Android应用程序不断崩溃（Android Studio）

Question

我想在android studio中设计一个简单的计算器，但是每当我在模拟器上运行我的应用程序时，它都会崩溃。经过几次尝试后，它最终打开并显示UI，但每当我点击一个按钮时，它就会崩溃。我是新来的android工作室，所以一些提示如何我的代码导致它崩溃，将不胜感激。

这是我的XML：

<?xml version="1.0" encoding="utf-8"?><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="com.calc.basiccalculator.MainActivity" 
tools:layout_editor_absoluteY="81dp" 
tools:layout_editor_absoluteX="0dp"> 

<TextView 
    android:id="@+id/outputText" 
    android:layout_width="0dp" 
    android:layout_height="47dp" 
    android:text="0" 
    android:textAlignment="textEnd" 
    android:textSize="33dp" 
    android:layout_marginRight="17dp" 
    android:layout_marginBottom="19dp" 
    android:layout_marginEnd="17dp" 

    tools:layout_constraintTop_creator="1" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/equals" 
    android:layout_marginStart="17dp" 
    app:layout_constraintRight_toRightOf="parent" 
    android:layout_marginTop="18dp" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="parent" 
    app:layout_constraintTop_toTopOf="parent" 
    android:layout_marginLeft="17dp" /> 

<Button 
    android:id="@+id/one" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="1" 
    android:onClick="pressOne" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/zero" 
    app:layout_constraintRight_toRightOf="@+id/four" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/four" /> 

<Button 
    android:id="@+id/three" 
    android:layout_width="0dp" 
    android:layout_height="0dp" 
    android:text="3" 
    android:onClick="pressThree" 
    tools:layout_constraintTop_creator="1" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toBottomOf="@+id/two" 
    app:layout_constraintRight_toRightOf="@+id/six" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/six" 
    app:layout_constraintTop_toTopOf="@+id/two" /> 

    <Button 
    android:id="@+id/four" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="4" 
     android:onClick="pressFour" 
     tools:layout_constraintRight_creator="1" 
     tools:layout_constraintBottom_creator="1" 
     app:layout_constraintBottom_toTopOf="@+id/one" 
     app:layout_constraintRight_toRightOf="@+id/seven" 
     tools:layout_constraintLeft_creator="1" 
     app:layout_constraintLeft_toLeftOf="@+id/seven" /> 

<Button 
    android:id="@+id/five" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="5" 
    android:onClick="pressFive" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/two" 
    app:layout_constraintRight_toRightOf="@+id/two" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/two" /> 

<Button 
    android:id="@+id/two" 
    android:layout_width="124dp" 
    android:layout_height="75dp" 
    android:onClick="pressTwo" 
    android:text="2" 
    tools:layout_constraintRight_creator="1" 
    app:layout_constraintRight_toRightOf="parent" 
    app:layout_constraintBaseline_toBaselineOf="@+id/one" 
    tools:layout_constraintBaseline_creator="1" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="parent" 
    tools:layout_editor_absoluteY="433dp" /> 

<Button 
    android:id="@+id/six" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="6" 
    android:onClick="pressSix" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/three" 
    app:layout_constraintRight_toRightOf="@+id/nine" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/nine" /> 

<Button 
    android:id="@+id/eight" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="8" 
    android:onClick="pressEight" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/five" 
    app:layout_constraintRight_toRightOf="@+id/five" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/five" /> 

<Button 
    android:id="@+id/nine" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="9" 
    android:onClick="pressNine" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/six" 
    app:layout_constraintRight_toRightOf="@+id/subtract" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/subtract" /> 

<Button 
    android:id="@+id/seven" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:onClick="pressSeven" 
    android:text="7" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/four" 
    app:layout_constraintRight_toRightOf="@+id/clear" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/clear" /> 

<Button 
    android:id="@+id/zero" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="0" 
    android:onClick="pressZero" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toBottomOf="parent" 
    app:layout_constraintRight_toRightOf="@+id/one" 
    tools:layout_constraintLeft_creator="1" 
    android:layout_marginBottom="16dp" 
    app:layout_constraintLeft_toLeftOf="@+id/one" 
    app:layout_constraintHorizontal_bias="0.0" /> 

<Button 
    android:id="@+id/clear" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="CE" 
    android:onClick="clear" 
    app:layout_constraintRight_toLeftOf="@+id/plus" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/seven" 
    android:layout_marginStart="16dp" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="parent" 
    android:layout_marginLeft="16dp" /> 

<Button 
    android:id="@+id/subtract" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="-" 
    android:onClick="pressSubtract" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/nine" 
    app:layout_constraintRight_toRightOf="@+id/divide" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/divide" /> 

<Button 
    android:id="@+id/plus" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="+" 
    android:onClick="pressPlus" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/multiply" 
    app:layout_constraintRight_toRightOf="@+id/multiply" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/multiply" /> 

<Button 
    android:id="@+id/multiply" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="*" 
    android:onClick="pressMultiply" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/eight" 
    app:layout_constraintRight_toRightOf="@+id/eight" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/eight" /> 

<Button 
    android:id="@+id/divide" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="/" 
    android:onClick="pressDivide" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toTopOf="@+id/subtract" 
    android:layout_marginStart="1dp" 
    android:layout_marginEnd="16dp" 
    app:layout_constraintRight_toRightOf="parent" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toRightOf="@+id/plus" 
    android:layout_marginLeft="1dp" 
    android:layout_marginRight="16dp" /> 

<Button 
    android:id="@+id/backspace" 
    android:layout_width="0dp" 
    android:layout_height="75dp" 
    android:text="DEL" 
    android:onClick="pressBack" 
    tools:layout_constraintRight_creator="1" 
    app:layout_constraintRight_toRightOf="@+id/clear" 
    app:layout_constraintBaseline_toBaselineOf="@+id/plus" 
    tools:layout_constraintBaseline_creator="1" 
    tools:layout_constraintLeft_creator="1" 
    app:layout_constraintLeft_toLeftOf="@+id/clear" 
    app:layout_constraintHorizontal_bias="0.0" /> 

<Button 
    android:id="@+id/equals" 
    android:layout_width="0dp" 
    android:layout_height="53dp" 
    android:text="=" 
    android:onClick="pressEquals" 
    tools:layout_constraintTop_creator="1" 
    tools:layout_constraintRight_creator="1" 
    tools:layout_constraintBottom_creator="1" 
    app:layout_constraintBottom_toBottomOf="@+id/divide" 
    app:layout_constraintRight_toRightOf="@+id/divide" 
    android:layout_marginTop="84dp" 
    tools:layout_constraintLeft_creator="1" 
    android:layout_marginBottom="75dp" 
    app:layout_constraintLeft_toLeftOf="@+id/divide" 
    app:layout_constraintTop_toTopOf="parent" /> 

</android.support.constraint.ConstraintLayout> 

这是我的代码：

package com.calc.basiccalculator; 

import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.widget.TextView; 

public class MainActivity extends AppCompatActivity { 

    String operation; 
    CharSequence num1; 
    CharSequence num2; 
    TextView t; 
    String n1; 
    String n2; 
    int number1; 
    int number2; 
    int output; 
    String out; 
    CharSequence temp; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    t = (TextView) findViewById(R.id.outputText); 
    operation = ""; 
    num1 = ""; 
    num2 = ""; 
    n1 = ""; 
    n2 = ""; 
    number1 = 1; 
    number2 = 0; 
    output = 0; 
    out = ""; 
    temp = ""; 
} 

public void pressOne() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("1"); 
    } 
    else { 
     t.append("1"); 
    } 
} 
public void pressTwo() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("2"); 
    } 
    else { 
     t.append("2"); 
    } 
} 
public void pressThree() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("3"); 
    } 
    else { 
     t.append("3"); 
    } 
} 
public void pressFour() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("4"); 
    } 
    else { 
     t.append("4"); 
    } 
} 
public void pressFive() { 
    temp = t.getText(); 
    if (temp == "0" && operation == "") { 
     t.clearComposingText(); 
     t.setText("5"); 
    } 
    else { 
     t.append("5"); 
    } 
} 
public void pressSix() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("6"); 
    } 
    else { 
     t.append("6"); 
    } 
} 
public void pressSeven() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("7"); 
    } 
    else { 
     t.append("7"); 
    } 
} 
public void pressEight() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("8"); 
    } 
    else { 
     t.append("8"); 
    } 
} 
public void pressNine() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("9"); 
    } 
    else { 
     t.append("9"); 
    } 
} 
public void pressZero() { 
    temp = t.getText(); 
    if (temp == "0") { 
     t.clearComposingText(); 
     t.setText("0"); 
    } 
    else { 
     t.append("0"); 
    } 
} 
public void pressSubtract() { 
    num1 = t.getText(); 
    t.clearComposingText(); 
    operation = "-"; 
} 
public void pressPlus() { 
     num1 = t.getText(); 
     t.clearComposingText(); 
     operation = "+"; 
} 
public void pressMultiply() { 
    num1 = t.getText(); 
    t.clearComposingText(); 
    operation = "*"; 
} 
public void pressDivide() { 
    num1 = t.getText(); 
    t.clearComposingText(); 
    operation = "/"; 
} 
public void clear() { 
    t.clearComposingText(); 
} 
public void pressEquals() { 
    if (operation == "+") { 
     num2 = t.getText(); 
     n1 = num1.toString(); 
     n2 = num2.toString(); 
     number1 = Integer.parseInt(n1); 
     number2 = Integer.parseInt(n2); 
     output = number1 + number2; 
    } 
    if (operation == "-") { 
     num2 = t.getText(); 
     n1 = num1.toString(); 
     n2 = num2.toString(); 
     number1 = Integer.parseInt(n1); 
     number2 = Integer.parseInt(n2); 
     output = number1 - number2; 
    } 
    if (operation == "*") { 
     num2 = t.getText(); 
     n1 = num1.toString(); 
     n2 = num2.toString(); 
     number1 = Integer.parseInt(n1); 
     number2 = Integer.parseInt(n2); 
     output = number1 * number2; 
    } 
    if (operation == "/") { 
     num2 = t.getText(); 
     n1 = num1.toString(); 
     n2 = num2.toString(); 
     number1 = Integer.parseInt(n1); 
     number2 = Integer.parseInt(n2); 
     output = number1/number2; 
    } 
    t.clearComposingText(); 
    out = String.valueOf(output); 
    t.append(out); 
    operation = ""; 

    } 
} 

Answer 1

你可以很容易地发现，通过调查日志输出造成任何崩溃的错误，你会发现在日志中Android监视器窗口，如下图所示。

在分配中使用android:onClick属性的XML布局的方法，该方法必须是公开和接受查看作为其唯一的参数。这在Android Developer reference中有解释。

代码中的方法都缺少View参数。

public void onClickExampleMethod(View view) { 
// Handle click 
} 

Answer 2

的onClick方法声明应尽可能

public void methodName(View v) {} 

请改变你的方法为：

public void pressOne(View v) {...} 
public void pressTwo(View v) {...} 
public void pressThree(View v) {...} 
public void pressFour(View v) {...} 
public void pressFive(View v) {...}