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  • Activity的绘制流程简单分析（基于android 4.0源码进行分析）

    要明白这个流程，我们还得从第一部开始，大家都知道 在activity里面 setcontentview 调用结束以后 就可以看到程序加载好我们的布局文件了，从而让我们在手机上看到这个画面。

    那么我们来看一下这个源码是如何实现的。

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    /**
         * Set the activity content from a layout resource.  The resource will be
         * inflated, adding all top-level views to the activity.
         *
         * @param layoutResID Resource ID to be inflated.
         *
         * [url=home.php?mod=space&uid=189949]@See[/url] #setContentView(android.view.View)
         * @see #setContentView(android.view.View, android.view.ViewGroup.LayoutParams)
         */
        public void setContentView(int layoutResID) {
            getWindow().setContentView(layoutResID);
            initActionBar();
        }

    我们这里看到是调用了getwindow的返回值 来调用setcontentview 方法的。

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    /**     * Retrieve the current {@link android.view.Window} for the activity.
         * This can be used to directly access parts of the Window API that
         * are not available through Activity/Screen.
         *
         * [url=home.php?mod=space&uid=309376]@return[/url] Window The current window, or null if the activity is not
         *         visual.
         */
        public Window getWindow() {
            return mWindow;
        }

    我们再来看看mWindow 这个值是从哪来的。

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    final void attach(Context context, ActivityThread aThread,            Instrumentation instr, IBinder token, int ident,
                Application application, Intent intent, ActivityInfo info,
                CharSequence title, Activity parent, String id,
                NonConfigurationInstances lastNonConfigurationInstances,
                Configuration config) {
            attachBaseContext(context);
     
            mFragments.attachActivity(this);
             
            mWindow = PolicyManager.makeNewWindow(this);
            mWindow.setCallback(this);
            mWindow.getLayoutInflater().setPrivateFactory(this);
            if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
                mWindow.setSoftInputMode(info.softInputMode);
            }
            if (info.uiOptions != 0) {
                mWindow.setUiOptions(info.uiOptions);
            }
            mUiThread = Thread.currentThread();
             
            mMainThread = aThread;
            mInstrumentation = instr;
            mToken = token;
            mIdent = ident;
            mApplication = application;
            mIntent = intent;
            mComponent = intent.getComponent();
            mActivityInfo = info;
            mTitle = title;
            mParent = parent;
            mEmbeddedID = id;
            mLastNonConfigurationInstances = lastNonConfigurationInstances;
     
            mWindow.setWindowManager(null, mToken, mComponent.flattenToString(),
                    (info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
            if (mParent != null) {
                mWindow.setContainer(mParent.getWindow());
            }
            mWindowManager = mWindow.getWindowManager();
            mCurrentConfig = config;
        }

    注意看11行的代码 我们发现这个mWindow的值 是通过 makeNewWindow这个方法来实现的。我们再来看看这个方法，当然了我们要先找到这个类，这个类位于

    <ignore_js_op>

     

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    /* * Copyright (C) 2008 The Android Open Source Project
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *      http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
     
    package com.android.internal.policy;
     
    import android.content.Context;
    import android.view.FallbackEventHandler;
    import android.view.LayoutInflater;
    import android.view.Window;
    import android.view.WindowManagerPolicy;
     
    import com.android.internal.policy.IPolicy;
     
    /**
     * {@hide}
     */
     
    public final class PolicyManager {
        private static final String POLICY_IMPL_CLASS_NAME =
            "com.android.internal.policy.impl.Policy";
     
        private static final IPolicy sPolicy;
     
        static {
            // Pull in the actual implementation of the policy at run-time
            try {
                Class policyClass = Class.forName(POLICY_IMPL_CLASS_NAME);
                sPolicy = (IPolicy)policyClass.newInstance();
            } catch (ClassNotFoundException ex) {
                throw new RuntimeException(
                        POLICY_IMPL_CLASS_NAME + " could not be loaded", ex);
            } catch (InstantiationException ex) {
                throw new RuntimeException(
                        POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex);
            } catch (IllegalAccessException ex) {
                throw new RuntimeException(
                        POLICY_IMPL_CLASS_NAME + " could not be instantiated", ex);
            }
        }
     
        // Cannot instantiate this class
        private PolicyManager() {}
     
        // The static methods to spawn new policy-specific objects
        public static Window makeNewWindow(Context context) {
            return sPolicy.makeNewWindow(context);
        }
     
        public static LayoutInflater makeNewLayoutInflater(Context context) {
            return sPolicy.makeNewLayoutInflater(context);
        }
     
        public static WindowManagerPolicy makeNewWindowManager() {
            return sPolicy.makeNewWindowManager();
        }
     
        public static FallbackEventHandler makeNewFallbackEventHandler(Context context) {
            return sPolicy.makeNewFallbackEventHandler(context);
        }
    }

    这里发现是一个反射的动态加载，我们暂时不去深究他，继续看代码，找到Policy这个类，他位于<ignore_js_op>

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    /* * Copyright (C) 2008 The Android Open Source Project
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *      http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
     
    package com.android.internal.policy.impl;
     
    import android.content.Context;
    import android.util.Log;
    import android.view.FallbackEventHandler;
    import android.view.LayoutInflater;
    import android.view.Window;
    import android.view.WindowManagerPolicy;
     
    import com.android.internal.policy.IPolicy;
    import com.android.internal.policy.impl.PhoneLayoutInflater;
    import com.android.internal.policy.impl.PhoneWindow;
    import com.android.internal.policy.impl.PhoneWindowManager;
     
    /**
     * {@hide}
     */
     
    // Simple implementation of the policy interface that spawns the right
    // set of objects
    public class Policy implements IPolicy {
        private static final String TAG = "PhonePolicy";
     
        private static final String[] preload_classes = {
            "com.android.internal.policy.impl.PhoneLayoutInflater",
            "com.android.internal.policy.impl.PhoneWindow",
            "com.android.internal.policy.impl.PhoneWindow$1",
            "com.android.internal.policy.impl.PhoneWindow$ContextMenuCallback",
            "com.android.internal.policy.impl.PhoneWindow$DecorView",
            "com.android.internal.policy.impl.PhoneWindow$PanelFeatureState",
            "com.android.internal.policy.impl.PhoneWindow$PanelFeatureState$SavedState",
        };
     
        static {
            // For performance reasons, preload some policy specific classes when
            // the policy gets loaded.
            for (String s : preload_classes) {
                try {
                    Class.forName(s);
                } catch (ClassNotFoundException ex) {
                    Log.e(TAG, "Could not preload class for phone policy: " + s);
                }
            }
        }
     
        public Window makeNewWindow(Context context) {
            return new PhoneWindow(context);
        }
     
        public LayoutInflater makeNewLayoutInflater(Context context) {
            return new PhoneLayoutInflater(context);
        }
     
        public WindowManagerPolicy makeNewWindowManager() {
            return new PhoneWindowManager();
        }
     
        public FallbackEventHandler makeNewFallbackEventHandler(Context context) {
            return new PhoneFallbackEventHandler(context);
        }
    }

    看62行代码，到这里我们就发现了 在activity里 getwindow 返回的 实际上就是这个phonewindow对象！！！！！！！！！！！！！！我们继续看这个phonewindow类 他位于<ignore_js_op>注意在这里我就不放这个类的源码了，因为2000多行。。。我只抽部分重要的说一下

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    /**
     * Android-specific Window.
     * <p>
     * todo: need to pull the generic functionality out into a base class
     * in android.widget.
     */
    public class PhoneWindow extends Window implements MenuBuilder.Callback {
     
        private final static String TAG = "PhoneWindow";
     
        private final static boolean SWEEP_OPEN_MENU = false;
     
        /**
         * Simple callback used by the context menu and its submenus. The options
         * menu submenus do not use this (their behavior is more complex).
         */
        final DialogMenuCallback mContextMenuCallback = new DialogMenuCallback(FEATURE_CONTEXT_MENU);
     
        final TypedValue mMinWidthMajor = new TypedValue();
        final TypedValue mMinWidthMinor = new TypedValue();
     
        // This is the top-level view of the window, containing the window decor.
        private DecorView mDecor;
     
        // This is the view in which the window contents are placed. It is either
        // mDecor itself, or a child of mDecor where the contents go.
        private ViewGroup mContentParent;
     
        SurfaceHolder.Callback2 mTakeSurfaceCallback;
         
        InputQueue.Callback mTakeInputQueueCallback;
         
        private boolean mIsFloating;
     
        private LayoutInflater mLayoutInflater;
     
        private TextView mTitleView;
         
        private ActionBarView mActionBar;
        private ActionMenuPresenterCallback mActionMenuPresenterCallback;
        private PanelMenuPresenterCallback mPanelMenuPresenterCallback;
     
        private DrawableFeatureState[] mDrawables;
     
        private PanelFeatureState[] mPanels;

    看22和23行代码 我们就知道 这个DectorView 就是我们绘制view的时候 最顶层的那个view。换句话说就是最根部的视图。

    而且 再继续跟代码 我们会发现 他就是phonewindow的一个内部类 注意看他是继承的framelayout

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    private final class DecorView extends FrameLayout implements RootViewSurfaceTaker {
           /* package */int mDefaultOpacity = PixelFormat.OPAQUE;
     
           /** The feature ID of the panel, or -1 if this is the application's DecorView */
           private final int mFeatureId;
     
           private final Rect mDrawingBounds = new Rect();
     
           private final Rect mBackgroundPadding = new Rect();
     
           private final Rect mFramePadding = new Rect();
     
           private final Rect mFrameOffsets = new Rect();
     
           private boolean mChanging;
     
           private Drawable mMenuBackground;
           private boolean mWatchingForMenu;
           private int mDownY;
     
           private ActionMode mActionMode;
           private ActionBarContextView mActionModeView;
           private PopupWindow mActionModePopup;
           private Runnable mShowActionModePopup;
     
           public DecorView(Context context, int featureId) {
               super(context);
               mFeatureId = featureId;
           }

    所以到这里我们可以发现 在activity里调用setconteview的时候 最终就是调用的phonewindow的这个方法

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    @Overridepublic void setContentView(int layoutResID) {
      if (mContentParent == null) {
        installDecor();
      } else {
        mContentParent.removeAllViews();
      }
      mLayoutInflater.inflate(layoutResID, mContentParent);
      final Callback cb = getCallback();
      if (cb != null && !isDestroyed()) {
        cb.onContentChanged();
      }
    }

    这里代码其实也很好理解，如果是第一次调用就installDecor 否则就remove所有的view 我们来看这个installdector的代码

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    private void installDecor() {        if (mDecor == null) {
                mDecor = generateDecor();
                mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
                mDecor.setIsRootNamespace(true);
            }
            if (mContentParent == null) {
                mContentParent = generateLayout(mDecor);
     
                mTitleView = (TextView)findViewById(com.android.internal.R.id.title);
                if (mTitleView != null) {
                    if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) {
                        View titleContainer = findViewById(com.android.internal.R.id.title_container);
                        if (titleContainer != null) {
                            titleContainer.setVisibility(View.GONE);
                        } else {
                            mTitleView.setVisibility(View.GONE);
                        }
                        if (mContentParent instanceof FrameLayout) {
                            ((FrameLayout)mContentParent).setForeground(null);
                        }
                    } else {
                        mTitleView.setText(mTitle);
                    }
                } else {
                    mActionBar = (ActionBarView) findViewById(com.android.internal.R.id.action_bar);
                    if (mActionBar != null) {
                        mActionBar.setWindowCallback(getCallback());
                        if (mActionBar.getTitle() == null) {
                            mActionBar.setWindowTitle(mTitle);
                        }
                        final int localFeatures = getLocalFeatures();
                        if ((localFeatures & (1 << FEATURE_PROGRESS)) != 0) {
                            mActionBar.initProgress();
                        }
                        if ((localFeatures & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) {
                            mActionBar.initIndeterminateProgress();
                        }
     
                        boolean splitActionBar = false;
                        final boolean splitWhenNarrow =
                                (mUiOptions & ActivityInfo.UIOPTION_SPLIT_ACTION_BAR_WHEN_NARROW) != 0;
                        if (splitWhenNarrow) {
                            splitActionBar = getContext().getResources().getBoolean(
                                    com.android.internal.R.bool.split_action_bar_is_narrow);
                        } else {
                            splitActionBar = getWindowStyle().getBoolean(
                                    com.android.internal.R.styleable.Window_windowSplitActionBar, false);
                        }
                        final ActionBarContainer splitView = (ActionBarContainer) findViewById(
                                com.android.internal.R.id.split_action_bar);
                        if (splitView != null) {
                            mActionBar.setSplitView(splitView);
                            mActionBar.setSplitActionBar(splitActionBar);
                            mActionBar.setSplitWhenNarrow(splitWhenNarrow);
     
                            final ActionBarContextView cab = (ActionBarContextView) findViewById(
                                    com.android.internal.R.id.action_context_bar);
                            cab.setSplitView(splitView);
                            cab.setSplitActionBar(splitActionBar);
                            cab.setSplitWhenNarrow(splitWhenNarrow);
                        } else if (splitActionBar) {
                            Log.e(TAG, "Requested split action bar with " +
                                    "incompatible window decor! Ignoring request.");
                        }
     
                        // Post the panel invalidate for later; avoid application onCreateOptionsMenu
                        // being called in the middle of onCreate or similar.
                        mDecor.post(new Runnable() {
                            public void run() {
                                // Invalidate if the panel menu hasn't been created before this.
                                PanelFeatureState st = getPanelState(FEATURE_OPTIONS_PANEL, false);
                                if (!isDestroyed() && (st == null || st.menu == null)) {
                                    invalidatePanelMenu(FEATURE_ACTION_BAR);
                                }
                            }
                        });
                    }
                }
            }
        }

    注意看第八行代码 这个就是绘制activity根布局最关键的地方  这个函数一共有300行左右 我也不能全部放上来，有兴趣的同学可以自己看一下源码，我在这截取部分重要的说。

    其实重要的代码就是这么一些

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    int layoutResource;
            int features = getLocalFeatures();
            // System.out.println("Features: 0x" + Integer.toHexString(features));
            if ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0) {
                if (mIsFloating) {
                    TypedValue res = new TypedValue();
                    getContext().getTheme().resolveAttribute(
                            com.android.internal.R.attr.dialogTitleIconsDecorLayout, res, true);
                    layoutResource = res.resourceId;
                } else {
                    layoutResource = com.android.internal.R.layout.screen_title_icons;
                }
                // XXX Remove this once action bar supports these features.
                removeFeature(FEATURE_ACTION_BAR);
                // System.out.println("Title Icons!");
            } else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0
                    && (features & (1 << FEATURE_ACTION_BAR)) == 0) {
                // Special case for a window with only a progress bar (and title).
                // XXX Need to have a no-title version of embedded windows.
                layoutResource = com.android.internal.R.layout.screen_progress;
                // System.out.println("Progress!");
            } else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) {
                // Special case for a window with a custom title.
                // If the window is floating, we need a dialog layout
                if (mIsFloating) {
                    TypedValue res = new TypedValue();
                    getContext().getTheme().resolveAttribute(
                            com.android.internal.R.attr.dialogCustomTitleDecorLayout, res, true);
                    layoutResource = res.resourceId;
                } else {
                    layoutResource = com.android.internal.R.layout.screen_custom_title;
                }
                // XXX Remove this once action bar supports these features.
                removeFeature(FEATURE_ACTION_BAR);
            } else if ((features & (1 << FEATURE_NO_TITLE)) == 0) {
                // If no other features and not embedded, only need a title.
                // If the window is floating, we need a dialog layout
                if (mIsFloating) {
                    TypedValue res = new TypedValue();
                    getContext().getTheme().resolveAttribute(
                            com.android.internal.R.attr.dialogTitleDecorLayout, res, true);
                    layoutResource = res.resourceId;
                } else if ((features & (1 << FEATURE_ACTION_BAR)) != 0) {
                    if ((features & (1 << FEATURE_ACTION_BAR_OVERLAY)) != 0) {
                        layoutResource = com.android.internal.R.layout.screen_action_bar_overlay;
                    } else {
                        layoutResource = com.android.internal.R.layout.screen_action_bar;
                    }
                } else {
                    layoutResource = com.android.internal.R.layout.screen_title;
                }
                // System.out.println("Title!");
            } else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) {
                layoutResource = com.android.internal.R.layout.screen_simple_overlay_action_mode;
            } else {
                // Embedded, so no decoration is needed.
                layoutResource = com.android.internal.R.layout.screen_simple;
                // System.out.println("Simple!");
            }
     
            mDecor.startChanging();
     
            View in = mLayoutInflater.inflate(layoutResource, null);
            decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));

    这个layoutResource的值 实际上就代表了窗口修饰的哪些布局文件，你看最后两行代码就知道

    当我们确定了这个布局文件以后就把她add 到decor这个对象里。

    所以我们就能想明白 为啥 我们的requestWindowFeature这个方法一定要在setContentview前面调用才有作用了~~

    然后给大家随便看下布局文件吧，就是系统自带的这些跟布局。

    <ignore_js_op>

     

    这种大家肯定经常用了，就是上面有个标题 然后下面就放我们自己的布局文件来展示内容

    当然了还有人喜欢用全屏的screen_simple，他的代码也是很简单的。这里不截图上代码

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    <?xml version="1.0" encoding="utf-8"?><!--
    /* //device/apps/common/assets/res/layout/screen_simple.xml
    **
    ** Copyright 2006, The Android Open Source Project
    **
    ** Licensed under the Apache License, Version 2.0 (the "License");
    ** you may not use this file except in compliance with the License.
    ** You may obtain a copy of the License at
    **
    **     http://www.apache.org/licenses/LICENSE-2.0
    **
    ** Unless required by applicable law or agreed to in writing, software
    ** distributed under the License is distributed on an "AS IS" BASIS,
    ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    ** See the License for the specific language governing permissions and
    ** limitations under the License.
    */
     
    This is an optimized layout for a screen, with the minimum set of features
    enabled.
    -->
     
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:fitsSystemWindows="true"
        android:orientation="vertical">
        <ViewStub android:id="@+id/action_mode_bar_stub"
                  android:inflatedId="@+id/action_mode_bar"
                  android:layout="@layout/action_mode_bar"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content" />
        <FrameLayout
             android:id="@android:id/content"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:foregroundInsidePadding="false"
             android:foregroundGravity="fill_horizontal|top"
             android:foreground="?android:attr/windowContentOverlay" />
    </LinearLayout>

    那 注意 33行代码  android:id="@android:id/content" 这个地方跟我们上一张的博客 那边有一样的地方，都是用的这个id content为根布局的，有兴趣的同学可以看看我们view教程05的结尾部分，

    两个串起来看就能明白了~~~

    然后看一下这个函数 另外一个重要的代码

    [Java] 纯文本查看 复制代码
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    ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);        if (contentParent == null) {
                throw new RuntimeException("Window couldn't find content container view");
            }
     
            if ((features & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) {
                ProgressBar progress = getCircularProgressBar(false);
                if (progress != null) {
                    progress.setIndeterminate(true);
                }
            }
     
            // Remaining setup -- of background and title -- that only applies
            // to top-level windows.
            if (getContainer() == null) {
                Drawable drawable = mBackgroundDrawable;
                if (mBackgroundResource != 0) {
                    drawable = getContext().getResources().getDrawable(mBackgroundResource);
                }
                mDecor.setWindowBackground(drawable);
                drawable = null;
                if (mFrameResource != 0) {
                    drawable = getContext().getResources().getDrawable(mFrameResource);
                }
                mDecor.setWindowFrame(drawable);
     
                // System.out.println("Text=" + Integer.toHexString(mTextColor) +
                // " Sel=" + Integer.toHexString(mTextSelectedColor) +
                // " Title=" + Integer.toHexString(mTitleColor));
     
                if (mTitleColor == 0) {
                    mTitleColor = mTextColor;
                }
     
                if (mTitle != null) {
                    setTitle(mTitle);
                }
                setTitleColor(mTitleColor);
            }
     
            mDecor.finishChanging();
     
            return contentParent;

    返回值是contentParent 而他的值实际上就是我们那个布局文件里装内容的android id content，很好理解吧

    所以generateLayout这个函数的作用就是 确定一下我们activity的显示风格还有把content这个framelayout的值

    给mContentParent,然后通过第8行的代码就把我们的布局文件添加到这个freamlayout里了。

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    @Override
       public void setContentView(int layoutResID) {
           if (mContentParent == null) {
               installDecor();
           } else {
               mContentParent.removeAllViews();
           }
           mLayoutInflater.inflate(layoutResID, mContentParent);
           final Callback cb = getCallback();
           if (cb != null && !isDestroyed()) {
               cb.onContentChanged();
           }
       }

    最终由ActivityManagerService 这个类还显示我们的decorview。

    最后我们再把前面的流程简单复述一下

    启动一个activity的时候，我们最终是调用的phonewindow的setcontent方法 ，这个方法会创建一个decorview对象

    然后再过一遍窗口属性这个流程，最后取得android id content 这个framelayout，然后将布局文件添加到这个framelayout里面

    最后由activitymanagerservice负责把这个最终的界面展示出来~~~

    自定义view 07 将会讲一下view的绘制流程~
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  • 原文地址：https://www.cnblogs.com/Free-Thinker/p/4616476.html
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