我有一个项目，通过使用Zxing lib来吸引学生
和Parse.com存储学生信息，但我遇到了问题
从parse.com检索学生姓名时，有时会显示null或我在异常查询中写的任何内容。
这是我在android studio中的java代码。
/**
* Initializes controls, values...
*/
private void init() {
scanButton = (Button) findViewById(R.id.scan_buttun);
scanButton.setOnClickListener(this);
HomeButton = (Button) findViewById(R.id.s_home);
HomeButton.setOnClickListener(this);
saveButton = (Button) findViewById(R.id.save_button);
saveButton.setOnClickListener(this);
showButton = (Button) findViewById(R.id.show_button);
showButton.setOnClickListener(this);
resultTextView = (TextView) findViewById(R.id.result_txt);
}
/ *通过扫描来获取学生ID * /
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
IntentResult scanResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, data);
if(scanResult != null) {
Log.i("SCAN", "scan result: " + scanResult);
re = scanResult.getContents();
resultTextView.setText("Student " + re + " is successfully done" );
} else
Log.e("SCAN", "Sorry, the scan was unsuccessful...");
}
/ *使用来自Parse.com * /
的ID来检索学生姓名public String getStudentInfo (String id_s) {
ParseQuery<ParseObject> query = ParseQuery.getQuery("Student");
query.getInBackground(id_s, new GetCallback<ParseObject>() {
public void done(ParseObject object, ParseException e) {
if (e == null) {
name = object.getString("Name");
} else {
name = "nothing";
}
}
});
return name;
}
@Override
public void onClick(View view) {
int id = view.getId();
if (id == R.id.scan_buttun) {
// start scanning
IntentIntegrator intentIntegrator = new IntentIntegrator(this);
intentIntegrator.initiateScan();
}
if (id == R.id.s_home) {
// start scanning
startActivity(new Intent(scan.this, DriverHome.class));
}
if (id == R.id.save_button) {
// save id in array list
if (student.contains(re)) {
resultTextView.setText("Sorry " + re + " already existing");
} else {
student.add(re);
/* st = student.get(count);
count++;
getStudentInfo(st);*/
resultTextView.setText("Student " + re + " was saved and the total number of students is " + student.size());
}
}
/ *显示数组列表中的名称* /
if (id == R.id.show_button) {
for (int i = 0; i < student.size(); i++) {
student_id = student.get(i);
sName = getStudentInfo(student_id);
names.add(sName);
}
for (int i = 0; i < names.size(); i++) {
resultTextView.setText(names.get(i)+ " ");
}
}
}