Activity中获取view的高度和宽度为0的原因以及解决方案
在activity中可以调用View.getWidth、View.getHeight()、View.getMeasuredWidth() 、View.getgetMeasuredHeight()来获得某个view的宽度或高度，但是在onCreate()、onStrart()、onResume()方法中会返回0，这是应为当前activity所代表的界面还没显示出来没有添加到WindowPhone的DecorView上或要获取的view没有被添加到DecorView上或者该View的visibility属性为gone 或者该view的width或height真的为0 所以只有上述条件都不成立时才能得到非0的width和height
所以要想获取到的width和height为真实有效的 则有以下方法
1.在该View的事件回调里使用 这时候该view已经被显示即被添加到DecorView上 如点击事件 触摸事件 焦点事件等
1 View view=findViewById(R.id.tv); 2 view.setOnClickListener(new OnClickListener() { 3 4 @Override 5 public void onClick(View v) { 6 int width = v.getWidth(); 7 } 8 });
2.在activity被显示出来时即添加到了DecorView上时获取宽和高如onWindowFocusChanged() 回调方法
1 @Override 2 public void onWindowFocusChanged(boolean hasFocus) { 3 View iv1 = findViewById(R.id.iv1); 4 View iv2=findViewById(R.id.iv2); 5 String msg1="iv1' width:"+iv1.getWidth()+" height:"+iv1.getHeight()+" measuredWidth:"+iv1.getMeasuredWidth()+"measuredHeight:"+iv1.getMeasuredHeight(); 6 String msg2="iv2' width:"+iv2.getWidth()+" height:"+iv2.getHeight()+" measuredWidth:"+iv2.getMeasuredWidth()+"measuredHeight:"+iv2.getMeasuredHeight(); 7 i("onWindowFocusChanged() "+msg1); 8 i("onWindowFocusChanged() "+msg2); 9 super.onWindowFocusChanged(hasFocus); 10 }
3.或在onResume方法最后开线程300毫秒左右后获取宽和高 因为onResume执行完后300毫秒后 界面就显示出来了
当然地2种和地3种方法要保证获取宽高的view是在setContentView时设进去的View或它的子View
1 view.postDelayed(new Runnable() { 2 3 @Override 4 public void run() { 5 View iv1 = findViewById(R.id.iv1); 6 View iv2=findViewById(R.id.iv2); 7 String msg1="iv1' width:"+iv1.getWidth()+" height:"+iv1.getHeight()+" measuredWidth:"+iv1.getMeasuredWidth()+"measuredHeight:"+iv1.getMeasuredHeight(); 8 String msg2="iv2' width:"+iv2.getWidth()+" height:"+iv2.getHeight()+" measuredWidth:"+iv2.getMeasuredWidth()+"measuredHeight:"+iv2.getMeasuredHeight(); 9 i("onWindowFocusChanged() "+msg1); 10 i("onWindowFocusChanged() "+msg2); 11 } 12 }, 300);
4.在onCreate()或onResume()等方法中需要获取宽高时使用getViewTreeObserver().addOnGlobalLayoutListener()来添为view加回调在回调里获得宽度或者高度获取完后让view删除该回调
1 view.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { 2 3 @Override 4 public void onGlobalLayout() { 5 view.postDelayed(new Runnable() { 6 7 @Override 8 public void run() { 9 View iv1 = findViewById(R.id.iv1); 10 View iv2=findViewById(R.id.iv2); 11 String msg1="iv1' width:"+iv1.getWidth()+" height:"+iv1.getHeight()+" measuredWidth:"+iv1.getMeasuredWidth()+"measuredHeight:"+iv1.getMeasuredHeight(); 12 String msg2="iv2' width:"+iv2.getWidth()+" height:"+iv2.getHeight()+" measuredWidth:"+iv2.getMeasuredWidth()+"measuredHeight:"+iv2.getMeasuredHeight(); 13 i("onWindowFocusChanged() "+msg1); 14 i("onWindowFocusChanged() "+msg2); 15 } 16 }, 300); 17 } 18 });
5.在窗口焦点发生变化时获取宽高 onResume完后就会把界面渲染到窗口上 渲染完后将执行窗口焦点花生变化回调 所以onResume到 onWindowFocusChanged为把界面渲染到窗口的时间
1 boolean measure; 2 View iv1; 3 View iv2; 4 @Override 5 public void onWindowFocusChanged(boolean hasFocus) { 6 super.onWindowFocusChanged(hasFocus); 7 if(hasFocus && !measure){ 8 measure=true; 9 measure(); 10 } 11 } 12 private void findViews(){ 13 iv1 = findViewById(R.id.iv1); 14 iv2 =findViewById(R.id.iv2); 15 } 16 private void measure(){ 17 String msg1="iv1' width:"+iv1.getWidth()+" height:"+iv1.getHeight()+" measuredWidth:"+iv1.getMeasuredWidth()+"measuredHeight:"+iv1.getMeasuredHeight(); 18 String msg2="iv2' width:"+iv2.getWidth()+" height:"+iv2.getHeight()+" measuredWidth:"+iv2.getMeasuredWidth()+"measuredHeight:"+iv2.getMeasuredHeight(); 19 i("onWindowFocusChanged() "+msg1); 20 i("onWindowFocusChanged() "+msg2); 21 }
