java - 当我将 0 添加到一个数字时，结果始终为零。其他数字都还好

Question

我正在尝试制作一个应用程序，将我已经编写的两个数字相加，并在下一个 Activity 中显示结果。我让它可以处理非零数字，但是当我将 0 添加到另一个数字时，结果始终为零。我知道这是因为默认值 0。但它与其他值一起工作正常。当我添加除零以外的任何数字时，它都可以正常工作，但是当包含 0 时，整个结果将变为零。请帮我。谢谢!

主要 Activity

package com.example.david.magic;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;


public class MainActivity extends AppCompatActivity {


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

    public void no (View view){
        EditText editTextOne = (EditText) findViewById(R.id.textView);
        EditText editTextTwo = (EditText) findViewById(R.id.textView1);
        int firstNumber = Integer.parseInt(editTextOne.getText().toString());
        int secondNumber = Integer.parseInt(editTextTwo.getText().toString());
        int sum = firstNumber + secondNumber;
        // Now send the result sum to the Activity B through intent.
        Intent intent = new Intent(this, Main2Activity.class);
        intent.putExtra("RESULT_SUM", sum);
        startActivity(intent);


    }

    public void yes (View view){
        EditText editTextOned = (EditText) findViewById(R.id.resultno);
        EditText editTextTwod = (EditText) findViewById(R.id.textView);
        int firstNumberd = Integer.parseInt(editTextOned.getText().toString());
        int secondNumberd = Integer.parseInt(editTextTwod.getText().toString());
        int sumd = firstNumberd + secondNumberd;
        // Now send the result sum to the Activity B through intent.
        Intent intent = new Intent(this, Main2Activity.class);
        intent.putExtra("RESULT_SUMd", sumd);
        startActivity(intent);


    }}

Activity 主

<?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=".MainActivity">

    <Button
        android:id="@+id/Button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.217"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.961"
        android:text="Yes"
        android:onClick="yes"/>

    <Button
        android:id="@+id/Button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.739"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.961"
        android:text="No"
        android:onClick="no"/>

    <EditText
        android:id="@+id/textView"
        android:layout_width="182dp"
        android:layout_height="58dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="1"
        android:visibility="invisible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/textView1"
        android:layout_width="174dp"
        android:layout_height="49dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="0"
        android:visibility="invisible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.381" />

    <EditText
        android:id="@+id/resultno"
        android:layout_width="170dp"
        android:layout_height="50dp"
        android:layout_marginEnd="104dp"
        android:layout_marginRight="104dp"
        app:layout_constraintEnd_toEndOf="parent"
        android:text="0"
        android:visibility="invisible"
        tools:layout_editor_absoluteY="128dp" />

    <ImageView
        android:layout_width="366dp"
        android:layout_height="282dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:background="@drawable/one"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.289" />


</android.support.constraint.ConstraintLayout>

Main2Activity

package com.example.david.magic;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class Main2Activity extends AppCompatActivity {

    String fud;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);


        EditText hi = findViewById(R.id.textView2);
        Bundle extras = getIntent().getExtras();
        if (extras != null) {

            int sum = getIntent().getIntExtra("RESULT_SUM", 0);

            hi.setText(String.valueOf(sum));
        }


        EditText bye = findViewById(R.id.textView2);
        Bundle extra = getIntent().getExtras();
        if (extras != null) {

            int sumd = getIntent().getIntExtra("RESULT_SUMd", 0);

            bye.setText(String.valueOf(sumd));
        }
    }

    public void yyes (View view){
        EditText editTextOne = (EditText) findViewById(R.id.textView2);
        EditText editTextTwo = (EditText) findViewById(R.id.textView1);
        int firstNumber = Integer.parseInt(editTextOne.getText().toString());
        int secondNumber = Integer.parseInt(editTextTwo.getText().toString());
        int sum = firstNumber + secondNumber;
        // Now send the result sum to the Activity B through intent.
        Intent intent = new Intent(this, Main3Activity.class);
        intent.putExtra("RESULT_SUM1", sum);
        startActivity(intent);


    }

    public void nno (View view){
        EditText editTextOne1 = (EditText) findViewById(R.id.saysno);
        EditText editTextTwo1 = (EditText) findViewById(R.id.textView2);
        int firstNumber1 = Integer.parseInt(editTextOne1.getText().toString());
        int secondNumber1 = Integer.parseInt(editTextTwo1.getText().toString());
        int sum2 = secondNumber1;
        // Now send the result sum to the Activity B through intent.
        Intent nno = new Intent(this, Main3Activity.class);
        nno.putExtra("RESULT_SUM2", sum2);
        startActivity(nno);


    }
}


activity_main2

<?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=".Main2Activity">


    <EditText
        android:id="@+id/textView2"
        android:layout_width="147dp"
        android:layout_height="51dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:visibility="invisible"
        android:text=""
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/Button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.217"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.961"
        android:text="Yes"
        android:onClick="yyes"/>

    <Button
        android:id="@+id/Button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.739"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.961"
        android:text="No"
        android:onClick="nno"/>



    <EditText
        android:id="@+id/textView1"
        android:layout_width="174dp"
        android:layout_height="49dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="2"
        android:visibility="invisible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.381" />

    <EditText
        android:id="@+id/saysno"
        android:layout_width="170dp"
        android:layout_height="50dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="196dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="196dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:text="0"
        android:visibility="invisible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
    <ImageView
        android:layout_width="366dp"
        android:layout_height="282dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:background="@drawable/two"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.289" />


</android.support.constraint.ConstraintLayout>

Answer 1

问题来自这部分代码:

 EditText hi = findViewById(R.id.textView2);
    Bundle extras = getIntent().getExtras();
    if (extras != null) {

        int sum = getIntent().getIntExtra("RESULT_SUM", 0);

        hi.setText(String.valueOf(sum));
    }


    EditText bye = findViewById(R.id.textView2);
    Bundle extra = getIntent().getExtras();
    if (extras != null) {

        int sumd = getIntent().getIntExtra("RESULT_SUMd", 0);

        bye.setText(String.valueOf(sumd));
    }

无论您单击"is"或“否”，extras不为空。因此，当您单击“否”时，您会在第一个 if 中获得正确的值。 。但第二if总是被触发。因为，在这两种情况下，您都为 textView2 调用 setText，bye.setText(String.valueOf(sumd));将正确的值覆盖为 0，因为“RESULT_SUMd”为空且 0 为默认值。

让我用注释解释一下代码内部(没有情况):

EditText hi = findViewById(R.id.textView2);
Bundle extras = getIntent().getExtras();
//always true
if (extras != null) {
    // sum is set with right value
    int sum = getIntent().getIntExtra("RESULT_SUM", 0);

    //textView2 display the right sum
    hi.setText(String.valueOf(sum));
}


EditText bye = findViewById(R.id.textView2);
Bundle extra = getIntent().getExtras();

//always true
if (extras != null) {
    //no result_sumd found
    //sumd == 0
    int sumd = getIntent().getIntExtra("RESULT_SUMd", 0);

    //textView2 text is override with 0, value of sumd
    bye.setText(String.valueOf(sumd));
}

当然，如果您单击"is"，一切都会正常，因为在这种情况下定义了“RESULT_SUMd”。

到目前为止，我建议您添加另一个标志(以表达 Intent 来自是/否)并添加更好的 if flow:

在第一个 Activity 中:

public void no (View view){
    EditText editTextOne = (EditText) findViewById(R.id.textView);
    EditText editTextTwo = (EditText) findViewById(R.id.textView1);
    int firstNumber = Integer.parseInt(editTextOne.getText().toString());
    int secondNumber = Integer.parseInt(editTextTwo.getText().toString());
    int sum = firstNumber + secondNumber;
    // Now send the result sum to the Activity B through intent.
    Intent intent = new Intent(this, Main2Activity.class);
    intent.putExtra("RESULT_SUM", sum);

    //add extra flag
    intent.putExtra("FROM_NO", true);
    startActivity(intent);


}

public void yes (View view){
    EditText editTextOned = (EditText) findViewById(R.id.resultno);
    EditText editTextTwod = (EditText) findViewById(R.id.textView);
    int firstNumberd = Integer.parseInt(editTextOned.getText().toString());
    int secondNumberd = Integer.parseInt(editTextTwod.getText().toString());
    int sumd = firstNumberd + secondNumberd;
    // Now send the result sum to the Activity B through intent.
    Intent intent = new Intent(this, Main2Activity.class);
    intent.putExtra("RESULT_SUMd", sumd);
    startActivity(intent);


}}

在第二个 Activity 中:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    // hi is enough
    EditText hi = findViewById(R.id.textView2);
    Bundle extras = getIntent().getExtras();
    if (extras != null) {
        boolean fromNo = getIntent().getExtras().getBoolean("FROM_NO", false); 
        //use of ternary to make it simple
        int sum = getIntent().getIntExtra(fromNo?"RESULT_SUM":"RESULT_SUMd", 0);
        hi.setText(String.valueOf(sum));
    }

 }