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

XML文件

<?xml version="1.0" encoding="utf-8"?>
<com.app.MyLinearLayoutxmlns: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.app.MyViewandroid:id="@+id/my_view"android:layout_width="match_parent"android:layout_height="100dp"android:background="@android:color/holo_blue_light"/><com.app.MyButtonandroid:id="@+id/my_btn"android:layout_width="match_parent"android:layout_height="100dp"android:background="@android:color/holo_red_light"/>
</com.app.MyLinearLayout>

Activity文件

const val TAG = "Yang"
class MainActivity : AppCompatActivity() {private var mViewGroup : LinearLayout ?= nullprivate var mButton : Button ?= nullprivate var mView : View?= nullprivate 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", "<-------requestLayout------->")// 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 = layoutParamslayoutParams.height += 100}
}

requestLayout()方法

• 不修改View的布局参数

 mMainHandler.postDelayed({Log.i("yang", "<-------requestLayout------->")// 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", "<-------requestLayout------->")mView?.updateView()
}, 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", "<-------forceLayout------->")// 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", "<-------forceLayout------->")mView?.updateView()
}, 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，没有改变View的可见性、改变View的大小或位置，不会调用onMeasure、onLayout、onSizeChanged、onDraw
  • 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