安卓獲取輸入法高度與ViewTreeObserver講解

摘要： 目錄 為了方便部分精力少的朋友， 本文開始就直接介紹安卓獲取輸入法高度的方法，然後再逐步講解。 安卓獲取輸入法高度 前言 在某些場景下， 比如寫一個聊天介面，包括輸入框和傳送以及上面的訊息列表，簡單的使用LinearLayout或者RelativeLayout佈局，當點選輸入框...

目錄

為了方便部分精力少的朋友， 本文開始就直接介紹安卓獲取輸入法高度的方法，然後再逐步講解。

安卓獲取輸入法高度

前言

在某些場景下， 比如寫一個聊天介面，包括輸入框和傳送以及上面的訊息列表，簡單的使用LinearLayout或者RelativeLayout佈局，當點選輸入框，鍵盤彈起後，通常是不會遮擋輸入框和傳送的（有時就比較蛋疼了，不知為啥，它就是遮擋），因為它們也隨鍵盤彈了起來。但佈局再複雜點，比如說再加個表情欄或者更多欄，這樣你肯定要手動控制輸入框的高度了。因此，你就必須手動控制輸入框的升降，但問題是升多高呢？？？這時，就要想辦法獲取輸入法高度了(～￣▽￣)～

由於目前安卓上還沒有提供直接獲取輸入法高度的api，因此只好我們自己想辦法獲取它的高度了。

注： 此思路由國外一大神提出，附上他的ofollow,noindex" target="_blank">Github ;

清單

這裡有兩個檔案：

• interface KeyboardHeightObserver
• class KeyboardHeightProvider

前一個用在待觀測頁面的作為回撥函式， 後面是主要的方法所在的類了。

開始

文章後面會附上原始碼，引入這兩個檔案後，在要獲取輸入法高度的頁面，首先實現介面KeyboardHeightObserver，即第一個檔案，並重寫裡面的方法；

然後再定義變數 KeyboardHeightProvider keyboardHeightProvider;

例項化

/**
* Construct a new KeyboardHeightProvider
*
* @param activity The parent activity
* @param layoutIdR.layout.*
*/
// 以上為建構函式的相關注釋，當然這裡是我修改的，這樣可以同時支援觀測多個頁面
keyboardHeightProvider = new KeyboardHeightProvider(this, R.layout.activity_chat);

new Handler().post(new Runnable() {
@Override
public void run() {
keyboardHeightProvider.start();
}
});

這時還要在onStart()函式裡面加上 keyboardHeightProvider.setKeyboardHeightObserver(this); 即：

@Override
public void onStart() {
super.onStart();
// 這裡使用了剛才實現的介面
keyboardHeightProvider.setKeyboardHeightObserver(this);
}

考慮更全的話， 還可以加上以下語句：

@Override
public void onPause() {
super.onPause();
keyboardHeightProvider.setKeyboardHeightObserver(null);
}

@Override
public void onDestroy() {
super.onDestroy();
keyboardHeightProvider.close();
}

這樣一來，在回撥函式 onKeyboardHeightChanged裡面就回收到回撥結果了，大功告成！

ViewTreeObserver講解

這裡就結合上面輸入法的例子，講講ViewTreeObserver。

獲取輸入法高度原理

思路

在要獲取輸入法高度的頁面，建立一個看不見的彈窗，即寬為0，高為全屏，併為彈窗設定全域性佈局監聽器。當佈局有變化，比如有輸入法彈窗出現或消失時， 監聽器回撥函式就會被呼叫。而其中的關鍵就是當輸入法彈出時， 它會把之前我們建立的那個看不見的彈窗往上擠， 這樣我們建立的那個彈窗的位置就變化了，只要獲取它底部高度的變化值就可以間接的獲取輸入法的高度了。

實現

首先建立類KeyboardHeightProvider， 繼承自PopupWindow；

然後構造器內完成相關初始化：

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);

// 設定寬高
setWidth(0);
setHeight(WindowManager.LayoutParams.MATCH_PARENT);

然後就是重點，為popupView的觀測者（感覺用 ViewTreeObserver還是更合適）設定全域性佈局監聽器

popupView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
if (popupView != null) {
handleOnGlobalLayout();
}
}
});

其中handleOnGlobalLayout函式功能則是：獲取彈窗高度，並作差得出輸入法高度，以及通知回撥。

/**
* 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，大概就是這樣(*￣3￣)╭

關於ViewTreeObserver

定義

首先自然要給出官方的定義：

/**
 * 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.
 */

翻譯過來大概是

// 原諒我英語不好（╯︿╰）， 不過我發現谷歌翻譯的效果還是不錯的

/**
* 檢視樹觀察器用於註冊可以在檢視樹中通知全域性
* 更改的偵聽器。此類全域性事件包括但不限於
* 整個樹的佈局，繪圖過程的開始，觸控模式更改.... 
* 
* ViewTreeObserver永遠不應由應用程式例項化，因為它由檢視層次結構提供
* 。有關更多資訊，請參閱{@link android.view.View＃getViewTreeObserver（）}
* 。 
*/

繼承

java.lang.Object
↳android.view.ViewTreeObserver

直接繼承自Object，沒有另外的繼承關係

摘要

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.

另外方法挺多的， 我就不列舉了。

獲取View高度的三種方法

注： 此處參考了 小馬快跑 的部落格

在某些時候，我們要獲取view的高度，但獲取到的為0，為什麼呢？這樣通常時由於頁面還未測量導致的，比如在onCreate中呼叫的話就會直接返回0。這是就需要我們手動獲取了。

View的MeasureSpec.UNSPECIFIED

通過設定View的MeasureSpec.UNSPECIFIED來測量：

int w = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
int h = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
view.measure(w, h);
//獲得寬高
int viewWidth=view.getMeasuredWidth();
int viewHeight=view.getMeasuredHeight();

設定我們的SpecMode為UNSPECIFIED，然後去呼叫onMeasure測量寬高，就可以得到寬高。

ViewTreeObserver .addOnGlobalLayoutListener

通過ViewTreeObserver .addOnGlobalLayoutListener來獲得寬高，當獲得正確的寬高後，請移除這個觀察者，否則回撥會多次執行：

//獲得ViewTreeObserver 
ViewTreeObserver observer=view.getViewTreeObserver();
//註冊觀察者，監聽變化
observer.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
//判斷ViewTreeObserver 是否alive，如果存活的話移除這個觀察者
if(observer.isAlive()){
observer.removeGlobalOnLayoutListener(this);
//獲得寬高
int viewWidth=view.getMeasuredWidth();
int viewHeight=view.getMeasuredHeight();
}
}
});

ViewTreeObserver .addOnPreDrawListener

通過ViewTreeObserver .addOnPreDrawListener來獲得寬高，在執行onDraw之前已經執行了onLayout()和onMeasure()，可以得到寬高了，當獲得正確的寬高後，請移除這個觀察者，否則回撥會多次執行

//獲得ViewTreeObserver 
ViewTreeObserver observer=view.getViewTreeObserver();
//註冊觀察者，監聽變化
observer.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
if(observer.isAlive()){
observer.removeOnDrawListener(this);
}
//獲得寬高
int viewWidth=view.getMeasuredWidth();
int viewHeight=view.getMeasuredHeight();
return true;
}
});

原始碼

interface KeyboardHeightObserver

public interface KeyboardHeightObserver {
/**
* Called when the keyboard height has changed, 0 means keyboard is closed,
* >= 1 means keyboard is opened.
*
* @param heightThe height of the keyboard in pixels
* @param orientationThe orientation either: Configuration.ORIENTATION_PORTRAIT or
*Configuration.ORIENTATION_LANDSCAPE
*/
void onKeyboardHeightChanged(int height, int orientation);
}

class KeyboardHeightProvider

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 layoutIdR.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);
}
}
}