/holo_green_light"
    android:gravity="center"
    android:orientation="vertical">
    <com.gallery20.app.MyView
        android:id="@+id/my_view"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:background="@android:color/holo_blue_light"/>
    <com.gallery20.app.MyButton
        android:id="@+id/my_btn"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:background="@android:color/holo_red_light"/>
</com.gallery20.app.MyLinearLayout>

Activity文件

const val TAG = "Yang"
class MainActivity : AppCompatActivity() {
    private var mViewGroup : LinearLayout ?= null
    private var mButton : Button ?= null
    private var mView : View?= null
    private var mMainHandler = Handler(Looper.getMainLooper())
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        mViewGroup = findViewById(R.id.my_ll)
        mButton = findViewById(R.id.my_btn)
        mView = findViewById(R.id.my_view)
        mMainHandler.postDelayed({
            Log.i("yang", "")
            // 请求重新布局
            mView?.requestLayout()
        }, 2000)
    }
}

自定义View代码

class MyButton(context: Context, attrs: AttributeSet) : AppCompatButton(context, attrs) {
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
Log.d(TAG, "MyButton onMeasure")
}
override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
super.onLayout(changed, l, t, r, b)
Log.d(TAG, "MyButton onLayout")
}
override fun onDraw(canvas: Canvas?) {
super.onDraw(canvas)
Log.d(TAG, "MyButton onDraw")
}
}
class MyLinearLayout(context: Context, attrs: AttributeSet) : LinearLayout(context, attrs) {
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
Log.d(TAG, "MyLinearLayout onMeasure")
}
override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
super.onLayout(changed, l, t, r, b)
Log.d(TAG, "MyLinearLayout onLayout")
}
override fun onDraw(canvas: Canvas?) {
super.onDraw(canvas)
Log.d(TAG, "MyLinearLayout onDraw")
}
}
class MyView(context: Context, attrs: AttributeSet) : View(context, attrs) {
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec)
Log.d(TAG, "MyView onMeasure")
}
override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
super.onLayout(changed, l, t, r, b)
Log.d(TAG, "MyView onLayout")
}
override fun onDraw(canvas: Canvas?) {
super.onDraw(canvas)
Log.d(TAG, "MyView onDraw")
}
fun updateView() {
val layoutParams = layoutParams
layoutParams.height += 100
}
}

requestLayout()方法

• 不修改View的布局参数

 mMainHandler.postDelayed({
Log.i("yang", "")
// 请求重新布局
mView?.requestLayout()
}, 2000)
// log 
2024-06-09 08:42:24.081  4438-4438  yang                    I  <-------requestLayout------->
2024-06-09 08:42:24.089  4438-4438  Yang                    D  MyView onMeasure
2024-06-09 08:42:24.089  4438-4438  Yang                    D  MyLinearLayout onMeasure
2024-06-09 08:42:24.089  4438-4438  Yang                    D  MyView onLayout
2024-06-09 08:42:24.089  4438-4438  Yang                    D  MyLinearLayout onLayout
2024-06-09 08:42:24.089  4438-4438  Yang                    D  MyLinearLayout onDraw
2024-06-09 08:42:24.089  4438-4438  Yang                    D  MyView onDraw

• 修改View的布局参数

mMainHandler.postDelayed({
Log.i("yang", "")
mView?.updateView()
// 请求重新布局
mView?.requestLayout()
}, 2000)
// log
2024-06-09 08:50:21.373  4943-4943  yang                 I  <-------requestLayout------->
2024-06-09 08:50:21.376  4943-4943  Yang                 D  MyView onMeasure
2024-06-09 08:50:21.376  4943-4943  Yang                 D  MyLinearLayout onMeasure
2024-06-09 08:50:21.376  4943-4943  Yang                 D  MyView onLayout
2024-06-09 08:50:21.376  4943-4943  Yang                 D  MyButton onLayout
2024-06-09 08:50:21.376  4943-4943  Yang                 D  MyLinearLayout onLayout
2024-06-09 08:50:21.377  4943-4943  Yang                 D  MyLinearLayout onDraw
2024-06-09 08:50:21.377  4943-4943  Yang                 D  MyView onDraw
2024-06-09 08:50:21.384  4943-4943  Yang                 D  MyView onDraw 

forceLayout()方法

• 不修改View的布局参数

mMainHandler.postDelayed({
Log.i("yang", "")
// 请求重新布局
mView?.forceLayout()
}, 2000)
// log 
没有改变View的可见性、改变View的大小或位置，无任何Log输出

• 修改View的布局参数

mMainHandler.postDelayed({
Log.i("yang", "")
mView?.updateView()
// 请求重新布局
mView?.forceLayout()
}, 2000)
// log
2024-06-09 08:57:53.732  5625-5625  yang                   I  <-------forceLayout------->
2024-06-09 08:57:53.741  5625-5625  Yang                   D  MyView onMeasure
2024-06-09 08:57:53.741  5625-5625  Yang                   D  MyLinearLayout onMeasure
2024-06-09 08:57:53.741  5625-5625  Yang                   D  MyView onLayout
2024-06-09 08:57:53.741  5625-5625  Yang                   D  MyButton onLayout
2024-06-09 08:57:53.741  5625-5625  Yang                   D  MyLinearLayout onLayout
2024-06-09 08:57:53.741  5625-5625  Yang                   D  MyLinearLayout onDraw
2024-06-09 08:57:53.742  5625-5625  Yang                   D  MyView onDraw
2024-06-09 08:57:53.748  5625-5625  Yang                   D  MyView onDraw

总结

• forceLayout()和requestLayout()的主要区别在于影响范围：
  • forceLayout()将当前View标记为需要重新布局，但并不会立即触发布局过程。只有在下次draw(Canvas)方法被调用时，才会对其进行重新布局
  • requestLayout()将当前View以及其所有父View标记为需要重新布局。并不意味兄弟View也会被重新测量和布局。只有当这个View的父View的布局参数（如宽度、高度、权重等）发生变化，或者父View的onLayout()方法被重写改变子View的布局方式时，兄弟View才可能会被重新测量和布局
  • 仅调用forceLayout()或requestLayout()并不会影响到其兄弟View的测量和布局，除非父View的布局参数或布局方式发生了变化