PolicyManager.java

最新推荐文章于 2021-02-27 08:07:49 发布

原创最新推荐文章于 2021-02-27 08:07:49 发布 · 1.2k 阅读

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本文深入解析了Android系统中PolicyManager类的功能与实现细节，重点介绍了其静态方法如何创建特定策略对象，如WindowManagerPolicy和FallbackEventHandler，并展示了这些方法的具体应用场景。

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frameworks/base/core/java/com/android/internal/policy/PolicyManager.java

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);
    }   
}

PolicyManager.makeNewWindowManager()在frameworks/base/services/java/com/android/server/wm/WindowManagerService.java中被调用。

PolicyManager.makeNewFallbackEventHandler()在frameworks/base/core/java/android/view/ViewRootImpl.java中被调用。

它们的实现在Policy.java里面。

frameworks/base/policy/src/com/android/internal/policy/impl/Policy.java

// 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);
    }
}

可以看出makeNewWindowManager()返回的是WindowManagerPolicy类型，由PhoneWindowManager()得到。

makeNewFallbackEventHandler()返回的是FallbackEventHandler类型，由PhoneFallbackEventHandler()得到。

PhoneWindowManager继承自WindowManagerPolicy，WindowManagerPolicy是一个接口。

public interface WindowManagerPolicy {
    // Policy flags.  These flags are also defined in frameworks/base/include/ui/Input.h.
    public final static int FLAG_WAKE = 0x00000001;
    public final static int FLAG_WAKE_DROPPED = 0x00000002;