Android 軟體盤彈出可能會遮擋住介面上的某些控制元件。當 windowSoftInputMode 為 adjustPan 時，一般不會擋住 EditText，但是假如 EditText 下面是一個登入按鈕，那麼這個按鈕就可能被擋住，但有時我們希望使用者輸完密碼可以直接點選登入按鈕，而不用把軟鍵盤收起來。這時就需要用到 adjustResize，這種模式能夠獲取到軟鍵盤的高度，這樣我們就能夠精確的對介面進行控制。

在閱讀本章之前，你應該瞭解 windowSoftInputMode 的一些屬性，特別是 adjustResize，如果還不熟悉，建議先閱讀Android 軟鍵盤之 windowSoftInputMode 分析

QQ 登入介面很好的解決了軟鍵盤遮擋問題，當然在大屏手機上軟鍵盤並不會擋住登入按鈕。今天我們也來模仿一個 QQ 登入介面，最終效果如下：

監聽軟鍵盤彈出及收起事件

step1. 指定 windowSoftInputMode=”adjustResize”

在 AndroidManifest.xml 中相應的 Activity 設定 android:windowSoftInputMode=”adjustResize”，也可以在 java 程式碼中設定。

step2. 監聽 contentView 寬高(layout) 變化

獲取 ViewTreeObserver 並監聽 OnGlobalLayoutListener, 當viewTree的佈局發生變化時onGlobalLayout將會回撥。我們新建一個KeyboardHelper輔助類。

KeyboardHelper.java

public class KeyboardHelper {
    private Activity activity;
    private OnKeyboardStatusChangeListener onKeyboardStatusChangeListener;
    private int windowBottom = -1;
    private int keyboardHeight = 0;

    public KeyboardHelper(Activity activity) {
        this.activity = activity;
        activity.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE);
        if
 
 (activity.getRequestedOrientation() != ActivityInfo.SCREEN_ORIENTATION_PORTRAIT) {
            activity.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        }
    }

    public void onCreate() {
        View content = activity.findViewById(android.R.id.content);
        // content.addOnLayoutChangeListener(listener); 這個方法有時會出現一些問題
        content.getViewTreeObserver().addOnGlobalLayoutListener(onGlobalLayoutListener);
    }

    public void onDestroy() {
        View content = activity.findViewById(android.R.id.content);
        ViewUtils.removeOnGlobalLayoutListener(content, onGlobalLayoutListener);
    }

    private OnGlobalLayoutListener onGlobalLayoutListener = new OnGlobalLayoutListener() {
        @Override
        public void onGlobalLayout() {
            Rect rect = new Rect();
            activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(rect);
            Log.d("KeyboardHelper", "onGlobalLayout: " + rect + ", " + windowBottom);
            int newBottom = rect.bottom;
            if (windowBottom != -1 && windowBottom != newBottom) {
                if (newBottom < windowBottom) {
                    // keyboard pop
                    keyboardHeight = windowBottom - newBottom;
                    if (onKeyboardStatusChangeListener != null) {
                        onKeyboardStatusChangeListener.onKeyboardPop(keyboardHeight);
                    }
                } else {
                    // keyboard close
                    if (onKeyboardStatusChangeListener != null) {
                        onKeyboardStatusChangeListener.onKeyboardClose(keyboardHeight);
                    }
                }
            }
            windowBottom = newBottom;
        }
    };

    public void setOnKeyboardStatusChangeListener(
            OnKeyboardStatusChangeListener onKeyboardStatusChangeListener) {
        this.onKeyboardStatusChangeListener = onKeyboardStatusChangeListener;
    }

    public interface OnKeyboardStatusChangeListener {

        void onKeyboardPop(int keyboardHeight);

        void onKeyboardClose(int keyboardHeight);
    }
}

ViewUtils.java

public class ViewUtils {

    public static void removeOnGlobalLayoutListener(View view, ViewTreeObserver.OnGlobalLayoutListener onGlobalLayoutListener) {
        if (Build.VERSION.SDK_INT < 16) {
            view.getViewTreeObserver().removeGlobalOnLayoutListener(onGlobalLayoutListener);
        } else {
            view.getViewTreeObserver().removeOnGlobalLayoutListener(onGlobalLayoutListener);
        }
    }

}

程式碼比較簡單，無非是獲取window的可視座標，通過比較bottom的值來判斷軟鍵盤是彈出還是收起。

實現 QQ 登入介面

有了這個 KeyBoardHelper，那麼要實現和 QQ 登入介面一樣的效果就不難了。我們甚至不需要任何自定義控制元件。思路是在軟鍵盤彈出時，把登入按鈕以上的佈局往上移，只要為其設定一個負值的 topMargin 即可。

如圖所示：

MainActivity 程式碼如下：

public class MainActivity extends Activity {

    private int bottomHeight;
    private KeyboardHelper keyboardHelper;
    private View layoutBottom;
    private View layoutContent;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_qq_login);

        layoutContent = findViewById(R.id.layout_content);
        layoutBottom = findViewById(R.id.layout_bottom);
        keyboardHelper = new KeyboardHelper(this);
        keyboardHelper.onCreate();
        keyboardHelper.setOnKeyboardStatusChangeListener(onKeyBoardStatusChangeListener);
        layoutBottom.post(new Runnable() {
            @Override
            public void run() {
                bottomHeight = layoutBottom.getHeight();
            }
        });
    }

    private OnKeyboardStatusChangeListener onKeyBoardStatusChangeListener = new OnKeyboardStatusChangeListener() {

        @Override
        public void onKeyboardPop(int keyboardHeight) {

            final int height = keyboardHeight;
            if (bottomHeight > height) {
                layoutBottom.setVisibility(View.GONE);
            } else {
                int offset = bottomHeight - height;
                final ViewGroup.MarginLayoutParams lp = (MarginLayoutParams) layoutContent
                        .getLayoutParams();
                lp.topMargin = offset;
                layoutContent.setLayoutParams(lp);
            }

        }

        @Override
        public void onKeyboardClose(int keyboardHeight) {
            if (View.VISIBLE != layoutBottom.getVisibility()) {
                layoutBottom.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        layoutBottom.setVisibility(View.VISIBLE);
                    }
                }, 300);
            }
            final ViewGroup.MarginLayoutParams lp = (MarginLayoutParams) layoutContent
                    .getLayoutParams();
            if (lp.topMargin != 0) {
                lp.topMargin = 0;
                layoutContent.setLayoutParams(lp);
            }

        }
    };

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

佈局檔案：activity_qq_login.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/layout_root"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:id="@+id/layout_content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:paddingTop="50dp">

        <ImageView
            android:id="@+id/imageView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginTop="18dp"
            android:contentDescription="marginTop68dp"
            android:scaleType="centerInside"
            android:src="@drawable/qq_ava"
            android:visibility="visible" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="18dp"
            android:background="#f3f0f0"
            android:paddingBottom="100dp"
            android:paddingLeft="10dp"
            android:paddingRight="10dp"
            android:paddingTop="100dp"
            android:text="這裡為了演示增加一個TextView使登陸按鈕在鍵盤底部"
            android:textColor="#333333"
            android:textSize="13sp" />

        <LinearLayout
            android:id="@+id/layout_ed"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="#ffffff"
            android:divider="@drawable/divider"
            android:orientation="vertical"
            android:showDividers="middle">

            <EditText
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:background="@null"
                android:hint="QQ號/手機號/郵箱"
                android:padding="10dp"
                android:textColor="#000000"
                android:textColorHint="#d2d2d2"
                android:textCursorDrawable="@null" />

            <EditText
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:background="@null"
                android:hint="密碼"
                android:padding="10dp"
                android:textColor="#000000"
                android:textColorHint="#d2d2d2"
                android:textCursorDrawable="@null" />
        </LinearLayout>

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginLeft="14dp"
            android:layout_marginRight="14dp"
            android:layout_marginTop="14dp"
            android:background="@drawable/btn_login"
            android:text="登陸"
            android:textSize="17sp" />

        <RelativeLayout
            android:id="@+id/layout_bottom"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <TextView
                android:id="@+id/tv_cannot_login"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentBottom="true"
                android:layout_margin="14dp"
                android:text="無法登陸？"
                android:textColor="@color/action_bar_bg"
                android:textSize="14sp" />

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentBottom="true"
                android:layout_alignParentRight="true"
                android:layout_margin="14dp"
                android:text="新使用者"
                android:textColor="@color/action_bar_bg"
                android:textSize="14sp" />
        </RelativeLayout>
    </LinearLayout>

    <include
        android:id="@+id/appbar"
        layout="@layout/appbar"
        android:layout_width="match_parent"
        android:layout_height="50dp" />

</FrameLayout>