本文主要是介绍View-＞View测量布局中requestLayout和forceLayout的区别，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
XML文件
<?xml version="1.0" encoding="utf-8"?>
<com.gallery20.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.gallery20.app.MyViewandroid:id="@+id/my_view"android:layout_width="match_parent"android:layout_height="100dp"android:background="@android:color/holo_blue_light"/><com.gallery20.app.MyButtonandroid: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 ?= 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()// 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", "<-------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()// 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
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