android自定义PopupWindow，不显示内容

public class PopWindow extends PopupWindow {
	private Context mContext;
	private View mPopView;
	private OnAnimationDismissListener mOnAnimationDismissListener;

	public PopWindow(Context context, View contentView) {
		super(contentView, LayoutParams.MATCH_PARENT, <span style="font-family: Arial, Helvetica, sans-serif;">contentView.getMeasuredHeight()</span><span style="font-family: Arial, Helvetica, sans-serif;">, true);</span>
		Log.e("TAG", "" + contentView.getMeasuredHeight());
		
		this.mContext = context;
		this.mPopView = contentView;
		init();
	}

	private void init() {
		LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
				LinearLayout.LayoutParams.MATCH_PARENT,
				LinearLayout.LayoutParams.WRAP_CONTENT);
		mPopView.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED);
		mPopView.setLayoutParams(lp);
		setContentView(mPopView);
		setBackgroundDrawable(new ColorDrawable(Color
				.parseColor("#00000000")));
		setFocusable(true);
		setOutsideTouchable(true);
	}

	public void show(View anchor, int xoff, int yoff) {
		showAsDropDown(anchor, xoff, yoff);
		update();
		Animation anim = AnimationUtils.loadAnimation(mContext, R.anim.down);
		mPopView.startAnimation(anim);
	}

	@Override
	public void dismiss() {
		Animation anim = AnimationUtils.loadAnimation(mContext, R.anim.up);
		anim.setAnimationListener(new SimpleAnimationListener() {
			@Override
			public void onAnimationStart(Animation animation) {
				if (null != mOnAnimationDismissListener)
					mOnAnimationDismissListener.onStart();
			}

			@Override
			public void onAnimationEnd(Animation animation) {
				new Handler().post(new Runnable() {
					@Override
					public void run() {
						PopWindow.super.dismiss();
					}
				});
			}
		});
		mPopView.startAnimation(anim);
	}

	public void setOnAnimationDismissListener(
			OnAnimationDismissListener onAnimationDismissListener) {
		this.mOnAnimationDismissListener = onAnimationDismissListener;
	}

	public interface OnAnimationDismissListener {
		public void onStart();
	}
}

这里调用的在外部调用show()的时候发现，显示不了PopWindow，通过logcat发现这里的contentView.getMeasuredHeight()返回的是0。

所以这里就不能这样子使用了。改成如下方法即可：

public PopWindow(Context context, View contentView) {
		super(contentView, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT, true);
		Log.e("TAG", "" + contentView.getMeasuredHeight());
//......
}

总结：很多时候涉及到宽高来设定View或者窗口大小的时候，都需要注意如果需要从其他的view获取这个大小，看看取得的值是否是0。

有时候需要借助addOnGlobalLayoutListener()方法，等布局大小等全部都已经确定好了在获取相应view的宽高。