WindowManager.java
/*
* Copyright 2020 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 androidx.window;
import android.app.Activity;
import android.content.Context;
import android.content.ContextWrapper;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.core.util.Consumer;
import androidx.window.extensions.ExtensionInterface;
import java.util.concurrent.Executor;
/**
* Main interaction point with the WindowManager library. An instance of this class allows
* polling the current state of the device and display, and registering callbacks for changes in
* the corresponding states.
*/
public final class WindowManager {
/**
* Visual context that was registered with this instance of {@link WindowManager} at creation.
* This is used to find the token identifier of the window when requesting layout information
* from the {@link ExtensionInterface}.
*/
private Context mContext;
/**
* The backend that supplies the information through this class.
*/
private WindowBackend mWindowBackend;
/**
* Get an instance of the class initialized with and connected to the provided {@link Context}.
* All methods of this class will return information that is associated with this visual
* context.
* @param context A visual context, such as an {@link Activity} or a {@link ContextWrapper}
* around one, to use for initialization.
* @param windowBackend Backing server class that will provide information for this instance.
* Pass a custom {@link WindowBackend} implementation for testing,
* or {@code null} to use the default implementation.
*/
public WindowManager(@NonNull Context context, @Nullable WindowBackend windowBackend) {
if (getActivityFromContext(context) == null) {
throw new IllegalArgumentException("Used non-visual Context to obtain an instance of "
+ "WindowManager. Please use an Activity or a ContextWrapper around one "
+ "instead.");
}
mContext = context;
mWindowBackend = windowBackend != null
? windowBackend : ExtensionWindowBackend.getInstance(context);
}
/**
* Get current window layout information for the associated {@link Context}. Must be called
* only after the it is attached to the window and the layout pass has happened.
* @see Activity#onAttachedToWindow()
* @see WindowLayoutInfo
*/
@NonNull
public WindowLayoutInfo getWindowLayoutInfo() {
return mWindowBackend.getWindowLayoutInfo(mContext);
}
/**
* Get the current device state.
* @see DeviceState
*/
@NonNull
public DeviceState getDeviceState() {
return mWindowBackend.getDeviceState();
}
/**
* Register a callback for layout changes of the window of the current visual {@link Context}.
* Must be called only after the it is attached to the window.
* @see Activity#onAttachedToWindow()
*/
public void registerLayoutChangeCallback(@NonNull Executor executor,
@NonNull Consumer<WindowLayoutInfo> callback) {
mWindowBackend.registerLayoutChangeCallback(mContext, executor, callback);
}
/**
* Unregister a callback for window layout changes of the window.
*/
public void unregisterLayoutChangeCallback(@NonNull Consumer<WindowLayoutInfo> callback) {
mWindowBackend.unregisterLayoutChangeCallback(callback);
}
/**
* Register a callback for device state changes.
*/
public void registerDeviceStateChangeCallback(@NonNull Executor executor,
@NonNull Consumer<DeviceState> callback) {
mWindowBackend.registerDeviceStateChangeCallback(executor, callback);
}
/**
* Unregister a callback for device state changes.
*/
public void unregisterDeviceStateChangeCallback(@NonNull Consumer<DeviceState> callback) {
mWindowBackend.unregisterDeviceStateChangeCallback(callback);
}
/**
* Unwrap the hierarchy of {@link ContextWrapper}-s until {@link Activity} is reached.
* @return Base {@link Activity} context or {@code null} if not available.
*/
@Nullable
static Activity getActivityFromContext(Context context) {
while (context instanceof ContextWrapper) {
if (context instanceof Activity) {
return (Activity) context;
}
context = ((ContextWrapper) context).getBaseContext();
}
return null;
}
}