代码来源

public class KeyboardChangeListener implements ViewTreeObserver.OnGlobalLayoutListener {    private static final String TAG = "ListenerHandler";    private View mContentView;    private int mOriginHeight;    private int mPreHeight;    private KeyBoardListener mKeyBoardListen;    public interface KeyBoardListener {        /**         * call back         * @param isShow true is show else hidden         * @param keyboardHeight keyboard height         */        void onKeyboardChange(boolean isShow, int keyboardHeight);    }    public void setKeyBoardListener(KeyBoardListener keyBoardListen) {        this.mKeyBoardListen = keyBoardListen;    }    public KeyboardChangeListener(Activity contextObj) {        if (contextObj == null) {            Log.i(TAG, "contextObj is null");            return;        }        mContentView = findContentView(contextObj);        if (mContentView != null) {            addContentTreeObserver();        }    }    private View findContentView(Activity contextObj) {        return contextObj.findViewById(android.R.id.content);    }    private void addContentTreeObserver() {        mContentView.getViewTreeObserver().addOnGlobalLayoutListener(this);    }    @Override    public void onGlobalLayout() {        Rect rect = new Rect();        mContentView.getWindowVisibleDisplayFrame(rect);        int currHeight = rect.bottom - rect.top;        if (currHeight == 0) {            Log.i(TAG, "currHeight is 0");            return;        }        boolean hasChange = false;        if (mPreHeight == 0) {            mPreHeight = currHeight;            mOriginHeight = currHeight;        } else {            if (mPreHeight != currHeight) {                hasChange = true;                mPreHeight = currHeight;            } else {                hasChange = false;            }        }        if (hasChange) {            boolean isShow;            int keyboardHeight = 0;            if (mOriginHeight == currHeight) {                //hidden                isShow = false;            } else {                //show                keyboardHeight = mOriginHeight - currHeight;                isShow = true;            }            if (mKeyBoardListen != null) {                mKeyBoardListen.onKeyboardChange(isShow, keyboardHeight);            }        }    }    public void destroy() {        if (mContentView != null) {            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {                mContentView.getViewTreeObserver().removeOnGlobalLayoutListener(this);            }        }    }}

    通过GlobalLayoutChangeListener进行监听，如果widonw的可视空间减小了，那么久表示软键盘弹出。如果变大了就表示软键盘收起。

    实际上还可以加上一个阈值，比如增大了超过200个像素才当做弹出，这样会更加准确。

    使用起来也并不复杂

public class MainActivity extends AppCompatActivity implements KeyboardChangeListener.KeyBoardListener {    private static final String TAG = "MainActivity";    private KeyboardChangeListener mKeyboardChangeListener;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        // dosomething while show the keyboard!        mKeyboardChangeListener = new KeyboardChangeListener(this);        mKeyboardChangeListener.setKeyBoardListener(this);    }    @Override    public void onKeyboardChange(boolean isShow, int keyboardHeight) {        Log.d(TAG, "onKeyboardChange() called with: " + "isShow = [" + isShow + "], keyboardHeight = [" + keyboardHeight + "]");    }}

    另外还有一个非常重要的条件，就是相应的activity需要设置

android:windowSoftInputMode="adjustResize"

    如果当键盘出现的时候屏幕大小不会改变，那么就会无法读取键盘状态。