借鑑大神的方法，防止鍵盤擋住EditText輸入框

在頁面中，總會遇到軟鍵盤彈出遮擋住EditText不方便用戶輸入，借鑑大神的如下方法：
使用很簡單，複製下面的SoftHideKeyBoardUtil工具類到項目中，在BaseActivity或者需要彈起鍵盤的Activity的onCreate方法中加入如下代碼即可

SoftHideKeyBoardUtil.assistActivity(this);

SoftHideKeyBoardUtil工具類

import android.app.Activity;
import android.graphics.Rect;
import android.os.Build;
import android.view.View;
import android.view.ViewTreeObserver;
import android.widget.FrameLayout;

public class SoftHideKeyBoardUtil {
    public static void assistActivity (Activity activity) {
        new SoftHideKeyBoardUtil(activity);
    }
    private View mChildOfContent;
    private int usableHeightPrevious;
    private FrameLayout.LayoutParams frameLayoutParams;
    //爲適應華爲小米等手機鍵盤上方出現黑條或不適配
    private int contentHeight;//獲取setContentView本來view的高度
    private boolean isfirst = true;//只用獲取一次
    private  int statusBarHeight;//狀態欄高度
    private SoftHideKeyBoardUtil(Activity activity) {
        //1､找到Activity的最外層佈局控件，它其實是一個DecorView,它所用的控件就是FrameLayout
        FrameLayout content = activity.findViewById(android.R.id.content);
        //2､獲取到setContentView放進去的View
        mChildOfContent = content.getChildAt(0);
        //3､給Activity的xml佈局設置View樹監聽，當佈局有變化，如鍵盤彈出或收起時，都會回調此監聽
        mChildOfContent.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            //4､軟鍵盤彈起會使GlobalLayout發生變化
            public void onGlobalLayout() {
                if (isfirst) {
                    contentHeight = mChildOfContent.getHeight();//兼容華爲等機型
                    isfirst = false;
                }
                //5､當前佈局發生變化時，對Activity的xml佈局進行重繪
                possiblyResizeChildOfContent();
            }
        });
        //6､獲取到Activity的xml佈局的放置參數
        frameLayoutParams = (FrameLayout.LayoutParams) mChildOfContent.getLayoutParams();
    }

    // 獲取界面可用高度，如果軟鍵盤彈起後，Activity的xml佈局可用高度需要減去鍵盤高度
    private void possiblyResizeChildOfContent() {
        //1､獲取當前界面可用高度，鍵盤彈起後，當前界面可用佈局會減少鍵盤的高度
        int usableHeightNow = computeUsableHeight();
        //2､如果當前可用高度和原始值不一樣
        if (usableHeightNow != usableHeightPrevious) {
            //3､獲取Activity中xml中佈局在當前界面顯示的高度
            int usableHeightSansKeyboard = mChildOfContent.getRootView().getHeight();
            //4､Activity中xml佈局的高度-當前可用高度
            int heightDifference = usableHeightSansKeyboard - usableHeightNow;
            //5､高度差大於屏幕1/4時，說明鍵盤彈出
            if (heightDifference > (usableHeightSansKeyboard/4)) {
                // 6､鍵盤彈出了，Activity的xml佈局高度應當減去鍵盤高度
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT){
                    frameLayoutParams.height = usableHeightSansKeyboard - heightDifference + statusBarHeight;
                } else {
                    frameLayoutParams.height = usableHeightSansKeyboard - heightDifference;
                }
            } else {
                frameLayoutParams.height = contentHeight;
            }
            //7､ 重繪Activity的xml佈局
            mChildOfContent.requestLayout();
            usableHeightPrevious = usableHeightNow;
        }
    }
    private int computeUsableHeight() {
        Rect r = new Rect();
        mChildOfContent.getWindowVisibleDisplayFrame(r);
        // 全屏模式下：直接返回r.bottom，r.top其實是狀態欄的高度
        return (r.bottom - r.top);
    }
}