Android Activity之 setContentView()总结

 public void setContentView(int layoutResID) {
        getWindow().setContentView(layoutResID);
        initActionBar();
    }

 @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();
        }
    }

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) {
	               //根据FEATURE_NO_TITLE隐藏，或者设置mTitleView的值
	            	//...
	            } else {
	                mActionBar = (ActionBarView) findViewById(com.android.internal.R.id.action_bar);
	                if (mActionBar != null) {
	                	//设置ActionBar标题、图标神马的；根据FEATURE初始化Actionbar的一些显示
	                	//...
	                }
	            }
	        }
	}

 public View findViewById(int id) {
        return getDecorView().findViewById(id);
    }

 <!-- The set of attributes that describe a Windows's theme. -->
    <declare-styleable name="Window">
        <attr name="windowBackground" />
        <attr name="windowContentOverlay" />
        <attr name="windowFrame" />
        <attr name="windowNoTitle" />
        <attr name="windowFullscreen" />
        <attr name="windowOverscan" />
        <attr name="windowIsFloating" />
        <attr name="windowIsTranslucent" />
        <attr name="windowShowWallpaper" />
        <attr name="windowAnimationStyle" />
        <attr name="windowSoftInputMode" />
        <attr name="windowDisablePreview" />
        <attr name="windowNoDisplay" />
        <attr name="textColor" />
        <attr name="backgroundDimEnabled" />
        <attr name="backgroundDimAmount" />

<?xml version="1.0" encoding="utf-8"?>

<!--
This is a custom layout for a screen.
-->

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:fitsSystemWindows="true">
    <!-- Popout bar for action modes -->
    <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/title_container" 
        android:layout_width="match_parent" 
        android:layout_height="?android:attr/windowTitleSize"
        style="?android:attr/windowTitleBackgroundStyle">
    </FrameLayout>
    <FrameLayout android:id="@android:id/content"
        android:layout_width="match_parent" 
        android:layout_height="0dip"
        android:layout_weight="1"
        android:foregroundGravity="fill_horizontal|top"
        android:foreground="?android:attr/windowContentOverlay" />
</LinearLayout>

 *
 * 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.example.android.ui;

import com.example.android.displayingbitmaps.BuildConfig;
import com.example.android.util.Utils;

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;


/**
 * Simple FragmentActivity to hold the main {@link ImageGridFragment} and not much else.
 */
public class ImageGridActivity extends FragmentActivity {
    private static final String TAG = "ImageGridActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        if (BuildConfig.DEBUG) {
            Utils.enableStrictMode();
        }
        super.onCreate(savedInstanceState);

        if (getSupportFragmentManager().findFragmentByTag(TAG) == null) {
            final FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
            ft.add(android.R.id.content, new ImageGridFragment(), TAG);
            //不要企图去你自己工程去找上面ID，是系统的

            ft.commit();
        }
    }
}