Activity全屏沉浸状态

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    ImageView mImage;
    View mDecorView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_layout);

        //ButterKnife.bind(this);

        mDecorView = getWindow().getDecorView();
        // 让图片铺满屏幕
        mDecorView.setSystemUiVisibility(
                View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                        | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);
        hideSystemUI();

    }
    private void hideSystemUI() {
        mDecorView.setSystemUiVisibility(
                View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                        | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                        | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                        | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                        | View.SYSTEM_UI_FLAG_FULLSCREEN);
    }

    private void showSystemUI() {
        mDecorView.setSystemUiVisibility(
                View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                        | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                        | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
    }
    public void click(View v) {
        // 只需要处理隐藏 SystemBar 就行了，因为显示 SystemBar 是由系统完成的
        hideSystemUI();
    }
}