Activity的全屏模式如下，因为兼容android6.0，就直接动态代码实现：

1. //在activity的onCreate方法中先调用此方法在setContent进行实现全屏模式

2. private void setFullScreenMode(){

3. //设置永不休眠模式

4. getWindow().setFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,

5. WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

6. //隐藏系统工具栏方式一

7. getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LOW_PROFILE);

8. //隐藏底部导航栏

9. View decorView = getWindow().getDecorView();

10. if (Build.VERSION.SDK_INT > 11 && Build.VERSION.SDK_INT < 19) {

11. decorView.setSystemUiVisibility(View.GONE);

12. } else if (Build.VERSION.SDK_INT >= 19) {

13. decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

14. | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY

15. | View.SYSTEM_UI_FLAG_FULLSCREEN);

16. }

17. decorView.setOnSystemUiVisibilityChangeListener(new View.OnSystemUiVisibilityChangeListener(){

18. @Override

19. public void onSystemUiVisibilityChange(int visibility) {

20. View decorView = getWindow().getDecorView();

21. int uiState=decorView.getSystemUiVisibility();

22. if (Build.VERSION.SDK_INT > 11 && Build.VERSION.SDK_INT < 19) {

23. if(uiState!=View.GONE) decorView.setSystemUiVisibility(View.GONE);

24. } else if (Build.VERSION.SDK_INT >= 19) {

25. if(uiState!=(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

26. | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY

27. | View.SYSTEM_UI_FLAG_FULLSCREEN))

28. decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

29. | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY

30. | View.SYSTEM_UI_FLAG_FULLSCREEN);

31. }

32. }

33. });

34. }

然而，现实对话框的时候，在华为的平板上，下面本来被隐藏的导航栏显示了出来，而且activity被上下压缩，很不美观，最开始以为是theme引起的，结果然并卵，网上也没有查到相关资料，好吧，我没就从dialog入手吧。

dialog内部其实也是一个Window，然后将视图资源加载进去，那么初步怀疑出现这种情况的原因：dialog弹出来后用了dialog的window,这个window很显然是默认的属性不是全屏的。

既然上面实现全屏模式是通过设置Window的属性，那么就依葫芦画瓢将dialog的window也想如上设置，将上面方法更改，参数传递一个Window进去，代码如下：

1. public void showDialog(){

2. AlertDialog dialog=new AlertDialog.Builder(_rootActivity)

3. .setTitle("确定删除班级"+nameView.getText().toString()+"吗？")

4. .setPositiveButton("是", this)

5. .setNegativeButton("否", null)

6. .create();

7. final Window window=dialog.getWindow();

8. setFullScreenMode(window);

9. dialog.show();

10. }

11. private void setFullScreenMode(Window window){

12. //设置永不休眠模式

13. window.setFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,

14. WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

15. //隐藏系统工具栏方式一

16. window.getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LOW_PROFILE);

17. //隐藏底部导航栏

18. View decorView = window.getDecorView();

19. if (Build.VERSION.SDK_INT > 11 && Build.VERSION.SDK_INT < 19) {

20. decorView.setSystemUiVisibility(View.GONE);

21. } else if (Build.VERSION.SDK_INT >= 19) {

22. decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

23. | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY

24. | View.SYSTEM_UI_FLAG_FULLSCREEN);

25. }

26. decorView.setOnSystemUiVisibilityChangeListener(new View.OnSystemUiVisibilityChangeListener(){

27. @Override

28. public void onSystemUiVisibilityChange(int visibility) {

29. View decorView = getWindow().getDecorView();

30. int uiState=decorView.getSystemUiVisibility();

31. if (Build.VERSION.SDK_INT > 11 && Build.VERSION.SDK_INT < 19) {

32. if(uiState!=View.GONE) decorView.setSystemUiVisibility(View.GONE);

33. } else if (Build.VERSION.SDK_INT >= 19) {

34. if(uiState!=(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

35. | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY

36. | View.SYSTEM_UI_FLAG_FULLSCREEN))

37. decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION

38. | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY

39. | View.SYSTEM_UI_FLAG_FULLSCREEN);

40. }

41. }

42. });

43. }

Ok,经过测试上面问题完全解决，弹出来的对话框不会在改变activity的宽高了