Android View绘制13问13答

1.View的绘制流程分几步,从哪开始?哪个过程结束以后能看到view?

答:从ViewRoot的performTraversals开始,经过measure,layout,draw 三个流程。draw流程结束以后就可以在屏幕上看到view了。

 

2.view的测量宽高和实际宽高有区别吗?

答:基本上百分之99的情况下都是可以认为没有区别的。有两种情况,有区别。第一种 就是有的时候会因为某些原因 view会多次测量,那第一次测量的宽高 肯定和最后实际的宽高 是不一定相等的,但是在这种情况下

最后一次测量的宽高和实际宽高是一致的。此外,实际宽高是在layout流程里确定的,我们可以在layout流程里 将实际宽高写死 写成硬编码,这样测量的宽高和实际宽高就肯定不一样了,虽然这么做没有意义 而且也不好。

 

3.view的measureSpec 由谁决定?顶级view呢?

答:由view自己的layoutparams和父容器  一起决定自己的measureSpec。一旦确定了spec,onMeasure中就可以确定view的宽高了。

顶级view就稍微特殊一点,对于decorView的测量在ViewRootImpl的源码里。

 1  
 2 
 3   //desire的这2个参数就代表屏幕的宽高,
 4   childWidthMeasureSpec = getRootMeasureSpec(desiredWindowWidth, lp.width);
 5   childHeightMeasureSpec = getRootMeasureSpec(desiredWindowHeight, lp.height);
 6   performMeasure(childWidthMeasureSpec, childHeightMeasureSpec);
 7 
 8 
 9 
10   //decorView的measureSpec就是在这里确定的,其实比普通view的measurespec要简单的多
11   //代码就不分析了 一目了然的东西
12   private static int getRootMeasureSpec(int windowSize, int rootDimension) {
13         int measureSpec;
14         switch (rootDimension) {
15 
16         case ViewGroup.LayoutParams.MATCH_PARENT:
17             // Window can't resize. Force root view to be windowSize.
18             measureSpec = MeasureSpec.makeMeasureSpec(windowSize, MeasureSpec.EXACTLY);
19             break;
20         case ViewGroup.LayoutParams.WRAP_CONTENT:
21             // Window can resize. Set max size for root view.
22             measureSpec = MeasureSpec.makeMeasureSpec(windowSize, MeasureSpec.AT_MOST);
23             break;
24         default:
25             // Window wants to be an exact size. Force root view to be that size.
26             measureSpec = MeasureSpec.makeMeasureSpec(rootDimension, MeasureSpec.EXACTLY);
27             break;
28         }
29         return measureSpec;
30 }
View Code

 

4.对于普通view来说,他的measure过程中,与父view有关吗?如果有关,这个父view也就是viewgroup扮演了什么角色?

答:看源码:

  1 //对于普通view的measure来说 是由这个view的 父view ,也就是viewgroup来触发的。
  2 //也就是下面这个measureChildWithMargins方法
  3 
  4 protected void measureChildWithMargins(View child,
  5             int parentWidthMeasureSpec, int widthUsed,
  6             int parentHeightMeasureSpec, int heightUsed) {
  7          //第一步 先取得子view的 layoutParams 参数值   
  8         final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
  9 
 10         //然后开始计算子view的spec的值,注意这里看到 计算的时候除了要用子view的 layoutparams参数以外
 11         //还用到了父view 也就是viewgroup自己的spec的值
 12         final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec,
 13                 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin
 14                         + widthUsed, lp.width);
 15         final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec,
 16                 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin
 17                         + heightUsed, lp.height);
 18 
 19         child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
 20 }
 21 
 22 
 23 
 24 
 25 
 26 
 27 //这个算view的spec的方法 看上去一大串 但是真的逻辑非常简单 就是根据父亲viewgroup
 28 //的meaurespec 同时还有view自己的params来确定 view自己的measureSpec。
 29 //注意这里的参数是padding,这个值的含义是 父容器已占用的控件的大小 所以view的Specsize
 30 //的值 你们可以看到 是要减去这个padding的值的。总大小-已经用的 =可用的。 很好理解。
 31 
 32 //然后就是下面的switch逻辑 要自己梳理清楚。其实也不难,主要是下面几条原则
 33 //如果view采用固定宽高,也就是写死的数值那种。那就不管父亲的spec的值了,view的spec 就肯定是exactly 并且大小遵循layout参数里设置的大小。
 34 
 35 //如果view的宽高是match_parent ,那么就要看父容器viewgroup的 spec的值了,如果父view的spec是exactly模式,
 36 //那view也肯定是exactly,并且大小就是父容器剩下的空间。如果父容器是at_most模式,那view也是at_most 并且不会超过剩余空间大小
 37 
 38 //如果view的宽高是wrap_content, 那就不管父容器的spec了,view的spec一定是at_most 并且不会超过父view 剩余空间的大小。
 39 
 40 
 41 public static int getChildMeasureSpec(int spec, int padding, int childDimension) {
 42         int specMode = MeasureSpec.getMode(spec);
 43         int specSize = MeasureSpec.getSize(spec);
 44 
 45         int size = Math.max(0, specSize - padding);
 46 
 47         int resultSize = 0;
 48         int resultMode = 0;
 49 
 50         switch (specMode) {
 51         // Parent has imposed an exact size on us
 52         case MeasureSpec.EXACTLY:
 53             if (childDimension >= 0) {
 54                 resultSize = childDimension;
 55                 resultMode = MeasureSpec.EXACTLY;
 56             } else if (childDimension == LayoutParams.MATCH_PARENT) {
 57                 // Child wants to be our size. So be it.
 58                 resultSize = size;
 59                 resultMode = MeasureSpec.EXACTLY;
 60             } else if (childDimension == LayoutParams.WRAP_CONTENT) {
 61                 // Child wants to determine its own size. It can't be
 62                 // bigger than us.
 63                 resultSize = size;
 64                 resultMode = MeasureSpec.AT_MOST;
 65             }
 66             break;
 67 
 68         // Parent has imposed a maximum size on us
 69         case MeasureSpec.AT_MOST:
 70             if (childDimension >= 0) {
 71                 // Child wants a specific size... so be it
 72                 resultSize = childDimension;
 73                 resultMode = MeasureSpec.EXACTLY;
 74             } else if (childDimension == LayoutParams.MATCH_PARENT) {
 75                 // Child wants to be our size, but our size is not fixed.
 76                 // Constrain child to not be bigger than us.
 77                 resultSize = size;
 78                 resultMode = MeasureSpec.AT_MOST;
 79             } else if (childDimension == LayoutParams.WRAP_CONTENT) {
 80                 // Child wants to determine its own size. It can't be
 81                 // bigger than us.
 82                 resultSize = size;
 83                 resultMode = MeasureSpec.AT_MOST;
 84             }
 85             break;
 86 
 87         // Parent asked to see how big we want to be
 88         case MeasureSpec.UNSPECIFIED:
 89             if (childDimension >= 0) {
 90                 // Child wants a specific size... let him have it
 91                 resultSize = childDimension;
 92                 resultMode = MeasureSpec.EXACTLY;
 93             } else if (childDimension == LayoutParams.MATCH_PARENT) {
 94                 // Child wants to be our size... find out how big it should
 95                 // be
 96                 resultSize = View.sUseZeroUnspecifiedMeasureSpec ? 0 : size;
 97                 resultMode = MeasureSpec.UNSPECIFIED;
 98             } else if (childDimension == LayoutParams.WRAP_CONTENT) {
 99                 // Child wants to determine its own size.... find out how
100                 // big it should be
101                 resultSize = View.sUseZeroUnspecifiedMeasureSpec ? 0 : size;
102                 resultMode = MeasureSpec.UNSPECIFIED;
103             }
104             break;
105         }
106         return MeasureSpec.makeMeasureSpec(resultSize, resultMode);
107     }
View Code

 

5.view的meaure和onMeasure有什么关系?

答:看源码:

 1 //view的measure是final 方法 我们子类无法修改的。
 2  public final void measure(int widthMeasureSpec, int heightMeasureSpec) {
 3         boolean optical = isLayoutModeOptical(this);
 4         if (optical != isLayoutModeOptical(mParent)) {
 5             Insets insets = getOpticalInsets();
 6             int oWidth  = insets.left + insets.right;
 7             int oHeight = insets.top  + insets.bottom;
 8             widthMeasureSpec  = MeasureSpec.adjust(widthMeasureSpec,  optical ? -oWidth  : oWidth);
 9             heightMeasureSpec = MeasureSpec.adjust(heightMeasureSpec, optical ? -oHeight : oHeight);
10         }
11 
12         // Suppress sign extension for the low bytes
13         long key = (long) widthMeasureSpec << 32 | (long) heightMeasureSpec & 0xffffffffL;
14         if (mMeasureCache == null) mMeasureCache = new LongSparseLongArray(2);
15 
16         if ((mPrivateFlags & PFLAG_FORCE_LAYOUT) == PFLAG_FORCE_LAYOUT ||
17                 widthMeasureSpec != mOldWidthMeasureSpec ||
18                 heightMeasureSpec != mOldHeightMeasureSpec) {
19 
20             // first clears the measured dimension flag
21             mPrivateFlags &= ~PFLAG_MEASURED_DIMENSION_SET;
22 
23             resolveRtlPropertiesIfNeeded();
24 
25             int cacheIndex = (mPrivateFlags & PFLAG_FORCE_LAYOUT) == PFLAG_FORCE_LAYOUT ? -1 :
26                     mMeasureCache.indexOfKey(key);
27             if (cacheIndex < 0 || sIgnoreMeasureCache) {
28                 // measure ourselves, this should set the measured dimension flag back
29                 onMeasure(widthMeasureSpec, heightMeasureSpec);
30                 mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT;
31             } else {
32                 long value = mMeasureCache.valueAt(cacheIndex);
33                 // Casting a long to int drops the high 32 bits, no mask needed
34                 setMeasuredDimensionRaw((int) (value >> 32), (int) value);
35                 mPrivateFlags3 |= PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT;
36             }
37 
38             // flag not set, setMeasuredDimension() was not invoked, we raise
39             // an exception to warn the developer
40             if ((mPrivateFlags & PFLAG_MEASURED_DIMENSION_SET) != PFLAG_MEASURED_DIMENSION_SET) {
41                 throw new IllegalStateException("View with id " + getId() + ": "
42                         + getClass().getName() + "#onMeasure() did not set the"
43                         + " measured dimension by calling"
44                         + " setMeasuredDimension()");
45             }
46 
47             mPrivateFlags |= PFLAG_LAYOUT_REQUIRED;
48         }
49 
50         mOldWidthMeasureSpec = widthMeasureSpec;
51         mOldHeightMeasureSpec = heightMeasureSpec;
52 
53         mMeasureCache.put(key, ((long) mMeasuredWidth) << 32 |
54                 (long) mMeasuredHeight & 0xffffffffL); // suppress sign extension
55     }
56 
57 //不过可以看到的是在measure方法里调用了onMeasure方法
58 //所以就能知道 我们在自定义view的时候一定是重写这个方法!
59  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
60         setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),
61                 getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));
62     }
View Code

 

6.简要分析view的measure流程?

答:先回顾问题4,viewgroup 算出子view的spec以后 会调用子view的measure方法,而子view的measure方法 我们问题5也看过了实际上是调用的onMeasure方法

所以我们只要分析好onMeasure方法即可,注意onMeasure方法的参数 正是他的父view算出来的那2个spec的值(这里view的measure方法会把这个spec里的specSize值做略微的修改 这个部分 不做分析 因为measure方法修改specSize的部分很简单)。

 1  //可以看出来这个就是setMeasuredDimension方法的调用 这个方法看名字就知道就是确定view的测量宽高的
 2 //所以我们分析的重点就是看这个getDefaultSize 方法 是怎么确定view的测量宽高的
 3  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 4         setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),
 5                 getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));
 6     }
 7 
 8 
 9 //这个方法特别简单 基本可以认为就是近似的返回spec中的specSize,除非你的specMode是UNSPECIFIED
10 //UNSPECIFIED 这个一般都是系统内部测量才用的到,这种时候返回size 也就是getSuggestedMinimumWidth的返回值
11  public static int getDefaultSize(int size, int measureSpec) {
12         int result = size;
13         int specMode = MeasureSpec.getMode(measureSpec);
14         int specSize = MeasureSpec.getSize(measureSpec);
15 
16         switch (specMode) {
17         case MeasureSpec.UNSPECIFIED:
18             result = size;
19             break;
20         case MeasureSpec.AT_MOST:
21         case MeasureSpec.EXACTLY:
22             result = specSize;
23             break;
24         }
25         return result;
26 }
27 
28 //跟view的背景相关 这里不多做分析了
29 protected int getSuggestedMinimumWidth() {
30         return (mBackground == null) ? mMinWidth : max(mMinWidth, mBackground.getMinimumWidth());
31     }
View Code

 

7.自定义view中 如果onMeasure方法 没有对wrap_content 做处理 会发生什么?为什么?怎么解决?

答:如果没有对wrap_content做处理 ,那即使你在xml里设置为wrap_content.其效果也和match_parent相同。看问题4的分析。我们可以知道view自己的layout为wrap,那mode就是at_most(不管父亲view是什么specmode).

这种模式下宽高就是等于specSize(getDefaultSize函数分析可知),而这里的specSize显然就是parentSize的大小。也就是父容器剩余的大小。那不就和我们直接设置成match_parent是一样的效果了么?

解决方式就是在onMeasure里 针对wrap 来做特殊处理 比如指定一个默认的宽高,当发现是wrap_content 就设置这个默认宽高即可。

 

8.ViewGroup有onMeasure方法吗?为什么?

答:没有,这个方法是交给子类自己实现的。不同的viewgroup子类 肯定布局都不一样,那onMeasure索性就全部交给他们自己实现好了。

 

9.为什么在activity的生命周期里无法获得测量宽高?有什么方法可以解决这个问题吗?

答:因为measure的过程和activity的生命周期  没有任何关系。你无法确定在哪个生命周期执行完毕以后 view的measure过程一定走完。可以尝试如下几种方法 获取view的测量宽高。

 1 //重写activity的这个方法
 2 public void onWindowFocusChanged(boolean hasFocus) {
 3         super.onWindowFocusChanged(hasFocus);
 4         if (hasFocus) {
 5             int width = tv.getMeasuredWidth();
 6             int height = tv.getMeasuredHeight();
 7             Log.v("burning", "width==" + width);
 8             Log.v("burning", "height==" + height);
 9 
10         }
11     }
View Code

或者重写这个方法

 1  @Override
 2     protected void onStart() {
 3         super.onStart();
 4         tv.post(new Runnable() {
 5             @Override
 6             public void run() {
 7                 int width = tv.getMeasuredWidth();
 8                 int height = tv.getMeasuredHeight();
 9             }
10         });
11     }
View Code

再或者:

 1  @Override
 2     protected void onStart() {
 3         super.onStart();
 4         ViewTreeObserver observer = tv.getViewTreeObserver();
 5         observer.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
 6             @Override
 7             public void onGlobalLayout() {
 8                 int width = tv.getMeasuredWidth();
 9                 int height = tv.getMeasuredHeight();
10                 tv.getViewTreeObserver().removeOnGlobalLayoutListener(this);
11             }
12         });
13     }
View Code

 

10.layout和onLayout方法有什么区别?

答:layout是确定本身view的位置 而onLayout是确定所有子元素的位置。layout里面 就是通过serFrame方法设设定本身view的 四个顶点的位置。这4个位置以确定 自己view的位置就固定了

然后就调用onLayout来确定子元素的位置。view和viewgroup的onlayout方法都没有写。都留给我们自己给子元素布局

 

11.draw方法 大概有几个步骤?

答: 一共是4个步骤, 绘制背景---------绘制自己--------绘制chrildren----绘制装饰。

 

12.setWillNotDraw方法有什么用?

答:这个方法在view里。

 1  /**
 2      * If this view doesn't do any drawing on its own, set this flag to
 3      * allow further optimizations. By default, this flag is not set on
 4      * View, but could be set on some View subclasses such as ViewGroup.
 5      *
 6      * Typically, if you override {@link #onDraw(android.graphics.Canvas)}
 7      * you should clear this flag.
 8      *
 9      * @param willNotDraw whether or not this View draw on its own
10      */
11     public void setWillNotDraw(boolean willNotDraw) {
12         setFlags(willNotDraw ? WILL_NOT_DRAW : 0, DRAW_MASK);
13     }
View Code

用于设置标志位的 也就是说 如果你的自定义view 不需要draw的话,就可以设置这个方法为true。这样系统知道你这个view 不需要draw 可以优化执行速度。viewgroup 一般都默认设置这个为true,因为viewgroup多数都是只负责布局

不负责draw的。而view 这个标志位 默认一般都是关闭的。

 

13.自定义view 有哪些需要注意的点?

答:主要是要处理wrap_content 和padding。否则xml 那边设置这2个属性就根本没用了。还有不要在view中使用handler 因为人家已经提供了post方法。如果是继承自viewGroup,那在onMeasure和onLayout里面 也要考虑

padding和layout的影响。也就是说specSize 要算一下 。最后就是如果view的动画或者线程需要停止,可以考虑在onDetachedFromWindow里面来做。

针对上述的几点,给出几个简单的自定义view 供大家理解。

给出一个圆形的view 范例:

 1 package com.example.administrator.motioneventtest;
 2 
 3 import android.content.Context;
 4 import android.graphics.Canvas;
 5 import android.graphics.Color;
 6 import android.graphics.Paint;
 7 import android.util.AttributeSet;
 8 import android.view.View;
 9 
10 /**
11  * Created by Administrator on 2016/2/4.
12  */
13 public class CircleView extends View {
14 
15     private int mColor = Color.RED;
16     private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
17 
18     private void init() {
19         mPaint.setColor(mColor);
20     }
21 
22     @Override
23     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
24         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
25         int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
26         int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);
27         int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
28         int heightSpecSize = MeasureSpec.getSize(heightMeasureSpec);
29 
30         //处理为wrap_content时的情况
31         if (widthSpecMode == MeasureSpec.AT_MOST && heightSpecMode == MeasureSpec.AT_MOST) {
32             setMeasuredDimension(200, 200);
33         } else if (widthSpecMode == MeasureSpec.AT_MOST) {
34             setMeasuredDimension(200, heightSpecSize);
35         } else if (heightSpecMode == MeasureSpec.AT_MOST) {
36             setMeasuredDimension(widthSpecSize, 200);
37         }
38 
39     }
40 
41     @Override
42     protected void onDraw(Canvas canvas) {
43         super.onDraw(canvas);
44         //处理padding的情况
45         final int paddingLeft = getPaddingLeft();
46         final int paddingRight = getPaddingRight();
47         final int paddingTop = getPaddingTop();
48         final int paddingBottom = getPaddingBottom();
49 
50 
51         int width = getWidth() - paddingLeft - paddingRight;
52         int height = getHeight() - paddingTop - paddingBottom;
53         int radius = Math.min(width, height) / 2;
54         canvas.drawCircle(paddingLeft + width / 2, paddingTop + height / 2, radius, mPaint);
55     }
56 
57     public CircleView(Context context, AttributeSet attrs, int defStyleAttr) {
58         super(context, attrs, defStyleAttr);
59         init();
60     }
61 
62     public CircleView(Context context) {
63         super(context);
64         init();
65 
66     }
67 
68     public CircleView(Context context, AttributeSet attrs) {
69         super(context, attrs);
70         init();
71     }
72 }
View Code

然后下面再给出一个范例,稍微复杂一点是自定义viewgroup了(主要是加强对onMeasure和onLayout的理解), 需求如下:

一个水平的viewgroup,内部的子元素 为了简单 我们假定他们的宽高都是一样的。来写一个这样的简单的viewgroup。

 1 package com.example.administrator.motioneventtest;
 2 
 3 import android.content.Context;
 4 import android.util.AttributeSet;
 5 import android.util.Log;
 6 import android.view.View;
 7 import android.view.ViewGroup;
 8 
 9 /**
10  * Created by Administrator on 2016/2/4.
11  */
12 //这里我们只处理了padding的状态 没有处理margin的状态,子view的margin 对measure和layout的影响
13 //就留给读者自己完成了
14 public class CustomHorizontalLayout extends ViewGroup {
15 
16     //设置默认的控件最小是多少 这里不提供自定义属性了 写死在代码里 你们可以自行拓展
17     final int minHeight = 0;
18     final int minWidth = 0;
19 
20 
21     public CustomHorizontalLayout(Context context) {
22         super(context);
23     }
24 
25     public CustomHorizontalLayout(Context context, AttributeSet attrs) {
26         super(context, attrs);
27     }
28 
29     public CustomHorizontalLayout(Context context, AttributeSet attrs, int defStyleAttr) {
30         super(context, attrs, defStyleAttr);
31     }
32 
33     @Override
34     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
35         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
36         int measureWidth = 0;
37         int measureHeight = 0;
38         final int childCount = getChildCount();
39         measureChildren(widthMeasureSpec, heightMeasureSpec);
40         int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);
41         int widthSpecSize = MeasureSpec.getSize(widthMeasureSpec);
42         int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);
43         int heightSpecSize = MeasureSpec.getSize(heightMeasureSpec);
44         final View childView = getChildAt(0);
45         final int paddingLeft = getPaddingLeft();
46         final int paddingRight = getPaddingRight();
47         final int paddingTop = getPaddingTop();
48         final int paddingBottom = getPaddingBottom();
49         //没有子控件 时 我们的宽高要作特殊处理
50         if (childCount == 0) {
51             //当没有子控件时,如果长宽有一个为wrap 那么就让这个控件以最小的形式展现
52             //这里我们最小设置为0
53             if (widthSpecMode == MeasureSpec.AT_MOST || heightSpecMode == MeasureSpec.AT_MOST) {
54                 setMeasuredDimension(minWidth, minHeight);
55             } else {
56                 //否则根据我们的layout属性来
57                 setMeasuredDimension(getLayoutParams().width, getLayoutParams().height);
58             }
59 
60         } else if (widthSpecMode == MeasureSpec.AT_MOST && heightSpecMode == MeasureSpec.AT_MOST) {
61             measureWidth = childView.getMeasuredWidth() * childCount;
62             measureHeight = childView.getMeasuredHeight();
63             setMeasuredDimension(paddingLeft + measureWidth + paddingRight, paddingTop + measureHeight + paddingBottom);
64         } else if (heightSpecMode == MeasureSpec.AT_MOST) {
65             measureHeight = childView.getMeasuredHeight();
66             setMeasuredDimension(paddingLeft + paddingRight + widthSpecSize, paddingTop + paddingBottom + measureHeight);
67         } else if (widthSpecMode == MeasureSpec.AT_MOST) {
68             measureWidth = childView.getMeasuredWidth() * childCount;
69             setMeasuredDimension(paddingLeft + paddingRight + measureWidth, paddingTop + paddingBottom + heightSpecSize);
70         }
71     }
72 
73     @Override
74     protected void onLayout(boolean changed, int l, int t, int r, int b) {
75         final int paddingLeft = getPaddingLeft();
76         final int paddingRight = getPaddingRight();
77         final int paddingTop = getPaddingTop();
78         final int paddingBottom = getPaddingBottom();
79         //左边初始位置为0
80         int childLeft = 0 + paddingLeft;
81         final int childCount = getChildCount();
82         for (int i = 0; i < childCount; i++) {
83             final View childView = getChildAt(i);
84             if (childView.getVisibility() != View.GONE) {
85                 final int childWidth = childView.getMeasuredWidth();
86                 childView.layout(childLeft, 0 + paddingTop, childLeft + childWidth, paddingTop + childView.getMeasuredHeight());
87                 childLeft += childWidth;
88             }
89         }
90     }
91 }
View Code

 

posted @ 2016-02-04 16:06  希尔瓦娜斯女神  阅读(4644)  评论(1编辑  收藏  举报