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getWidth和getMeasuredWidth在何时可以得到正确数值
getMeasuredWidth在源码中的解释如下:
/** * Like {@link #getMeasuredWidthAndState()}, but only returns the * raw width component (that is the result is masked by * {@link #MEASURED_SIZE_MASK}). * * @return The raw measured width of this view. */ public final int getMeasuredWidth() { return mMeasuredWidth & MEASURED_SIZE_MASK; } /** * Return the full width measurement information for this view as computed * by the most recent call to {@link #measure(int, int)}. This result is a bit mask * as defined by {@link #MEASURED_SIZE_MASK} and {@link #MEASURED_STATE_TOO_SMALL}. * This should be used during measurement and layout calculations only. Use * {@link #getWidth()} to see how wide a view is after layout. * * @return The measured width of this view as a bit mask. */ public final int getMeasuredWidthAndState() { return mMeasuredWidth; }大致意思也就是说返回最后一次调用onMeasure所测量得到的宽度。
getWidth在源码中返回View的宽度 单位是pixels
/** * Return the width of the your view. * * @return The width of your view, in pixels. */ @ViewDebug.ExportedProperty(category = "layout") public final int getWidth() { return mRight - mLeft; }
写一个Demo测试一下 代码如下:
public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); MLinearLayout root = new MLinearLayout(this); setContentView(root); } class MLinearLayout extends LinearLayout { public MLinearLayout(Context context) { super(context); setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.MATCH_PARENT)); addView(new MTextView(context)); Log.i("AAA","LinearLayout MLinearLayout Width:"+getWidth() +" Height:"+getHeight()); Log.i("AAA","LinearLayout MLinearLayout MeasuredWidth:"+getMeasuredWidth() +" MeasuredHeight:"+getMeasuredHeight()); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { // TODO Auto-generated method stub super.onMeasure(widthMeasureSpec, heightMeasureSpec); Log.i("AAA","LinearLayout onMeasure Width:"+getWidth() +" Height:"+getHeight()); Log.i("AAA","LinearLayout onMeasure MeasuredWidth:"+getMeasuredWidth() +" MeasuredHeight:"+getMeasuredHeight()); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { // TODO Auto-generated method stub super.onLayout(changed, l, t, r, b); Log.i("AAA","LinearLayout onLayout Width:"+getWidth() +" Height:"+getHeight()); Log.i("AAA","LinearLayout onLayout MeasuredWidth:"+getMeasuredWidth() +" MeasuredHeight:"+getMeasuredHeight()); } } class MTextView extends TextView { public MTextView(Context context) { super(context); setLayoutParams(new LayoutParams(200, 300)); setText("测试"); Log.i("AAA"," TextView MTextView Width:"+getWidth() +" Height:"+getHeight()); Log.i("AAA"," TextView MTextView MeasuredWidth:"+getMeasuredWidth() +" MeasuredHeight:"+getMeasuredHeight()); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { // TODO Auto-generated method stub super.onMeasure(widthMeasureSpec, heightMeasureSpec); Log.i("AAA"," TextView onMeasure Width:"+getWidth() +" Height:"+getHeight()); Log.i("AAA"," TextView onMeasure MeasuredWidth:"+getMeasuredWidth() +" MeasuredHeight:"+getMeasuredHeight()); } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { // TODO Auto-generated method stub super.onLayout(changed, left, top, right, bottom); Log.i("AAA"," TextView onLayout Width:"+getWidth() +" Height:"+getHeight()); Log.i("AAA"," TextView onLayout MeasuredWidth:"+getMeasuredWidth() +" MeasuredHeight:"+getMeasuredHeight()); } } }
运行之后得到的结果如下:
I/AAA ( 3631): TextView MTextView Width:0 Height:0
I/AAA ( 3631): TextView MTextView MeasuredWidth:0 MeasuredHeight:0
I/AAA ( 3631): LinearLayout MLinearLayout Width:0 Height:0
I/AAA ( 3631): LinearLayout MLinearLayout MeasuredWidth:0 MeasuredHeight:0
I/AAA ( 3631): TextView onMeasure Width:0 Height:0
I/AAA ( 3631): TextView onMeasure MeasuredWidth:200 MeasuredHeight:300
I/AAA ( 3631): LinearLayout onMeasure Width:0 Height:0
I/AAA ( 3631): LinearLayout onMeasure MeasuredWidth:1024 MeasuredHeight:502
I/AAA ( 3631): TextView onLayout Width:200 Height:300
I/AAA ( 3631): TextView onLayout MeasuredWidth:200 MeasuredHeight:300
I/AAA ( 3631): LinearLayout onLayout Width:1024 Height:502
I/AAA ( 3631): LinearLayout onLayout MeasuredWidth:1024 MeasuredHeight:502
I/AAA ( 3631): TextView onMeasure Width:200 Height:300
I/AAA ( 3631): TextView onMeasure MeasuredWidth:200 MeasuredHeight:300
I/AAA ( 3631): LinearLayout onMeasure Width:1024 Height:502
I/AAA ( 3631): LinearLayout onMeasure MeasuredWidth:1024 MeasuredHeight:502
I/AAA ( 3631): TextView onLayout Width:200 Height:300
I/AAA ( 3631): TextView onLayout MeasuredWidth:200 MeasuredHeight:300
I/AAA ( 3631): LinearLayout onLayout Width:1024 Height:502
I/AAA ( 3631): LinearLayout onLayout MeasuredWidth:1024 MeasuredHeight:502
结论:
1.在构造方法中无论是getWidth还是getMeasuredWidth都是得不到正确数值的。
2.getMeasuredWidth得到正确数值需要在调用过onMeasure之后。
3.getWidth得到正确数值需要调用过onLayout之后。
VIew的绘制过程:http://www.cnblogs.com/cowboybusy/archive/2012/08/26/2718888.html