我试图在一个应用程序中使用两个 View 来得出用户的行星重量。在多次重写 java 之后，我终于让它工作了......主要是，但是在公共(public)类 Planets 上它告诉我“公共(public)类型的行星必须在它自己的文件中定义。”我进入 list 并为它做了一个 Activity ，但这没有任何帮助。 Planets 已经是我的一个 xml 文件的名称。如何将公共(public)类型放入其自己的文件中？
activity_main.xml:
<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" >
<TextView
android:id="@+id/askwtTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="17dp"
android:layout_marginTop="19dp"
android:text="@string/askwt" />
<EditText
android:id="@+id/inputwtEditText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/askwtTextView"
android:layout_below="@+id/askwtTextView"
android:layout_marginTop="26dp"
android:ems="10"
android:inputType="numberDecimal" />
<Button
android:id="@+id/enterButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/inputwtEditText"
android:layout_below="@+id/inputwtEditText"
android:layout_marginTop="38dp"
android:onClick="buttonclick"
android:text="@string/enter" />
</RelativeLayout>
行星.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView
android:id="@+id/planetTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/planet" />
<TextView
android:id="@+id/textViewform2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="" />
<RadioGroup
android:id="@+id/radioGroup1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<RadioButton
android:id="@+id/mercuryRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:checked="true"
android:text="@string/mercury" />
<RadioButton
android:id="@+id/venusRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/venus" />
<RadioButton
android:id="@+id/earthRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/earth" />
<RadioButton
android:id="@+id/marsRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:checked="true"
android:text="@string/mars" />
<RadioButton
android:id="@+id/jupiterRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/jupiter" />
<RadioButton
android:id="@+id/saturnRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/saturn" />
<RadioButton
android:id="@+id/uranusRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:checked="true"
android:text="@string/uranus" />
<RadioButton
android:id="@+id/neptuneRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/neptune" />
<RadioButton
android:id="@+id/plutoRadio"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/pluto" />
</RadioGroup>
<Button
android:id="@+id/selectButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="buttonclick2"
android:text="@string/select" />
<TextView
android:id="@+id/textViewform2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout
Java:
package com.deitel.planetaryweight;
import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.widget.*;
import android.view.View;
import android.view.Menu;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.EditText;
import android.widget.TextView;
import java.text.DecimalFormat;
public class MainActivity extends Activity {
/* You should get used to declaring everything with the correct visibility. Good practice is to make everything private and use public mutator methods */
//Global variable
private double weight;
private Button enter; // creates a button
// Views
private EditText wtEntry;
private TextView txtForm2;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Start with first screen
setContentView(R.layout.activity_main);
enter = (Button) findViewById(R.id.enterButton);
//creates an editext and assigns the resource id of the xml edittext.
wtEntry = (EditText)findViewById(R.id.inputwtEditText);
txtForm2 = (TextView)findViewById(R.id.textViewform2);
}
// Button clicks shouldn't do anything but perform clicky actions. Leave field initialization, view creation, etc to the Activity.
//buttonclick for form 1
public void buttonclick(View view){
//Receives the input from the edittext, converts it to a double (number).
weight = Double.parseDouble(wtEntry.getText().toString());
TextView t2 = null;
//change the value of the textview on screen 2 to the calculation value
t2.setText(Double.toString(weight));
// If you want a new layout, it's best to start a new activity.
// It looks like you want to get information back, so use startActivityForResult().
// setContentView(R.layout.planets);
Intent dataIntent = new Intent(this, Planets.class);
dataIntent.putExtra("com.deitel.identifier.DATA_WEIGHT", weight);
startActivityForResult(dataIntent, Activity.RESULT_OK);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// Check that the resultCode is the same as we started the activity with
if(resultCode == Activity.RESULT_OK){
// get the double from the Intent, using the same string name (package prefixed)
// or a default value if it didn't get set.
double resultWeight = data.getDoubleExtra("com.deitel.identifier.RESULT_WEIGHT", 0.0);
// Now do something with resultWeight
}
}
}
// PlanetChooser.class
public class Planets extends Activity {
// constants, usually denoted by uppercase and declared static and final
public static final double MERCURYFORCE = 0.38;
public static final double VENUSFORCE = 0.91;
public static final double EARTHFORCE = 1.00;
public static final double MARSFORCE = 0.38;
public static final double JUPITERFORCE = 2.34;
public static final double SATURNFORCE = 1.06;
public static final double URANUSFORCE = 0.92;
public static final double NEPTUNEFORCE = 1.19;
public static final double PLUTOFORCE = 0.06;
private RadioButton mercury, venus, earth, mars, jupiter, saturn, uranus, neptune, pluto;
// No need to use the Double object as opposed to the primitive unless you have good reason
private double mercurypf, venuspf, earthpf, marspf, jupiterpf, saturnpf, uranuspf, neptunepf, plutopf, weight;
// One variable will suffice, it seems.
private double resultForce;
public void onCreate(Bundle s){
super.onCreate(s);
setContentView(R.layout.planets);
mercury = (RadioButton) findViewById(R.id.mercuryRadio);
venus = (RadioButton) findViewById(R.id.venusRadio);
earth = (RadioButton) findViewById(R.id.earthRadio);
mars = (RadioButton) findViewById(R.id.marsRadio);
jupiter = (RadioButton) findViewById(R.id.jupiterRadio);
saturn = (RadioButton) findViewById(R.id.saturnRadio);
uranus = (RadioButton) findViewById(R.id.uranusRadio);
neptune = (RadioButton) findViewById(R.id.neptuneRadio);
pluto = (RadioButton) findViewById(R.id.plutoRadio);
}
public void buttonclick2(View view){
/*
It looks to me here you're looking to see which box is checked, and set a value based on
that planet. Since instance variables (in this case mercurypf, jupiterpf, etc) are initialized
to the default value (0), there's no need to set them manually.
*/
// Code used to determine which planet RadioButton is checked:
if(mercury.isChecked()) {
resultForce = MERCURYFORCE * weight;
}
if(venus.isChecked()){
resultForce = VENUSFORCE * weight;
}
if(earth.isChecked()){
resultForce = EARTHFORCE * weight;
}
if(mars.isChecked()){
resultForce = MARSFORCE * weight;
}
if(jupiter.isChecked()){
resultForce =JUPITERFORCE * weight;
}
if(saturn.isChecked()){
resultForce = SATURNFORCE * weight;
}
if(uranus.isChecked()){
resultForce = URANUSFORCE * weight;
}
if(neptune.isChecked()){
resultForce = NEPTUNEFORCE * weight;
}
if(pluto.isChecked()){
resultForce = PLUTOFORCE * weight;
}
// Create a new data Intent to pass back to the calling activity, set the result code,
// and manually finish() this activity.
Intent dataIntent = new Intent(this, null);
dataIntent.getDoubleExtra("com.deitel.identifier.RESULT_DATA", resultForce);
setResult(Activity.RESULT_OK, dataIntent);
finish();
}
}
list :
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.deitel.planetaryweight"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/title_activity_main" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name="Planets" android:label="@string/title_planets"></activity>
</application>
</manifest>
最佳答案
您的 Java 文件名为 MainActivity.java(它定义的公共(public)类的名称)。从中删除 Planets 类，并将该类放入 Planets.java 文件中。这几乎就是 Java 希望的样子。
关于android - 公共(public)类必须在其自己的文件中定义，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/13405691/