Android 摄像头预览悬浮窗，可拖动，可显示在其他app上方

市面上常见的摄像头悬浮窗，如微信、手机QQ的视频通话功能，有如下特点：

• 整屏页面能切换到一个小的悬浮窗
• 悬浮窗能运行在其他app上方
• 悬浮窗能跳回整屏页面，并且悬浮窗消失

我们探讨过用CameraX打开摄像头预览，结合可改变大小和浮动的activity，实现了应用内摄像头预览悬浮Activity。这个悬浮Activity是在应用内使用的。要让悬浮窗在其他app上，需要结合悬浮窗 System Alert Window。

本文用CameraX实现摄像头预览悬浮窗，能显示在其他app上方，可拖动，可跳回activity。

这个例子的相关代码放进了单独的模块。使用时注意gradle里的细微差别。

引入依赖

模块gradle的一些配置，使用的Android SDK版本为31，启用databinding

plugins {
    id 'com.android.library'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
    id 'kotlin-kapt'
}

android {
    compileSdk 31

    defaultConfig {
        minSdk 21
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        consumerProguardFiles "consumer-rules.pro"
    }
    dataBinding {
        enabled = true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    implementation 'androidx.appcompat:appcompat:1.4.0'
    implementation 'com.google.android.material:material:1.4.0'
    implementation project(path: ':baselib')
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

    implementation "androidx.camera:camera-core:1.1.0-alpha11"
    implementation "androidx.camera:camera-camera2:1.1.0-alpha11"
    implementation "androidx.camera:camera-lifecycle:1.1.0-alpha11"
    implementation "androidx.camera:camera-view:1.0.0-alpha31"
    implementation "androidx.camera:camera-extensions:1.0.0-alpha31"
}

引入CameraX依赖（CameraX 核心库是用camera2实现的），目前主要用1.1.0-alpha11版本

权限

manifest中申请权限

<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera.any" />

<!-- 悬浮窗的权限 -->
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

动态申请相机权限 Manifest.permission.CAMERA

private static final int REQ_CAMERA = 2;

    if (PackageManager.PERMISSION_GRANTED != ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)) {
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, REQ_CAMERA);
    }

后面需要MeFloatingCameraXAct与FloatingCameraXService配合使用。

manifest中注册Activity和Service

<activity
    android:name=".camera.MeFloatingCameraXAct"
    android:exported="true"
    android:launchMode="singleTop" />

<service android:name=".camera.FloatingCameraXService" />

MeFloatingCameraXAct

这个activity提供一个简单的摄像头预览界面，并且提供入口启动悬浮窗。

layout me_act_floating_preivew_x.xml

<?xml version="1.0" encoding="utf-8"?>
<layout>

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/container"
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <androidx.camera.view.PreviewView
                android:id="@+id/previewView"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />
        </FrameLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:gravity="center"
            android:orientation="vertical"
            android:padding="4dp">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal">

                <Button
                    android:id="@+id/start"
                    style="@style/NormalBtn"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="打开摄像头" />

                <Button
                    android:id="@+id/end"
                    style="@style/NormalBtn"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="4dp"
                    android:text="停止摄像头" />

                <Button
                    android:id="@+id/go_floating"
                    style="@style/NormalBtn"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="4dp"
                    android:text="切换到悬浮窗" />

                <Button
                    android:id="@+id/close_act"
                    style="@style/NormalBtn"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="4dp"
                    android:text="关闭" />

            </LinearLayout>

        </LinearLayout>

    </RelativeLayout>
</layout>

完整代码如下

// package com.rustfisher.mediasamples.camera;
import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import androidx.databinding.DataBindingUtil;
import com.google.common.util.concurrent.ListenableFuture;
import com.rustfisher.mediasamples.R;
import com.rustfisher.mediasamples.databinding.MeActFloatingPreivewXBinding;

import java.util.concurrent.ExecutionException;


/**
 * @author an.rustfisher.com
 * @date 2022-1-06 23:53
 */
public class MeFloatingCameraXAct extends AppCompatActivity {
    private static final String TAG = "rfDevX";
    private static final int REQ_CAMERA = 2;
    public static final String K_START_CAMERA = "start_camera"; // 直接启动摄像头

    private MeActFloatingPreivewXBinding mBinding;
    private ListenableFuture<ProcessCameraProvider> mCameraProviderFuture;
    private ProcessCameraProvider mCameraProvider;
    private boolean mRunning = false;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mBinding = DataBindingUtil.setContentView(this, R.layout.me_act_floating_preivew_x);
        final boolean startNow = getIntent().getBooleanExtra(K_START_CAMERA, false);
        mCameraProviderFuture = ProcessCameraProvider.getInstance(this);
        mCameraProviderFuture.addListener(() -> {
            try {
                mCameraProvider = mCameraProviderFuture.get();
                Log.d(TAG, "获取到了 cameraProvider");
                if (startNow) {
                    bindPreview(mCameraProvider);
                }
            } catch (ExecutionException | InterruptedException e) {
                // 这里不用处理
            }
        }, ContextCompat.getMainExecutor(this));
        mBinding.start.setOnClickListener(v -> {
            if (mCameraProvider != null && !mRunning) {
                bindPreview(mCameraProvider);
            }
        });
        mBinding.end.setOnClickListener(v -> {
            mCameraProvider.unbindAll();
            mRunning = false;
        });
        mBinding.goFloating.setOnClickListener(v -> {
            startService(new Intent(getApplicationContext(), FloatingCameraXService.class));
            finish();
        });
        mBinding.closeAct.setOnClickListener(v -> {
            Toast.makeText(getApplicationContext(), "关闭摄像头示例", Toast.LENGTH_SHORT).show();
            stopService(new Intent(getApplicationContext(), FloatingCameraXService.class));
            finish();
        });

        if (PackageManager.PERMISSION_GRANTED != ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, REQ_CAMERA);
        }
    }

    @Override
    public void onBackPressed() {
        Toast.makeText(getApplicationContext(), "请点击关闭按钮", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQ_CAMERA) {
            if (grantResults[0] != PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(getApplicationContext(), "请允许相机权限", Toast.LENGTH_SHORT).show();
            }
        }
    }

    private void bindPreview(ProcessCameraProvider cameraProvider) {
        if (cameraProvider == null) {
            Toast.makeText(getApplicationContext(), "没获取到相机", Toast.LENGTH_SHORT).show();
            return;
        }
        Toast.makeText(getApplicationContext(), "相机启动", Toast.LENGTH_SHORT).show();
        Preview preview = new Preview.Builder().build();

        CameraSelector cameraSelector = new CameraSelector.Builder()
                .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                .build();

        preview.setSurfaceProvider(mBinding.previewView.getSurfaceProvider());

        cameraProvider.bindToLifecycle(this, cameraSelector, preview);
        mRunning = true;
    }
}

CameraX启动预览的代码可以参考 https://an.rustfisher.com/android/jetpack/camerax/simple-preview/

悬浮窗

layout

先给悬浮窗准备一个layout

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#000">

    <androidx.camera.view.PreviewView
        android:id="@+id/preview_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <ImageView
        android:id="@+id/to_big"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:padding="4dp"
        android:src="@drawable/me_to_big"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

图片请自备

FloatingCameraXService

FloatingCameraXService实现LifecycleOwner接口，为了方便CameraX绑定生命周期组件。

// package com.rustfisher.mediasamples.camera;
import android.app.Service;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.os.Build;
import android.os.IBinder;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.camera.core.CameraSelector;
import androidx.camera.core.Preview;
import androidx.camera.lifecycle.ProcessCameraProvider;
import androidx.camera.view.PreviewView;
import androidx.core.content.ContextCompat;
import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.LifecycleOwner;
import androidx.lifecycle.LifecycleRegistry;

import com.google.common.util.concurrent.ListenableFuture;
import com.rustfisher.mediasamples.R;

import java.util.concurrent.ExecutionException;


/**
 * 摄像头预览悬浮窗的服务
 *
 * @author an.rustfisher.com
 * @date 2022-01-06 23:53
 */
public class FloatingCameraXService extends Service implements LifecycleOwner {
    private static final String TAG = "rfDevFloatingCameraX";

    private WindowManager mWM;
    private View mFloatView;
    private LifecycleRegistry mLifecycleRegistry;

    private ListenableFuture<ProcessCameraProvider> mCameraProviderFuture;
    private ProcessCameraProvider mCameraProvider;

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        mLifecycleRegistry = new LifecycleRegistry(this);
        mLifecycleRegistry.setCurrentState(Lifecycle.State.CREATED);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Log.d(TAG, "onStartCommand , " + startId);
        if (mFloatView == null) {
            Log.d(TAG, "onStartCommand: 创建悬浮窗");
            initUi();
        }
        mLifecycleRegistry.setCurrentState(Lifecycle.State.STARTED);
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        Log.d(TAG, "onDestroy");
        if (mFloatView != null) {
            mWM.removeView(mFloatView);
        }
        mLifecycleRegistry.setCurrentState(Lifecycle.State.DESTROYED);
        super.onDestroy();
    }

    private void initUi() {
        DisplayMetrics metrics = getApplicationContext().getResources().getDisplayMetrics();
        int width = metrics.widthPixels;
        int height = metrics.heightPixels;

        mWM = (WindowManager) getSystemService(WINDOW_SERVICE);
        LayoutInflater inflater = (LayoutInflater) getBaseContext().getSystemService(LAYOUT_INFLATER_SERVICE);
        mFloatView = inflater.inflate(R.layout.me_floating_camerax, null);

        int layoutType;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            layoutType = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
        } else {
            layoutType = WindowManager.LayoutParams.TYPE_TOAST;
        }

        WindowManager.LayoutParams floatLp = new WindowManager.LayoutParams(
                (int) (width * (0.4f)), // 这里可以定小一点
                (int) (height * (0.3f)),// 为方便展示 这里给的尺寸比较大
                layoutType,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                PixelFormat.TRANSLUCENT
        );

        floatLp.gravity = Gravity.CENTER;
        floatLp.x = 0;
        floatLp.y = 0;

        mFloatView.findViewById(R.id.to_big).setOnClickListener(v -> {
            stopSelf();
            Intent intent = new Intent(getApplicationContext(), MeFloatingCameraXAct.class);
            intent.putExtra(MeFloatingCameraXAct.K_START_CAMERA, true);
            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            startActivity(intent);
        });

        mWM.addView(mFloatView, floatLp);

        mFloatView.setOnTouchListener(new View.OnTouchListener() {
            final WindowManager.LayoutParams floatWindowLayoutUpdateParam = floatLp;
            double x;
            double y;
            double px;
            double py;

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                    case MotionEvent.ACTION_DOWN:
                        x = floatWindowLayoutUpdateParam.x;
                        y = floatWindowLayoutUpdateParam.y;
                        px = event.getRawX();
                        py = event.getRawY();
                        break;
                    case MotionEvent.ACTION_MOVE:
                        floatWindowLayoutUpdateParam.x = (int) ((x + event.getRawX()) - px);
                        floatWindowLayoutUpdateParam.y = (int) ((y + event.getRawY()) - py);
                        mWM.updateViewLayout(mFloatView, floatWindowLayoutUpdateParam);
                        break;
                }
                return false;
            }
        });

        mCameraProviderFuture = ProcessCameraProvider.getInstance(this);
        mCameraProviderFuture.addListener(() -> {
            try {
                mCameraProvider = mCameraProviderFuture.get();
                Log.d(TAG, "[service]获取到了cameraProvider");
                bindPreview(mCameraProvider, mFloatView.findViewById(R.id.preview_view));
            } catch (ExecutionException | InterruptedException e) {
                // 这里不用处理
            }
        }, ContextCompat.getMainExecutor(this));
    }

    @NonNull
    @Override
    public Lifecycle getLifecycle() {
        return mLifecycleRegistry;
    }

    private void bindPreview(ProcessCameraProvider cameraProvider, PreviewView previewView) {
        if (cameraProvider == null) {
            Toast.makeText(getApplicationContext(), "没获取到相机", Toast.LENGTH_SHORT).show();
            return;
        }
        Toast.makeText(getApplicationContext(), "相机启动", Toast.LENGTH_SHORT).show();
        Preview preview = new Preview.Builder().build();
        CameraSelector cameraSelector = new CameraSelector.Builder()
                .requireLensFacing(CameraSelector.LENS_FACING_BACK)
                .build();
        preview.setSurfaceProvider(previewView.getSurfaceProvider());
        cameraProvider.bindToLifecycle(this, cameraSelector, preview);
    }
}

这里悬浮窗view创建完毕后，再去请求摄像头和打开预览。

LifeCycle

生命周期请参考LifeCycle

WindowManager

创建悬浮窗view，并且添加到窗口中。主要使用WindowManager提供的方法。

创建WindowManager.LayoutParams的时候，指定宽高，根据API版本选择layoutType。

启动预览

启动预览部分bindPreview代码与前面的类似。用bindToLifecycle方法。

运行测试

运行到手机上，打开这个Activity就可以看到摄像头预览。图像宽高比正常，没有拉伸现象。
缩小成悬浮窗后，可以拖动。可从悬浮窗跳回Activity。

• 荣耀 EMUI 3.1 Lite，Android 5.1 运行正常
• Redmi 9A，MIUI 12.5.1稳定版，Android 10 运行正常

小结

结合悬浮窗功能与摄像头得到的预览悬浮窗，可以运行在其他app上方。
注意引导用户开启悬浮窗权限和摄像头权限。

参考

• Android 应用内悬浮窗
• Android CameraX 打开摄像头预览
• 生命周期 LifeCycle
• Android 悬浮窗 System Alert Window