如何在我的Android应用中录制视频？

不必从头编写代码，你可以在GitHub上使用库。例如：https://github.com/CameraKit/camerakit-android（或 https://github.com/google/cameraview，或 https://github.com/hujiaweibujidao/CameraView等）。然后你只需要：

private CameraKitView cameraKitView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    cameraKitView = findViewById(R.id.camera);
}

@Override
protected void onStart() {
    super.onStart();
    cameraKitView.onStart();
}

@Override
protected void onResume() {
    super.onResume();
    cameraKitView.onResume();
}

@Override
protected void onPause() {
    cameraKitView.onPause();
    super.onPause();
}

@Override
protected void onStop() {
    cameraKitView.onStop();
    super.onStop();
}

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    cameraKitView.onRequestPermissionsResult(requestCode, permissions, grantResults);
}