自定义View获取宽高

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:

代码:

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;  

8.  public TestLayout(Context context) {  
9.  this(context, null);  
10.  }  

12.  public TestLayout(Context context, AttributeSet attrs) {  
13.  this(context, attrs, 0);  
14.  }  

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.  }  

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.  }  

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.  }  

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.  }  

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.  }  

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:

**[html]** [view plain](http://blog.csdn.net/mchenys/article/details/50408819# "view plain") [copy](http://blog.csdn.net/mchenys/article/details/50408819# "copy")

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  

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.

自定义View获取宽高

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