自定义View常用的获取宽高信息

自定义View的时候经常少不了获取View的宽高信息,当然不一定是自定义View的时候才会需要获取宽高信息,其他情况下我们也会有这样的需求,获取方式和获取的时机也十分讲究.下面分别从这几个api讲起:

1.构造方法

2.onFinishInflate

3.onSizeChanged

4.onMeasure

5.onWindowFocusChanged

6.onLayout

7.View.getViewTreeObserver().addOnGlobalLayoutListener

以上几种方式获取的时机各有不同,且回调次数和条件也不相同.先来看看demo,下面是一个自定义的FrameLayout的子类,包含2个TextView控件.

布局如下:

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  1. <?xml version="1.0" encoding="utf-8"?>  
  2. <mchenys.net.csdn.blog.testlayout.view.TestLayout  
  3.     xmlns:android="http://schemas.android.com/apk/res/android"  
  4.     xmlns:tools="http://schemas.android.com/tools"  
  5.     android:layout_width="match_parent"  
  6.     android:layout_height="match_parent"  
  7.     >  
  8.     <TextView  
  9.         android:layout_width="match_parent"  
  10.         android:layout_height="300dp"  
  11.         android:background="#f00"  
  12.         android:gravity="center"  
  13.         android:text="First Part"  
  14.         android:textSize="30sp"/>  
  15.   
  16.     <TextView  
  17.         android:layout_width="match_parent"  
  18.         android:layout_height="match_parent"  
  19.         android:layout_marginTop="300dp"  
  20.         android:background="#00f"  
  21.         android:gravity="center"  
  22.         android:text="Second Part"  
  23.         android:textSize="30sp"/>  
  24. </mchenys.net.csdn.blog.testlayout.view.TestLayout>  
代码:
[java] view plain copy
  1. /** 
  2.  * Created by mChenys on 2015/12/23. 
  3.  */  
  4. public class TestLayout extends FrameLayout {  
  5.     private View mFistPart, mSecondPart;  
  6.     private int mFistHeight, mSecondHeight;  
  7.   
  8.     public TestLayout(Context context) {  
  9.         this(context, null);  
  10.     }  
  11.   
  12.     public TestLayout(Context context, AttributeSet attrs) {  
  13.         this(context, attrs, 0);  
  14.     }  
  15.   
  16.     public TestLayout(Context context, AttributeSet attrs, int defStyleAttr) {  
  17.         super(context, attrs, defStyleAttr);  
  18.         System.out.println("----------Constructor-------------");  
  19.         mFistPart = getChildAt(0);  
  20.         mSecondPart = getChildAt(1);  
  21.         System.out.println("mFistPart:" + mFistPart + " mSecondPart:" + mSecondPart);  
  22.     }  
  23.   
  24.     @Override  
  25.     protected void onFinishInflate() {  
  26.         super.onFinishInflate();  
  27.         mFistPart = getChildAt(0);  
  28.         mSecondPart = getChildAt(1);  
  29.         mFistHeight = mFistPart.getMeasuredHeight();  
  30.         mSecondHeight = mSecondPart.getMeasuredHeight();  
  31.         System.out.println("----------onFinishInflate-------------");  
  32.         System.out.println("mFistPart:" + mFistPart + " mSecondPart:" + mSecondPart);  
  33.         System.out.println("mFistPart.getMeasuredHeight():" + mFistHeight + " mSecondPart.getMeasuredHeight():" + mSecondHeight);  
  34.         System.out.println("mFistPart.getHeight():" + mFistPart.getHeight() + " mSecondPart.getHeight():" + mSecondPart.getHeight());  
  35.         mFistPart.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {  
  36.             @TargetApi(Build.VERSION_CODES.JELLY_BEAN)  
  37.             @Override  
  38.             public void onGlobalLayout() {  
  39.                 System.out.println("----------addOnGlobalLayoutListener-------------");  
  40.                 mFistPart.getViewTreeObserver().removeOnGlobalLayoutListener(this);  
  41.                 System.out.println("mFistPart.getMeasuredHeight():" + mFistPart.getMeasuredHeight() + "mFistPart.getHeight():" + mFistPart.getMeasuredHeight());  
  42.             }  
  43.         });  
  44.         mSecondPart.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {  
  45.             @TargetApi(Build.VERSION_CODES.JELLY_BEAN)  
  46.             @Override  
  47.             public void onGlobalLayout() {  
  48.                 System.out.println("----------addOnGlobalLayoutListener-------------");  
  49.                 mSecondPart.getViewTreeObserver().removeOnGlobalLayoutListener(this);  
  50.                 System.out.println("mFistPart.getMeasuredHeight():" + mSecondPart.getMeasuredHeight() + "mFistPart.getHeight():" + mSecondPart.getMeasuredHeight());  
  51.             }  
  52.         });  
  53.     }  
  54.   
  55.     @Override  
  56.     protected void onSizeChanged(int w, int h, int oldw, int oldh) {  
  57.         super.onSizeChanged(w, h, oldw, oldh);  
  58.         mFistHeight = mFistPart.getMeasuredHeight();  
  59.         mSecondHeight = mSecondPart.getMeasuredHeight();  
  60.         System.out.println("----------onSizeChanged-------------");  
  61.         System.out.println("mFistPart:" + mFistPart + " mSecondPart:" + mSecondPart);  
  62.         System.out.println("mFistPart.getMeasuredHeight():" + mFistHeight + " mSecondPart.getMeasuredHeight():" + mSecondHeight);  
  63.         System.out.println("mFistPart.getHeight():" + mFistPart.getHeight() + " mSecondPart.getHeight():" + mSecondPart.getHeight());  
  64.     }  
  65.   
  66.     @Override  
  67.     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  
  68.         super.onMeasure(widthMeasureSpec, heightMeasureSpec);  
  69.         mFistHeight = mFistPart.getMeasuredHeight();  
  70.         mSecondHeight = mSecondPart.getMeasuredHeight();  
  71.         System.out.println("----------onMeasure-------------");  
  72.         System.out.println("mFistPart:" + mFistPart + " mSecondPart:" + mSecondPart);  
  73.         System.out.println("mFistPart.getMeasuredHeight():" + mFistHeight + " mSecondPart.getMeasuredHeight():" + mSecondHeight);  
  74.         System.out.println("mFistPart.getHeight():" + mFistPart.getHeight() + " mSecondPart.getHeight():" + mSecondPart.getHeight());  
  75.     }  
  76.   
  77.     @Override  
  78.     public void onWindowFocusChanged(boolean hasWindowFocus) {  
  79.         super.onWindowFocusChanged(hasWindowFocus);  
  80.         mFistHeight = mFistPart.getMeasuredHeight();  
  81.         mSecondHeight = mSecondPart.getMeasuredHeight();  
  82.         System.out.println("----------onWindowFocusChanged-------------");  
  83.         System.out.println("mFistPart:" + mFistPart + " mSecondPart:" + mSecondPart + " hasWindowFocus:" + hasWindowFocus);  
  84.         System.out.println("mFistPart.getMeasuredHeight():" + mFistHeight + " mSecondPart.getMeasuredHeight():" + mSecondHeight);  
  85.         System.out.println("mFistPart.getHeight():" + mFistPart.getHeight() + " mSecondPart.getHeight():" + mSecondPart.getHeight());  
  86.     }  
  87.   
  88.     @Override  
  89.     protected void onLayout(boolean changed, int left, int top, int right, int bottom) {  
  90.         super.onLayout(changed, left, top, right, bottom);  
  91.         mFistHeight = mFistPart.getMeasuredHeight();  
  92.         mSecondHeight = mSecondPart.getMeasuredHeight();  
  93.         System.out.println("----------onLayout-------------");  
  94.         System.out.println("mFistPart:" + mFistPart + " mSecondPart:" + mSecondPart);  
  95.         System.out.println("mFistPart.getMeasuredHeight():" + mFistHeight + " mSecondPart.getMeasuredHeight():" + mSecondHeight);  
  96.         System.out.println("mFistPart.getHeight():" + mFistPart.getHeight() + " mSecondPart.getHeight():" + mSecondPart.getHeight());  
  97.     }  
  98. }  
上面每一种方法都分别打印了该自定义控件的2个子控件引用,2个子控件的getMeasuredHeight和2个子控件的getHeight,来看下log:

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  1. System.out: ----------Constructor-------------  
  2. System.out: mFistPart:null mSecondPart:null  
  3. System.out: ----------onFinishInflate-------------  
  4. System.out: mFistPart:android.support.v7.widget.AppCompatTextView{fb4034c V.ED..... ......ID 0,0-0,0} mSecondPart:android.support.v7.widget.AppCompatTextView{16ebf95 V.ED..... ......ID 0,0-0,0}  
  5. System.out: mFistPart.getMeasuredHeight():0 mSecondPart.getMeasuredHeight():0  
  6. System.out: mFistPart.getHeight():0 mSecondPart.getHeight():0  
  7. System.out: ----------onMeasure-------------  
  8. System.out: mFistPart:android.support.v7.widget.AppCompatTextView{fb4034c V.ED..... ......ID 0,0-0,0} mSecondPart:android.support.v7.widget.AppCompatTextView{16ebf95 V.ED..... ......ID 0,0-0,0}  
  9. System.out: mFistPart.getMeasuredHeight():600 mSecondPart.getMeasuredHeight():328  
  10. System.out: mFistPart.getHeight():0 mSecondPart.getHeight():0  
  11.   
  12. System.out: ----------onMeasure-------------  
  13. System.out: mFistPart:android.support.v7.widget.AppCompatTextView{fb4034c V.ED..... ......ID 0,0-0,0} mSecondPart:android.support.v7.widget.AppCompatTextView{16ebf95 V.ED..... ......ID 0,0-0,0}  
  14. System.out: mFistPart.getMeasuredHeight():600 mSecondPart.getMeasuredHeight():424  
  15. System.out: mFistPart.getHeight():0 mSecondPart.getHeight():0  
  16. System.out: ----------onSizeChanged-------------  
  17. System.out: mFistPart:android.support.v7.widget.AppCompatTextView{fb4034c V.ED..... ......ID 0,0-0,0} mSecondPart:android.support.v7.widget.AppCompatTextView{16ebf95 V.ED..... ......ID 0,0-0,0}  
  18. System.out: mFistPart.getMeasuredHeight():600 mSecondPart.getMeasuredHeight():424  
  19. System.out: mFistPart.getHeight():0 mSecondPart.getHeight():0  
  20. System.out: ----------onLayout-------------  
  21. System.out: mFistPart:android.support.v7.widget.AppCompatTextView{fb4034c V.ED..... ......ID 0,0-720,600} mSecondPart:android.support.v7.widget.AppCompatTextView{16ebf95 V.ED..... ......ID 0,600-720,1024}  
  22. System.out: mFistPart.getMeasuredHeight():600 mSecondPart.getMeasuredHeight():424  
  23. System.out: mFistPart.getHeight():600 mSecondPart.getHeight():424  
  24. System.out: ----------addOnGlobalLayoutListener-------------  
  25. System.out: mFistPart.getMeasuredHeight():600mFistPart.getHeight():600  
  26. System.out: ----------addOnGlobalLayoutListener-------------  
  27. System.out: mFistPart.getMeasuredHeight():424mFistPart.getHeight():424  
  28. System.out: ----------onWindowFocusChanged-------------  
  29. System.out: mFistPart:android.support.v7.widget.AppCompatTextView{fb4034c V.ED..... ......ID 0,0-720,600} mSecondPart:android.support.v7.widget.AppCompatTextView{16ebf95 V.ED..... ......ID 0,600-720,1024} hasWindowFocus:true  
  30. System.out: mFistPart.getMeasuredHeight():600 mSecondPart.getMeasuredHeight():424  
  31. System.out: mFistPart.getHeight():600 mSecondPart.getHeight():424  
  32. System.out: ----------onMeasure-------------  
  33. System.out: mFistPart:android.support.v7.widget.AppCompatTextView{fb4034c V.ED..... ......ID 0,0-720,600} mSecondPart:android.support.v7.widget.AppCompatTextView{16ebf95 V.ED..... ......ID 0,600-720,1024}  
  34. System.out: mFistPart.getMeasuredHeight():600 mSecondPart.getMeasuredHeight():424  
  35. System.out: mFistPart.getHeight():600 mSecondPart.getHeight():424  
  36. System.out: ----------onLayout-------------  
  37. System.out: mFistPart:android.support.v7.widget.AppCompatTextView{fb4034c V.ED..... ......ID 0,0-720,600} mSecondPart:android.support.v7.widget.AppCompatTextView{16ebf95 V.ED..... ......ID 0,600-720,1024}  
  38. System.out: mFistPart.getMeasuredHeight():600 mSecondPart.getMeasuredHeight():424  
  39. System.out: mFistPart.getHeight():600 mSecondPart.getHeight():424  

总结:

1.从执行顺序分析

Constructor->onFinishInflate->onMeasure..->onSizeChanged->onLayout->addOnGlobalLayoutListener->onWindowFocusChanged->onMeasure->onLayout

由上可知,onMeasure和onLayout会被多次调用.


2.从api上分析

1)Constructor:构造方法,View初始化的时候调用,在这里是无法获取其子控件的引用的.更加无法获取宽高了.

2)onFinishInflate:当布局初始化完毕后回调,在这里可以获取所有直接子View的引用,但是无法获取宽高.

3)onMeasure:当测量控件宽高时回调,当调用了requestLayout()也会回调onMeasure.在这里一定可以通过getMeasuredHeight()和getMeasuredWidth()来获取控件的高和宽,但不一定可以通过getHeight()和getWidth()来获取控件宽高,因为getHeight()和getWidth()必须要等onLayout方法回调之后才能确定.

4)onSizeChanged:当控件的宽高发生变化时回调,和onMeasure一样,一定可以通过getMeasuredHeight()和getMeasuredWidth()来获取控件的高和宽,因为它是在onMeasure方法执行之后和onLayout方法之前回调的.

5)onLayout:当确定控件的位置时回调,当调用了requestLayout()也会回调onLayout.在这里一定可以通过getHeight()和getWidth()获取控件的宽高,同时由于onMeasure方法比onLayout方法先执行,所以在这里也可以通过getMeasuredHeight()和getMeasuredWidth()来获取控件的高和宽.

6)addOnGlobalLayoutListener:当View的位置确定完后会回调改监听方法,它是紧接着onLayout方法执行而执行的,只要onLayout方法调用了,那么addOnGlobalLayoutListener的监听器就会监听到.在这里getMeasuredHeight()和getMeasuredWidth()和getHeight()和getWidth()都可以获取到宽高.

7)onWindowFocusChanged:当View的焦点发送改变时回调,在这里getMeasuredHeight()和getMeasuredWidth()和getHeight()和getWidth()都可以获取到宽高.Activity也可以通过重写该方法来判断当前的焦点是否发送改变了;需要注意的是这里View获取焦点和失去焦点都会回调.


那么,上面分析了那么多方法来获取控件的宽高,那到底用哪一种呢?

具体要用哪一种,是需要根据View的宽高是否会发生变化来决定:

1.如果自定义的View在使用的过程中宽高信息是不会改变的,那么上面方式3~方式7都可以使用.

2.如果自定义的View在使用过程中宽高信息都会发生改变的,而且又需要获取一开始时的宽高信息,那么建议使用View.getViewTreeObserver().addOnGlobalLayoutListener(OnGlobalLayoutListener listener)的方式,因为这种方式有getViewTreeObserver().removeOnGlobalLayoutListener(this);来避免回调函数因宽高信息的变化而多次调用,如果使用其他方式的话,就要借助额外的变量来保证获取到的宽高是View的初始高度.

posted @ 2016-09-19 11:03  vegatate  阅读(540)  评论(0编辑  收藏  举报