摄像头和SurfaceView奇怪的行为 [英] Strange behaviour with Camera and SurfaceView
问题描述
我要疯了与使用SurfaceView的。
I'm going crazy with the use of SurfaceView.
我已经开发了一个应用程序，它在固定的时间间隔拍摄照片。它与我的设备与Androd 2.3效果很好。下面是一个示例code：
I've developed an app which takes pictures at fixed time intervals. It works well with my device with Androd 2.3. Here is a sample code:
public class MainActivity extends Activity
{
private Camera mCamera;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button captureButton = (Button) findViewById(R.id.button_capture);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
takeAPicture();
}
}
);
}
private PictureCallback mPicture = new PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera)
{
// ... save image ...
camera.release();
camera = null;
}
};
private void takeAPicture()
{
mCamera = getCameraInstance();
mCamera.takePicture(null, null, mPicture);
}
}
在同一code不与Android 4.1的工作。谷歌上搜索了一下，我发现，大多数现代的Android设备，现在检查一个SurfaceView存在并具有非零的宽度和高度。所以，我修改了上面的code如下：
The same code does not work with Android 4.1. Googling a bit I've found that "most of the modern Android devices now check that a SurfaceView exists and has a non-zero width and height". So I've modified the above code as follows:
public class MainActivity extends Activity
{
private Camera mCamera;
private CameraPreview mPreview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button captureButton = (Button) findViewById(R.id.button_capture);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
takeAPicture();
}
}
);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
private PictureCallback mPicture = new PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera)
{
// ... save image ...
camera.release();
camera = null;
}
};
private void takeAPicture()
{
mCamera = getCameraInstance();
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
mCamera.takePicture(null, null, mPicture);
}
}
在那里摄像头preVIEW是：
where CameraPreview is:
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
public CameraPreview(Context context, Camera camera)
{
super(context);
mCamera = camera;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
// deprecated setting, but required on Android versions prior to 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder)
{
// The Surface has been created, now tell the camera where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log.d(MainActivity.TAG, "Error setting camera preview: " + e.getMessage());
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// empty. Take care of releasing the Camera preview in your activity.
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
if (mHolder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
Log.d(MainActivity.TAG, "Error starting camera preview: " + e.getMessage());
}
}
}
但PictureCallback不调用和应用程序的用户界面消失。用户界面是一个简单的的FrameLayout和一个按钮如下：
But the PictureCallback is not invoked and the user interface of the app disappear. The user interface is simply a FrameLayout and a button as follows:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<FrameLayout
android:id="@+id/camera_preview"
android:layout_width="100dp"
android:layout_height="100dp" />
<Button
android:id="@+id/button_capture"
android:text="Capture"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
怎么了？
请注意，如果我做的：
public class MainActivity extends Activity
{
private Camera mCamera;
private CameraPreview mPreview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mCamera = getCameraInstance();
mPreview = new CameraPreview(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
Button captureButton = (Button) findViewById(R.id.button_capture);
captureButton.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
mCamera.takePicture(null, null, mPicture);
}
}
);
}
当然，从本PictureCallback的mCamera.release（）的，它完美的作品与Android 4.1的设备上。任何意见？
of course removing the mCamera.release() from the PictureCallback, it works perfectly on a device with Android 4.1. Any comment?
推荐答案
在点击，您可以创建相机preVIEW 的一个实例 - 这是好的，但需要时间和一些回调。你不能叫 mCamera.takePicture（）直到 SurfaceView 准备 - 这不会需要很长时间，但你仍然需要在这里的延迟。最简单的变化将是调用 mCamera.takePicture（）从相机preview.surfaceCreated（）。
On click, you create an instance of CameraPreview - which is fine, but takes time and some callbacks. You cannot call mCamera.takePicture() until the SurfaceView is ready - this won't take long, but still you need a delay here. The easiest change would be to call mCamera.takePicture() from your CameraPreview.surfaceCreated().
这篇关于摄像头和SurfaceView奇怪的行为的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
