android双屏之副屏待机显示图片

摘要：android原生有双屏的机制，但需要芯片厂商适配框架后在底层实现。本文在基于芯发8766已实现底层适配的基础上，仅针对上层Launcher部分对系统进行改造，从而实现在开机后副屏显示一张待机图片。

副屏布局

由于仅显示一张图片，故布局仅需填充ImageView

Index: vendor/mediatek/proprietary/packages/apps/Launcher3/res/layout/presentation_image.xml
===================================================================
--- vendor/mediatek/proprietary/packages/apps/Launcher3/res/layout/presentation_image.xml	(不存在的)
+++ vendor/mediatek/proprietary/packages/apps/Launcher3/res/layout/presentation_image.xml	(版本 1687)
@@ -0,0 +1,6 @@
+<ImageView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/image_view"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:scaleType="centerInside" />

关于android:scaleType的详细说明和用法，可参考官网API
或者以下BLOG：
Android的ImageView scaleType八大属性，你都了解吗？
android学习笔记之ImageView的scaleType属性

准备一张符合副屏分辨率的图片

博主所使用的副屏为320x240，图片格式为JPG

Index: vendor/mediatek/proprietary/packages/apps/Launcher3/res/mipmap-hdpi/presents.jpg

副屏图片管理类

新增图换图片功能，在显示以上图片的基础上，如果所指定路径有替换的图片文件，则使用替换的图片文件。

Index: vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/presentation/ImagePresentation.java
===================================================================
--- vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/presentation/ImagePresentation.java	(不存在的)
+++ vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/presentation/ImagePresentation.java	(版本 1687)
@@ -0,0 +1,48 @@
+package com.android.launcher3.presentation;
+
+import android.app.Presentation;
+import android.content.Context;
+import android.graphics.ColorMatrix;
+import android.graphics.ColorMatrixColorFilter;
+import android.net.Uri;
+import android.os.Bundle;
+import android.os.Environment;
+import android.util.Log;
+import android.view.Display;
+import android.widget.ImageView;
+
+import com.android.launcher3.R;
+
+import java.io.File;
+
+public class ImagePresentation extends Presentation {
+    private static final String TAG = "ImagePresentation";
+
+    ImageView imageView;
+
+    public ImagePresentation(Context context, Display display) {
+        super(context, display);
+    }
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.presentation_image);
+
+        imageView = findViewById(R.id.image_view);
+        imageView.setImageResource(R.mipmap.presents);
+    }
+
+    @Override
+    protected void onStart() {
+        super.onStart();
+        String path = Environment.getExternalStorageDirectory().getAbsolutePath() + "/presents_replace.jpg";
+        File imageFile = new File(path);
+        if (imageFile.exists()) {
+            imageView.setImageURI(Uri.fromFile(new File(path)));
+        } else {
+            Log.d(TAG, "The replacement image does not exist, use the original image");
+        }
+    }
+}

在Launcher部分的实现

由于需要开机后显示待机的图片，并且副屏的内容默认是投射填充主屏的内容，故开机后会有准备阶段，主要显示一部分Launcher的内容，在完全准备好后，再显示副屏的待机图片。

Index: vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/Launcher.java
===================================================================
--- vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/Launcher.java	(版本 1678)
+++ vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/Launcher.java	(版本 1687)
@@ -70,6 +70,7 @@
 import android.app.NotificationChannel;
 import android.app.NotificationManager;
 import android.app.PendingIntent;
+import android.app.Presentation;
 import android.appwidget.AppWidgetHostView;
 import android.appwidget.AppWidgetManager;
 import android.content.ActivityNotFoundException;
@@ -86,6 +87,7 @@
 import android.graphics.Bitmap;
 import android.graphics.Rect;
 import android.graphics.RectF;
+import android.hardware.display.DisplayManager;
 import android.os.Build;
 import android.os.Bundle;
 import android.os.CancellationSignal;
@@ -99,6 +101,7 @@
 import android.text.method.TextKeyListener;
 import android.util.Log;
 import android.util.SparseArray;
+import android.view.Display;
 import android.view.KeyEvent;
 import android.view.KeyboardShortcutGroup;
 import android.view.KeyboardShortcutInfo;
@@ -168,6 +171,7 @@
 import com.android.launcher3.popup.PopupContainerWithArrow;
 import com.android.launcher3.popup.PopupDataProvider;
 import com.android.launcher3.popup.SystemShortcut;
+import com.android.launcher3.presentation.ImagePresentation;
 import com.android.launcher3.qsb.QsbContainerView;
 import com.android.launcher3.statemanager.StateManager;
 import com.android.launcher3.statemanager.StateManager.StateHandler;
@@ -387,6 +391,11 @@
 
     private StringCache mStringCache;
 
+    // @ + {
+    private DisplayManager mDisplayManager;
+    private Presentation secondaryPresentation;
+    // @ + }
+
     @Override
     @TargetApi(Build.VERSION_CODES.S)
     protected void onCreate(Bundle savedInstanceState) {
@@ -453,6 +462,34 @@
 
         super.onCreate(savedInstanceState);
 
+        // @ + {
+        mDisplayManager = (DisplayManager) getSystemService(Context.DISPLAY_SERVICE);
+        mDisplayManager.registerDisplayListener(new DisplayManager.DisplayListener() {
+            @Override
+            public void onDisplayAdded(int displayId) {
+                Log.d(TAG, "onDisplayAdded");
+            }
+
+            @Override
+            public void onDisplayRemoved(int displayId) {
+                Log.d(TAG, "onDisplayRemoved");
+            }
+
+            @Override
+            public void onDisplayChanged(int displayId) {}
+        }, null);
+
+        Display[] displays = mDisplayManager.getDisplays();
+        for (Display display : displays) {
+            if (display.getDisplayId() != Display.DEFAULT_DISPLAY) {
+                secondaryPresentation = new ImagePresentation(this, display);
+                //secondaryPresentation = new VideoPresentation(this, display);
+                secondaryPresentation.show();
+                break;
+            }
+        }
+        // @ + }
+
         LauncherAppState app = LauncherAppState.getInstance(this);
         mOldConfig = new Configuration(getResources().getConfiguration());
         mModel = app.getModel();
@@ -1718,6 +1755,12 @@
 
         mOverlayManager.onActivityDestroyed(this);
         mUserChangedCallbackCloseable.close();
+
+        // @ + {
+        if (secondaryPresentation != null && secondaryPresentation.isShowing()) {
+            secondaryPresentation.dismiss();
+        }
+        // @ + }
     }
 
     public LauncherAccessibilityDelegate getAccessibilityDelegate() {

扩展 —— 副屏视频布局

能显示图片，自然也能播放视频

Index: vendor/mediatek/proprietary/packages/apps/Launcher3/res/layout/presentation_video.xml
===================================================================
--- vendor/mediatek/proprietary/packages/apps/Launcher3/res/layout/presentation_video.xml	(不存在的)
+++ vendor/mediatek/proprietary/packages/apps/Launcher3/res/layout/presentation_video.xml	(版本 1687)
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<VideoView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/video_view"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:scaleType="centerCrop" />

准备一段符合副屏分辨率的视频

博主所使用的副屏为320x240，视频格式为MP4

Index: vendor/mediatek/proprietary/packages/apps/Launcher3/res/raw/video_320_240.mp4

副屏视频管理类

播放的视频内容需要根据副屏的比例进行缩放，并且根据实际情况实现循环播放。

Index: vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/presentation/VideoPresentation.java
===================================================================
--- vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/presentation/VideoPresentation.java	(不存在的)
+++ vendor/mediatek/proprietary/packages/apps/Launcher3/src/com/android/launcher3/presentation/VideoPresentation.java	(版本 1687)
@@ -0,0 +1,68 @@
+package com.android.launcher3.presentation;
+
+import android.app.Presentation;
+import android.content.Context;
+import android.graphics.Point;
+import android.net.Uri;
+import android.os.Bundle;
+import android.util.Log;
+import android.view.Display;
+import android.view.ViewGroup;
+import android.widget.VideoView;
+
+import com.android.launcher3.R;
+
+public class VideoPresentation extends Presentation {
+    private static final String TAG = "VideoPresentation";
+    private VideoView videoView;
+
+    public VideoPresentation(Context context, Display display) {
+        super(context, display);
+    }
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.presentation_video);
+        videoView = findViewById(R.id.video_view);
+
+        Uri videoUri = Uri.parse("android.resource://" + getContext().getPackageName() + "/" + R.raw.video_320_240);
+        videoView.setVideoURI(videoUri);
+
+        videoView.setOnPreparedListener(mp -> {
+            int videoWidth = mp.getVideoWidth();
+            int videoHeight = mp.getVideoHeight();
+
+            Point screenSize = new Point();
+            getDisplay().getRealSize(screenSize);
+            int screenWidth = screenSize.x;
+            int screenHeight = screenSize.y;
+
+            float widthRatio = (float) screenWidth / videoWidth;
+            float heightRatio = (float) screenHeight / videoHeight;
+            float scale = Math.min(widthRatio, heightRatio);
+
+            ViewGroup.LayoutParams params = videoView.getLayoutParams();
+            params.width = (int) (videoWidth * scale);
+            params.height = (int) (videoHeight * scale);
+            videoView.setLayoutParams(params);
+        });
+
+        videoView.setOnCompletionListener(mp -> {
+            videoView.start(); // replay
+        });
+
+        
+
+        videoView.start();
+    }
+
+    @Override
+    protected void onStop() {
+        super.onStop();
+        if (videoView != null) {
+            videoView.stopPlayback();
+        }
+    }
+}
+