如何录制Android应用Activity指定区域视频（无需Root与录屏权限）

Great question! The key here is to avoid system-level screen recording APIs (like MediaProjection) entirely—since those require permissions and show full-screen prompts. Instead, we'll capture your app's own UI directly (within your Activity) and record audio separately, then combine them into a video. This is exactly how apps like the one you referenced work.

Core Approach #

We’ll break this into 3 straightforward steps:

1. Capture frames from the 10dp-offset region of your Activity
2. Record microphone audio
3. Merge the frames and audio into a single video file

1. Capture the Target UI Region #

Since we’re capturing your app’s own View hierarchy, we don’t need any special screen recording permissions. Here’s how to target the 10dp-padding region:

First, convert 10dp to pixel values (adjusts for device density):

int paddingDp = 10;
float density = getResources().getDisplayMetrics().density;
int paddingPx = (int) (paddingDp * density + 0.5f); // Round to nearest pixel

Then capture the relevant region of your Activity’s root View. We’ll use View.draw() for broad compatibility (works pre-API 24):

// Get the root view of your Activity
ViewGroup rootView = findViewById(android.R.id.content);

// Calculate the size of the region to capture
int captureWidth = rootView.getWidth() - 2 * paddingPx;
int captureHeight = rootView.getHeight() - 2 * paddingPx;

// Create a bitmap to hold the captured frame
Bitmap frameBitmap = Bitmap.createBitmap(captureWidth, captureHeight, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(frameBitmap);

// Offset the canvas to only draw the region 10dp inside the Activity bounds
canvas.translate(-paddingPx, -paddingPx);
rootView.draw(canvas);

// Now frameBitmap contains the exact region you want to record

For smooth video, use a Handler to trigger captures at your desired frame rate (e.g., 25 frames per second). Reuse the same Bitmap object to avoid memory bloat.

2. Record Audio #

To capture voice, you’ll need the RECORD_AUDIO permission (unavoidable for audio recording). Add it to your AndroidManifest.xml:

<uses-permission android:name="android.permission.RECORD_AUDIO" />

Request the permission dynamically (required for API 23+), then initialize the audio recorder:

MediaRecorder audioRecorder = new MediaRecorder();
File audioTempFile = new File(getExternalFilesDir(null), "temp_audio.mp4");

try {
    audioRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    audioRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
    audioRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
    audioRecorder.setOutputFile(audioTempFile.getAbsolutePath());
    
    audioRecorder.prepare();
    audioRecorder.start();
} catch (IOException e) {
    e.printStackTrace();
}

3. Combine Frames and Audio into Video #

Use MediaCodec (to encode frames into a video stream) and MediaMuxer (to merge video and audio tracks) to create the final MP4 file.

Quick Overview of the Process:

1. Configure MediaCodec with your capture resolution, frame rate, and H.264 codec (video/avc).
2. Feed each captured Bitmap into the codec as a video frame.
3. Once recording stops, stop the audio recorder and use MediaMuxer to write both the video and audio tracks to a single output file.

If you want to simplify this step, lightweight open-source libraries can handle encoding/muxing without heavy dependencies like FFmpeg.

Why This Works #

• No Root/Screen Record Permissions: We’re only capturing your app’s own UI, not the entire system screen. This avoids the system’s screen recording prompt and root requirements.
• Targeted Region: The canvas offset ensures we precisely record the area 10dp inside your Activity’s bounds.
• Audio Included: Independent audio capture via MediaRecorder lets us merge voice with the video seamlessly.

Important Considerations #

• Performance: Reuse Bitmap objects and avoid unnecessary object creation to prevent memory leaks.
• Frame Rate: Stick to 20-30 FPS for smooth, standard-quality video.
• Permission Handling: Always check and request RECORD_AUDIO permission at runtime for Android 6.0+.

内容的提问来源于stack exchange，提问作者Ashutosh Kumar