Android開發 - 獲取系統輸入法高度的正確姿勢

摘要： 問題與解決 在Android應用的開發中，有一些需求需要我們獲取到輸入法的高度，但是官方的API並沒有提供類似的方法，所以我們需要自己來實現。 查閱了網上很多資料，試過以後都不理想。 比如有的方法通過監聽佈局的變化來計算輸入法的高度，這種方式在Activity的配置中配置為"...

問題與解決

在Android應用的開發中，有一些需求需要我們獲取到輸入法的高度，但是官方的API並沒有提供類似的方法，所以我們需要自己來實現。

查閱了網上很多資料，試過以後都不理想。

比如有的方法通過監聽佈局的變化來計算輸入法的高度，這種方式在Activity的配置中配置為"android:windowSoftInputMode="adjustResize""時沒有問題，可以正確獲取輸入法的高度，因為佈局此時確實會動態的調整。

但是當Activity配置為"android:windowSoftInputMode="adjustNothing""時，佈局不會在輸入法彈出時進行調整，上面的方式就會撲街。

不過經過一番探索和測試，終於發現了一種方式可以在即使設定為adjustNothing時也可以正確計算高度放方法。

其實也就兩個類，我也做了一些修改，解決了一些問題，這裡也貼出來：

• KeyboardHeightObserver.java

/**
 * The observer that will be notified when the height of 
 * the keyboard has changed
 */
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);
}

• KeyboardHeightProvider.java

/**
 * 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
*/
public KeyboardHeightProvider(Activity activity) {
super(activity);
this.activity = activity;

LayoutInflater inflator = (LayoutInflater) activity.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
this.popupView = inflator.inflate(R.layout.keyboard_popup_window, null, false);
setContentView(popupView);

setSoftInputMode(LayoutParams.SOFT_INPUT_ADJUST_RESIZE | LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);
setInputMethodMode(PopupWindow.INPUT_METHOD_NEEDED);

parentView = activity.findViewById(android.R.id.content);

setWidth(0);
setHeight(LayoutParams.MATCH_PARENT);

popupView.getViewTreeObserver().addOnGlobalLayoutListener(new 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);
}
}
}

使用方法

此處以在Activity中的使用進行舉例。

實現介面

引入這兩個類後，在當前Activity中實現介面KeyboardHeightObserver：

@Override
public void onKeyboardHeightChanged(int height, int orientation) {
String or = orientation == Configuration.ORIENTATION_PORTRAIT ? "portrait" : "landscape";
Logger.d(TAG, "onKeyboardHeightChanged in pixels: " + height + " " + or);
}

定義並初始化

在當前Activity定義成員變數，並在onCreate()中進行初始化

private KeyboardHeightProvider mKeyboardHeightProvider;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
...
mKeyboardHeightProvider = new KeyboardHeightProvider(this);
new Handler().post(() -> mKeyboardHeightProvider.start());
}

生命週期處理

初始化完成後，我們要在Activity中的生命週期中也要進行處理，以免記憶體洩露。

@Override
protected void onResume() {
super.onResume();
mKeyboardHeightProvider.setKeyboardHeightObserver(this);
}

@Override
protected void onPause() {
super.onPause();
mKeyboardHeightProvider.setKeyboardHeightObserver(null);
}

@Override
protected void onDestroy() {
super.onDestroy();
mKeyboardHeightProvider.close();
}

總結

此時我們就可以正確獲取的當前輸入法的高度了，即使android:windowSoftInputMode="adjustNothing"時也可以正確獲取到，這正是這個方法的強大之處，利用這個方法可以實現比如類似微信聊天的介面，流暢切換輸入框，表情框等。

如有更多疑問，請參考我的其它Android相關部落格：我的部落格地址