我对使用SurfaceView感到疯狂。
我开发了一个应用程序,该应用程序以固定的时间间隔拍照。它与我的Androd 2.3设备配合使用时效果很好。这是一个示例代码:
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);
}
}
相同的代码不适用于Android 4.1。仔细搜索一下,我发现“大多数现代Android设备现在都会检查SurfaceView是否存在并且宽度和高度不为零”。所以我修改了上面的代码,如下所示:
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);
}
}
CameraPreview在哪里:
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());
}
}
}
但是不会调用PictureCallback,并且该应用程序的用户界面会消失。用户界面只是一个FrameLayout和一个按钮,如下所示:
<?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,如果我这样做:
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PictureCallback中删除mCamera.release(),它在配备Android 4.1的设备上完美运行。任何意见?
点击后,您将创建-的实例,CameraPreview
这很好,但是会花费一些时间和一些回调。mCamera.takePicture()
在SurfaceView准备就绪之前,您无法打电话-这不会花很长时间,但是仍然需要在这里稍作延迟。最简单的改变将调用mCamera.takePicture()从你的CameraPreview.surfaceCreated()
。
本文收集自互联网,转载请注明来源。
如有侵权,请联系[email protected] 删除。
我来说两句