java - Android studio计算器-点击操作按钮后editText内容消失

Question

我正在 android studio 中做一个简单的计算器，我的代码如下所示:

MainActivity.java:

package com.example.ja.calculator;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity {


String total="";
double v1, v2;
String sign="";

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
}

public void onClick(View v){
    Button button = (Button)v;
    String str=button.getText().toString();
    total+=str;
    EditText edit=(EditText)findViewById(R.id.editText);
    edit.setText(total);
}

public void OnAdd(View v){
    v1 = Double.parseDouble(total);
    total = "";
    Button button = (Button)v;
    String str = button.getText().toString();
    sign = str;
    EditText edit = (EditText)findViewById(R.id.editText);
    edit.setText("");
}

public void OnCalculate(View v){
    EditText edit = (EditText)findViewById(R.id.editText);
    String str2 = edit.getText().toString();
    v2 = Double.parseDouble(str2);
    double grand_total = 0;
    if(sign.equals("+")){
        grand_total = v1 + v2;
    }

    else if(sign.equals("-")){
        grand_total = v1 - v2;
    }

    else if(sign.equals("x")){
        grand_total = v1 * v2;
    }

    else if(sign.equals(":")){
        grand_total = v1 / v2;
    }

    edit.setText(grand_total+"");
}

public void OnClear(View v){
    EditText edit = (EditText)findViewById(R.id.editText);
    edit.setText("");
    total = "";

}

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

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

内容主要:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.example.ja.calculator.MainActivity"
tools:showIn="@layout/activity_main">

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:inputType="number"
    android:ems="10"
    android:id="@+id/editText"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="1"
    android:id="@+id/button"
    android:layout_centerVertical="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="2"
    android:id="@+id/button2"
    android:layout_alignTop="@+id/button"
    android:layout_toRightOf="@+id/button"
    android:layout_toEndOf="@+id/button"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="3"
    android:id="@+id/button3"
    android:layout_alignTop="@+id/button2"
    android:layout_toRightOf="@+id/button2"
    android:layout_toEndOf="@+id/button2"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="4"
    android:id="@+id/button4"
    android:layout_above="@+id/button"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="5"
    android:id="@+id/button5"
    android:layout_above="@+id/button2"
    android:layout_toLeftOf="@+id/button3"
    android:layout_toStartOf="@+id/button3"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="6"
    android:id="@+id/button6"
    android:layout_above="@+id/button3"
    android:layout_alignLeft="@+id/button3"
    android:layout_alignStart="@+id/button3"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="7"
    android:id="@+id/button7"
    android:layout_above="@+id/button4"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="8"
    android:id="@+id/button8"
    android:layout_alignTop="@+id/button7"
    android:layout_toRightOf="@+id/button4"
    android:layout_toEndOf="@+id/button4"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="9"
    android:id="@+id/button9"
    android:layout_alignTop="@+id/button8"
    android:layout_toRightOf="@+id/button5"
    android:layout_toEndOf="@+id/button5"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="0"
    android:id="@+id/button0"
    android:layout_below="@+id/button"
    android:layout_toRightOf="@+id/button"
    android:layout_toEndOf="@+id/button"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="."
    android:id="@+id/buttonDot"
    android:layout_below="@+id/button"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:height="80dp"
    android:onClick="onClick" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="="
    android:id="@+id/buttonEQ"
    android:layout_below="@+id/button3"
    android:layout_alignLeft="@+id/button3"
    android:layout_alignStart="@+id/button3"
    android:height="80dp"
    android:onClick="OnCalculate" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="+"
    android:id="@+id/buttonAdd"
    android:height="64dp"
    android:layout_alignBottom="@+id/buttonEQ"
    android:layout_alignLeft="@+id/buttonSub"
    android:layout_alignStart="@+id/buttonSub"
    android:onClick="OnAdd" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="-"
    android:id="@+id/buttonSub"
    android:height="64dp"
    android:layout_above="@+id/buttonAdd"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"
    android:onClick="OnAdd" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="x"
    android:id="@+id/buttonMul"
    android:height="64dp"
    android:layout_above="@+id/buttonSub"
    android:layout_alignLeft="@+id/buttonSub"
    android:layout_alignStart="@+id/buttonSub"
    android:onClick="OnAdd" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text=":"
    android:id="@+id/buttonDiv"
    android:layout_above="@+id/buttonMul"
    android:layout_alignLeft="@+id/buttonMul"
    android:layout_alignStart="@+id/buttonMul"
    android:height="64dp"
    android:onClick="OnAdd" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="CE"
    android:id="@+id/buttonCE"
    android:height="64dp"
    android:layout_above="@+id/buttonDiv"
    android:layout_toRightOf="@+id/button9"
    android:layout_toEndOf="@+id/button9"
    android:onClick="OnClear" />

问题是，当我单击某个数字，然后单击操作(+、-、/、*)时，之前单击的数字消失了，如何修复它，以便我可以看到完整的操作，例如 5* 5 在点击“=”之前，然后只是为了结果而改变？

Answer 1

public void OnAdd(View v) {
    v1 = Double.parseDouble(total);
    total = "";
    Button button = (Button) v;
    String str = button.getText().toString();
    sign = str;
    EditText edit = (EditText) findViewById(R.id.editText); ** edit.setText("");
}

点击的数字被清除之前的原因是您将文本设置为“”。 (看 **)如果您的计算器能够正确工作，您应该对代码进行以下更改。

public void OnAdd(View v) {
    v1 = Double.parseDouble(total);
    Button button = (Button) v;
    String str = button.getText().toString();
    sign = str;
    total += str;
    EditText edit = (EditText) findViewById(R.id.editText);
    edit.setText(total);
}

现在符号将被附加到整个字符串中。并且它会被写回editText。