我尝试使用片段进行活动，在不同类型的计算器之间切换。我有没有空的构造函数错误，所以我继续，我的空构造函数出错：空白的最终字段FragmentsSliderActivity可能尚未初始化。
不知道如何解决这个错误。
Logcat：
09-21 15:37:12.385: E/AndroidRuntime(5465): FATAL EXCEPTION: main
09-21 15:37:12.385: E/AndroidRuntime(5465): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tutos/com.tutos.FragmentsSliderActivity}: android.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment com.tutos.PageMilieuFragment: make sure class name exists, is public, and has an empty constructor that is public
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.app.ActivityThread.access$700(ActivityThread.java:159)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.os.Handler.dispatchMessage(Handler.java:99)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.os.Looper.loop(Looper.java:176)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.app.ActivityThread.main(ActivityThread.java:5419)
09-21 15:37:12.385: E/AndroidRuntime(5465): at java.lang.reflect.Method.invokeNative(Native Method)
09-21 15:37:12.385: E/AndroidRuntime(5465): at java.lang.reflect.Method.invoke(Method.java:525)
09-21 15:37:12.385: E/AndroidRuntime(5465): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
09-21 15:37:12.385: E/AndroidRuntime(5465): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
09-21 15:37:12.385: E/AndroidRuntime(5465): at dalvik.system.NativeStart.main(Native Method)
09-21 15:37:12.385: E/AndroidRuntime(5465): Caused by: android.support.v4.app.Fragment$InstantiationException: Unable to instantiate fragment com.tutos.PageMilieuFragment: make sure class name exists, is public, and has an empty constructor that is public
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.support.v4.app.Fragment.instantiate(Fragment.java:395)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.support.v4.app.Fragment.instantiate(Fragment.java:359)
09-21 15:37:12.385: E/AndroidRuntime(5465): at com.tutos.FragmentsSliderActivity.onCreate(FragmentsSliderActivity.java:25)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.app.Activity.performCreate(Activity.java:5372)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
09-21 15:37:12.385: E/AndroidRuntime(5465): ... 11 more
09-21 15:37:12.385: E/AndroidRuntime(5465): Caused by: java.lang.InstantiationException: can't instantiate class com.tutos.PageMilieuFragment; no empty constructor
09-21 15:37:12.385: E/AndroidRuntime(5465): at java.lang.Class.newInstanceImpl(Native Method)
09-21 15:37:12.385: E/AndroidRuntime(5465): at java.lang.Class.newInstance(Class.java:1130)
09-21 15:37:12.385: E/AndroidRuntime(5465): at android.support.v4.app.Fragment.instantiate(Fragment.java:384)
09-21 15:37:12.385: E/AndroidRuntime(5465): ... 16 more
我的片段与计算器。
package com.tutos;
import android.app.Activity;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
public class PageMilieuFragment extends Fragment {
public PageMilieuFragment(){}
Button button0;
Button button1;
Button button2;
Button button3;
Button button4;
Button button5;
Button button6;
Button button7;
Button button8;
Button button9;
Button buttonPlus;
Button buttonMoins;
Button buttonDiv;
Button buttonMul;
Button buttonC;
Button buttonEgal;
Button buttonPoint;
EditText ecran;
private double chiffre1;
private boolean clicOperateur = false;
private boolean update = false;
private String operateur = "";
private final Activity FragmentsSliderActivity;
public PageMilieuFragment(Activity FragmentsSliderActivity){
this.FragmentsSliderActivity = FragmentsSliderActivity;
}
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
button0 = (Button) FragmentsSliderActivity.findViewById(R.id.button0);
button1 = (Button) FragmentsSliderActivity.findViewById(R.id.button1);
button2 = (Button) FragmentsSliderActivity.findViewById(R.id.button2);
button3 = (Button) FragmentsSliderActivity.findViewById(R.id.button3);
button4 = (Button) FragmentsSliderActivity.findViewById(R.id.button4);
button5 = (Button) FragmentsSliderActivity.findViewById(R.id.button5);
button6 = (Button) FragmentsSliderActivity.findViewById(R.id.button6);
button7 = (Button) FragmentsSliderActivity.findViewById(R.id.button7);
button8 = (Button) FragmentsSliderActivity.findViewById(R.id.button8);
button9 = (Button) FragmentsSliderActivity.findViewById(R.id.button9);
buttonPoint = (Button) FragmentsSliderActivity.findViewById(R.id.buttonPoint);
buttonPlus = (Button) FragmentsSliderActivity.findViewById(R.id.buttonPlus);
buttonMoins = (Button) FragmentsSliderActivity.findViewById(R.id.buttonMoins);
buttonDiv = (Button) FragmentsSliderActivity.findViewById(R.id.buttonDivision);
buttonMul = (Button) FragmentsSliderActivity.findViewById(R.id.buttonMultiplier);
buttonC = (Button) FragmentsSliderActivity.findViewById(R.id.buttonC);
buttonEgal = (Button) FragmentsSliderActivity.findViewById(R.id.buttonEgal);
ecran = (EditText) FragmentsSliderActivity.findViewById(R.id.EditText01);
buttonPlus.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
plusClick();
}
});
buttonMoins.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
moinsClick();
}
});
buttonDiv.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
divClick();
}
});
buttonMul.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
mulClick();
}
});
buttonC.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
resetClick();
}
});
buttonEgal.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
egalClick();
}
});
buttonPoint.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick(".");
}
});
button0.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("0");
}
});
button1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("1");
}
});
button2.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("2");
}
});
button3.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("3");
}
});
button4.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("4");
}
});
button5.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("5");
}
});
button6.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("6");
}
});
button7.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("7");
}
});
button8.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("8");
}
});
button9.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
chiffreClick("9");
}
});
return inflater.inflate(R.layout.page_milieu_layout, container, false);
}
public void chiffreClick(String str) {
if(update){
update = false;
}else{
if(!ecran.getText().equals("0"))
str = ecran.getText() + str;
}
ecran.setText(str);
}
public void plusClick(){
if(clicOperateur){
calcul();
ecran.setText(String.valueOf(chiffre1));
}else{
chiffre1 = Double.valueOf(ecran.getText().toString()).doubleValue();
clicOperateur = true;
}
operateur = "+";
update = true;
}
public void moinsClick(){
if(clicOperateur){
calcul();
ecran.setText(String.valueOf(chiffre1));
}else{
chiffre1 = Double.valueOf(ecran.getText().toString()).doubleValue();
clicOperateur = true;
}
operateur = "-";
update = true;
}
public void mulClick(){
if(clicOperateur){
calcul();
ecran.setText(String.valueOf(chiffre1));
}else{
chiffre1 = Double.valueOf(ecran.getText().toString()).doubleValue();
clicOperateur = true;
}
operateur = "*";
update = true;
}
public void divClick(){
if(clicOperateur){
calcul();
ecran.setText(String.valueOf(chiffre1));
}else{
chiffre1 = Double.valueOf(ecran.getText().toString()).doubleValue();
clicOperateur = true;
}
operateur = "/";
update = true;
}
public void egalClick(){
calcul();
update = true;
clicOperateur = false;
}
public void resetClick(){
clicOperateur = false;
update = true;
chiffre1 = 0;
operateur = "";
ecran.setText("");
}
private void calcul(){
if(operateur.equals("+")){
chiffre1 = chiffre1 + Double.valueOf(ecran.getText().toString()).doubleValue();
ecran.setText(String.valueOf(chiffre1));
}
if(operateur.equals("-")){
chiffre1 = chiffre1 - Double.valueOf(ecran.getText().toString()).doubleValue();
ecran.setText(String.valueOf(chiffre1));
}
if(operateur.equals("*")){
chiffre1 = chiffre1 * Double.valueOf(ecran.getText().toString()).doubleValue();
ecran.setText(String.valueOf(chiffre1));
}
if(operateur.equals("/")){
try{
chiffre1 = chiffre1 / Double.valueOf(ecran.getText().toString()).doubleValue();
ecran.setText(String.valueOf(chiffre1));
}catch(ArithmeticException e){
ecran.setText("0");
}
}
}
}
我的FragmentsSliderActivity
package com.tutos;
import java.util.List;
import java.util.Vector;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
public class FragmentsSliderActivity extends FragmentActivity {
private PagerAdapter mPagerAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
super.setContentView(R.layout.viewpager);
List<Fragment> fragments = new Vector<Fragment>();
fragments.add(Fragment.instantiate(this,PageMilieuFragment.class.getName()));
fragments.add(Fragment.instantiate(this,PageDroiteFragment.class.getName()));
this.mPagerAdapter = new MyPagerAdapter(super.getSupportFragmentManager(), fragments);
ViewPager pager = (ViewPager) super.findViewById(R.id.viewpager);
pager.setAdapter(this.mPagerAdapter);
}
}
帮助PLZ !!!