如果单击，我尝试启动相机的 SurfaceCallback Button，但我不能，如果我没有Camera.setPreviewCallback()调用，尽管它在我SurfaceHolder.Callback()从onCreat()方法中调用，如下面的代码所示
public class HeartRateMonitor extends ActionBarActivity {
private static final String TAG = "HeartRateMonitor";
private static SurfaceView preview = null;
private static SurfaceHolder previewHolder = null;
private static Camera camera ;
private static View image = null;
private static TextView text = null;
private static WakeLock wakeLock = null;
private static long startTime = 0;
static Context context;
static CircleButton cb ;
static int txt ;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
PlaceholderFragment p = new PlaceholderFragment() ;
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.contain, p)
.commit();
}
preview = (SurfaceView) findViewById(R.id.preview);
previewHolder = preview.getHolder();
previewHolder.addCallback(surfaceCallback);
previewHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
image = findViewById(R.id.image);
text = (TextView) findViewById(R.id.text);
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
wakeLock = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK, "DoNotDimScreen");
HeartRateMonitor.context = getApplicationContext();
}
class PlaceholderFragment extends Fragment implements View.OnClickListener {
// this Fragment for Circular Button .
View rootView ;
public PlaceholderFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.start, container, false);
cb = (CircleButton) rootView.findViewById(R.id.startButton);
cb.setImageResource(R.drawable.start);
cb.isClickable();
cb.findViewById(R.id.startButton).setOnClickListener(this);
return rootView;
}
@Override
public void onClick(View v) {
// Toast.makeText(getActivity(), "Button clicked", Toast.LENGTH_SHORT).show();
cb.setImageResource(R.drawable.stop);
start();
}
}
public void start(){
// here i want start preview .
}
@Override
protected void onResume() {
super.onResume();
wakeLock.acquire();
camera = Camera.open();
startTime = System.currentTimeMillis();
}
@Override
public void onPause() {
super.onPause();
wakeLock.release();
camera = null;
}
private static PreviewCallback previewCallback = new PreviewCallback() {
@Override
public void onPreviewFrame(byte[] data, Camera cam) {
// process preview data here .
}
};
private static SurfaceHolder.Callback surfaceCallback = new SurfaceHolder.Callback() {
@Override
public void surfaceCreated(SurfaceHolder holder) {
try {
camera.setPreviewDisplay(previewHolder);
camera.setPreviewCallback(previewCallback);
} catch (Throwable t) {
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
Camera.Parameters parameters = camera.getParameters();
parameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
Camera.Size size = getSmallestPreviewSize(width, height, parameters);
if (size != null) {
parameters.setPreviewSize(size.width, size.height);
}
camera.setParameters(parameters);
camera.startPreview();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// Ignore
}
};
private static Camera.Size getSmallestPreviewSize(int width, int height, Camera.Parameters parameters) {
Camera.Size result = null;
for (Camera.Size size : parameters.getSupportedPreviewSizes()) {
if (size.width <= width && size.height <= height) {
if (result == null) {
result = size;
} else {
int resultArea = result.width * result.height;
int newArea = size.width * size.height;
if (newArea < resultArea) result = size;
}
}
}
return result;
}
}