Question

我是android的新手并试图开发简单的计算器，但这个致命的例外：主要发生请帮助。

我对我的onClickListner进行了评论，但它确实没有帮助。

package com.example.calculatorsinglescreen;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {

EditText value1,value2,myoperator,result;
Button ok;
String strvalue1,strvalue2,stroperator,strresult;
int ivalue1,ivalue2,ioperator,iresult;

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

    value1 = (EditText) findViewById(R.id.txtvalue1);
    value2 = (EditText) findViewById(R.id.txtvalue2);
    myoperator = (EditText) findViewById(R.id.txtoperator);
    result = (EditText) findViewById(R.id.txtresult);
    ok = (Button) findViewById(R.id.btnok);

    strvalue1 = value1.getText().toString();
    strvalue2 = value2.getText().toString();
    stroperator = myoperator.getText().toString();

    ivalue1 = Integer.parseInt(strvalue1);
    ivalue2 = Integer.parseInt(strvalue2);





    ok.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {

            if (stroperator.equals("+")) {

                Toast msg = Toast.makeText(MainActivity.this, "If is running", Toast.LENGTH_LONG);
                msg.show();

                }

        }
    });
}



@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.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();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

}

这是我的XML文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
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"
tools:context="com.example.calculatorsinglescreen.MainActivity" >

<TextView
    android:id="@+id/value1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:layout_margin="20dp"
    android:text="Value 1" />

<TextView
    android:id="@+id/value2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/value1"
    android:layout_margin="20dp"
    android:text="Value 2" />

<TextView
    android:id="@+id/operator"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/value2"
    android:layout_margin="20dp"
    android:text="Operator" />

<EditText
    android:id="@+id/txtvalue1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_toRightOf="@+id/value1"
    android:layout_alignBaseline="@+id/value1"
    android:layout_alignParentRight="true"
    android:ems="10" >

    <requestFocus />
</EditText>

<EditText
    android:id="@+id/txtoperator"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/operator"
    android:layout_below="@+id/txtvalue2"
    android:layout_toRightOf="@+id/operator"
    android:layout_alignParentRight="true"
    android:ems="10" />

<EditText
    android:id="@+id/txtvalue2"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/value2"
    android:layout_toRightOf="@+id/value2"
    android:layout_below="@+id/txtvalue1"
    android:layout_alignParentRight="true"
    android:ems="10" />

<Button
    android:id="@+id/btnok"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:text="Ok" />

<TextView
    android:id="@+id/result"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/btnok"
    android:layout_margin="40dp"
    android:text="Result" />

<EditText
    android:id="@+id/txtresult"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/result"
    android:layout_toRightOf="@+id/result"
    android:ems="10" />

这是我的LogCat以获得更清晰的视图：

10-18 17:51:25.468: D/AndroidRuntime(742): Shutting down VM
10-18 17:51:25.468: W/dalvikvm(742): threadid=1: thread exiting with uncaught exception (group=0x40015560)
10-18 17:51:25.488: E/AndroidRuntime(742): FATAL EXCEPTION: main
10-18 17:51:25.488: E/AndroidRuntime(742): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.calculatorsinglescreen/com.example.calculatorsinglescreen.MainActivity}: java.lang.NumberFormatException: unable to parse '' as integer
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.os.Looper.loop(Looper.java:123)
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.app.ActivityThread.main(ActivityThread.java:3683)
10-18 17:51:25.488: E/AndroidRuntime(742):  at java.lang.reflect.Method.invokeNative(Native Method)
10-18 17:51:25.488: E/AndroidRuntime(742):  at java.lang.reflect.Method.invoke(Method.java:507)
10-18 17:51:25.488: E/AndroidRuntime(742):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-18 17:51:25.488: E/AndroidRuntime(742):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-18 17:51:25.488: E/AndroidRuntime(742):  at dalvik.system.NativeStart.main(Native Method)
10-18 17:51:25.488: E/AndroidRuntime(742): Caused by: java.lang.NumberFormatException: unable to parse '' as integer
10-18 17:51:25.488: E/AndroidRuntime(742):  at java.lang.Integer.parseInt(Integer.java:362)
10-18 17:51:25.488: E/AndroidRuntime(742):  at java.lang.Integer.parseInt(Integer.java:332)
10-18 17:51:25.488: E/AndroidRuntime(742):  at com.example.calculatorsinglescreen.MainActivity.onCreate(MainActivity.java:34)
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-18 17:51:25.488: E/AndroidRuntime(742):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
10-18 17:51:25.488: E/AndroidRuntime(742):  ... 11 more

Answer 1

这是错误

java.lang.ClassCastException: android.widget.TextView

检查你的第24行，看看你是否在java中投射了正确的小部件 - （xml），这个错误意味着不兼容的投射小部件大声笑......

如果一切看起来都正确 - （平均小部件在java中转换为各自的类）然后清理重建并重新启动..

编辑：它工作了......你已经解决了，但是有一个新错误

java.lang.NumberFormatException:

因为这一点

ivalue1 = Integer.parseInt(strvalue1);
ivalue2 = Integer.parseInt(strvalue2);
ioperator = Integer.parseInt(stroperator);

所以将这些改为

Integer.valueOf(strvalue1); do that as follows

并查看你的代码..你的字符串值是在oncreate期间从edittext中提取的，这意味着应用程序在onresume（在应用程序显示时调用）之前的oncreate中启动，并且在oncreate期间用户无法启动调整你的应用程序，并进一步输入值，所以当你从edittext中提取时，你的字符串是空的，所以基本上我说的是删除这些行

strvalue1 = value1.getText().toString();

并将它们放入点击事件中...我对你足够清醒?? ..

EDIT2：总体代码按钮单击

ok.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View arg0) {
         strvalue1 = value1.getText().toString();
         strvalue2 = value2.getText().toString();
         stroperator = myoperator.getText().toString();

         ivalue1 =  Integer.valueOf(strvalue1);
         ivalue2 =  Integer.valueOf(strvalue2);

        if (stroperator.equals("+")) {

           Toast.makeText(MainActivity.this, "If is running", Toast.LENGTH_LONG).show();

            }

    }
});

Answer 2

从代码中删除ioperator = Integer.parseInt(stroperator);。我想你试图将运算符转换为整数。

Answer 3

ioperator = Integer.parseInt(stroperator);

如果你的意思是这样的操作符+， - ，/，*，你只能转换为thr char或保留在字符串中并执行以下操作：

private int plus(int ivalue1 , int ivalue2 , String operator ){
    if(operator.equal("+")){
        return ivalue1 + ivalue2;
    }
 return 0;
}

致命异常：主要Android Eclipse

3 个答案: