Question

怎样获取到headview上控件的监听事件

Answer 1

首先我们自己写一个控件,这个控件非常简单:
[java]
public class MyImageView extends ImageView {

public MyImageView(Context context, AttributeSet attrs) {

super(context, attrs);
}
public MyImageView(Context context)
{
super(context);
}

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

super.onMeasure(widthMeasureSpec, heightMeasureSpec);

System.out.println("onMeasure 我被调用了"+System.currentTimeMillis());
}

@Override
protected void onDraw(Canvas canvas) {

super.onDraw(canvas);
System.out.println("onDraw
我被调用了"+System.currentTimeMillis());
}

}

布局文件:
[java]

<com.test.MyImageView
android:id="@+id/imageview"

android:layout_width="wrap_content"
android:layout_height="wrap_content"

android:src="@drawable/test" />

测试的Activity的onCreate():
[java]
@Override
public void
onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.main);

System.out.println("执行完毕.."+System.currentTimeMillis());
}

现在我们现在来看一下结果:

说明等onCreate方法执行完了,我们定义的控件才会被度量(measure),所以我们在onCreate方法里面通过view.getHeight()获取控件的高度或者宽度肯定是0,因为它自己还没有被度量,也就是说他自己都不知道自己有多高,而你这时候去获取它的尺寸,肯定是不行的.

现在碰到这个问题我们不能不解决,在网上找到了如下办法:
[java]

//------------------------------------------------方法一
int w =
View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
int h =
View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);

imageView.measure(w, h);
int height =imageView.getMeasuredHeight();

int width =imageView.getMeasuredWidth();

textView.append("\n"+height+","+width);

//-----------------------------------------------方法二

ViewTreeObserver vto = imageView.getViewTreeObserver();

vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {

public boolean onPreDraw() {
int height =
imageView.getMeasuredHeight();
int width =
imageView.getMeasuredWidth();

textView.append("\n"+height+","+width);
return true;
}

});
//-----------------------------------------------方法三

ViewTreeObserver vto2 = imageView.getViewTreeObserver();

vto2.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

@Override
public void onGlobalLayout() {

imageView.getViewTreeObserver().removeGlobalOnLayoutListener(this);

textView.append("\n\n"+imageView.getHeight()+","+imageView.getWidth());

}
});

这三个方法是哪里找到现在已经忘了.

现在要讨论的是当我们需要时候使用哪个方法呢?
现在把测试的Activity改成如下:
[java]

@Override
public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.main);

final ImageView imageView = (ImageView) findViewById(R.id.imageview);

//------------------------------------------------方法一

int w =
View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
int
h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);

imageView.measure(w, h);
int height =imageView.getMeasuredHeight();

int width =imageView.getMeasuredWidth();

textView.append("\n"+height+","+width);

System.out.println("执行完毕.."+System.currentTimeMillis());
}

接着来看下面几种方式输出结果:
把测试Activity改成如下:
[java]
@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);
setContentView(R.layout.main);

final ImageView imageView = (ImageView) findViewById(R.id.imageview);

-----------------------------------------------方法二
ViewTreeObserver
vto = imageView.getViewTreeObserver();
vto.addOnPreDrawListener(new
ViewTreeObserver.OnPreDrawListener() {
public boolean onPreDraw() {

int height = imageView.getMeasuredHeight();
int
width = imageView.getMeasuredWidth();

textView.append("\n"+height+","+width);
return true;

}
});
}

结果如下:

方法三就不再测试了同方法二!!!

那么方法而和方法三在执行上有什么区别呢?
我们在布局文件中加入一个TextView来记录这个控件的宽高.
[java]

<ScrollView
android:layout_width="wrap_content"

android:layout_height="wrap_content" >

<TextView

android:id="@+id/text"
android:layout_width="wrap_content"

android:layout_height="wrap_content" />
</ScrollView>

先来测试方法而:
[java]
@Override
public void onCreate(Bundle
savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.main);
final ImageView imageView = (ImageView)