Android开发教程之获取系统输入法高度的正确姿势

问题与解决

在Android应用的开发中，有一些需求需要我们获取到输入法的高度，但是官方的API并没有提供类似的方法，所以我们需要自己来实现。

查阅了网上很多资料，试过以后都不理想。

比如有的方法通过监听布局的变化来计算输入法的高度，这种方式在Activity的配置中配置为"android:windowSoftInputMode="adjustResize""时没有问题，可以正确获取输入法的高度，因为布局此时确实会动态的调整。

但是当Activity配置为"android:windowSoftInputMode="adjustNothing""时，布局不会在输入法弹出时进行调整，上面的方式就会扑街。

不过经过一番探索和测试，终于发现了一种方式可以在即使设置为adjustNothing时也可以正确计算高度放方法。

同时也感谢这位外国朋友：

GitHub地址

方法如下

其实也就两个类，我也做了一些修改，解决了一些问题，这里也贴出来：

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 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);
}

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

此处以在Activity中的使用进行举例。

实现接口

引入这两个类后，在当前Activity中实现接口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);
}

定义并初始化

在当前Activity定义成员变量，并在onCreate()中进行初始化

private KeyboardHeightProvider mKeyboardHeightProvider;

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

生命周期处理

初始化完成后，我们要在Activity中的生命周期中也要进行处理，以免内存泄露。

@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();
}

总结

此时我们就可以正确获取的当前输入法的高度了，即使android:windowSoftInputMode="adjustNothing"时也可以正确获取到，这正是这个方法的强大之处，利用这个方法可以实现比如类似微信聊天的界面，流畅切换输入框，表情框等。

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