PolicyManager类位于framework\base\core\java\com\android\internal\policy目录中的PolicyManager.java文件中。PolicyManager主要用于创建Window类、LayoutInflater类和WindowManagerPolicy类，它扮演着简单工厂模式中的工厂类角色，而抽象产品角色由IPolicy接口实现，具体产品角色由Policy类实现。它们的关系如下图所示：
从下面三个类的代码可以看出，都使用了hide注解，因此，这三个类都是不对外公开的API，只限于Framework内部使用。
抽象产品类IPolicy实现如下（IPolicy.java）：
package com.android.internal.policy;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.Window;
import android.view.WindowManagerPolicy;
/**
* {@hide}
*/
/* The implementation of this interface must be called Policy and contained
* within the com.android.internal.policy.impl package */
public interface IPolicy {
public Window makeNewWindow(Context context);
public LayoutInflater makeNewLayoutInflater(Context context);
public WindowManagerPolicy makeNewWindowManager();
}
具体产品类Policy实现如下（Policy.java）：
package com.android.internal.policy.impl;
import android.content.Context;
import android.util.Log;
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";
//需要在Policy类创建时预先加载的一些类
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 {
// 出于性能考虑，在Policy类加载时提前加载会用到的相关类
for (String s : preload_classes) {
try {
//加载指定类到Java虚拟机中，并执行类中的静态代码段
Class.forName(s);
} catch (ClassNotFoundException ex) {
Log.e(TAG, "Could not preload class for phone policy: " + s);
}
}
}
public PhoneWindow makeNewWindow(Context context) {
return new PhoneWindow(context);
}
public PhoneLayoutInflater makeNewLayoutInflater(Context context) {
return new PhoneLayoutInflater(context);
}
//PhoneWindowManager实现了WindowManagerPolicy接口
//这里返回值直接写成WindowManagerPolicy更合理些
public PhoneWindowManager makeNewWindowManager() {
return new PhoneWindowManager();
}
}
工厂类PolicyManager实现如下（PolicyManager.java）：
package com.android.internal.policy;import android.content.Context;
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 {
// 运行时动态装载IPolicy实现类
try {
//加载Policy类的同时会执行其中的静态代码段
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);
}
}
// 构造函数私有，保证是单例类
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();
}
}
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