Android软键盘windowSoftInputMode的使用与原理(原理篇)

文章目录

  • 前言
  • 一、可见性原理
    • 1.stateUnchanged
    • 2.stateHidden和stateAlwaysHidden
    • 3.stateVisible和stateAlwaysVisible
    • 4.stateUnspecified
  • 二、显示方式原理
    • 1.adjustResize
    • 2.adjustPan
    • 3.adjustNothing
    • 4.adjustUnspecified

前言

上一篇文章Android软键盘windowSoftInputMode的使用与原理使用篇介绍了windowSoftInputMode各个属性的具体作用,下面我们在源码层面来分析一下各个属性的实现原理(基于Android9)。

一、可见性原理

要去分析软键盘的隐藏和显示首先要搞懂Android系统的软键盘架构是怎样的,看下图:
Android软键盘windowSoftInputMode的使用与原理(原理篇)_第1张图片
InputMethodManagerService(下文也称IMMS)负责管理系统的所有输入法,包括输入法service(InputMethodService简称IMS)加载及切换。程序获得焦点时,就会通过InputMethodManager向InputMethodManagerService通知自己获得焦点并请求绑定自己到当前输入法上。同时,当程序的某个需要输入法的view比如EditorView获得焦点时就会通过InputMethodManager向InputMethodManagerService请求显示输入法,而这时InputMethodManagerService收到请求后,会将请求的EditText的数据通信接口发送给当前输入法,并请求显输入法。输入法收到请求后,就显示自己的UI dialog,同时保存目标view的数据结构,当用户实现输入后,直接通过view的数据通信接口将字符传递到对应的View。

除此之外我们还要了解Android的窗口管理系统,看下图:
Android软键盘windowSoftInputMode的使用与原理(原理篇)_第2张图片

WindowManagerService(下文也称WMS)非常复杂,负责管理系统所有窗口,我们只需要知道当窗口发生变化(焦点状态和大小)他会通知到app进程。

当app的窗口也就是页面的Focus状态发生变化(例如:进入一个新的窗口,这个窗口的Focus状态变成ture,上一个窗口变成false),事件会回调到ViewRootImpl的WindowInputEventReceiver中,经过一系列调用之后会进入到IMMS的startInputOrWindowGainedFocusInternalLocked方法中,看一下这个方法的核心代码:

    @NonNull
    private InputBindResult startInputOrWindowGainedFocusInternalLocked(
            @StartInputReason int startInputReason, IInputMethodClient client,
            @NonNull IBinder windowToken, @StartInputFlags int startInputFlags,
            @SoftInputModeFlags int softInputMode, int windowFlags, EditorInfo attribute,
            IInputContext inputContext, @MissingMethodFlags int missingMethods,
            int unverifiedTargetSdkVersion, @UserIdInt int userId) {
            
        ......省略........
        
        InputBindResult res = null;
        switch (softInputMode & LayoutParams.SOFT_INPUT_MASK_STATE) {
            case LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED:
                if (!isTextEditor || !doAutoShow) {
                    if (LayoutParams.mayUseInputMethod(windowFlags)) {
                        // There is no focus view, and this window will
                        // be behind any soft input window, so hide the
                        // soft input window if it is shown.
                        if (DEBUG) Slog.v(TAG, "Unspecified window will hide input");
                        hideCurrentInputLocked(
                                mCurFocusedWindow, InputMethodManager.HIDE_NOT_ALWAYS, null,
                                SoftInputShowHideReason.HIDE_UNSPECIFIED_WINDOW);

                        // If focused display changed, we should unbind current method
                        // to make app window in previous display relayout after Ime
                        // window token removed.
                        // Note that we can trust client's display ID as long as it matches
                        // to the display ID obtained from the window.
                        if (cs.selfReportedDisplayId != mCurTokenDisplayId) {
                            unbindCurrentMethodLocked();
                        }
                    }
                } else if (isTextEditor && doAutoShow
                        && (softInputMode & LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) != 0) {
                    // There is a focus view, and we are navigating forward
                    // into the window, so show the input window for the user.
                    // We only do this automatically if the window can resize
                    // to accommodate the IME (so what the user sees will give
                    // them good context without input information being obscured
                    // by the IME) or if running on a large screen where there
                    // is more room for the target window + IME.
                    if (DEBUG) Slog.v(TAG, "Unspecified window will show input");
                    if (attribute != null) {
                        res = startInputUncheckedLocked(cs, inputContext, missingMethods,
                                attribute, startInputFlags, startInputReason);
                        didStart = true;
                    }
                    showCurrentInputLocked(windowToken, InputMethodManager.SHOW_IMPLICIT, null,
                            SoftInputShowHideReason.SHOW_AUTO_EDITOR_FORWARD_NAV);
                }
                break;
            case LayoutParams.SOFT_INPUT_STATE_UNCHANGED:
                // Do nothing.
                break;
            case LayoutParams.SOFT_INPUT_STATE_HIDDEN:
                if ((softInputMode & LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) != 0) {
                    if (DEBUG) Slog.v(TAG, "Window asks to hide input going forward");
                    hideCurrentInputLocked(mCurFocusedWindow, 0, null,
                            SoftInputShowHideReason.HIDE_STATE_HIDDEN_FORWARD_NAV);
                }
                break;
            case LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN:
                if (DEBUG) Slog.v(TAG, "Window asks to hide input");
                hideCurrentInputLocked(mCurFocusedWindow, 0, null,
                        SoftInputShowHideReason.HIDE_ALWAYS_HIDDEN_STATE);
                break;
            case LayoutParams.SOFT_INPUT_STATE_VISIBLE:
                if ((softInputMode & LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) != 0) {
                    if (DEBUG) Slog.v(TAG, "Window asks to show input going forward");
                    if (InputMethodUtils.isSoftInputModeStateVisibleAllowed(
                            unverifiedTargetSdkVersion, startInputFlags)) {
                        if (attribute != null) {
                            res = startInputUncheckedLocked(cs, inputContext, missingMethods,
                                    attribute, startInputFlags, startInputReason);
                            didStart = true;
                        }
                        showCurrentInputLocked(windowToken, InputMethodManager.SHOW_IMPLICIT, null,
                                SoftInputShowHideReason.SHOW_STATE_VISIBLE_FORWARD_NAV);
                    } else {
                        Slog.e(TAG, "SOFT_INPUT_STATE_VISIBLE is ignored because"
                                + " there is no focused view that also returns true from"
                                + " View#onCheckIsTextEditor()");
                    }
                }
                break;
            case LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE:
                if (DEBUG) Slog.v(TAG, "Window asks to always show input");
                if (InputMethodUtils.isSoftInputModeStateVisibleAllowed(
                        unverifiedTargetSdkVersion, startInputFlags)) {
                    if (attribute != null) {
                        res = startInputUncheckedLocked(cs, inputContext, missingMethods,
                                attribute, startInputFlags, startInputReason);
                        didStart = true;
                    }
                    showCurrentInputLocked(windowToken, InputMethodManager.SHOW_IMPLICIT, null,
                            SoftInputShowHideReason.SHOW_STATE_ALWAYS_VISIBLE);
                } else {
                    Slog.e(TAG, "SOFT_INPUT_STATE_ALWAYS_VISIBLE is ignored because"
                            + " there is no focused view that also returns true from"
                            + " View#onCheckIsTextEditor()");
                }
                break;
        }

可以看到windowSoftInputMode的六个stateXXX就是在这里处理的,当窗口的focus状态变成true的时候(无论是前进还是后退)都会走到这个里面。下面我们逐个分析:

1.stateUnchanged

当 Activity 转至前台时保留软键盘最后所处的任何状态,无论是可见还是隐藏。

case LayoutParams.SOFT_INPUT_STATE_UNCHANGED:
                // Do nothing.
                break;

可以看到这里的保留状态就是Do nothing,不做任何操作,之前是显示就是显示,隐藏就是隐藏。

2.stateHidden和stateAlwaysHidden

当用户选择 Activity 时 — 也就是说,当用户确实是向前导航到 Activity,而不是因离开另一 Activity 而返回时 — 隐藏软键盘。

 case LayoutParams.SOFT_INPUT_STATE_HIDDEN:
                if ((softInputMode & LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) != 0) {
                    if (DEBUG) Slog.v(TAG, "Window asks to hide input going forward");
                    hideCurrentInputLocked(mCurFocusedWindow, 0, null,
                            SoftInputShowHideReason.HIDE_STATE_HIDDEN_FORWARD_NAV);
                }
                break;
 case LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN:
                if (DEBUG) Slog.v(TAG, "Window asks to hide input");
                hideCurrentInputLocked(mCurFocusedWindow, 0, null,
                        SoftInputShowHideReason.HIDE_ALWAYS_HIDDEN_STATE);
                break;

从代码上看stateHidden只比stateAlwaysHidden多了一个LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION的判断,LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION标识窗口是通过前进获取的焦点,简单来说就是跳转到一个新页面而非返回到当前页面,stateHidden只有在向前跳转的时候才会去调用hideCurrentInputLocked方法隐藏输入法,而stateAlwaysHidden则没有这个判断,任何情况下窗口获取到焦点都会去隐藏输入法。

3.stateVisible和stateAlwaysVisible

当用户选择 Activity 时 — 也就是说,当用户确实是向前导航到 Activity,而不是因离开另一 Activity 而返回时 — 显示软键盘。
当 Activity 的主窗口有输入焦点时始终显示软键盘。

case LayoutParams.SOFT_INPUT_STATE_VISIBLE:
                if ((softInputMode & LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) != 0) {
                    if (DEBUG) Slog.v(TAG, "Window asks to show input going forward");
                    if (InputMethodUtils.isSoftInputModeStateVisibleAllowed(
                            unverifiedTargetSdkVersion, startInputFlags)) {
                        if (attribute != null) {
                            res = startInputUncheckedLocked(cs, inputContext, missingMethods,
                                    attribute, startInputFlags, startInputReason);
                            didStart = true;
                        }
                        showCurrentInputLocked(windowToken, InputMethodManager.SHOW_IMPLICIT, null,
                                SoftInputShowHideReason.SHOW_STATE_VISIBLE_FORWARD_NAV);
                    } else {
                        Slog.e(TAG, "SOFT_INPUT_STATE_VISIBLE is ignored because"
                                + " there is no focused view that also returns true from"
                                + " View#onCheckIsTextEditor()");
                    }
                }
                break;
 case LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE:
                if (DEBUG) Slog.v(TAG, "Window asks to always show input");
                if (InputMethodUtils.isSoftInputModeStateVisibleAllowed(
                        unverifiedTargetSdkVersion, startInputFlags)) {
                    if (attribute != null) {
                        res = startInputUncheckedLocked(cs, inputContext, missingMethods,
                                attribute, startInputFlags, startInputReason);
                        didStart = true;
                    }
                    showCurrentInputLocked(windowToken, InputMethodManager.SHOW_IMPLICIT, null,
                            SoftInputShowHideReason.SHOW_STATE_ALWAYS_VISIBLE);
                } else {
                    Slog.e(TAG, "SOFT_INPUT_STATE_ALWAYS_VISIBLE is ignored because"
                            + " there is no focused view that also returns true from"
                            + " View#onCheckIsTextEditor()");
                }
                break;

和隐藏一样,显示也是同样的套路,这里就不多说了。
在显示的时候会去调用isSoftInputModeStateVisibleAllowed方法判断允许显示,看一下这个方法:

    static boolean isSoftInputModeStateVisibleAllowed(int targetSdkVersion,
            @StartInputFlags int startInputFlags) {
        if (targetSdkVersion < Build.VERSION_CODES.P) {
            // for compatibility.
            return true;
        }
        if ((startInputFlags & StartInputFlags.VIEW_HAS_FOCUS) == 0) {
            return false;
        }
        if ((startInputFlags & StartInputFlags.IS_TEXT_EDITOR) == 0) {
            return false;
        }
        return true;
    }

在安卓9以下会直接返回true,安卓9以上就加了两个判断,这里就解释了为什么安卓9之后软键盘不能自动弹出了,具体可以看上一篇文章。
进入判断后会去判断输入法进程有没有开启,没有开启会去调用startInputUncheckedLocked开启,开启之后会去掉用showCurrentInputLocked显示软键盘。

4.stateUnspecified

不指定软键盘的状态(隐藏还是可见)。 将由系统选择合适的状态,或依赖主题中的设置。
系统自己去选择显示还是隐藏,这里就不介绍了,有兴趣的自己去研究一下。

case LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED:
                if (!isTextEditor || !doAutoShow) {
                    if (LayoutParams.mayUseInputMethod(windowFlags)) {
                        // There is no focus view, and this window will
                        // be behind any soft input window, so hide the
                        // soft input window if it is shown.
                        if (DEBUG) Slog.v(TAG, "Unspecified window will hide input");
                        hideCurrentInputLocked(
                                mCurFocusedWindow, InputMethodManager.HIDE_NOT_ALWAYS, null,
                                SoftInputShowHideReason.HIDE_UNSPECIFIED_WINDOW);

                        // If focused display changed, we should unbind current method
                        // to make app window in previous display relayout after Ime
                        // window token removed.
                        // Note that we can trust client's display ID as long as it matches
                        // to the display ID obtained from the window.
                        if (cs.selfReportedDisplayId != mCurTokenDisplayId) {
                            unbindCurrentMethodLocked();
                        }
                    }
                } else if (isTextEditor && doAutoShow
                        && (softInputMode & LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) != 0) {
                    // There is a focus view, and we are navigating forward
                    // into the window, so show the input window for the user.
                    // We only do this automatically if the window can resize
                    // to accommodate the IME (so what the user sees will give
                    // them good context without input information being obscured
                    // by the IME) or if running on a large screen where there
                    // is more room for the target window + IME.
                    if (DEBUG) Slog.v(TAG, "Unspecified window will show input");
                    if (attribute != null) {
                        res = startInputUncheckedLocked(cs, inputContext, missingMethods,
                                attribute, startInputFlags, startInputReason);
                        didStart = true;
                    }
                    showCurrentInputLocked(windowToken, InputMethodManager.SHOW_IMPLICIT, null,
                            SoftInputShowHideReason.SHOW_AUTO_EDITOR_FORWARD_NAV);
                }
                break;

二、显示方式原理

显示方式比较复杂,牵扯到很多方面,首先是在PhoneWindowManager(属于系统进程)的layoutWindowLw方法中,这个方法主要是设置窗口的一些位置大小参数,当软键盘弹出或收起的时候都会走到这里去重新设置窗口的大小,看一下我精简后的相关代码:

public void layoutWindowLw(WindowState win, WindowState attached, DisplayFrames displayFrames) {

        final int type = attrs.type;
        final int fl = PolicyControl.getWindowFlags(win, attrs);
        final int pfl = attrs.privateFlags;
        final int sim = attrs.softInputMode;
        final int requestedSysUiFl = PolicyControl.getSystemUiVisibility(null, attrs);
        final int sysUiFl = requestedSysUiFl | getImpliedSysUiFlagsForLayout(attrs);

        final Rect pf = mTmpParentFrame;
        final Rect df = mTmpDisplayFrame;
        final Rect of = mTmpOverscanFrame;
        final Rect cf = mTmpContentFrame;
        final Rect vf = mTmpVisibleFrame;
        final Rect dcf = mTmpDecorFrame;
        final Rect sf = mTmpStableFrame;
        Rect osf = null;
        dcf.setEmpty();

        final boolean hasNavBar = (isDefaultDisplay && mHasNavigationBar
                && mNavigationBar != null && mNavigationBar.isVisibleLw());

        final int adjust = sim & SOFT_INPUT_MASK_ADJUST;

        final boolean requestedFullscreen = (fl & FLAG_FULLSCREEN) != 0
                || (requestedSysUiFl & View.SYSTEM_UI_FLAG_FULLSCREEN) != 0;

        final boolean layoutInScreen = (fl & FLAG_LAYOUT_IN_SCREEN) == FLAG_LAYOUT_IN_SCREEN;
        final boolean layoutInsetDecor = (fl & FLAG_LAYOUT_INSET_DECOR) == FLAG_LAYOUT_INSET_DECOR;

        sf.set(displayFrames.mStable);

        if (adjust != SOFT_INPUT_ADJUST_RESIZE) {
            cf.set(displayFrames.mDock);
        } else {
            cf.set(displayFrames.mContent);
        }
        applyStableConstraints(sysUiFl, fl, cf, displayFrames);
        if (adjust != SOFT_INPUT_ADJUST_NOTHING) {
            vf.set(displayFrames.mCurrent);
        } else {
            vf.set(cf);
        }
    }

首先方法里有很多Rect类型的参数被mTmpXXXFrame赋值,我们知道Rect是用来表示一个矩形区域,这里就是用来表示窗口尺寸的,我们需要关注Rect cf = mTmpContentFrameRect vf = mTmpVisibleFrame; 这两个参数,cf表示的是窗口内容区域的尺寸(可以理解为可供开发者使用的区域),vf表示的是窗口可见区域的尺寸;当输入法弹出或收起时根据设置的windowSoftInputMode不同这里的尺寸会发生变化,最终窗口大小的改变会回调到应用进程的ViewRootImpl中,最后到ViewRootHandler中的MSG_RESIZED事件里。

1.adjustResize

根据上面的代码我们发现当设置SOFT_INPUT_ADJUST_RESIZE时cf(内容区域)会被设置成displayFrames.mContent(展示区域)vf(可见区域)会被设置成displayFrames.mCurrent,注意这里有个地方容易混淆,cf和displayFrames.mContent表达的东西不一样,当软键盘弹出的时候我们可以理解为app窗口的展示区域变小了,但是内容区域没有变小,虽然被软键盘遮住了,但是内容区域也是可以使用的。
这里cf被设置成displayFrames.mContent就代表被软键盘遮住的地方应该是不能被使用的,最终这个cf会被回调到MSG_RESIZED中,我们来看一下代码:

    public void handleMessage(Message msg) {
        switch (msg.what) {
            ........
            case MSG_RESIZED: {
                // Recycled in the fall through...
                SomeArgs args = (SomeArgs) msg.obj;
                if (mWinFrame.equals(args.arg1)
                        && mPendingOverscanInsets.equals(args.arg5)
                        && mPendingContentInsets.equals(args.arg2)
                        && mPendingStableInsets.equals(args.arg6)
                        && mPendingDisplayCutout.get().equals(args.arg9)
                        && mPendingVisibleInsets.equals(args.arg3)
                        && mPendingOutsets.equals(args.arg7)
                        && mPendingBackDropFrame.equals(args.arg8)
                        && args.arg4 == null
                        && args.argi1 == 0
                        && mDisplay.getDisplayId() == args.argi3) {
                    break;
                }
            } // fall through...
            case MSG_RESIZED_REPORT:
                if (mAdded) {
                    SomeArgs args = (SomeArgs) msg.obj;

                    final int displayId = args.argi3;
                    MergedConfiguration mergedConfiguration = (MergedConfiguration) args.arg4;
                    final boolean displayChanged = mDisplay.getDisplayId() != displayId;

                    if (!mLastReportedMergedConfiguration.equals(mergedConfiguration)) {
                        // If configuration changed - notify about that and, maybe,
                        // about move to display.
                        performConfigurationChange(mergedConfiguration, false /* force */,
                                displayChanged
                                        ? displayId : INVALID_DISPLAY /* same display */);
                    } else if (displayChanged) {
                        // Moved to display without config change - report last applied one.
                        onMovedToDisplay(displayId, mLastConfigurationFromResources);
                    }

                    final boolean framesChanged = !mWinFrame.equals(args.arg1)
                            || !mPendingOverscanInsets.equals(args.arg5)
                            || !mPendingContentInsets.equals(args.arg2)
                            || !mPendingStableInsets.equals(args.arg6)
                            || !mPendingDisplayCutout.get().equals(args.arg9)
                            || !mPendingVisibleInsets.equals(args.arg3)
                            || !mPendingOutsets.equals(args.arg7);

                    mWinFrame.set((Rect) args.arg1);
                    mPendingOverscanInsets.set((Rect) args.arg5);
                    mPendingContentInsets.set((Rect) args.arg2);
                    mPendingStableInsets.set((Rect) args.arg6);
                    mPendingDisplayCutout.set((DisplayCutout) args.arg9);
                    mPendingVisibleInsets.set((Rect) args.arg3);
                    mPendingOutsets.set((Rect) args.arg7);
                    mPendingBackDropFrame.set((Rect) args.arg8);
                    mForceNextWindowRelayout = args.argi1 != 0;
                    mPendingAlwaysConsumeNavBar = args.argi2 != 0;

                    args.recycle();

                    if (msg.what == MSG_RESIZED_REPORT) {
                        reportNextDraw();
                    }

                    if (mView != null && framesChanged) {
                        forceLayout(mView);
                    }
                    requestLayout();
                }
                break;
            .........
        }
    }

SomeArgs中的args.arg2就是我们之前设置的cf,
1.进入到MSG_RESIZED中后会判断SomeArgs中的参数是不是和之前一样,如果不同就会走到MSG_RESIZED_REPORT中,
2.这里将尺寸信息保存之后就会去调用forceLayout(mView)—>ViewTree里每个View/ViewGroup打上layout、draw标记,也就是说每个View/ViewGroup 最后都会执行三大流程,最后requestLayout()—>触发执行三大流程。

既然记录了尺寸的变化,继续跟踪这些值怎么使用。调用requestLayout()将会触发执行performTraversals()方法:

#ViewRootImpl.java
    private void performTraversals() {
        if (mFirst || windowShouldResize || insetsChanged ||
                viewVisibilityChanged || params != null || mForceNextWindowRelayout) {
            ...
            boolean hwInitialized = false;
            //内容边界是否发生变化
            boolean contentInsetsChanged = false;
            try {
                ...
                //内容区域变化----------->1
                contentInsetsChanged = !mPendingContentInsets.equals(
                        mAttachInfo.mContentInsets);

                if (contentInsetsChanged || mLastSystemUiVisibility !=
                        mAttachInfo.mSystemUiVisibility || mApplyInsetsRequested
                        || mLastOverscanRequested != mAttachInfo.mOverscanRequested
                        || outsetsChanged) {
                    ...
                    //分发Inset----------->2
                    dispatchApplyInsets(host);
                    contentInsetsChanged = true;
                }
                ...
            } catch (RemoteException e) {
            }
            ...
        }
        ...
    }

1.当设置SOFT_INPUT_ADJUST_RESIZE,键盘弹起时内容区域发生变化,因此会执行dispatchApplyInsets()。
2.分发Inset。
这些记录的值会存储在AttachInfo对应的变量里。
该方法调用栈如下:
Android软键盘windowSoftInputMode的使用与原理(原理篇)_第3张图片
dispatchApplyWindowInsets(WindowInsets insets)里的insets构成是通过计算之前记录在mPendingXX里的边界值。
最终调用fitSystemWindowsInt():

#View.java
    private boolean fitSystemWindowsInt(Rect insets) {
        //FITS_SYSTEM_WINDOWS 为xml里设置     android:fitsSystemWindows="true"
        //对于DecorView的子布局LinearLayout来说,默认fitsSystemWindows=true
        if ((mViewFlags & FITS_SYSTEM_WINDOWS) == FITS_SYSTEM_WINDOWS) {
            ...
            //设置View的padding
            internalSetPadding(localInsets.left, localInsets.top,
                    localInsets.right, localInsets.bottom);
            return res;
        }
        return false;
    }

    protected void internalSetPadding(int left, int top, int right, int bottom) {
        ...
        if (mPaddingLeft != left) {
            changed = true;
            mPaddingLeft = left;
        }
        if (mPaddingTop != top) {
            changed = true;
            mPaddingTop = top;
        }
        if (mPaddingRight != right) {
            changed = true;
            mPaddingRight = right;
        }
        if (mPaddingBottom != bottom) {
            changed = true;
            mPaddingBottom = bottom;
        }

        if (changed) {
            requestLayout();
            invalidateOutline();
        }
    }

看到这答案就呼之欲出了,DecorView的子布局LinearLayout设置padding,最终会影响LinearLayout子布局的高度,一层层传递下去,就会影响到Demo里的Activity 布局文件的高度。

小结
当设置SOFT_INPUT_ADJUST_RESIZE 时,DecorView的子布局padding会改变,最后影响子孙布局的高度。

2.adjustPan

当设置SOFT_INPUT_ADJUST_PAN时cf(内容区域)会被设置成displayFrames.mDockvf(可见区域)同样被设置成displayFrames.mCurrent,displayFrames.mDock是什么呢?

    /** During layout, the current screen borders along which input method windows are placed. */
    public final Rect mDock = new Rect();

布局期间,输入法窗口所在的当前屏幕边框. 我理解其实就是除去导航栏和状态栏的app可使用内容区域,后来通过断点验证果然是的,SOFT_INPUT_ADJUST_RESIZE将cf设置成可见区域,而SOFT_INPUT_ADJUST_PAN这里cf被设置成内容区域,这也就意味着app可以使用被输入法挡住的部分。
最终同样会到MSG_RESIZED中:
SomeArgs中的args.arg2也就是cf的大小是没有变化的,但是args.arg3也就是vf变了,所以依然会进入MSG_RESIZED_REPORT中,也依然会去调用forceLayout(mView)和requestLayout()—>触发执行三大流程。

但是由于内容区域没有发生变化,这里不会再去执行dispatchApplyInsets()。那SOFT_INPUT_ADJUST_PAN的处理在哪里呢?
我们知道SOFT_INPUT_ADJUST_PAN的效果是页面整体向上移动,布局移动无非就是坐标发生改变,或者内容滚动了,不管是何种形式最终都需要通过对Canvas进行位移才能实现移动的效果。在performDraw->draw方法中有一个scrollToRectOrFocus方法:

#View.java
    boolean scrollToRectOrFocus(Rect rectangle, boolean immediate) {
        //窗口内容区域
        final Rect ci = mAttachInfo.mContentInsets;
        //窗口可见区域
        final Rect vi = mAttachInfo.mVisibleInsets;
        //滚动距离
        int scrollY = 0;
        boolean handled = false;

        if (vi.left > ci.left || vi.top > ci.top
                || vi.right > ci.right || vi.bottom > ci.bottom) {
            scrollY = mScrollY;
            //找到当前有焦点的View------------>(1)
            final View focus = mView.findFocus();
            ...
            if (focus == lastScrolledFocus && !mScrollMayChange && rectangle == null) {
                //焦点没有发生切换,不做操作
            } else {
                // We need to determine if the currently focused view is
                // within the visible part of the window and, if not, apply
                // a pan so it can be seen.
                mLastScrolledFocus = new WeakReference<View>(focus);
                mScrollMayChange = false;
                if (DEBUG_INPUT_RESIZE) Log.v(mTag, "Need to scroll?");
                // Try to find the rectangle from the focus view.
                if (focus.getGlobalVisibleRect(mVisRect, null)) {
                    ...
                    //找到当前焦点与可见区域的相交部分
                    //mVisRect 为当前焦点在Window里的可见部分
                    if (mTempRect.intersect(mVisRect)) {
                        if (mTempRect.height() >
                                (mView.getHeight()-vi.top-vi.bottom)) {
                            ...
                        }
                        else if (mTempRect.top < vi.top) {
                            //如果当前焦点位置在窗口可见区域上边,说明焦点View应该往下移动到可见区域里边
                            scrollY = mTempRect.top - vi.top;
                        } else if (mTempRect.bottom > (mView.getHeight()-vi.bottom)) {
                            //如果当前焦点位置在窗口可见区域之下,说明其应该往上移动到可见区域里边------->(2)
                            scrollY = mTempRect.bottom - (mView.getHeight()-vi.bottom);
                        } else {
                            //无需滚动------->(3)
                            scrollY = 0;
                        }
                        handled = true;
                    }
                }
            }
        }

        if (scrollY != mScrollY) {
            //滚动距离发生变化
            if (!immediate) {
                if (mScroller == null) {
                    mScroller = new Scroller(mView.getContext());
                }
                //开始设置滚动----------->(4)
                mScroller.startScroll(0, mScrollY, 0, scrollY-mScrollY);
            } else if (mScroller != null) {
                mScroller.abortAnimation();
            }
            //赋值给成员变量
            mScrollY = scrollY;
        }
        return handled;
    }

1.对于上面的Demo来说,当前的焦点View就是EditText,点击哪个EditText,哪个就获得焦点。
2.对于输入框2来说,因为键盘弹出会遮住它,通过计算满足"当前焦点位置在窗口可见区域之下,说明其应该往上移动到可见区域里边" 条件,因此srolly > 0。
3.而对于输入框1来说,当键盘弹出时,它没有被键盘遮挡,走到else分支,因此scrollY = 0。
4.滚动是借助Scoller.java类完成的。

上面的操作实际上就是为了确认滚动值,并记录在成员变量mScrollY里,继续来看如何使用滚动值呢?

#ViewRootImpl.java
    private boolean draw(boolean fullRedrawNeeded) {
        ...
        boolean animating = mScroller != null && mScroller.computeScrollOffset();
        final int curScrollY;
        //获取当前需要滚动的scroll值
        if (animating) {
            curScrollY = mScroller.getCurrY();
        } else {
            curScrollY = mScrollY;
        }
        ...
        
        int xOffset = -mCanvasOffsetX;
        //记录在yOffset里
        int yOffset = -mCanvasOffsetY + curScrollY;
        
        boolean useAsyncReport = false;
        if (!dirty.isEmpty() || mIsAnimating || accessibilityFocusDirty) {
            if (mAttachInfo.mThreadedRenderer != null && mAttachInfo.mThreadedRenderer.isEnabled()) {
                ...
                //对于走硬件加速绘制
                if (mHardwareYOffset != yOffset || mHardwareXOffset != xOffset) {
                    //记录偏移量到mHardwareYOffset里
                    mHardwareYOffset = yOffset;
                    mHardwareXOffset = xOffset;
                    invalidateRoot = true;
                }
                ..
                mAttachInfo.mThreadedRenderer.draw(mView, mAttachInfo, this);
            } else {
                //软件绘制
                //传入yOffset
                if (!drawSoftware(surface, mAttachInfo, xOffset, yOffset,
                        scalingRequired, dirty, surfaceInsets)) {
                    return false;
                }
            }
        }
        ...
        return useAsyncReport;
    }

滚动值分别传递给了硬件加速绘制分支和软件绘制分支,在各自的分支里对Canvas进行平移,具体如何平移此处不细说了,大家可以继续跟踪代码分析。

小结

1、当设置SOFT_INPUT_ADJUST_PAN时,如果发现键盘遮住了当前有焦点的View,那么会对RootView(此处Demo里DecorView作为RootView)的Canvas进行平移,直至有焦点的View显示到可见区域为止。
2、这就是为什么点击输入框2的时候布局会整体向上移动的原因。

3.adjustNothing

当设置成SOFT_INPUT_ADJUST_NOTHING时cf(内容区域)会被设置成displayFrames.mDockvf(可见区域)会被设置成cf,其实这里就相当于窗口尺寸参数没有变化,就不会回调到MSG_RESIZED中,自然布局也不会有什么改变。

4.adjustUnspecified

设置了SOFT_INPUT_ADJUST_UNSPECIFIED,其内部最终使用SOFT_INPUT_ADJUST_PAN和SOFT_INPUT_ADJUST_RESIZE之一进行展示。接下来就来探究选择的标准是什么。
softInputMode 没有设值的时候,默认是SOFT_INPUT_ADJUST_UNSPECIFIED模式。
还是从ViewRootImpl.java的performTraversals()方法开始分析:

    private void performTraversals() {
        ...
        if (mFirst || mAttachInfo.mViewVisibilityChanged) {
            mAttachInfo.mViewVisibilityChanged = false;
            //先查看有没有提前设置了模式
            int resizeMode = mSoftInputMode &
                    WindowManager.LayoutParams.SOFT_INPUT_MASK_ADJUST;
            
            //如果没有设置,那么默认为0,也就是SOFT_INPUT_ADJUST_UNSPECIFIED
            if (resizeMode == WindowManager.LayoutParams.SOFT_INPUT_ADJUST_UNSPECIFIED) {
                //查看mScrollContainers 数组有没有元素(View 作为元素) -------->(1)
                final int N = mAttachInfo.mScrollContainers.size();
                for (int i=0; i<N; i++) {
                    if (mAttachInfo.mScrollContainers.get(i).isShown()) {
                        //如果有元素,则设置为SOFT_INPUT_ADJUST_RESIZE 模式
                        resizeMode = WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE;
                    }
                }
                if (resizeMode == 0) {
                    //如果没有设置为resize模式,则设置pan模式
                    resizeMode = WindowManager.LayoutParams.SOFT_INPUT_ADJUST_PAN;
                }
                if ((lp.softInputMode &
                        WindowManager.LayoutParams.SOFT_INPUT_MASK_ADJUST) != resizeMode) {
                    lp.softInputMode = (lp.softInputMode &
                            ~WindowManager.LayoutParams.SOFT_INPUT_MASK_ADJUST) |
                            resizeMode;
                    //最后赋值给params,让Window属性生效
                    params = lp;
                }
            }
        }
        ...
    }

上一篇文章已经说过了,这里主要是通过mAttachInfo.mScrollContainers判断是否有可滚动的view,如果有就设置成SOFT_INPUT_ADJUST_RESIZE,如果没有就设置成SOFT_INPUT_ADJUST_PAN。

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