[TOC]
为了方便部分精力少的朋友， 本文开始就直接介绍安卓获取输入法高度的方法，然后再逐步讲解。
在某些场景下， 比如写一个聊天界面，包括输入框和发送以及上面的消息列表，简单的使用 LinearLayout 或者 RelativeLayout 布局，当点击输入框，键盘弹起后，通常是不会遮挡输入框和发送的（有时就比较蛋疼了，不知为啥，它就是遮挡），因为它们也随键盘弹了起来。但布局再复杂点，比如说再加个表情栏或者更多栏，这样你肯定要手动控制输入框的高度了。因此，你就必须手动控制输入框的升降，但问题是升多高呢？？？这时，就要想办法获取输入法高度了(～￣▽￣)～
由于目前安卓上还没有提供直接获取输入法高度的 api，因此只好我们自己想办法获取它的高度了。
注： 此思路由国外一大神提出，附上他的 Github ;
这里有两个文件：
前一个用在待观测页面的作为回调函数， 后面是主要的方法所在的类了。
文章后面会附上源码，引入这两个文件后，在要获取输入法高度的页面，首先实现接口 KeyboardHeightObserver，即第一个文件，并重写里面的方法；
然后再定义变量 KeyboardHeightProvider keyboardHeightProvider; 实例化
/**
* Construct a new KeyboardHeightProvider
*
* @param activity The parent activity
* @param layoutId R.layout.*
*/
// 以上为构造函数的相关注释，当然这里是我修改的，这样可以同时支持观测多个页面
keyboardHeightProvider = new KeyboardHeightProvider(this, R.layout.activity_chat);
new Handler().post(new Runnable() {
@Override
public void run() {
keyboardHeightProvider.start();
}
});
这时还要在 onStart()函数里面加上 keyboardHeightProvider.setKeyboardHeightObserver(this); 即：
@Override
public void onStart() {
super.onStart();
// 这里使用了刚才实现的接口
keyboardHeightProvider.setKeyboardHeightObserver(this);
}
考虑更全的话， 还可以加上以下语句：
@Override
public void onPause() {
super.onPause();
keyboardHeightProvider.setKeyboardHeightObserver(null);
}
@Override
public void onDestroy() {
super.onDestroy();
keyboardHeightProvider.close();
}
这样一来，在回调函数 onKeyboardHeightChanged 里面就回收到回调结果了，大功告成！
这里就结合上面输入法的例子，讲讲 ViewTreeObserver。
在要获取输入法高度的页面，创建一个看不见的弹窗，即宽为 0，高为全屏，并为弹窗设置全局布局监听器。当布局有变化，比如有输入法弹窗出现或消失时， 监听器回调函数就会被调用。而其中的关键就是当输入法弹出时， 它会把之前我们创建的那个看不见的弹窗往上挤， 这样我们创建的那个弹窗的位置就变化了，只要获取它底部高度的变化值就可以间接的获取输入法的高度了。
首先创建类 KeyboardHeightProvider， 继承自 PopupWindow ；
然后构造器内完成相关初始化：
super(activity);
this.activity = activity;
LayoutInflater inflator = (LayoutInflater) activity.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
this.popupView = inflator.inflate(layoutId, null, false);
setContentView(popupView);
setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE | WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);
setInputMethodMode(PopupWindow.INPUT_METHOD_NEEDED);
parentView = activity.findViewById(android.R.id.content);
// 设置宽高
setWidth(0);
setHeight(WindowManager.LayoutParams.MATCH_PARENT);
然后就是重点，为 popupView 的观测者（感觉用 ViewTreeObserver 还是更合适）设置全局布局监听器
popupView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
if (popupView != null) {
handleOnGlobalLayout();
}
}
});
其中 handleOnGlobalLayout 函数功能则是：获取弹窗高度，并作差得出输入法高度，以及通知回调。
/**
* Popup window itself is as big as the window of the Activity.
* The keyboard can then be calculated by extracting the popup view bottom
* from the activity window height.
*/
private void handleOnGlobalLayout() {
Point screenSize = new Point();
activity.getWindowManager().getDefaultDisplay().getSize(screenSize);
Rect rect = new Rect();
popupView.getWindowVisibleDisplayFrame(rect);
// REMIND, you may like to change this using the fullscreen size of the phone
// and also using the status bar and navigation bar heights of the phone to calculate
// the keyboard height. But this worked fine on a Nexus.
int orientation = getScreenOrientation();
int keyboardHeight = screenSize.y - rect.bottom;
if (keyboardHeight == 0) {
notifyKeyboardHeightChanged(0, orientation);
}
else if (orientation == Configuration.ORIENTATION_PORTRAIT) {
this.keyboardPortraitHeight = keyboardHeight;
notifyKeyboardHeightChanged(keyboardPortraitHeight, orientation);
}
else {
this.keyboardLandscapeHeight = keyboardHeight;
notifyKeyboardHeightChanged(keyboardLandscapeHeight, orientation);
}
}
嗯，大概就是这样(*￣ 3 ￣)╭
首先自然要给出官方的定义：
/**
* A view tree observer is used to register listeners that can be notified of global
* changes in the view tree. Such global events include, but are not limited to,
* layout of the whole tree, beginning of the drawing pass, touch mode change....
*
* A ViewTreeObserver should never be instantiated by applications as it is provided
* by the views hierarchy. Refer to {@link android.view.View#getViewTreeObserver()}
* for more information.
*/
翻译过来大概是
// 原谅我英语不好（╯︿╰）， 不过我发现谷歌翻译的效果还是不错的
/**
* 视图树观察器用于注册可以在视图树中通知全局
* 更改的侦听器。此类全局事件包括但不限于
* 整个树的布局，绘图过程的开始，触摸模式更改....
*
* ViewTreeObserver 永远不应由应用程序实例化，因为它由视图层次结构提供
* 。有关更多信息，请参阅{@link android.view.View ＃ getViewTreeObserver （）}
* 。
*/
java.lang.Object
↳ android.view.ViewTreeObserver
直接继承自 Object，没有另外的继承关系
| Nested Classes | | --- | ---- | ---- | | interface | ViewTreeObserver.OnDrawListener | Interface definition for a callback to be invoked when the view tree is about to be drawn. | | interface | ViewTreeObserver.OnGlobalFocusChangeListener | Interface definition for a callback to be invoked when the focus state within the view tree changes. | | interface | ViewTreeObserver.OnGlobalLayoutListener | Interface definition for a callback to be invoked when the global layout state or the visibility of views within the view tree changes. | | interface | ViewTreeObserver.OnPreDrawListener | Interface definition for a callback to be invoked when the view tree is about to be drawn. | | interface | ViewTreeObserver.OnScrollChangedListener | Interface definition for a callback to be invoked when something in the view tree has been scrolled. | | interface | ViewTreeObserver.OnTouchModeChangeListener | Interface definition for a callback to be invoked when the touch mode changes. |
这里的 markdown 语法不知为啥没用。。。排版完善的可以参考这里
另外方法挺多的， 我就不列举了。
注： 此处参考了小马快跑 的博客
在某些时候，我们要获取 view 的高度，但获取到的为 0，为什么呢？这样通常时由于页面还未测量导致的，比如在 onCreate 中调用的话就会直接返回 0。这是就需要我们手动获取了。
通过设置 View 的 MeasureSpec.UNSPECIFIED 来测量：
int w = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
int h = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
view.measure(w, h);
//获得宽高
int viewWidth=view.getMeasuredWidth();
int viewHeight=view.getMeasuredHeight();
设置我们的 SpecMode 为 UNSPECIFIED，然后去调用 onMeasure 测量宽高，就可以得到宽高。
通过 ViewTreeObserver .addOnGlobalLayoutListener 来获得宽高，当获得正确的宽高后，请移除这个观察者，否则回调会多次执行：
//获得 ViewTreeObserver
ViewTreeObserver observer=view.getViewTreeObserver();
//注册观察者，监听变化
observer.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
//判断 ViewTreeObserver 是否 alive，如果存活的话移除这个观察者
if(observer.isAlive()){
observer.removeGlobalOnLayoutListener(this);
//获得宽高
int viewWidth=view.getMeasuredWidth();
int viewHeight=view.getMeasuredHeight();
}
}
});
通过 ViewTreeObserver .addOnPreDrawListener 来获得宽高，在执行 onDraw 之前已经执行了 onLayout()和 onMeasure()，可以得到宽高了，当获得正确的宽高后，请移除这个观察者，否则回调会多次执行
//获得 ViewTreeObserver
ViewTreeObserver observer=view.getViewTreeObserver();
//注册观察者，监听变化
observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
if(observer.isAlive()){
observer.removeOnDrawListener(this);
}
//获得宽高
int viewWidth=view.getMeasuredWidth();
int viewHeight=view.getMeasuredHeight();
return true;
}
});
public interface KeyboardHeightObserver {
/**
* Called when the keyboard height has changed, 0 means keyboard is closed,
* >= 1 means keyboard is opened.
*
* @param height The height of the keyboard in pixels
* @param orientation The orientation either: Configuration.ORIENTATION_PORTRAIT or
* Configuration.ORIENTATION_LANDSCAPE
*/
void onKeyboardHeightChanged(int height, int orientation);
}
import android.app.Activity;
import android.content.res.Configuration;
import android.graphics.Point;
import android.graphics.Rect;
import android.graphics.drawable.ColorDrawable;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewTreeObserver;
import android.view.WindowManager;
import android.widget.PopupWindow;
/**
* The keyboard height provider, this class uses a PopupWindow
* to calculate the window height when the floating keyboard is opened and closed.
*/
public class KeyboardHeightProvider extends PopupWindow {
/** The tag for logging purposes */
private final static String TAG = "sample_KeyboardHeightProvider";
/** The keyboard height observer */
private KeyboardHeightObserver observer;
/** The cached landscape height of the keyboard */
private int keyboardLandscapeHeight;
/** The cached portrait height of the keyboard */
private int keyboardPortraitHeight;
/** The view that is used to calculate the keyboard height */
private View popupView;
/** The parent view */
private View parentView;
/** The root activity that uses this KeyboardHeightProvider */
private Activity activity;
/**
* Construct a new KeyboardHeightProvider
*
* @param activity The parent activity
* @param layoutId R.layout.*
*/
public KeyboardHeightProvider(Activity activity, int layoutId) {
super(activity);
this.activity = activity;
LayoutInflater inflator = (LayoutInflater) activity.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
this.popupView = inflator.inflate(layoutId, null, false);
setContentView(popupView);
setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE | WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);
setInputMethodMode(PopupWindow.INPUT_METHOD_NEEDED);
parentView = activity.findViewById(android.R.id.content);
setWidth(0);
setHeight(WindowManager.LayoutParams.MATCH_PARENT);
popupView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
if (popupView != null) {
handleOnGlobalLayout();
}
}
});
}
/**
* Start the KeyboardHeightProvider, this must be called after the onResume of the Activity.
* PopupWindows are not allowed to be registered before the onResume has finished
* of the Activity.
*/
public void start() {
if (!isShowing() && parentView.getWindowToken() != null) {
setBackgroundDrawable(new ColorDrawable(0));
showAtLocation(parentView, Gravity.NO_GRAVITY, 0, 0);
}
}
/**
* Close the keyboard height provider,
* this provider will not be used anymore.
*/
public void close() {
this.observer = null;
dismiss();
}
/**
* Set the keyboard height observer to this provider. The
* observer will be notified when the keyboard height has changed.
* For example when the keyboard is opened or closed.
*
* @param observer The observer to be added to this provider.
*/
public void setKeyboardHeightObserver(KeyboardHeightObserver observer) {
this.observer = observer;
}
/**
* Get the screen orientation
*
* @return the screen orientation
*/
private int getScreenOrientation() {
return activity.getResources().getConfiguration().orientation;
}
/**
* Popup window itself is as big as the window of the Activity.
* The keyboard can then be calculated by extracting the popup view bottom
* from the activity window height.
*/
private void handleOnGlobalLayout() {
Point screenSize = new Point();
activity.getWindowManager().getDefaultDisplay().getSize(screenSize);
Rect rect = new Rect();
popupView.getWindowVisibleDisplayFrame(rect);
// REMIND, you may like to change this using the fullscreen size of the phone
// and also using the status bar and navigation bar heights of the phone to calculate
// the keyboard height. But this worked fine on a Nexus.
int orientation = getScreenOrientation();
int keyboardHeight = screenSize.y - rect.bottom;
if (keyboardHeight == 0) {
notifyKeyboardHeightChanged(0, orientation);
}
else if (orientation == Configuration.ORIENTATION_PORTRAIT) {
this.keyboardPortraitHeight = keyboardHeight;
notifyKeyboardHeightChanged(keyboardPortraitHeight, orientation);
}
else {
this.keyboardLandscapeHeight = keyboardHeight;
notifyKeyboardHeightChanged(keyboardLandscapeHeight, orientation);
}
}
private void notifyKeyboardHeightChanged(int height, int orientation) {
if (observer != null) {
observer.onKeyboardHeightChanged(height, orientation);
}
}
}
这是一个专为移动设备优化的页面（即为了让你能够在 Google 搜索结果里秒开这个页面），如果你希望参与 V2EX 社区的讨论，你可以继续到 V2EX 上打开本讨论主题的完整版本。
V2EX 是创意工作者们的社区，是一个分享自己正在做的有趣事物、交流想法，可以遇见新朋友甚至新机会的地方。
V2EX is a community of developers, designers and creative people.