Android getWidth和getMeasuredWidth的理解
前段时间了解了getWidth和getMeasuredWidth区别，有一段时间不看发现具体还又有些遗忘，所以在此还是要记下来，俗话说，好记性不如烂笔头，俗话诚不欺我。
首先，先来个图吧，下图为我从http://blog.sina.com.cn/s/blog_6e519585010152s5.html博客拷贝过来的一个图片，又是拿来主义了，在此非常感谢博主分享。
一定要注意：此处的getheight是在布局中的view，即view的父布局必须是个layout。下面继续引用：
Google文档的英文说明：
getWidth()：
Return the width of the your view.
Returns: the width of your view, in pixels
getMeasuredWidth()：
The width of this view as measured in the most recent call to measure(). This should be used during measurement and layout calculations only. Use getWidth() to see how wide a view is after layout.
Returns: the measured width of this view
前提知识点：
1. 在一个类初始化时，即在构造函数当中是得不到View的实际大小的（这个我测试过，的确）。大家可以试试，getWidth()和getMeasuredWidth()得到的结果都是0，但是可以从onDraw()方法或者dispatchDraw()方法里面获得。可以通过调用invalidate()来执行onDraw()和dispatchDraw()方法。
2. 这两个方法所得到的结果的单位是像素即pixel
正确的理解：
getWidth(): View在设定好布局后，整个View的宽度
getMeasuredWidth()：对View上的内容进行测量后得到的View内容占据的宽度。前提是你必须在父布局的onLayout()方法或者此View的onDraw()方法里调用measure(0,0)；（measure参数的值可以知己定义），否则得到的结果和getWidth()得到的结果是一样的。
这两个方法最主要的区别在于，是否使用了measure()方法，同时measure()使用的位置也很重要。
getHeight() 和 get MeasuredHeight() 区别同理。
好了，图片直观展示有了，文字描述也有了，下面该上代码了。public class MainActivity extends ActionBarActivity {
private LinearLayout mBackgroundLayout;
private TextViewTest mTextViewTest;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mBackgroundLayout = new MyLayout(this);
mBackgroundLayout.setLayoutParams(new LinearLayout.LayoutParams(
500,
500));
mTextViewTest = new TextViewTest(this);
mBackgroundLayout.addView(mTextViewTest);
setContentView(mBackgroundLayout);
}
public class MyLayout extends LinearLayout{
public MyLayout(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
@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("Tag", "--------------");
View mView=getChildAt(0);
mView.measure(0, 0);
}
}
public class TextViewTest extends TextView {
public TextViewTest(Context context) {
super(context);
// TODO Auto-generated constructor stub
setText("test test ");
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
// measure(0, 0);
Log.i("Tag", "width: " + getWidth() + ",height: " + getHeight());
Log.i("Tag", "MeasuredWidth: " + getMeasuredWidth()
+ ",MeasuredHeight: " + getMeasuredHeight());
}
}
}
下面在稍微改动一下，代码如下：
public class MainActivity extends ActionBarActivity {
private LinearLayout mBackgroundLayout;
private TextViewTest mTextViewTest;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mBackgroundLayout = new MyLayout(this);
mBackgroundLayout.setLayoutParams(new LinearLayout.LayoutParams(
LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT));
mTextViewTest = new TextViewTest(this);
mBackgroundLayout.addView(mTextViewTest);
setContentView(mBackgroundLayout);
}
public class MyLayout extends LinearLayout{
public MyLayout(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
@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("Tag", "--------------");
View mView=getChildAt(0);
mView.measure(0, 0);
}
}
public class TextViewTest extends TextView {
public TextViewTest(Context context) {
super(context);
// TODO Auto-generated constructor stub
setText("test test ");
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
// measure(0, 0);
Log.i("Tag", "width: " + getWidth() + ",height: " + getHeight());
Log.i("Tag", "MeasuredWidth: " + getMeasuredWidth()
+ ",MeasuredHeight: " + getMeasuredHeight());
}
}
}运行结果：
在改动一下：
public class MainActivity extends ActionBarActivity {
private TextViewTest mTextViewTest;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mTextViewTest = new TextViewTest(this);
setContentView(mTextViewTest);
}
public class TextViewTest extends TextView {
public TextViewTest(Context context) {
super(context);
// TODO Auto-generated constructor stub
setText("test test ");
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
measure(0, 0);
Log.i("Tag", "width: " + getWidth() + ",height: " + getHeight());
Log.i("Tag", "MeasuredWidth: " + getMeasuredWidth()
+ ",MeasuredHeight: " + getMeasuredHeight());
}
}
}
好了，相信通过这几个实验，可以看出来文字的验证描述了