java – 尝试使用Custom Class Array检索savedInstanceState的NullPointerException
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内容图文
我有一个问题,试图让我的程序在屏幕旋转时保持我的变量中的信息.现在它在旋转时重置所有东西.我的信息存储在一个名为Players的自定义类的数组中.我尝试过使用putParcelableArray和getParcelableArray,并在自定义类中使用Implemented Parcelable,并为其提供所需的代码.当我运行代码时,它弹出强制关闭菜单,调试器在我的代码上给出NullPointerException,用于检查savedInstanceState是否为空.
以下是出现问题的主要代码的一部分.
package nicholsoft.LevelCounter;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;
public class LevelCounter extends Activity implements OnClickListener {
public Player [] Players;
TextView p1text;
TextView p2text;
TextView p3text;
TextView p4text;
TextView p5text;
TextView p6text;
TextView p1Level;
ImageView p1Epic;
TextView p2Level;
ImageView p2Epic;
TextView p3Level;
ImageView p3Epic;
TextView p4Level;
ImageView p4Epic;
TextView p5Level;
ImageView p5Epic;
TextView p6Level;
ImageView p6Epic;
TextView tTitle;
private static final int MENU_EPIC_ON = 1;
private static final int MENU_EPIC_OFF = 2;
private static final int MENU_RESET_LEVELS = 3;
private static final int MENU_RESET_NAMES = 4;
private static final int MENU_RESET_ALL = 5;
private static final int MENU_QUIT = 6;
boolean Epic = false;
String Title;
int MaxLevel = 10;
int ilevel = 1;
String slevel = "1";
void ResetLevels(){
for(int x=0;x<6;x++){
Players[x].setLevel(1);
}
p1Level.setText(String.valueOf(Players[0].getPlayerLevel()));
p2Level.setText(String.valueOf(Players[1].getPlayerLevel()));
p3Level.setText(String.valueOf(Players[2].getPlayerLevel()));
p4Level.setText(String.valueOf(Players[3].getPlayerLevel()));
p5Level.setText(String.valueOf(Players[4].getPlayerLevel()));
p6Level.setText(String.valueOf(Players[5].getPlayerLevel()));
p1Epic.setImageResource(R.drawable.black);
p2Epic.setImageResource(R.drawable.black);
p3Epic.setImageResource(R.drawable.black);
p4Epic.setImageResource(R.drawable.black);
p5Epic.setImageResource(R.drawable.black);
p6Epic.setImageResource(R.drawable.black);
}
void SetNames(){
p1text.setText(Players[0].getName());
p2text.setText(Players[1].getName());
p3text.setText(Players[2].getName());
p4text.setText(Players[3].getName());
p5text.setText(Players[4].getName());
p6text.setText(Players[5].getName());
}
void ResetNames(){
for(int x=0;x<6;x++){
Players[x].setName("Player ".concat(String.valueOf(x+1)));
}
p1text.setText(Players[0].getName());
p2text.setText(Players[1].getName());
p3text.setText(Players[2].getName());
p4text.setText(Players[3].getName());
p5text.setText(Players[4].getName());
p6text.setText(Players[5].getName());
}
void ResetAll(){
ResetNames();
ResetLevels();
}
void MinusLevel(Player p){
if (p.getPlayerLevel()>1){
p.setLevel(p.getPlayerLevel()-1);
}
}
void PlusLevel(Player p){
if(p.getPlayerLevel()<MaxLevel){
p.setLevel(p.getPlayerLevel()+1);
}
}
void AskName(final Player p){
final AlertDialog.Builder alert = new AlertDialog.Builder(this);
final EditText input = new EditText(this);
alert.setView(input);
alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
String value = input.getText().toString().trim();
p.setName(value);
SetNames();
}
});
alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
dialog.cancel();
}
});
alert.show();
}
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.main);
Players = new Player[6];
for(int x=0;x<6;x++){
String playername = "Player ".concat(String.valueOf(x+1));
Players[x] = new Player(playername,1,false);
}
if(!savedInstanceState.isEmpty()){ //null pointer exception on start?
Players = (Player[]) savedInstanceState.getParcelableArray("LastPlayerState");
}
p1text = (TextView)this.findViewById(R.id.player_one_name);
p1text.setOnClickListener(this);
Button p1Minus = (Button)this.findViewById(R.id.p1Minus);
p1Minus.setOnClickListener(this);
Button p1Plus = (Button)this.findViewById(R.id.p1Plus);
p1Plus.setOnClickListener(this);
p2text = (TextView)this.findViewById(R.id.player_two_name);
p2text.setOnClickListener(this);
Button p2Minus = (Button)this.findViewById(R.id.p2Minus);
p2Minus.setOnClickListener(this);
Button p2Plus = (Button)this.findViewById(R.id.p2Plus);
p2Plus.setOnClickListener(this);
p3text = (TextView)this.findViewById(R.id.player_three_name);
p3text.setOnClickListener(this);
Button p3Minus = (Button)this.findViewById(R.id.p3Minus);
p3Minus.setOnClickListener(this);
Button p3Plus = (Button)this.findViewById(R.id.p3Plus);
p3Plus.setOnClickListener(this);
p4text = (TextView)this.findViewById(R.id.player_four_name);
p4text.setOnClickListener(this);
Button p4Minus = (Button)this.findViewById(R.id.p4Minus);
p4Minus.setOnClickListener(this);
Button p4Plus = (Button)this.findViewById(R.id.p4Plus);
p4Plus.setOnClickListener(this);
p5text = (TextView)this.findViewById(R.id.player_five_name);
p5text.setOnClickListener(this);
Button p5Minus = (Button)this.findViewById(R.id.p5Minus);
p5Minus.setOnClickListener(this);
Button p5Plus = (Button)this.findViewById(R.id.p5Plus);
p5Plus.setOnClickListener(this);
p6text = (TextView)this.findViewById(R.id.player_six_name);
p6text.setOnClickListener(this);
Button p6Minus = (Button)this.findViewById(R.id.p6Minus);
p6Minus.setOnClickListener(this);
Button p6Plus = (Button)this.findViewById(R.id.p6Plus);
p6Plus.setOnClickListener(this);
p1Level = (TextView)this.findViewById(R.id.p1Level);
p1Epic = (ImageView)this.findViewById(R.id.p1Epic);
p2Level = (TextView)this.findViewById(R.id.p2Level);
p2Epic = (ImageView)this.findViewById(R.id.p2Epic);
p3Level = (TextView)this.findViewById(R.id.p3Level);
p3Epic = (ImageView)this.findViewById(R.id.p3Epic);
p4Level = (TextView)this.findViewById(R.id.p4Level);
p4Epic = (ImageView)this.findViewById(R.id.p4Epic);
p5Level = (TextView)this.findViewById(R.id.p5Level);
p5Epic = (ImageView)this.findViewById(R.id.p5Epic);
p6Level = (TextView)this.findViewById(R.id.p6Level);
p6Epic = (ImageView)this.findViewById(R.id.p6Epic);
}
protected void onPause(){
Bundle b = new Bundle();
b.putParcelableArray("LastPlayerState", Players);
onSaveInstanceState(b);
}
// @Override
public void onClick(View v) {
switch(v.getId()){
case R.id.player_one_name:
AskName(Players[0]);
break;
case R.id.p1Minus:
MinusLevel(Players[0]);
ilevel = Players[0].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p1Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p1Epic.setImageResource(R.drawable.black);
}
p1Level.setText(slevel);
break;
case R.id.p1Plus:
PlusLevel(Players[0]);
ilevel = Players[0].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p1Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p1Epic.setImageResource(R.drawable.black);
}
p1Level.setText(slevel);
break;
case R.id.player_two_name:
AskName(Players[1]);
break;
case R.id.p2Minus:
MinusLevel(Players[1]);
ilevel = Players[1].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p2Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p2Epic.setImageResource(R.drawable.black);
}
p2Level.setText(slevel);
break;
case R.id.p2Plus:
PlusLevel(Players[1]);
ilevel = Players[1].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p2Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p2Epic.setImageResource(R.drawable.black);
}
p2Level.setText(slevel);
break;
case R.id.player_three_name:
AskName(Players[2]);
break;
case R.id.p3Minus:
MinusLevel(Players[2]);
ilevel = Players[2].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p3Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p3Epic.setImageResource(R.drawable.black);
}
p3Level.setText(slevel);
break;
case R.id.p3Plus:
PlusLevel(Players[2]);
ilevel = Players[2].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p3Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p3Epic.setImageResource(R.drawable.black);
}
p3Level.setText(slevel);
break;
case R.id.player_four_name:
AskName(Players[3]);
break;
case R.id.p4Minus:
MinusLevel(Players[3]);
ilevel = Players[3].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p4Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p4Epic.setImageResource(R.drawable.black);
}
p4Level.setText(slevel);
break;
case R.id.p4Plus:
PlusLevel(Players[3]);
ilevel = Players[3].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p4Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p4Epic.setImageResource(R.drawable.black);
}
p4Level.setText(slevel);
break;
case R.id.player_five_name:
AskName(Players[4]);
break;
case R.id.p5Minus:
MinusLevel(Players[4]);
ilevel = Players[4].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p5Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p5Epic.setImageResource(R.drawable.black);
}
p5Level.setText(slevel);
break;
case R.id.p5Plus:
PlusLevel(Players[4]);
ilevel = Players[4].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p5Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p5Epic.setImageResource(R.drawable.black);
}
p5Level.setText(slevel);
break;
case R.id.player_six_name:
AskName(Players[5]);
break;
case R.id.p6Minus:
MinusLevel(Players[5]);
ilevel = Players[5].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p6Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p6Epic.setImageResource(R.drawable.black);
}
p6Level.setText(slevel);
break;
case R.id.p6Plus:
PlusLevel(Players[5]);
ilevel = Players[5].getPlayerLevel();
slevel = String.valueOf(ilevel);
if(ilevel>=10){
p6Epic.setImageResource(R.drawable.epic);
}
if(ilevel<10){
p6Epic.setImageResource(R.drawable.black);
}
p6Level.setText(slevel);
break;
}
}
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
tTitle = (TextView)this.findViewById(R.id.title);
menu.add(0, MENU_EPIC_ON, 0, R.string.menu_epic_on);
menu.add(0, MENU_EPIC_OFF, 0, R.string.menu_epic_off);
menu.add(0, MENU_RESET_LEVELS, 0, R.string.menu_reset_levels);
menu.add(0, MENU_RESET_NAMES, 0, R.string.menu_reset_names);
menu.add(0, MENU_RESET_ALL, 0, R.string.menu_reset_all);
menu.add(0, MENU_QUIT, 0, R.string.menu_quit);
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case MENU_EPIC_ON:
Epic = true;
MaxLevel=20;
tTitle.setText("Epic");
return true;
case MENU_EPIC_OFF:
Epic = false;
MaxLevel=10;
tTitle.setText("Normal");
ResetLevels();
return true;
case MENU_RESET_LEVELS:
ResetLevels();
return true;
case MENU_RESET_NAMES:
ResetNames();
return true;
case MENU_RESET_ALL:
ResetAll();
return true;
case MENU_QUIT:
finish();
return true;
}
return false;
}
}
这是自定义类的代码
package nicholsoft.LevelCounter;
import android.os.Parcelable;
import android.os.Parcel;
public class Player implements Parcelable{
private String Name;
private int Level;
private boolean Epic;
public Player(String Name, int Level, boolean Epic){
this.setName(Name);
this.Level = Level;
this.Epic = Epic;
}
public void writeToParcel(Parcel out, int flags){
out.writeString(Name);
out.writeInt(Level);
}
public static final Parcelable.Creator CREATOR = new Parcelable.Creator(){
public Player createFromParcel(Parcel in){ return new Player(in);}
public Player[] newArray(int size){return new Player[size];}
};
private Player(Parcel in){
Name = in.readString();
Level = in.readInt();
}
public Player(){}
public int describeContents() {return 0;}
public String getName(){
return Name;
}
public int getPlayerLevel(){
return Level;
}
public boolean getPlayerEpic(){
return Epic;
}
public void setName(String name){
Name = name;
}
public void setLevel(int level){
Level = level;
}
public void setEpic(boolean epic){
Epic = epic;
}
}
任何帮助,将不胜感激.
解决方法:
从Activity.onCreate(Bundle)的API文档：
savedInstanceState If the activity is being re-initialized after previously being shut down then this Bundle contains the data it most recently supplied in onSaveInstanceState(Bundle). Note: Otherwise it is null.
Bundle可以为null,你应该检查一下.
if(savedInstanceState != null && !savedInstanceState.isEmpty()){
Players = (Player[]) savedInstanceState.getParcelableArray("LastPlayerState");
}
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