我正在动态地创建我的android项目中的所有元素。我试图获得一个按钮的宽度和高度,以便我可以旋转该按钮。我只是想学习如何使用android语言。但是,它返回0。
我做了一些研究,我看到它需要在其他地方而不是在onCreate()方法中完成。如果有人能给我一个如何做这件事的例子,那就太好了。
这是我当前的代码:
package com.animation;
import android.app.Activity;
import android.os.Bundle;
import android.view.animation.Animation;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.Button;
import android.widget.LinearLayout;
public class AnimateScreen extends Activity {
//Called when the activity is first created.
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LinearLayout ll = new LinearLayout(this);
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
layoutParams.setMargins(30, 20, 30, 0);
Button bt = new Button(this);
bt.setText(String.valueOf(bt.getWidth()));
RotateAnimation ra = new RotateAnimation(0,360,bt.getWidth() / 2,bt.getHeight() / 2);
ra.setDuration(3000L);
ra.setRepeatMode(Animation.RESTART);
ra.setRepeatCount(Animation.INFINITE);
ra.setInterpolator(new LinearInterpolator());
bt.startAnimation(ra);
ll.addView(bt,layoutParams);
setContentView(ll);
}
任何帮助都是感激的。
用法:
imageView.size { width, height ->
//your code
}
延伸:
fun <T : View> T.size(function: (Int, Int) -> Unit) {
if (isLaidOut && height != 0 && width != 0) {
function(width, height)
} else {
if (height == 0 || width == 0) {
var onLayoutChangeListener: View.OnLayoutChangeListener? = null
var onGlobalLayoutListener: ViewTreeObserver.OnGlobalLayoutListener? = null
onGlobalLayoutListener = object : ViewTreeObserver.OnGlobalLayoutListener {
override fun onGlobalLayout() {
if (isShown) {
removeOnLayoutChangeListener(onLayoutChangeListener)
viewTreeObserver.removeOnGlobalLayoutListener(this)
function(width, height)
}
}
}
onLayoutChangeListener = object : View.OnLayoutChangeListener {
override fun onLayoutChange(
v: View?,
left: Int,
top: Int,
right: Int,
bottom: Int,
oldLeft: Int,
oldTop: Int,
oldRight: Int,
oldBottom: Int
) {
val width = v?.width ?: 0
val height = v?.height ?: 0
if (width > 0 && height > 0) {
// remove after finish
viewTreeObserver.removeOnGlobalLayoutListener(onGlobalLayoutListener)
v?.removeOnLayoutChangeListener(this)
function(width, height)
}
}
}
viewTreeObserver.addOnGlobalLayoutListener(onGlobalLayoutListener)
addOnLayoutChangeListener(onLayoutChangeListener)
} else {
function(width, height)
}
}
}
带post的答案是不正确的,因为大小可能无法重新计算。
另一个重要的事情是视图和所有它的祖先必须是可见的。为此,我使用属性view . isshows。
下面是我的kotlin函数,它可以放在utils中的某个地方:
fun View.onInitialized(onInit: () -> Unit) {
viewTreeObserver.addOnGlobalLayoutListener(object : OnGlobalLayoutListener {
override fun onGlobalLayout() {
if (isShown) {
viewTreeObserver.removeOnGlobalLayoutListener(this)
onInit()
}
}
})
}
用法是:
myView.onInitialized {
Log.d(TAG, "width is: " + myView.width)
}