Android：使用用户输入填充水平进度条

Question

Ok so my program is supposed to help a user keep track of the progress they have made at any particular task.

It has an <EditText> view that will ask a user to input a number, the program has an OnClickListener() that will activate a sequence of code once the user clicks a button to add the numerical input.

The sequence turns this input into a string then an int. The int is added to the progress of a status bar (which is used only as a graphical representation of their progress).

I am getting no errors on Netbeans, and nothing seems to be intuitively wrong with what I wrote, but the app crashes every time I try to run it.This is my first time attempting progress bars so I might just be missing something I'm not seeing. Thanks for any help you are able to provide! I really appreciate it!

package com.example.progresstracker;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;

public class MainActivity extends Activity {

    Button add;
    ProgressBar mProgress;


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

        mProgress.setProgress(0);
        mProgress.setMax(100);
        add = (Button) findViewById(R.id.bAdd);
        mProgress = (ProgressBar) findViewById(R.id.prog);


        add.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                 EditText eText = (EditText) findViewById(R.id.edit);
                 String message = eText.getText().toString();
                 int num = Integer.parseInt(message);


                 mProgress.incrementProgressBy(num);



            }
        });



    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

Answer 1

Try putting this line

mProgress = (ProgressBar) findViewById(R.id.prog);

Before this line

mProgress.setProgress(0);

You need to initialise mProgress before you can start calling its methods.

Ps If you're getting errors its always useful to include the stack trace alongside your code.