如何解决我的 android studio 制作的 apk 无法正常工作
我正在使用 Android Studio 3.2 并且我的应用程序正在显示，但按钮没有触发操作请建议任何代码更改，以便它们触发应用程序上的事件
主活动代码是：
package com.example.myfalconcalculator;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
TextView expression;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button num1 = findViewById(R.id.num1);
expression = findViewById(R.id.expression);
Button num2 = findViewById(R.id.num2);
Button num3 = findViewById(R.id.num3);
Button num4 = findViewById(R.id.num4);
Button num5 = findViewById(R.id.num5);
Button num6 = findViewById(R.id.num6);
Button num7 = findViewById(R.id.num7);
Button num8 = findViewById(R.id.num8);
Button num9 = findViewById(R.id.num9);
Button num0 = findViewById(R.id.num0);
Button plus = findViewById(R.id.plus);
Button minus = findViewById(R.id.minus);
Button equalsTo = findViewById(R.id.equalsTo);
Button closeBrace = findViewById(R.id.closeBrace);
Button openBrace = findViewById(R.id.openBrace);
Button clear = findViewById(R.id.clear);
Button delete = findViewById(R.id.delete);
Button exponential = findViewById(R.id.exponential);
Button divideBy = findViewById(R.id.divideBy);
num1.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "1");
}
});
num2.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "2");
}
});
num3.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "3");
}
});
num4.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "4");
}
});
num5.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "5");
}
});
num6.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "6");
}
});
num7.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "7");
}
});
num8.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "8");
}
});
num9.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "9");
}
});
num0.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "0");
}
});
plus.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "+");
}
});
minus.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "-");
}
});
exponential.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "*");
}
});
divideBy.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "/");
}
});
equalsTo.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SimpleMathSolver mathSolver = new SimpleMathSolver(expression.getText().toString());
try {
expression.setText(String.valueOf(mathSolver.solve()));
} catch (Exception e) {
expression.setText("Input Not Valid");
}
}
});
closeBrace.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + ")");
}
});
openBrace.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText(expression.getText().toString() + "(");
}
});
clear.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
expression.setText("");
}
});
delete.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String tempExpression = expression.getText().toString().substring(0,expression.getText().toString().length()-1);
expression.setText(tempExpression);
}
});
}
}
package com.example.myfalconcalculator;
import java.util.Scanner;
import java.util.Stack;
public class SimpleMathSolver {
private String inputExp;
private final char PLUS = '+';
private final char MINUS = '-';
private final char MULTIPLY = '*';
private final char DIVIDE = '/';
private final char OPENBRACE = '(';
private final char CLOSEBRACE = ')';
public SimpleMathSolver(String inputExp) {
this.inputExp = inputExp;
}
public int solve() throws Exception {
String withoutBraceInputExp = solveBraces(this.inputExp);
return solveMath(withoutBraceInputExp);
}
private String solveBraces(String inputExp) throws Exception {
String output = inputExp;
int closeBraceIndex = output.indexOf(CLOSEBRACE);
while (closeBraceIndex >= 0) {
int openBraceIndex = output.substring(0,closeBraceIndex).lastIndexOf(OPENBRACE);
String solveStr = output.substring(openBraceIndex + 1,closeBraceIndex);
int value = solveMath(solveStr);
output = output.substring(0,openBraceIndex) + value
+ output.substring(closeBraceIndex + 1,output.length());
closeBraceIndex = output.indexOf(CLOSEBRACE);
}
return output;
}
private int solveMath(String inputExp) throws Exception {
Stack<Integer> numberStack = new Stack<Integer>();
Stack<Character> symbolStack = new Stack<Character>();
updateStacks(inputExp,numberStack,symbolStack);
solveMathSymbol(numberStack,symbolStack,DIVIDE);
solveMathSymbol(numberStack,MULTIPLY);
solveMathSymbol(numberStack,MINUS);
solveMathSymbol(numberStack,PLUS);
return numberStack.pop();
}
private void solveMathSymbol(Stack<Integer> numberStack,Stack<Character> symbolStack,char symbol) {
Stack<Integer> tempNumberStack = new Stack<Integer>();
Stack<Character> tempSymbolStack = new Stack<Character>();
while (symbolStack.size() > 0) {
char ch = symbolStack.pop();
if (ch == symbol) {
int pop1 = numberStack.pop();
int pop2 = numberStack.pop();
int out = 0;
switch (symbol) {
case PLUS:
out = pop2 + pop1;
break;
case MINUS:
out = pop2 - pop1;
break;
case MULTIPLY:
out = pop2 * pop1;
break;
case DIVIDE:
out = pop2 / pop1;
break;
}
numberStack.push(out);
} else {
tempSymbolStack.push(ch);
int numpop = numberStack.pop();
tempNumberStack.push(numpop);
}
}
while (tempSymbolStack.size() > 0) {
char charpop = tempSymbolStack.pop();
symbolStack.push(charpop);
int numpop = tempNumberStack.pop();
numberStack.push(numpop);
}
}
private void updateStacks(String inputExp,Stack<Integer> numberStack,Stack<Character> symbolStack)
throws Exception {
int number = 0;
for (int i = 0; i < inputExp.length(); i++) {
char ch = inputExp.charat(i);
if (Character.isDigit(ch)) {
number = number * 10 + Integer.parseInt(String.valueOf(ch));
} else {
numberStack.push(number);
number = 0;
if (ch == PLUS || ch == MINUS || ch == MULTIPLY || ch == DIVIDE) {
symbolStack.push(ch);
} else {
throw new Exception("UnkNown Math Symbol " + ch);
}
}
}
numberStack.push(number);
}
public static void main(String[] args) {
Scanner scanner = new Scanner(system.in);
String retryOp = "N";
do {
System.out.println("Enter Math Expression");
String inputExp = scanner.nextLine();
SimpleMathSolver solver = new SimpleMathSolver(inputExp);
try {
System.out.println("Result: " + solver.solve());
} catch (Exception ex) {
ex.printstacktrace();
}
System.out.println("Do you want to try this again");
retryOp = scanner.nextLine();
} while (retryOp.equalsIgnoreCase("Y"));
scanner.close();
System.exit(0);
}
}
这是活动的 main.xml 文件：
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<Button
android:id="@+id/closeBrace"
android:layout_width="74dp"
android:layout_height="76dp"
android:layout_marginEnd="6dp"
android:layout_marginRight="6dp"
android:layout_marginBottom="1dp"
android:text=")"
app:layout_constraintBottom_toTopOf="@+id/equalsTo"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/openBrace"
app:layout_constraintTop_toBottomOf="@+id/divideBy" />
<Button
android:id="@+id/openBrace"
android:layout_width="74dp"
android:layout_height="76dp"
android:layout_marginBottom="1dp"
android:text="("
app:layout_constraintBottom_toTopOf="@+id/equalsTo"
app:layout_constraintEnd_toStartOf="@+id/closeBrace"
app:layout_constraintStart_toEndOf="@+id/num9"
app:layout_constraintTop_toBottomOf="@+id/exponential" />
<Button
android:id="@+id/divideBy"
android:layout_width="74dp"
android:layout_height="76dp"
android:layout_marginEnd="6dp"
android:layout_marginRight="6dp"
android:text="/"
app:layout_constraintBottom_toTopOf="@+id/closeBrace"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/exponential"
app:layout_constraintTop_toBottomOf="@+id/minus" />
<Button
android:id="@+id/exponential"
android:layout_width="74dp"
android:layout_height="76dp"
android:text="*"
app:layout_constraintBottom_toTopOf="@+id/openBrace"
app:layout_constraintEnd_toStartOf="@+id/divideBy"
app:layout_constraintStart_toEndOf="@+id/num6"
app:layout_constraintTop_toBottomOf="@+id/plus" />
<Button
android:id="@+id/plus"
android:layout_width="74dp"
android:layout_height="76dp"
android:text="+"
app:layout_constraintBottom_toTopOf="@+id/exponential"
app:layout_constraintEnd_toStartOf="@+id/minus"
app:layout_constraintStart_toEndOf="@+id/num3"
app:layout_constraintTop_toBottomOf="@+id/delete" />
<Button
android:id="@+id/minus"
android:layout_width="74dp"
android:layout_height="76dp"
android:layout_marginEnd="6dp"
android:layout_marginRight="6dp"
android:text="-"
app:layout_constraintBottom_toTopOf="@+id/divideBy"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/plus"
app:layout_constraintTop_toBottomOf="@+id/delete" />
<Button
android:id="@+id/num0"
android:layout_width="252dp"
android:layout_height="76dp"
android:layout_marginStart="3dp"
android:layout_marginLeft="3dp"
android:layout_marginBottom="5dp"
android:text="0"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/equalsTo"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/num8" />
<Button
android:id="@+id/num5"
android:layout_width="84dp"
android:layout_height="76dp"
android:layout_marginBottom="2dp"
android:text="5"
app:layout_constraintBottom_toTopOf="@+id/num8"
app:layout_constraintEnd_toStartOf="@+id/num6"
app:layout_constraintStart_toEndOf="@+id/num4"
app:layout_constraintTop_toBottomOf="@+id/num2" />
<Button
android:id="@+id/num4"
android:layout_width="84dp"
android:layout_height="76dp"
android:layout_marginStart="5dp"
android:layout_marginLeft="5dp"
android:layout_marginBottom="1dp"
android:text="4"
app:layout_constraintBottom_toTopOf="@+id/num7"
app:layout_constraintEnd_toStartOf="@+id/num5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/num1" />
<Button
android:id="@+id/num6"
android:layout_width="84dp"
android:layout_height="76dp"
android:layout_marginEnd="1dp"
android:layout_marginRight="1dp"
android:layout_marginBottom="2dp"
android:text="6"
app:layout_constraintBottom_toTopOf="@+id/num9"
app:layout_constraintEnd_toStartOf="@+id/exponential"
app:layout_constraintStart_toEndOf="@+id/num5"
app:layout_constraintTop_toBottomOf="@+id/num3" />
<Button
android:id="@+id/num8"
android:layout_width="84dp"
android:layout_height="76dp"
android:layout_marginTop="1dp"
android:text="8"
app:layout_constraintBottom_toTopOf="@+id/num0"
app:layout_constraintEnd_toStartOf="@+id/num9"
app:layout_constraintStart_toEndOf="@+id/num7"
app:layout_constraintTop_toBottomOf="@+id/num5" />
<Button
android:id="@+id/num7"
android:layout_width="84dp"
android:layout_height="76dp"
android:layout_marginStart="5dp"
android:layout_marginLeft="5dp"
android:layout_marginTop="1dp"
android:text="7"
app:layout_constraintBottom_toTopOf="@+id/num0"
app:layout_constraintEnd_toStartOf="@+id/num8"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/num4" />
<Button
android:id="@+id/num9"
android:layout_width="84dp"
android:layout_height="76dp"
android:layout_marginTop="1dp"
android:layout_marginEnd="1dp"
android:layout_marginRight="1dp"
android:text="9"
app:layout_constraintBottom_toTopOf="@+id/num0"
app:layout_constraintEnd_toStartOf="@+id/openBrace"
app:layout_constraintStart_toEndOf="@+id/num8"
app:layout_constraintTop_toBottomOf="@+id/num6" />
<Button
android:id="@+id/num3"
android:layout_width="84dp"
android:layout_height="76dp"
android:text="3"
app:layout_constraintBottom_toTopOf="@+id/num6"
app:layout_constraintEnd_toStartOf="@+id/plus"
app:layout_constraintStart_toEndOf="@+id/num2"
app:layout_constraintTop_toBottomOf="@+id/clear" />
<Button
android:id="@+id/num2"
android:layout_width="84dp"
android:layout_height="76dp"
android:text="2"
app:layout_constraintBottom_toTopOf="@+id/num5"
app:layout_constraintEnd_toStartOf="@+id/num3"
app:layout_constraintStart_toEndOf="@+id/num1"
app:layout_constraintTop_toBottomOf="@+id/clear" />
<Button
android:id="@+id/equalsTo"
android:layout_width="150dp"
android:layout_height="76dp"
android:layout_marginEnd="6dp"
android:layout_marginRight="6dp"
android:layout_marginBottom="5dp"
android:text="="
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/num0"
app:layout_constraintTop_toBottomOf="@+id/num9" />
<Button
android:id="@+id/clear"
android:layout_width="252dp"
android:layout_height="76dp"
android:layout_marginStart="5dp"
android:layout_marginLeft="5dp"
android:layout_marginTop="8dp"
android:text="Clear"
app:layout_constraintEnd_toStartOf="@+id/delete"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/expression" />
<TextView
android:id="@+id/expression"
android:layout_width="400dp"
android:layout_height="331dp"
android:layout_marginStart="5dp"
android:layout_marginLeft="5dp"
android:layout_marginTop="6dp"
android:layout_marginEnd="6dp"
android:layout_marginRight="6dp"
android:layout_marginBottom="8dp"
android:text=""
app:layout_constraintBottom_toTopOf="@+id/clear"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/delete"
android:layout_width="148dp"
android:layout_height="76dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="6dp"
android:layout_marginRight="6dp"
android:text="Delete"
app:layout_constraintBottom_toTopOf="@+id/plus"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/clear"
app:layout_constraintTop_toBottomOf="@+id/expression" />
<Button
android:id="@+id/num1"
android:layout_width="84dp"
android:layout_height="76dp"
android:layout_marginStart="5dp"
android:layout_marginLeft="5dp"
android:text="1"
app:layout_constraintBottom_toTopOf="@+id/num4"
app:layout_constraintEnd_toStartOf="@+id/num2"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/clear" />
</android.support.constraint.ConstraintLayout>
请建议如何解决这个问题。
解决方法
你不能在 oncreate 之外执行 final Button num1 = findViewById(R.id.num1);，你所有的 findViewById(R.id.foo); 语句都必须在 onCreate 内部（或者至少在 onCreate 被调用之后）
Button button;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = findViewById<Button>(R.id.foo)
}
版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 dio@foxmail.com 举报，一经查实，本站将立刻删除。
