POPMUISE
我不知道ViewTreeObserver.addOnPreDrawListener()，我在测试项目中尝试过。使用您的代码，它看起来像这样：public void onCreate() {setContentView(R.layout.main);final TextView tv = (TextView)findViewById(R.id.image_test);final LayerDrawable ld = (LayerDrawable)tv.getBackground();final ViewTreeObserver obs = tv.getViewTreeObserver();obs.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw () {
Log.d(TAG, "onPreDraw tv height is " + tv.getHeight()); // bad for performance, remove on production
int height = tv.getHeight();
int topInset = height / 2;
ld.setLayerInset(1, 0, topInset, 0, 0);
tv.setBackgroundDrawable(ld);
return true;
}});}在我的测试项目onPreDraw()中被调用了两次，我认为在你的情况下它可能会导致无限循环。您可以尝试setBackgroundDrawable()仅在TextView更改高度时调用：private int mLastTvHeight = 0;public void onCreate() {setContentView(R.layout.main);final TextView tv = (TextView)findViewById(R.id.image_test);final LayerDrawable ld = (LayerDrawable)tv.getBackground();final ViewTreeObserver obs = mTv.getViewTreeObserver();obs.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw () {
Log.d(TAG, "onPreDraw tv height is " + tv.getHeight()); // bad for performance, remove on production
int height = tv.getHeight();
if (height != mLastTvHeight) {
mLastTvHeight = height;
int topInset = height / 2;
ld.setLayerInset(1, 0, topInset, 0, 0);
tv.setBackgroundDrawable(ld);
}
return true;
}});}但对于你想要实现的目标而言，这听起来有点复杂，而且对性能并不是很好。由kcoppock编辑这是我最终通过此代码完成的工作。戈蒂埃的回答让我达到了这一点，所以我宁愿接受这个答案而不是自己回答。我最终使用了ViewTreeObserver的addOnGlobalLayoutListener（）方法，就像这样（这是在onCreate（）中）：final TextView tv = (TextView)findViewById(R.id.image_test);ViewTreeObserver vto = tv.getViewTreeObserver();vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
LayerDrawable ld = (LayerDrawable)tv.getBackground();
ld.setLayerInset(1, 0, tv.getHeight() / 2, 0, 0);
}});似乎工作得很完美; 我检查了LogCat并没有看到任何异常活动。希望就是这样！谢谢！