Android监听键盘的显示和隐藏

爱被打了一巴掌 2022-10-05 05:50 214阅读 0赞

#### 一、原理 ####

当键盘发生变化的时候activity的布局也会发生变化，因此监听布局的变化即可监听到键盘的显示和隐藏。

#### 二、代码实现 ####

public class SoftKeyBoardListener { 
        private final View rootView;  //activity的根视图
        int rootViewVisibleHeight;  //纪录根视图的显示高度
        private OnSoftKeyBoardChangeListener onSoftKeyBoardChangeListener;
    
        public SoftKeyBoardListener(Activity activity) { 
            //获取activity的根视图
            rootView = activity.getWindow().getDecorView();
            //监听视图树中全局布局发生改变或者视图树中的某个视图的可视状态发生改变
            rootView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { 
                @Override
                public void onGlobalLayout() { 
                    //获取当前根视图在屏幕上显示的大小
                    Rect r = new Rect();
                    rootView.getWindowVisibleDisplayFrame(r);
                    int visibleHeight = r.height();
                    System.out.println("" + visibleHeight);
                    if (rootViewVisibleHeight == 0) { 
                        rootViewVisibleHeight = visibleHeight;
                        return;
                    }
                    //根视图显示高度没有变化，可以看作软键盘显示／隐藏状态没有改变
                    if (rootViewVisibleHeight == visibleHeight) { 
                        return;
                    }
                    //根视图显示高度变小超过200，可以看作软键盘显示了
                    if (rootViewVisibleHeight - visibleHeight > 200) { 
                        if (onSoftKeyBoardChangeListener != null) { 
                            onSoftKeyBoardChangeListener.keyBoardShow(rootViewVisibleHeight - visibleHeight);
                        }
                        rootViewVisibleHeight = visibleHeight;
                        return;
                    }
                    //根视图显示高度变大超过200，可以看作软键盘隐藏了
                    if (visibleHeight - rootViewVisibleHeight > 200) { 
                        if (onSoftKeyBoardChangeListener != null) { 
                            onSoftKeyBoardChangeListener.keyBoardHide(visibleHeight - rootViewVisibleHeight);
                        }
                        rootViewVisibleHeight = visibleHeight;
                    }
                }
            });
        }
    
        private void setOnSoftKeyBoardChangeListener(OnSoftKeyBoardChangeListener onSoftKeyBoardChangeListener) { 
            this.onSoftKeyBoardChangeListener = onSoftKeyBoardChangeListener;
        }
    
        public interface OnSoftKeyBoardChangeListener { 
            void keyBoardShow(int height);
    
            void keyBoardHide(int height);
        }
    
        public static void setListener(Activity activity, OnSoftKeyBoardChangeListener onSoftKeyBoardChangeListener) { 
            SoftKeyBoardListener softKeyBoardListener = new SoftKeyBoardListener(activity);
            softKeyBoardListener.setOnSoftKeyBoardChangeListener(onSoftKeyBoardChangeListener);
        }
    }