Activity和Window关联源码分析
在Activity中，存在一个Window对象，现针对这个存在的window对象和activity之间的关系，进行分析：
在Activity的attach()方法中，进行成员变量mWindow的创建和初始化。
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,
Object lastNonConfigurationInstance,
HashMap<String,Object> lastNonConfigurationChildInstances,
Configuration config) {
......
mWindow = PolicyManager.makeNewWindow(this);
mWindow.setCallback(this);
if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
mWindow.setSoftInputMode(info.softInputMode);
}
......
mWindow.setWindowManager(null, mToken, mComponent.flattenToString());
......
mWindowManager = mWindow.getWindowManager();
......
}
其中mWindow对象调用PolicyManager的静态方法makeNewWindow(this)
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);
}
}
......
// The static methods to spawn new policy-specific objects
public static Window makeNewWindow(Context context) {
return sPolicy.makeNewWindow(context);
}
......
}
在程序运行的时候，会调用静态代码块，生成一个IPolicy实例，实际上是通过类名反射出来的一个Policy对象，而PolicyManager.makeNewWindow返回的就是Policy的makeNewWindow,即是一个PhoneWindow。
public class Policy implements IPolicy {
......
public PhoneWindow makeNewWindow(Context context) {
return new PhoneWindow(context);
}
......
}
而PhoneWindow的创建，就是一个利用构造方法进行构造和初始化的过程：
public class PhoneWindow extends Window implements MenuBuilder.Callback {
......
public PhoneWindow(Context context) {
super(context);
mLayoutInflater = LayoutInflater.from(context);
}
......
}
在初始化之后，获取LayoutInflater对象，放在成员变量mLayoutInflater中，方便后面的mDecorView里面添加布局和子View。
在activity的attach()方法中，获取了mWindow对象之后，调用mWindow.setCallback()设置window的回调事件，而回调接口为在抽象类Window的内部：CallBack
public abstract class Window {
......
public interface Callback {
public boolean dispatchKeyEvent(KeyEvent event);
public boolean dispatchTouchEvent(MotionEvent event);
public boolean dispatchTrackballEvent(MotionEvent event);
public boolean dispatchPopulateAccessibilityEvent(AccessibilityEvent event);
public View onCreatePanelView(int featureId);
public boolean onCreatePanelMenu(int featureId, Menu menu);
public boolean onPreparePanel(int featureId, View view, Menu menu);
public boolean onMenuOpened(int featureId, Menu menu);
public boolean onMenuItemSelected(int featureId, MenuItem item);
public void onWindowAttributesChanged(WindowManager.LayoutParams attrs);
public void onContentChanged();
public void onWindowFocusChanged(boolean hasFocus);
public void onAttachedToWindow();
public void onDetachedFromWindow();
public void onPanelClosed(int featureId, Menu menu);
public boolean onSearchRequested();
}
......
}
而Activity又实现了此接口，自此，当PhoneWindow接受到系统的一系列事件，可以通过回调方法，在activity中进行接受和处理。
接着往下看，设置回调方法之后是判断软键盘的输入法显示模式（mWindow.setSoftInputMode(info.softInputMode)），再之后是设置mWindow的windowManager，这个方法在Window类中
public void setWindowManager(WindowManager wm, IBinder appToken, String appName) {
mAppToken = appToken;
mAppName = appName;
if (wm == null) {
wm = WindowManagerImpl.getDefault();
}
mWindowManager = new LocalWindowManager(wm);
}
因为外面传进来的WindowManager是null，会进if判断，调用windowManagerImpl的静态方法getDefault():
public class WindowManagerImpl implements WindowManager {
......
public static WindowManagerImpl getDefault(){
return mWindowManager;
}
......
private static WindowManagerImpl mWindowManager = new WindowManagerImpl();
}
将获取的windowManager对象，作为一个参数，传递至LocalWindowManager构造方法中，此时生成mWindowManager对象，LocalWindowManager对mDefaultDisplay进行了包裹，而这个mWindowManager可通过activity的getWindowManager()或者是getWindow().getWindowManager()获得。
private class LocalWindowManager implements WindowManager {
LocalWindowManager(WindowManager wm) {
mWindowManager = wm;
mDefaultDisplay = mContext.getResources().getDefaultDisplay(
mWindowManager.getDefaultDisplay());
}
......
public Display getDefaultDisplay() {
return mDefaultDisplay;
}
private final WindowManager mWindowManager;
private final Display mDefaultDisplay;
}
至此，activity和window的关联源码告一段落，总结一下：
1、Activity内部的Window对象，实际是PhoneWindow的实例
2、Activity的Window实例化过程，是在attach()方法中进行的，分别进行window构建和初始化，包括设置回调(setCallBack)、设置软键盘输入模式(setSoftInputMode)、和设置窗口管理器(setWindowManager)
3、Activity的getWindowManager()方法返回的，实际上是一个LocalWindowManager。
4、对于Activity内部的视图view操作，发生在PhoneWindow内部，即Activity的方法调用，最终会调取PhoneWindow内部方法，包括findViewById,setContentView等等
