Click here to Skip to main content
15,901,122 members
Please Sign up or sign in to vote.
1.44/5 (2 votes)
See more:
public class MainActivity extends AppCompatActivity {

EditText firstname, lastname, age;
Button insert, show;
TextView result;
RequestQueue requestQueue;
String insertUrl = "http://192.168.56.1:8080/tutorial/insertStudent.php";
String showUrl = "http://192.168.56.1:8080/tutorial/showStudents.php";

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);



firstname = (EditText)findViewById(R.id.firstname);
lastname = (EditText)findViewById(R.id.lastname);
lastname = (EditText)findViewById(R.id.age);
insert = (Button)findViewById(R.id.insertstudent);
show = (Button)findViewById(R.id.showstudent);
result = (TextView)findViewById(R.id.textView2);
requestQueue = Volley.newRequestQueue(getApplicationContext());

show.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST,
showUrl, new Response.Listener<jsonobject>() {
@Override
public void onResponse(JSONObject response) {
try {
JSONArray students = response.getJSONArray("students");
for (int i = 0; i < students.length(); i++) {
JSONObject student = students.getJSONObject(i);
String firstname = student.getString("firstname");
String lastname = student.getString("lastname");
String age = student.getString("age");
result.append(firstname + " " + lastname + " " + age + "\n");
}
result.append("===\n");
} catch (JSONException e) {
e.printStackTrace();
}

}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {

Toast.makeText(MainActivity.this,error.toString(), Toast.LENGTH_SHORT).show();
}

});
requestQueue.add(jsonObjectRequest);
int socketTimeout = 30000; // 30 seconds. You can change it
RetryPolicy policy = new DefaultRetryPolicy(socketTimeout,
DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
DefaultRetryPolicy.DEFAULT_BACKOFF_MULT) ;

jsonObjectRequest.setRetryPolicy(policy);
requestQueue.add(jsonObjectRequest);

}

});
insert.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
StringRequest request = new StringRequest(Request.Method.POST, insertUrl, new Response.Listener<string>() {
@Override
public void onResponse(String response) {

}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {

Toast.makeText(MainActivity.this,error.toString(),Toast.LENGTH_SHORT).show();

}
}) {
@Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String, String> parameters = new HashMap<String, String>();
parameters.put("firstname", firstname.getText().toString());
parameters.put("lastname", lastname.getText().toString());
parameters.put("age", age.getText().toString());
return parameters;
}

};

What I have tried:

i tried to insert the data into the database , but it shows null reference error,
can some one help me out of this,
thanks in advance
Posted
Updated 24-Feb-20 22:07pm
v2
Comments
Afzaal Ahmad Zeeshan 13-Sep-17 6:36am    
Which lines show the error?

You need to do a new Type somewhere, because the object is null.

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!
 
Share this answer
 
lastname = (EditText)findViewById(R.id.age);
should have been:
age = (EditText)findViewById(R.id.age);
 
Share this answer
 
Comments
youssef emad 2022 9-Mar-22 8:56am    
Excellent

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)



CodeProject, 20 Bay Street, 11th Floor Toronto, Ontario, Canada M5J 2N8 +1 (416) 849-8900