onMeasure多次调用问题

getWidth()与getMeasuredWidth()的区别

一般在自定义控件的时候getMeasuredWidth/getMeasuredHeight它的赋值在View的setMeasuredDimension中&＃xff0c;所以有时可以在onMeasure方法中看到利用getMeasuredWidth/getMeasuredHeight初始化别的参数。而getWidth/getHeight一直在onLayout完成后才会被赋值。一般情况下&＃xff0c;如果都完成了赋值&＃xff0c;两者值是相同的.&＃xff08;摘自鸿洋&＃xff09;
参考&＃xff1a;(Android视图绘制流程完全解析&＃xff0c;带你一步步深入了解View(二)&＃xff09;

关于View的onMeasure()、onSizeChanged()、onLayout()、onDraw()调用顺序
调用顺序应该是 构造函数——->onMeasure——->onSizeChanged——->onLayout——->onDraw
后面有可能 onMeasure——->onLayout——->onDraw
&＃xff08;摘自here&＃xff09;
并且是在onResume之后。

需要注意的是&＃xff0c;在setMeasuredDimension()方法调用之后&＃xff0c;我们才能使用getMeasuredWidth()和getMeasuredHeight()来获取视图测量出的宽高&＃xff0c;以此之前调用这两个方法得到的值都会是0。

视图大小的控制是由父视图、布局文件、以及视图本身共同完成的&＃xff0c;父视图会提供给子视图参考的大小&＃xff0c;而开发人员可以在XML文件中指定视图的大小&＃xff0c;然后视图本身会对最终的大小进行拍板。
参考:Android视图绘制流程完全解析&＃xff0c;带你一步步深入了解View(二)

onMeasure多次调用问题

Android如何绘制视图&＃xff0c;解释了为何onMeasure有时要调用多次
为什么FlowLayout的 onMeasure方法会执行4次&＃xff0c;onLayout方法会执行两次呢&＃xff0c;

父视图可能在它的子视图上调用一次以上的measure(int,int)方法。例如&＃xff0c;父视图可以使用unspecified dimensions来将它的每个子视图都测量一次来算出它们到底需要多大尺寸&＃xff0c;如果所有这些子视图没被限制的尺寸的和太大或太小&＃xff0c;那么它会用精确数值再次调用measure()&＃xff08;也就是说&＃xff0c;如果子视图不满意它们获得的区域大小&＃xff0c;那么父视图将会干涉并设置第二次测量规则&＃xff09;。

测试&＃xff1a;

&＃64;SuppressWarnings("deprecation")
public class MyActivity extends FragmentActivity {&＃64;TargetApi(Build.VERSION_CODES.LOLLIPOP)&＃64;Overrideprotected void onCreate(&＃64;Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.test3);Display display &＃61; getWindowManager().getDefaultDisplay();int displayWidth &＃61; display.getWidth();int displayHeight &＃61; display.getHeight();Log.e("111", "display.getWidth()&＃61;&＃61;" &＃43; displayWidth);//1080Log.e("111", "display.getHeight()&＃61;&＃61;" &＃43; displayHeight);//1812Log.e("111", "densityDpi&＃61;&＃61;" &＃43; getResources().getDisplayMetrics().densityDpi);//480Log.e("111", "density&＃61;&＃61;" &＃43; getResources().getDisplayMetrics().density);//3.0int statusHeight &＃61; getStatusHeight(this);Log.e("111", "statusHeight&＃61;&＃61;" &＃43; statusHeight);//72Log.e("111", "displayHeight-statusHeight&＃61;&＃61;" &＃43; (displayHeight - statusHeight));//1740int actionBarHeight &＃61; getActionBarHeight(this);Log.e("111", "actionBarHeight&＃61;&＃61;" &＃43; actionBarHeight);//168Log.e("111", "statusHeight&＃43;statusHeight&＃61;&＃61;" &＃43; (statusHeight &＃43; actionBarHeight));//240Log.e("111", "displayHeight-(statusHeight &＃43; actionBarHeight)&＃61;&＃61;" &＃43; (displayHeight - (statusHeight &＃43; actionBarHeight)));//1572}public int getStatusHeight(Context context) {int statusHeight &＃61; -1;try {Class clazz &＃61; Class.forName("com.android.internal.R$dimen");Object object &＃61; clazz.newInstance();int height &＃61; Integer.parseInt(clazz.getField("status_bar_height").get(object).toString());statusHeight &＃61; context.getResources().getDimensionPixelSize(height);} catch (Exception e) {e.printStackTrace();}return statusHeight;}public int getActionBarHeight(Context context) {TypedValue localTypedValue &＃61; new TypedValue();if (context.getTheme().resolveAttribute(android.R.attr.actionBarSize, localTypedValue, true)) {return TypedValue.complexToDimensionPixelSize(localTypedValue.data, context.getResources().getDisplayMetrics());}return 0;}}

布局&＃xff1a;

&＃64;SuppressLint("AppCompatCustomView")
public class RoundImageView extends ImageView {private Paint mPaint;private Bitmap bitmap;private Matrix mMatrix;private int mWidth;private int mRadius;private BitmapShader bitmapShader;private RectF mRoundRect;public RoundImageView(Context context) {super(context);init();}public RoundImageView(Context context, &＃64;Nullable AttributeSet attrs) {super(context, attrs);init();}public RoundImageView(Context context, &＃64;Nullable AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);init();}private void init() {mPaint &＃61; new Paint();mPaint.setAntiAlias(true);mMatrix &＃61; new Matrix();}&＃64;Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);Log.e("111", ".......onMeasure.......");Log.e("111", "0getHeight......." &＃43; getHeight());//0Log.e("111", "0getWidth......." &＃43; getWidth());//0//1560->1740(调用了两次onmeasure,第二次的1740&＃61;屏幕高1812-状态栏高72)Log.e("111", "0getMeasuredHeight......." &＃43; getMeasuredHeight());//1080->1080(调用了两次onmeasure)Log.e("111", "0getMeasuredWidth......." &＃43; getMeasuredWidth());Log.e("111", "0getSuggestedMinimumHeight......." &＃43; getSuggestedMinimumHeight());//0Log.e("111", "0getSuggestedMinimumWidth......." &＃43; getSuggestedMinimumWidth());//0mWidth &＃61; Math.min(getMeasuredWidth(), getMeasuredHeight());mRadius &＃61; mWidth / 2;setMeasuredDimension(mWidth, mWidth);//1080Log.e("111", ".......onMeasure......................");Log.e("111", "0getHeight......." &＃43; getHeight());//0Log.e("111", "0getWidth......." &＃43; getWidth());//0Log.e("111", "0getMeasuredHeight......." &＃43; getMeasuredHeight());//1080->1080Log.e("111", "0getMeasuredWidth......." &＃43; getMeasuredWidth());//1080-->1080Log.e("111", "0getSuggestedMinimumHeight......." &＃43; getSuggestedMinimumHeight());//0Log.e("111", "0getSuggestedMinimumWidth......." &＃43; getSuggestedMinimumWidth());//0}&＃64;Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);Log.e("111", ".......onSizeChanged.......");Log.e("111", "1getHeight......." &＃43; getHeight());//1080&＃xff08;setMeasuredDimension决定&＃xff09;Log.e("111", "1getWidth......." &＃43; getWidth());//1080Log.e("111", "1getMeasuredHeight......." &＃43; getMeasuredHeight());//1080Log.e("111", "1getMeasuredWidth......." &＃43; getMeasuredWidth());//1080Log.e("111", "1getSuggestedMinimumHeight......." &＃43; getSuggestedMinimumHeight());//0Log.e("111", "1getSuggestedMinimumWidth......." &＃43; getSuggestedMinimumWidth());//0mRoundRect &＃61; new RectF(0, 0, getWidth(), getHeight());}&＃64;Overrideprotected void onLayout(boolean changed, int left, int top, int right, int bottom) {super.onLayout(changed, left, top, right, bottom);Log.e("111", ".......onLayout.......");Log.e("111", "2getHeight......." &＃43; getHeight());//1080Log.e("111", "2getWidth......." &＃43; getWidth());//1080Log.e("111", "2getMeasuredHeight......." &＃43; getMeasuredHeight());//1080Log.e("111", "2getMeasuredWidth......." &＃43; getMeasuredWidth());//1080Log.e("111", "2getSuggestedMinimumHeight......." &＃43; getSuggestedMinimumHeight());//0Log.e("111", "2getSuggestedMinimumWidth......." &＃43; getSuggestedMinimumWidth());//0}&＃64;Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);Log.e("111", ".......onDraw.......");Log.e("111", "3getHeight......." &＃43; getHeight());//1080Log.e("111", "3getWidth......." &＃43; getWidth());//1080Log.e("111", "3getMeasuredHeight......." &＃43; getMeasuredHeight());//1080Log.e("111", "3getMeasuredWidth......." &＃43; getMeasuredWidth());//1080Log.e("111", "3getSuggestedMinimumHeight......." &＃43; getSuggestedMinimumHeight());//0Log.e("111", "3getSuggestedMinimumWidth......." &＃43; getSuggestedMinimumWidth());//0bitmap &＃61; BitmapFactory.decodeResource(getResources(), R.drawable.test);Log.e("111", ".bitmap.getHeight......." &＃43; bitmap.getHeight());//300Log.e("111", ".bitmap.getWidth........" &＃43; bitmap.getWidth());//300bitmapShader &＃61; new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);int bSize &＃61; Math.min(bitmap.getWidth(), bitmap.getHeight());float scale &＃61; mWidth * 1.0f / bSize;mMatrix.setScale(scale, scale);bitmapShader.setLocalMatrix(mMatrix);mPaint.setShader(bitmapShader);Log.e("111", "&＃61;&＃61;&＃61;drawCircle&＃61;&＃61;mRadius&＃61;" &＃43; mRadius);//540canvas.drawCircle(mRadius, mRadius, mRadius, mPaint);}
}


activity 用了NoActionBar的style

为什么getSuggestedMinimumHeight、Width打印为零

我们修改布局&＃xff1a;添加 android:minHeight&＃61;”100dp”和android:minWidth&＃61;”100dp”

再次打印如下&＃xff1a;

可见android:minHeight影响了getSuggestedMinimumHeight&＃xff0c;
而且getSuggestedMinimumHeight默认为零。

display.getWidth()&＃61;&＃61;1080
display.getHeight()&＃61;&＃61;1812
densityDpi&＃61;&＃61;480
density&＃61;&＃61;3.0
statusHeight&＃61;&＃61;72
displayHeight-statusHeight&＃61;&＃61;1740
actionBarHeight&＃61;&＃61;168
statusHeight&＃43;statusHeight&＃61;&＃61;240
displayHeight-(statusHeight &＃43; actionBarHeight)&＃61;&＃61;1572.......onMeasure.......
0getHeight.......0
0getWidth.......0
0getMeasuredHeight.......1560
0getMeasuredWidth.......1080
0getSuggestedMinimumHeight.......300
0getSuggestedMinimumWidth.......300
.......onMeasure......................
0getHeight.......0
0getWidth.......0
0getMeasuredHeight.......1080
0getMeasuredWidth.......1080
0getSuggestedMinimumHeight.......300
0getSuggestedMinimumWidth.......300.......onMeasure.......
0getHeight.......0
0getWidth.......0
0getMeasuredHeight.......1740
0getMeasuredWidth.......1080
0getSuggestedMinimumHeight.......300
0getSuggestedMinimumWidth.......300
.......onMeasure......................
0getHeight.......0
0getWidth.......0
0getMeasuredHeight.......1080
0getMeasuredWidth.......1080
0getSuggestedMinimumHeight.......300
0getSuggestedMinimumWidth.......300.......onSizeChanged.......
1getHeight.......1080
1getWidth.......1080
1getMeasuredHeight.......1080
1getMeasuredWidth.......1080
1getSuggestedMinimumHeight.......300
1getSuggestedMinimumWidth.......300.......onLayout.......
2getHeight.......1080
2getWidth.......1080
2getMeasuredHeight.......1080
2getMeasuredWidth.......1080
2getSuggestedMinimumHeight.......300
2getSuggestedMinimumWidth.......300.......onDraw.......
3getHeight.......1080
3getWidth.......1080
3getMeasuredHeight.......1080
3getMeasuredWidth.......1080
3getSuggestedMinimumHeight.......300
3getSuggestedMinimumWidth.......300.bitmap.getHeight.......300
.bitmap.getWidth........300
&＃61;&＃61;&＃61;drawCircle&＃61;&＃61;mRadius&＃61;540

onLayout、layout

Android的onLayout、layout方法讲解
onLayout方法是ViewGroup中子View的布局方法&＃xff0c;用于放置子View的位置。放置子View很简单&＃xff0c;只需在重写onLayout方法&＃xff0c;然后获取子View的实例&＃xff0c;调用子View的layout方法实现布局。在实际开发中&＃xff0c;一般要配合onMeasure测量方法一起使用。

&＃64;Override
protected abstract void onLayout(boolean changed,int l, int t, int r, int b);

该方法在ViewGroup中定义是抽象函数&＃xff0c;继承该类必须实现onLayout方法&＃xff0c;而ViewGroup的onMeasure并非必须重写的。View的放置都是根据一个矩形空间放置的&＃xff0c;onLayout传下来的l,t,r,b分别是放置父控件的矩形可用空间&＃xff08;除去margin和padding的空间&＃xff09;的左上角的left、top以及右下角right、bottom值。

public void layout(int l, int t, int r, int b);

该方法是View的放置方法&＃xff0c;在View类实现。调用该方法需要传入放置View的矩形空间左上角left、top值和右下角right、bottom值。这四个值是相对于父控件而言的。例如传入的是&＃xff08;10, 10, 100, 100&＃xff09;&＃xff0c;则该View在距离父控件的左上角位置(10, 10)处显示&＃xff0c;显示的大小是宽高是90(参数r,b是相对左上角的)&＃xff0c;这有点像绝对布局。

使用方法&＃xff1a;

public class MyViewGroup extends ViewGroup {// 子View的水平间隔private final static int padding &＃61; 20;public MyViewGroup(Context context, AttributeSet attrs) {super(context, attrs);// TODO Auto-generated constructor stub}&＃64;Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {// TODO Auto-generated method stub// 动态获取子View实例for (int i &＃61; 0, size &＃61; getChildCount(); i


自己的测试&＃xff1a;