我正在运行条形码扫描的示例代码,但是在按下主页按钮之后,我正在使用重新启动应用程序相机不起作用,我的黑屏。有人理解原因吗?
代码:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
autoFocusHandler = new Handler();
mCamera = getCameraInstance();
/* Instance barcode scanner */
scanner = new ImageScanner();
scanner.setConfig(0, Config.X_DENSITY, 3);
scanner.setConfig(0, Config.Y_DENSITY, 3);
mPreview = new CameraPreview(this, mCamera, previewCb, autoFocusCB);
FrameLayout preview = (FrameLayout)findViewById(R.id.cameraPreview);
preview.addView(mPreview);
scanText = (TextView)findViewById(R.id.scanText);
scanButton = (Button)findViewById(R.id.ScanButton);
scanButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
if (barcodeScanned) {
barcodeScanned = false;
scanText.setText("Scanning...");
mCamera.setPreviewCallback(previewCb);
mCamera.startPreview();
previewing = true;
mCamera.autoFocus(autoFocusCB);
}
}
});
}
public void onPause() {
super.onPause();
releaseCamera();
}
/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
Camera c = null;
try {
c = Camera.open();
} catch (Exception e){
}
return c;
}
private void releaseCamera() {
if (mCamera != null) {
previewing = false;
mCamera.setPreviewCallback(null);
mPreview.getHolder().removeCallback(mPreview);
mCamera.release();
mCamera = null;
}
}
private Runnable doAutoFocus = new Runnable() {
public void run() {
if (previewing)
mCamera.autoFocus(autoFocusCB);
}
};
PreviewCallback previewCb = new PreviewCallback() {
public void onPreviewFrame(byte[] data, Camera camera) {
Camera.Parameters parameters = camera.getParameters();
Size size = parameters.getPreviewSize();
Image barcode = new Image(size.width, size.height, "Y800");
barcode.setData(data);
int result = scanner.scanImage(barcode);
if (result != 0) {
previewing = false;
mCamera.setPreviewCallback(null);
mCamera.stopPreview();
SymbolSet syms = scanner.getResults();
for (Symbol sym : syms) {
scanText.setText("barcode result " + sym.getData());
barcodeScanned = true;
}
}
}
};
// Mimic continuous auto-focusing
AutoFocusCallback autoFocusCB = new AutoFocusCallback() {
public void onAutoFocus(boolean success, Camera camera) {
autoFocusHandler.postDelayed(doAutoFocus, 1000);
}
};
答案 0 :(得分:0)
您可以尝试在Camera.release()
方法中调用onPause()
。
答案 1 :(得分:0)
总是成对地做这样的事情。如果您在onPause()中释放相机,请在onResume()中获取并启动预览,而不是onCreate()。当你回到家时,你的活动将被暂停,但不会被销毁。因此,您释放相机,当您回来时,您的活动将恢复。由于除了onCreate()之外你从不重新初始化相机,这就是你没有看到预览的原因。