Java 什么'；我的计算器应用程序出了什么问题？
我正在尝试创建一个基本的计算器应用程序。我只是想让这个基本的应用程序工作，它包括一个十进制按钮以及。以下是我用java编写和收集的代码：Java 什么'；我的计算器应用程序出了什么问题？,java,android,Java,Android,我正在尝试创建一个基本的计算器应用程序。我只是想让这个基本的应用程序工作，它包括一个十进制按钮以及。以下是我用java编写和收集的代码： public class MainActivity extends Activity implements OnClickListener{ TextView main; private long operand1; private long operand2; private long result; private String operator; pr
public class MainActivity extends Activity implements OnClickListener{
TextView main;
private long operand1;
private long operand2;
private long result;
private String operator;
private StringBuilder set1;
private StringBuilder set2;
Button zero;
Button one;
Button two;
Button three;
Button four;
Button five;
Button six;
Button seven;
Button eight;
Button nine;
Button times;
Button clear;
Button equal;
Button decimal;
Button divide;
Button add;
Button subtract;
/* (non-Javadoc)
* @see android.app.Activity#onCreate(android.os.Bundle)
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// declare all buttons used within the layout
zero = (Button) findViewById(R.id.button0);
one = (Button) findViewById(R.id.button1);
two = (Button) findViewById(R.id.button2);
three = (Button) findViewById(R.id.button3);
four = (Button) findViewById(R.id.button4);
five = (Button) findViewById(R.id.button5);
six = (Button) findViewById(R.id.button6);
seven = (Button) findViewById(R.id.button7);
eight = (Button) findViewById(R.id.button8);
nine = (Button) findViewById(R.id.button9);
times = (Button) findViewById(R.id.buttontimes);
clear = (Button) findViewById(R.id.buttonClear);
equal = (Button) findViewById(R.id.buttonEqual);
decimal = (Button) findViewById(R.id.buttonDecimal);
divide = (Button) findViewById(R.id.buttondivide);
add = (Button) findViewById(R.id.buttonplus);
subtract = (Button) findViewById(R.id.buttonminus);
// declare main text view
TextView main = (TextView) findViewById(R.id.CalculatorText);
zero.setOnClickListener(this);
one.setOnClickListener(this);
two.setOnClickListener(this);
three.setOnClickListener(this);
four.setOnClickListener(this);
five.setOnClickListener(this);
six.setOnClickListener(this);
seven.setOnClickListener(this);
eight.setOnClickListener(this);
nine.setOnClickListener(this);
equal.setOnClickListener(this);
subtract.setOnClickListener(this);
times.setOnClickListener(this);
divide.setOnClickListener(this);
add.setOnClickListener(this);
clear.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch(v.getId()) {
case R.id.button0:
main.append(zero.getText());
if(operand1 == -1)
{
set1.append(zero.getText().toString());
}
else
{
set2.append(zero.getText().toString());
}
break;
case R.id.button1:
main.append(one.getText());
if(operand1 == -1)
{
set1.append(one.getText().toString());
}
else
{
set2.append(one.getText().toString());
operand2 = Long.parseLong(set2.toString());
}
break;
case R.id.button2:
main.append(two.getText());
if(operand1 == -1)
{
set1.append(two.getText().toString());
}
else
{
set2.append(two.getText().toString());
operand2 = Long.parseLong(set2.toString());
}
break;
case R.id.button3:
main.append(three.getText());
if(operand1 == -1)
{
set1.append(three.getText().toString());
}
else
{
set2.append(three.getText().toString());
}
break;
case R.id.button4:
main.append(four.getText());
if(operand1 == -1)
{
set1.append(four.getText().toString());
}
else
{
set2.append(four.getText().toString());
}
break;
case R.id.button5:
main.append(five.getText());
if(operand1 == -1)
{
set1.append(five.getText().toString());
}
else
{
set2.append(five.getText().toString());
}
break;
case R.id.button6:
main.append(six.getText());
if(operand1 == -1)
{
set1.append(six.getText().toString());
}
else
{
set2.append(six.getText().toString());
}
break;
case R.id.button7:
main.append(seven.getText());
if(operand1 == -1)
{
set1.append(seven.getText().toString());
}
else
{
set2.append(seven.getText().toString());
}
break;
case R.id.button8:
main.append(eight.getText());
if(operand1 == -1)
{
set1.append(eight.getText().toString());
}
else
{
set2.append(eight.getText().toString());
}
break;
case R.id.button9:
main.append(nine.getText());
if(operand1 == -1)
{
set1.append(nine.getText().toString());
}
else
{
set2.append(nine.getText().toString());
}
break;
case R.id.buttonplus:
if(operand1 == -1)
{
operator = "+";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttonminus:
if(operand1 == -1)
{
operator = "-";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttontimes:
if(operand1 == -1)
{
operator = "*";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttondivide:
if(operand1 == -1)
{
operator = "/";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttonEqual:
operand2 = Long.parseLong(set2.toString());
switch(operator)
{
case "+":
result = operand1 + operand2;
case "-":
result = operand1 - operand2;
case "*":
result = operand1 * operand2;
case "/":
result = operand1 / operand2;
}
main.setText(""+result);
operator = null;
operand1 = -1;
operand2 = -1;
set1.setLength(0);
set2.setLength(0);
break;
case R.id.buttonClear:
main.setText("");
operator = null;
operand1 = -1;
operand2 = -1;
set1.setLength(0);
set2.setLength(0);
break;
case R.id.buttonDecimal:
main.append(decimal.getText());
if(operand1 == -1)
{
set1.append(decimal.getText().toString());
}
else
{
set2.append(decimal.getText().toString());
}
break;
}
}
11-08 15:14:45.521 26350-26350/com.example.chrisjw1.lab2 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.chrisjw1.lab2, PID: 26350
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.append(java.lang.CharSequence)' on a null object reference
at com.example.lab2.MainActivity.onClick(MainActivity.java:138)
at android.view.View.performClick(View.java:4764)
at android.view.View$PerformClick.run(View.java:19833)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5290)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:908)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:703)
这意味着我从getText调用返回的数据为空。有人能帮我解决这个问题吗？
TextViewonClick（）TextViewonCreate（）TextViewTextView main = (TextView) findViewById(R.id.CalculatorText);
public class MainActivity extends Activity implements OnClickListener{
TextView main;
private long operand1;
private long operand2;
private long result;
private String operator;
private StringBuilder set1;
private StringBuilder set2;
Button zero;
Button one;
Button two;
Button three;
Button four;
Button five;
Button six;
Button seven;
Button eight;
Button nine;
Button times;
Button clear;
Button equal;
Button decimal;
Button divide;
Button add;
Button subtract;
/* (non-Javadoc)
* @see android.app.Activity#onCreate(android.os.Bundle)
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// declare all buttons used within the layout
zero = (Button) findViewById(R.id.button0);
one = (Button) findViewById(R.id.button1);
two = (Button) findViewById(R.id.button2);
three = (Button) findViewById(R.id.button3);
four = (Button) findViewById(R.id.button4);
five = (Button) findViewById(R.id.button5);
six = (Button) findViewById(R.id.button6);
seven = (Button) findViewById(R.id.button7);
eight = (Button) findViewById(R.id.button8);
nine = (Button) findViewById(R.id.button9);
times = (Button) findViewById(R.id.buttontimes);
clear = (Button) findViewById(R.id.buttonClear);
equal = (Button) findViewById(R.id.buttonEqual);
decimal = (Button) findViewById(R.id.buttonDecimal);
divide = (Button) findViewById(R.id.buttondivide);
add = (Button) findViewById(R.id.buttonplus);
subtract = (Button) findViewById(R.id.buttonminus);
//Use outside textview delcared
main = (TextView) findViewById(R.id.CalculatorText);
zero.setOnClickListener(this);
one.setOnClickListener(this);
two.setOnClickListener(this);
three.setOnClickListener(this);
four.setOnClickListener(this);
five.setOnClickListener(this);
six.setOnClickListener(this);
seven.setOnClickListener(this);
eight.setOnClickListener(this);
nine.setOnClickListener(this);
equal.setOnClickListener(this);
subtract.setOnClickListener(this);
times.setOnClickListener(this);
divide.setOnClickListener(this);
add.setOnClickListener(this);
clear.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch(v.getId()) {
case R.id.button0:
main.append(zero.getText());
if(operand1 == -1)
{
set1.append(zero.getText().toString());
}
else
{
set2.append(zero.getText().toString());
}
break;
case R.id.button1:
main.append(one.getText());
if(operand1 == -1)
{
set1.append(one.getText().toString());
}
else
{
set2.append(one.getText().toString());
operand2 = Long.parseLong(set2.toString());
}
break;
case R.id.button2:
main.append(two.getText());
if(operand1 == -1)
{
set1.append(two.getText().toString());
}
else
{
set2.append(two.getText().toString());
operand2 = Long.parseLong(set2.toString());
}
break;
case R.id.button3:
main.append(three.getText());
if(operand1 == -1)
{
set1.append(three.getText().toString());
}
else
{
set2.append(three.getText().toString());
}
break;
case R.id.button4:
main.append(four.getText());
if(operand1 == -1)
{
set1.append(four.getText().toString());
}
else
{
set2.append(four.getText().toString());
}
break;
case R.id.button5:
main.append(five.getText());
if(operand1 == -1)
{
set1.append(five.getText().toString());
}
else
{
set2.append(five.getText().toString());
}
break;
case R.id.button6:
main.append(six.getText());
if(operand1 == -1)
{
set1.append(six.getText().toString());
}
else
{
set2.append(six.getText().toString());
}
break;
case R.id.button7:
main.append(seven.getText());
if(operand1 == -1)
{
set1.append(seven.getText().toString());
}
else
{
set2.append(seven.getText().toString());
}
break;
case R.id.button8:
main.append(eight.getText());
if(operand1 == -1)
{
set1.append(eight.getText().toString());
}
else
{
set2.append(eight.getText().toString());
}
break;
case R.id.button9:
main.append(nine.getText());
if(operand1 == -1)
{
set1.append(nine.getText().toString());
}
else
{
set2.append(nine.getText().toString());
}
break;
case R.id.buttonplus:
if(operand1 == -1)
{
operator = "+";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttonminus:
if(operand1 == -1)
{
operator = "-";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttontimes:
if(operand1 == -1)
{
operator = "*";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttondivide:
if(operand1 == -1)
{
operator = "/";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttonEqual:
operand2 = Long.parseLong(set2.toString());
switch(operator)
{
case "+":
result = operand1 + operand2;
case "-":
result = operand1 - operand2;
case "*":
result = operand1 * operand2;
case "/":
result = operand1 / operand2;
}
main.setText(""+result);
operator = null;
operand1 = -1;
operand2 = -1;
set1.setLength(0);
set2.setLength(0);
break;
case R.id.buttonClear:
main.setText("");
operator = null;
operand1 = -1;
operand2 = -1;
set1.setLength(0);
set2.setLength(0);
break;
case R.id.buttonDecimal:
main.append(decimal.getText());
if(operand1 == -1)
{
set1.append(decimal.getText().toString());
}
else
{
set2.append(decimal.getText().toString());
}
break;
}
}
请把你的xml文件放进去
public class MainActivity extends Activity implements OnClickListener{
TextView main;
private long operand1;
private long operand2;
private long result;
private String operator;
private StringBuilder set1;
private StringBuilder set2;
Button zero;
Button one;
Button two;
Button three;
Button four;
Button five;
Button six;
Button seven;
Button eight;
Button nine;
Button times;
Button clear;
Button equal;
Button decimal;
Button divide;
Button add;
Button subtract;
/* (non-Javadoc)
* @see android.app.Activity#onCreate(android.os.Bundle)
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// declare all buttons used within the layout
zero = (Button) findViewById(R.id.button0);
one = (Button) findViewById(R.id.button1);
two = (Button) findViewById(R.id.button2);
three = (Button) findViewById(R.id.button3);
four = (Button) findViewById(R.id.button4);
five = (Button) findViewById(R.id.button5);
six = (Button) findViewById(R.id.button6);
seven = (Button) findViewById(R.id.button7);
eight = (Button) findViewById(R.id.button8);
nine = (Button) findViewById(R.id.button9);
times = (Button) findViewById(R.id.buttontimes);
clear = (Button) findViewById(R.id.buttonClear);
equal = (Button) findViewById(R.id.buttonEqual);
decimal = (Button) findViewById(R.id.buttonDecimal);
divide = (Button) findViewById(R.id.buttondivide);
add = (Button) findViewById(R.id.buttonplus);
subtract = (Button) findViewById(R.id.buttonminus);
//Use outside textview delcared
main = (TextView) findViewById(R.id.CalculatorText);
zero.setOnClickListener(this);
one.setOnClickListener(this);
two.setOnClickListener(this);
three.setOnClickListener(this);
four.setOnClickListener(this);
five.setOnClickListener(this);
six.setOnClickListener(this);
seven.setOnClickListener(this);
eight.setOnClickListener(this);
nine.setOnClickListener(this);
equal.setOnClickListener(this);
subtract.setOnClickListener(this);
times.setOnClickListener(this);
divide.setOnClickListener(this);
add.setOnClickListener(this);
clear.setOnClickListener(this);
}
@Override
public void onClick(View v) {
switch(v.getId()) {
case R.id.button0:
main.append(zero.getText());
if(operand1 == -1)
{
set1.append(zero.getText().toString());
}
else
{
set2.append(zero.getText().toString());
}
break;
case R.id.button1:
main.append(one.getText());
if(operand1 == -1)
{
set1.append(one.getText().toString());
}
else
{
set2.append(one.getText().toString());
operand2 = Long.parseLong(set2.toString());
}
break;
case R.id.button2:
main.append(two.getText());
if(operand1 == -1)
{
set1.append(two.getText().toString());
}
else
{
set2.append(two.getText().toString());
operand2 = Long.parseLong(set2.toString());
}
break;
case R.id.button3:
main.append(three.getText());
if(operand1 == -1)
{
set1.append(three.getText().toString());
}
else
{
set2.append(three.getText().toString());
}
break;
case R.id.button4:
main.append(four.getText());
if(operand1 == -1)
{
set1.append(four.getText().toString());
}
else
{
set2.append(four.getText().toString());
}
break;
case R.id.button5:
main.append(five.getText());
if(operand1 == -1)
{
set1.append(five.getText().toString());
}
else
{
set2.append(five.getText().toString());
}
break;
case R.id.button6:
main.append(six.getText());
if(operand1 == -1)
{
set1.append(six.getText().toString());
}
else
{
set2.append(six.getText().toString());
}
break;
case R.id.button7:
main.append(seven.getText());
if(operand1 == -1)
{
set1.append(seven.getText().toString());
}
else
{
set2.append(seven.getText().toString());
}
break;
case R.id.button8:
main.append(eight.getText());
if(operand1 == -1)
{
set1.append(eight.getText().toString());
}
else
{
set2.append(eight.getText().toString());
}
break;
case R.id.button9:
main.append(nine.getText());
if(operand1 == -1)
{
set1.append(nine.getText().toString());
}
else
{
set2.append(nine.getText().toString());
}
break;
case R.id.buttonplus:
if(operand1 == -1)
{
operator = "+";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttonminus:
if(operand1 == -1)
{
operator = "-";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttontimes:
if(operand1 == -1)
{
operator = "*";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttondivide:
if(operand1 == -1)
{
operator = "/";
operand1 = Long.parseLong(set1.toString());
main.append(operator);
}
break;
case R.id.buttonEqual:
operand2 = Long.parseLong(set2.toString());
switch(operator)
{
case "+":
result = operand1 + operand2;
case "-":
result = operand1 - operand2;
case "*":
result = operand1 * operand2;
case "/":
result = operand1 / operand2;
}
main.setText(""+result);
operator = null;
operand1 = -1;
operand2 = -1;
set1.setLength(0);
set2.setLength(0);
break;
case R.id.buttonClear:
main.setText("");
operator = null;
operand1 = -1;
operand2 = -1;
set1.setLength(0);
set2.setLength(0);
break;
case R.id.buttonDecimal:
main.append(decimal.getText());
if(operand1 == -1)
{
set1.append(decimal.getText().toString());
}
else
{
set2.append(decimal.getText().toString());
}
break;
}
}