Captura de Tela e Mídia
Explore como acessar recursos de captura de tela e dispositivos de mídia e integrá-los às suas aplicações Electron para desktop.
Captura de Tela e Mídia é uma aula grátis de Electron Desktop App Development no CoddyKit. Esta é a aula 3 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de Electron Desktop App Development, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de Electron Desktop App Development inclui 4 aulas no total.
Partes desta aula ainda não foram traduzidas e aparecem em inglês.
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!
Perguntas Frequentes
A aula “Captura de Tela e Mídia” é grátis?
Sim — o texto completo de “Captura de Tela e Mídia” é grátis para ler aqui na web. Para praticá-la interativamente (um editor de código integrado e um tutor de IA 24/7) e desbloquear o restante do curso de Electron Desktop App Development, atualize para CoddyKit PRO. O curso de Electron Desktop App Development inclui 4 aulas no total.
O que vou aprender em “Captura de Tela e Mídia”?
Explore como acessar recursos de captura de tela e dispositivos de mídia e integrá-los às suas aplicações Electron para desktop. Você pratica Electron Desktop App Development com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.
Preciso ter experiência prévia para começar Electron Desktop App Development?
Nenhuma experiência prévia é necessária. Electron Desktop App Development no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 3 de 4.
Quanto tempo leva a aula “Captura de Tela e Mídia”?
A maioria das aulas CoddyKit leva cerca de 5–10 minutos. Cada uma é compacta e interativa, então você faz progresso constante e retoma exatamente de onde parou entre web e app.
Posso escrever e executar código nesta aula de Electron Desktop App Development?
Sim. Cada aula de Electron Desktop App Development inclui um editor de código integrado, então você escreve e executa código real direto no navegador e recebe feedback de IA instantaneamente — nenhuma configuração local necessária.
Todas as aulas deste curso
- Trabalho com Módulos Nativos
- Aplicações na Bandeja e Emblemas
- Captura de Tela e Mídia
- Monitoramento de Energia e Hardware