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)
}
}
}
public final class ViewUtils {
public interface ViewUtilsListener {
void onDrawCompleted();
}
private ViewUtils() {
}
public static void onDraw(View view, ViewUtilsListener listener) {
view.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
if (view.getHeight() != 0 && view.getWidth() != 0) {
if (listener != null) {
listener.onDrawCompleted();
}
view.getViewTreeObserver().removeOnGlobalLayoutListener(this);
}
}
});
}
}
你可以这样用;
ViewUtils.onDraw(view, new ViewUtils.ViewUtilsListener() {
@Override
public void onDrawCompleted() {
int width = view.getWidth();
int height = view.getHeight();
}
});
我使用了这个解决方案，我认为它比onWindowFocusChanged()更好。如果你打开一个对话片段，然后旋转电话，onWindowFocusChanged将被调用只有当用户关闭对话框):
yourView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
// Ensure you call it only once :
yourView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
// Here you can get the size :)
}
});
编辑:由于removeGlobalOnLayoutListener已弃用，你现在应该做:
@SuppressLint("NewApi")
@SuppressWarnings("deprecation")
@Override
public void onGlobalLayout() {
// Ensure you call it only once :
if(android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.JELLY_BEAN) {
yourView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
}
else {
yourView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
}
// Here you can get the size :)
}
