Android onClick method error

Question

I am trying to make a simple calculator in android.

Details:

I have multiple buttons, and have set the onClick method in all of the button views. What i do is get the ID of individual by the switch statement. For testing purpose i have just made the percent button clickable, and tried to show the text of the button in the EditText.

But When I click the button the app crashe.

this is my code:

public class MainActivity extends Activity {

    Button  show_cam_ctrl,
            show_voice_ctrl,
            cal_btn_clear,
            cal_btn_del,
            cal_btn_percent,
            cal_btn_divide,
            cal_btn_plus,
            cal_btn_pi,
            cal_btn_root,
            cal_btn_dot,
            cal_btn_equal,
            cal_btn_power,
            cal_btn_ptrl,
            cal_btn_sin, cal_btn_cos, cal_btn_tan,
            cal_btn_sinIn, cal_btn_cosIn, cal_btn_tanIn,
            cal_btn_0, cal_btn_1, cal_btn_2, cal_btn_3, cal_btn_4, cal_btn_5, cal_btn_6, cal_btn_7, cal_btn_8, cal_btn_9;

    TextView ma_res_txt;

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

        //Control Buttons
        show_cam_ctrl = (Button) findViewById(R.id.show_cam_ctrl);
        show_voice_ctrl = (Button) findViewById(R.id.show_voice_ctrl);

        show_cam_ctrl.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(MainActivity.this,cam_calculator.class);
                startActivity(i);
            }
        });
        show_voice_ctrl.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i = new Intent(MainActivity.this,voice_calculator.class);
                startActivity(i);
            }
        });


    }

    //Calculator main page logic

    public void calculate(View v){

        ma_res_txt = (TextView) findViewById(R.id.ma_res_txt);
        String t;
        int length = ma_res_txt.getText().length();

        switch (v.getId()){


            case R.id.cal_btn_clear:{
                ma_res_txt.setText("");
                break;
            }
            case R.id.cal_btn_del:{
                String text = ma_res_txt.getText().toString();
                ma_res_txt.setText(text.substring(0, text.length() - 1));
            }


            case R.id.cal_btn_percent:{
                t = "%";
                ma_res_txt.setText(t);
                break;
            }


        }

    }






    @Override
    public void finish() {
        super.finish();
    }




}

logcat:

07-29 12:19:10.734 27279-27279/com.example.nadeemahmad.smartcalculator E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.nadeemahmad.smartcalculator, PID: 27279 java.lang.IllegalStateException: Could not find method calculate()(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.widget.Button with id 'cal_btn_percent' at android.view.View$DeclaredOnClickListener.resolveMethod(View.java:5076) at android.view.View$DeclaredOnClickListener.onClick(View.java:5035) at android.view.View.performClick(View.java:6205) at android.widget.TextView.performClick(TextView.java:11103) at android.view.View$PerformClick.run(View.java:23653) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6682) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)

Answer 1

Define id of all Buttons like

show_cam_ctrl = (Button) findViewById(R.id.show_cam_ctrl);

and then define particular function in particular button click event like below code;

 show_cam_ctrl.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
         calculate();
        }
    });

and then code for particular function outside of onCreate() method.

Answer 2

check your xml button code if you added calculate() in onClick then remove ()

  <Button 
   android:id="@+id/cal_btn_percent"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="calculate()" />

to change remove ()

<Button android:id="@+id/cal_btn_percent"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="calculate" />