Bildschirmaufnahme und Medien
Erkunden Sie, wie Sie auf Bildschirmaufnahmefunktionen und Mediengeräte zugreifen und diese in Ihre Electron-Desktopanwendungen integrieren.
Bildschirmaufnahme und Medien ist eine kostenlose Electron Desktop App Development-Lektion auf CoddyKit. Dies ist Lektion 3 von 4. Du kannst die komplette Lektion unten kostenlos lesen – dann übst du sie direkt im Browser mit einem integrierten Code-Editor und einem KI-Tutor rund um die Uhr. Sie ist Teil des Electron Desktop App Development-Lernpfads, und dein Fortschritt wird über Web und CoddyKit-App synchronisiert. Der Electron Desktop App Development-Kurs umfasst insgesamt 4 Lektionen.
Teile dieser Lektion wurden noch nicht übersetzt und werden auf Englisch angezeigt.
Accessing Camera & Screen
Electron lets your desktop app use native features like cameras, microphones, and even capture the screen. This opens up possibilities for video calls, screen recording, and more!
We'll explore how to list available devices, display live camera feeds, and capture your desktop or specific windows.
Discovering Your Devices
Before using a camera or microphone, you can discover what's available on the user's system. The navigator.mediaDevices.enumerateDevices() method provides a list of all connected media input and output devices.
Run this code to see your devices. You might need to grant permission to access devices.
const { app, BrowserWindow } = require('electron');
function createWindow() {
const win = new BrowserWindow({
width: 600,
height: 450,
webPreferences: {
nodeIntegration: true,
contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
}
});
const htmlContent = `
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Media Devices</title>
</head>
<body>
<h1>Available Media Devices</h1>
<ul id="device-list"></ul>
<script>
async function getMediaDevices() {
try {
const devices = await navigator.mediaDevices.enumerateDevices();
const list = document.getElementById('device-list');
if (devices.length === 0) {
list.innerHTML = '<li>No media devices found or permission denied.</li>';
return;
}
devices.forEach(device => {
const li = document.createElement('li');
li.textContent = `Kind: ${device.kind}, Label: ${device.label || 'Unknown'}`;
list.appendChild(li);
});
} catch (err) {
console.error('Error listing devices:', err);
document.getElementById('device-list').innerHTML = `<li>Error: ${err.message}</li>`;
}
}
getMediaDevices();
</script>
</body>
</html>
`;
win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}
app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
if (BrowserWindow.getAllWindows().length === 0) createWindow();
});Displaying Camera Stream
To display a live camera feed, we use navigator.mediaDevices.getUserMedia(). This method requests access to a media input device (like a camera) and, if granted, provides a MediaStream.
This stream can then be displayed in a <video> element. Try running this example:
const { app, BrowserWindow } = require('electron');
function createWindow() {
const win = new BrowserWindow({
width: 600,
height: 450,
webPreferences: {
nodeIntegration: true,
contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
}
});
const htmlContent = `
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Camera Stream</title>
</head>
<body>
<h1>My Camera Feed</h1>
<video id="camera-feed" autoplay style="width:100%; height:auto;"></video>
<p id="status"></p>
<script>
async function startCamera() {
const video = document.getElementById('camera-feed');
const status = document.getElementById('status');
try {
const stream = await navigator.mediaDevices.getUserMedia({
video: true // Request video access
});
video.srcObject = stream;
status.textContent = 'Camera feed active.';
} catch (err) {
console.error('Error accessing camera:', err);
status.textContent = `Error: ${err.message}. Please grant camera permission.`;
}
}
startCamera();
</script>
</body>
</html>
`;
win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}
app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
if (BrowserWindow.getAllWindows().length === 0) createWindow();
});User Permissions & Errors
Accessing media devices like cameras and microphones requires explicit user permission. When getUserMedia() is called, the operating system will typically prompt the user for consent.
- Your application should always be ready to handle cases where the user grants or denies permission.
- Catching errors from
getUserMedia()(e.g.,NotAllowedError) helps you inform the user about permission issues.
Understanding DesktopCapturer
Electron provides the desktopCapturer module, a powerful tool that allows your app to capture video and audio from the entire screen, specific windows, or individual displays.
This is essential for building features like screen sharing, screen recording, or even taking screenshots of other applications running on the user's desktop.
Getting Screen Sources
To capture a screen or window, you first need to get a list of available sources. desktopCapturer.getSources() provides these, including their IDs, names, and even thumbnails.
This method is available in the renderer process (but usually exposed via a preload script for security). For simplicity in this lesson, we'll access it directly.
const { app, BrowserWindow } = require('electron');
function createWindow() {
const win = new BrowserWindow({
width: 600,
height: 450,
webPreferences: {
nodeIntegration: true, // Required for desktopCapturer
contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
}
});
const htmlContent = `
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Screen Sources</title>
</head>
<body>
<h1>Available Screen Sources</h1>
<ul id="source-list"></ul>
<script>
const { desktopCapturer } = require('electron'); // Access desktopCapturer
async function getScreenSources() {
const list = document.getElementById('source-list');
try {
const sources = await desktopCapturer.getSources({
types: ['window', 'screen']
});
if (sources.length === 0) {
list.innerHTML = '<li>No screen or window sources found.</li>';
return;
}
sources.forEach(source => {
const li = document.createElement('li');
li.textContent = `ID: ${source.id}, Name: ${source.name}`;
if (source.thumbnail) {
const img = document.createElement('img');
img.src = source.thumbnail.toDataURL();
img.style.maxWidth = '100px';
img.style.marginLeft = '10px';
li.appendChild(img);
}
list.appendChild(li);
});
} catch (err) {
console.error('Error getting sources:', err);
list.innerHTML = `<li>Error: ${err.message}</li>`;
}
}
getScreenSources();
</script>
</body>
</html>
`;
win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}
app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
if (BrowserWindow.getAllWindows().length === 0) createWindow();
});Displaying a Screen Stream
Once you have a source ID (e.g., from a specific display or window), you can use navigator.mediaDevices.getUserMedia() again. This time, you pass a chromeMediaSource constraint with the desktopCapturer source ID.
This will capture the chosen screen/window and display it in a <video> element, similar to a camera feed.
const { app, BrowserWindow } = require('electron');
function createWindow() {
const win = new BrowserWindow({
width: 600,
height: 450,
webPreferences: {
nodeIntegration: true, // Required for desktopCapturer
contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
}
});
const htmlContent = `
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Screen Capture</title>
</head>
<body>
<h1>Screen Capture Demo</h1>
<button id="start-capture">Start Screen Capture</button>
<video id="screen-feed" autoplay style="width:100%; height:auto;"></video>
<p id="status"></p>
<script>
const { desktopCapturer } = require('electron');
document.getElementById('start-capture').addEventListener('click', async () => {
const video = document.getElementById('screen-feed');
const status = document.getElementById('status');
status.textContent = 'Searching for sources...';
try {
const sources = await desktopCapturer.getSources({
types: ['screen'], // Only screens for simplicity
thumbnailSize: { width: 1, height: 1 } // No large thumbnails needed
});
if (sources.length === 0) {
status.textContent = 'No screen sources found.';
return;
}
// Take the first screen found
const screenSource = sources[0];
status.textContent = `Capturing: ${screenSource.name}`;
const stream = await navigator.mediaDevices.getUserMedia({
audio: false, // Can be true for audio
video: {
mandatory: {
chromeMediaSource: 'desktop',
chromeMediaSourceId: screenSource.id,
minWidth: 1280, minHeight: 720,
maxWidth: 1920, maxHeight: 1080
}
}
});
video.srcObject = stream;
status.textContent = 'Screen capture active.';
} catch (err) {
console.error('Error capturing screen:', err);
status.textContent = `Error: ${err.message}.`;
}
});
</script>
</body>
</html>
`;
win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}
app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
if (BrowserWindow.getAllWindows().length === 0) createWindow();
});Basic Media Recording
After getting a MediaStream (from a camera or screen), you can record it using the browser's MediaRecorder API. This lets you save the stream as a video or audio file.
The MediaRecorder takes the stream and collects data chunks, which can then be combined into a Blob (e.g., a video file).
const { app, BrowserWindow } = require('electron');
function createWindow() {
const win = new BrowserWindow({
width: 600,
height: 450,
webPreferences: {
nodeIntegration: true,
contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
}
});
const htmlContent = `
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Media Recorder</title>
</head>
<body>
<h1>Simple Recorder</h1>
<button id="start-cam">Start Camera</button>
<button id="start-rec" disabled>Record</button>
<button id="stop-rec" disabled>Stop</button>
<video id="live-feed" autoplay muted style="width:100%; height:auto;"></video>
<a id="download-link" style="display:none;">Download Recording</a>
<p id="status"></p>
<script>
const startCamBtn = document.getElementById('start-cam');
const startRecBtn = document.getElementById('start-rec');
const stopRecBtn = document.getElementById('stop-rec');
const downloadLink = document.getElementById('download-link');
const liveFeed = document.getElementById('live-feed');
const status = document.getElementById('status');
let mediaRecorder;
let recordedChunks = [];
let currentStream;
startCamBtn.addEventListener('click', async () => {
try {
currentStream = await navigator.mediaDevices.getUserMedia({ video: true, audio: true });
liveFeed.srcObject = currentStream;
startRecBtn.disabled = false;
startCamBtn.disabled = true;
status.textContent = 'Camera ready. Click Record.';
} catch (err) {
status.textContent = `Error: ${err.message}`;
console.error('Error starting camera:', err);
}
});
startRecBtn.addEventListener('click', () => {
recordedChunks = [];
mediaRecorder = new MediaRecorder(currentStream);
mediaRecorder.ondataavailable = event => {
if (event.data.size > 0) {
recordedChunks.push(event.data);
}
};
mediaRecorder.onstop = () => {
const blob = new Blob(recordedChunks, { type: 'video/webm' });
const url = URL.createObjectURL(blob);
downloadLink.href = url;
downloadLink.download = 'electron-recording.webm';
downloadLink.style.display = 'block';
status.textContent = 'Recording stopped. Download available.';
};
mediaRecorder.start();
startRecBtn.disabled = true;
stopRecBtn.disabled = false;
status.textContent = 'Recording...';
});
stopRecBtn.addEventListener('click', () => {
mediaRecorder.stop();
startRecBtn.disabled = false;
stopRecBtn.disabled = true;
});
</script>
</body>
</html>
`;
win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}
app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
if (BrowserWindow.getAllWindows().length === 0) createWindow();
});Security Best Practices
When working with native media, always prioritize security. Granting access to cameras, microphones, or screen capture can be sensitive.
- Request Permissions Wisely: Only ask for permissions when absolutely necessary for your app's functionality.
- Inform Users: Clearly explain why your app needs access to these native features.
- Context Isolation & Preload Scripts: For real-world applications, use
contextIsolation: trueand exposedesktopCapturersecurely via a preload script. This prevents malicious scripts in the renderer from accessing Node.js APIs directly.
Quick Check: Native Media
Which of the following statements are true regarding accessing native media and screen capture in Electron?
Recap: Native Media
Great job! In this lesson, we explored how Electron applications can interact with native media features:
- We learned to use
navigator.mediaDevices.enumerateDevices()to list available cameras and microphones. - We accessed live camera feeds with
navigator.mediaDevices.getUserMedia(). - We discovered the
desktopCapturermodule for listing and capturing screen or window content. - We briefly touched upon using
MediaRecorderto save captured media streams. - Finally, we highlighted the importance of user permissions and security best practices when handling sensitive native features.
These tools empower you to build rich, interactive desktop applications with powerful media capabilities!
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Häufig gestellte Fragen
Ist die Lektion „Bildschirmaufnahme und Medien“ kostenlos?
Ja — der vollständige Text von „Bildschirmaufnahme und Medien“ ist hier im Web kostenlos zu lesen. Um sie interaktiv zu üben (integrierter Code-Editor und 24/7 KI-Tutor) und den Rest des Electron Desktop App Development-Kurses freizuschalten, upgrade auf CoddyKit PRO. Der Electron Desktop App Development-Kurs umfasst insgesamt 4 Lektionen.
Was lerne ich in „Bildschirmaufnahme und Medien“?
Erkunden Sie, wie Sie auf Bildschirmaufnahmefunktionen und Mediengeräte zugreifen und diese in Ihre Electron-Desktopanwendungen integrieren. Du übst Electron Desktop App Development mit praktischem Code, den du direkt im Browser ausführst, und ein 24/7 KI-Tutor beantwortet deine Fragen während du die Lektion bearbeitest.
Brauche ich Erfahrung, um Electron Desktop App Development zu starten?
Keine Vorkenntnisse erforderlich. Electron Desktop App Development auf CoddyKit ist für Anfänger bis fortgeschrittene Lernende strukturiert, sodass du hier starten oder von Anfang an beginnen und in deinem eigenen Tempo voranschreiten kannst. Dies ist Lektion 3 von 4.
Wie lange dauert die Lektion „Bildschirmaufnahme und Medien“?
Die meisten CoddyKit-Lektionen dauern etwa 5–10 Minuten. Jede ist kompakt und interaktiv, sodass du stetig Fortschritte machst und genau dort weitermachst, wo du aufgehört hast – im Web und in der App.
Kann ich in dieser Electron Desktop App Development-Lektion Code schreiben und ausführen?
Ja. Jede Electron Desktop App Development-Lektion enthält einen integrierten Code-Editor, sodass du echten Code direkt in deinem Browser schreibst und ausführst und sofort KI-Feedback erhältst — ohne lokale Einrichtung erforderlich.
Alle Lektionen in diesem Kurs
- Arbeiten mit nativen Modulen
- Tray-Anwendungen und Badges
- Bildschirmaufnahme und Medien
- Energie- und Hardwareüberwachung