【发布时间】：2016-12-22 08:50:26
【问题描述】：
我正在开发条形码扫描仪应用程序，在第一个 Activity 中单击按钮时，我将转到 BarcodeScanner Activity，我正在导入 Zxing 库功能。扫描完成后，我将转到第三个活动，我将在其中显示扫描的结果。单击第三个活动中的按钮后，我将回到第一个活动。对于具有 Marshmallow 的设备，代码运行良好。但是问题出现在版本低于棉花糖的设备上，从第三个活动返回到第一个活动后，当我再次按下按钮时，扫描仪活动出现但相机没有启动。它只是显示一个空白页。请帮忙。下面我发布了所有 3 项活动的代码。
First Activity:
public class FirstActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_first);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
getWindow().addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
getWindow().setStatusBarColor(Color.parseColor("#FDB50A"));
}
ImageView Scan= (ImageView) findViewById(R.id.scanButton);
Scan.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
FirstActivity.this.finish();
Intent nextPage= new Intent(FirstActivity.this,MainActivity.class);
startActivity(nextPage);
}
});
ScannerActivity:
public class MainActivity extends AppCompatActivity implements ZXingScannerView.ResultHandler{
Integer response = 0 ;
int currentIndex=0;
Boolean flash=false;
DataBaseHelper dataBaseHelper;
private ZXingScannerView mScannerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.e("onCreate", "onCreate");
checkPermissions();
mScannerView = new ZXingScannerView(this);
mScannerView.setResultHandler(this);
boolean cam= isCameraUsebyApp();
Log.d("cameraBar",cam+"");
if(cam)
{
mScannerView.stopCamera();
}
cam= isCameraUsebyApp();
Log.d("cameraBar",cam+"");
mScannerView.startCamera();
// FrameLayout frameLayout= new FrameLayout(this);
// FrameLayout.LayoutParams mainParam= new FrameLayout.LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT);
// frameLayout.setLayoutParams(mainParam);
// Button scanButton= new Button(this);
dataBaseHelper= new DataBaseHelper(this);
if(dataBaseHelper.checkDataBase()==false)
{
try {
dataBaseHelper.createDataBase();
} catch (IOException e)
{
e.printStackTrace();
}
}
else{
}
Log.d("AnimeshSQL","copy");
dataBaseHelper.openDataBase();
// List<String> data=dataBaseHelper.getQuotes("n",1);
// Log.d("AnimeshSQL",data.get(0).toString());
LayoutParams params =
new LinearLayout.LayoutParams(
LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT);
// scanButton.setBackground(getResources().getDrawable(R.drawable.round_button));
// scanButton.setText("Flash");
// scanButton.setOnClickListener(new View.OnClickListener() {
// @Override
// public void onClick(View v) {
// if(flash==false)
// {
// flash=true;
//
//
// }
// else
// {
// flash=false;
// }
// mScannerView.setFlash(flash);
// }
// });
// scanButton.setLayoutParams(params);
// frameLayout.addView(mScannerView);
// frameLayout.addView(scanButton);
// setContentView(mScannerView);
checkPermissions();
if(response == 1) {
mScannerView = null;
mScannerView = new ZXingScannerView(this);
setContentView(mScannerView);
response = 0;
}
}
public boolean isCameraUsebyApp() {
Camera camera = null;
try {
camera = Camera.open();
} catch (RuntimeException e) {
return true;
} finally {
if (camera != null) camera.release();
}
return false;
}
private void checkPermissions() {
try {
for (int i = currentIndex; i < permissions.length; i++) {
currentIndex = currentIndex + 1;
int result = ContextCompat.checkSelfPermission(context, permissions[i]);
if (result == PackageManager.PERMISSION_GRANTED) {
} else {
requestPermission(permissions[i]);
return;
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
Activity activity = this;
Context context = this;
String[] permissions = new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE};
private void requestPermission(String permission) {
//
ActivityCompat.requestPermissions(activity, new String[]{permission}, 101);
//
}
@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
switch (requestCode) {
case 101:
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
//
checkPermissions();
} else {
try {
// FuncUtils.showToast(context, permissions[0] + " Denied!!!");
} catch (Exception e) {
e.printStackTrace();
}
//
///
}
break;
}
}
@Override
public void onResume() {
super.onResume();
if(response == 1) {
mScannerView = null;
mScannerView = new ZXingScannerView(this);
setContentView(mScannerView);
response = 0;
}
mScannerView.setResultHandler(this);
mScannerView.startCamera();
}
@Override
public void onDestroy() {
super.onDestroy();
mScannerView.stopCamera();
}
@Override
protected void onRestart() {
super.onRestart();
Log.d("ani","onrestart");
}
@Override
public void handleResult(Result rawResult)
{
//Some codes to handle the result
Intent intent= new Intent(this,ScanResultActivity.class);
startActivity(intent);
//vbn
mScannerView.stopCamera();
MainActivity.this.finish();
}
}
Final Activity:
public class ScanResultActivity extends AppCompatActivity {
SharedPreferences prefs;
Button ok;
ImageView Hubbell,CI;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_scan_result);
prefs = getSharedPreferences("ScanPref", MODE_PRIVATE);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
getWindow().addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
getWindow().setStatusBarColor(Color.parseColor("#FDB50A"));
}
//Codes to show the data
ok.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
ScanResultActivity.this.finish();
Intent nextPage= new Intent(ScanResultActivity.this,FirstActivity.class);
startActivity(nextPage);
}
});
【问题讨论】：